阅读说明：本技术 太阳能电池以及具备该太阳能电池的电子设备 (Solar cell and electronic device provided with same ) 是由 宇津恒 市川满 于 2019-03-18 设计创作，主要内容包括：本发明提供在室外和室内这两种环境下都抑制太阳能电池的性能降低的太阳能电池。太阳能电池(1)具备光电转换基板(11)、配置于光电转换基板(11)的两个主面的每一个或光电转换基板(11)的一个主面的第一导电型半导体层(25)及第二导电型半导体层(35)、以及、与第一导电型半导体层(25)对应的第一电极层(27)及与第二导电型半导体层(35)对应的第二电极层(37),在与偏离太阳能电池而配置的遮光部件(70)组合使用的太阳能电池中,在光电转换基板(11)的主面,具有与遮光部件(70)对应的特定区域(60)和特定区域(60)以外的非特定区域,特定区域(60)中的电阻中的串联电阻分量与非特定区域中的电阻中的串联电阻分量相比,为高电阻。(Provided is a solar cell wherein the performance degradation of the solar cell is suppressed both in outdoor and indoor environments. A solar cell (1) comprising a photoelectric conversion substrate (11), a first conductivity type semiconductor layer (25) and a second conductivity type semiconductor layer (35) disposed on each of two main surfaces of the photoelectric conversion substrate (11) or on one main surface of the photoelectric conversion substrate (11), and a first electrode layer (27) corresponding to the first conductivity type semiconductor layer (25) and a second electrode layer (37) corresponding to the second conductivity type semiconductor layer (35), wherein the solar cell used in combination with a light shielding member (70) disposed so as to be offset from the solar cell has a specific region (60) corresponding to the light shielding member (70) and a non-specific region other than the specific region (60) on the main surface of the photoelectric conversion substrate (11), and wherein the series resistance component in the resistance in the specific region (60) is compared with the series resistance component in the resistance in the non-specific region, is high resistance.)

1. A solar cell comprising a photoelectric conversion substrate, a first conductive type semiconductor layer and a second conductive type semiconductor layer disposed on each of two main surfaces of the photoelectric conversion substrate or one main surface of the photoelectric conversion substrate, and a first electrode layer corresponding to the first conductive type semiconductor layer and a second electrode layer corresponding to the second conductive type semiconductor layer,

In a solar cell used in combination with a light shielding member disposed so as to be offset from the solar cell,

a specific region corresponding to the light shielding member and a non-specific region other than the specific region are provided on a main surface of the photoelectric conversion substrate,

the series resistance component in the resistance of the specific region is higher in resistance than the series resistance component in the resistance of the non-specific region.

2. The solar cell of claim 1,

the product Rs _ d × S _ d of the series resistance component Rs _ d in the specific region and the area S _ d of the specific region is 10 Ω · cm²More than 10000 omega cm and less than cm²。

3. The solar cell according to claim 1 or 2,

a product Rs _ p × S _ p of a series resistance component Rs _ p in the non-specific region and an area S _ p of the non-specific region is greater than 0 Ω · cm²And less than 10 omega cm²。

4. The solar cell according to any one of claims 1 to 3,

the area S _ d of the specific region is 0.25 times to 0.95 times the area of the main surface of the photoelectric conversion substrate.

5. The solar cell according to any one of claims 1 to 4,

the sectional area of the first electrode layer or the second electrode layer in the specific region is smaller than the sectional area of the first electrode layer or the second electrode layer in the non-specific region.

6. The solar cell according to any one of claims 1 to 4,

the first electrode layer or the second electrode layer in the non-specific region includes a transparent electrode layer and a metal electrode layer,

the first electrode layer or the second electrode layer in the specific region includes a transparent electrode layer, and does not include a metal electrode layer.

7. The solar cell according to any one of claims 1 to 6,

the solar cell is a back electrode type solar cell, and includes the first conductive type semiconductor layer and the second conductive type semiconductor layer disposed on one side of the other main surface opposite to the one main surface among the main surfaces of the photoelectric conversion substrate, and the first electrode layer corresponding to the first conductive type semiconductor layer and the second electrode layer corresponding to the second conductive type semiconductor layer.

8. The solar cell of claim 7,

the photoelectric conversion substrate is of a first conductivity type,

the entire surface of the specific region is covered with the second conductivity type semiconductor layer.

9. The solar cell of claim 7,

having a plurality of dividing regions that divide a main surface of the photoelectric conversion substrate into a plurality of regions so as to surround a plurality of the specific regions, respectively,

In each of the plurality of divided regions,

the first electrode layer and the second electrode layer each have a plurality of branch electrode layers in a stripe shape and a trunk electrode layer connected to one end of the plurality of branch electrode layers,

a part of the plurality of branch electrode layers of the first electrode layer or the second electrode layer surrounds at least a part of an outer edge of the specific region,

the main electrode layers of the first electrode layer and the second electrode layer have frame electrode layers surrounding the dividing regions.

10. The solar cell of claim 7,

the first electrode layer and the second electrode layer each have a plurality of branch electrode layers in a stripe shape and a trunk electrode layer connected to one end of the plurality of branch electrode layers,

at least one of the first electrode layer and the second electrode layer has a surrounding trunk electrode layer surrounding an outer edge of the specific region, and a band-shaped trunk electrode layer extending from the surrounding trunk electrode layer.

11. An electronic device is provided with:

the solar cell of any one of claims 1-10; and

one or more light blocking members are disposed on one of the main surfaces of the photoelectric conversion substrate in the solar cell, and are offset from the solar cell.

12. The electronic device of claim 11,

a sealing member is disposed between the solar cell and the light blocking member, and the sealing member is disposed on one side of the one main surface of the photoelectric conversion substrate and seals the photoelectric conversion substrate.

13. The electronic device of claim 11 or 12,

the light blocking member is a member for operating the electronic device.

Technical Field

The present invention relates to a solar cell and an electronic device including the solar cell.

Background

Electronic devices such as wearable devices and watches that are used in outdoor environments exposed to sunlight are desired to be equipped with solar cells. Patent document 1 discloses a wristwatch provided with a solar cell as such an electronic device.

In such an electronic device, gears, electronic components, decorative components, and the like constituting the electronic device may be arranged on the light incident surface side of the solar cell. In such a case, a shadow may be generated on the solar cell, which may result in a decrease in performance of the solar cell.

In this regard, patent document 1 describes a technique of preventing the flow of electricity and suppressing the reduction of the power generation efficiency of the solar cell by removing the transparent electrode or the solar cell itself (if the term described in patent document 1 is referred to as an opening or a slit provided in the transparent electrode or a through hole formed in the solar cell) at a portion of the solar cell overlapping with the decorative member applied to the dial (that is, a region where a shadow is generated in the solar cell).

Patent document 1: japanese laid-open patent publication No. 2015-55578

Electronic devices such as wearable devices and watches can be used even in an indoor environment where light is irradiated from a light source having relatively low light emission intensity such as a fluorescent lamp. In the case where scattered light or light from a plurality of light sources is irradiated to an electronic device at various incident angles, and a decorative member or the like is disposed to be offset from a solar cell in an indoor environment, it is expected that light is also irradiated to a portion of the solar cell which overlaps with a member disposed on the light incident surface side.

However, as in the solar cell described in patent document 1, if the transparent electrode or the solar cell itself is removed from the portion overlapping the decorative member in order to suppress the performance degradation of the solar cell in the outdoor environment and the electricity is not passed through, it is expected that the light irradiated to the portion overlapping the decorative member cannot be effectively used in the indoor environment, resulting in the performance degradation of the solar cell in the indoor environment.

Disclosure of Invention

The purpose of the present invention is to provide a solar cell in which the performance degradation of the solar cell is suppressed both in outdoor and indoor environments, and an electronic device provided with the solar cell.

The solar cell according to the present invention includes a photoelectric conversion substrate, a first conductive type semiconductor layer and a second conductive type semiconductor layer disposed on each of two main surfaces of the photoelectric conversion substrate or one main surface of the photoelectric conversion substrate, and a first electrode layer corresponding to the first conductive type semiconductor layer and a second electrode layer corresponding to the second conductive type semiconductor layer, and in the solar cell used in combination with a light shielding member disposed apart from the solar cell, the main surface of the photoelectric conversion substrate has a specific region corresponding to the light shielding member and a non-specific region other than the specific region, and a series resistance component in a resistance in the specific region is higher in resistance than a series resistance component in a resistance in the non-specific region.

An electronic device according to the present invention includes the solar cell described above, and one or more light-blocking members arranged offset from the solar cell on one of the main surfaces of the photoelectric conversion substrate in the solar cell.

According to the present invention, the performance degradation of the solar cell can be suppressed both in outdoor and indoor environments.

Drawings

Fig. 1 is a view of a part of the solar cell and the electronic device according to the present embodiment, as viewed from the back side.

Fig. 2 is a sectional view of a portion of the solar cell and electronic device of fig. 1 taken along line II-II.

Fig. 3 is a partial cross-sectional view of a solar cell according to a modification of the present embodiment.

Fig. 4A is a diagram showing an equivalent circuit of a solar cell used in circuit simulation.

Fig. 4B is a diagram showing an example of the current density of the equivalent circuit of the solar cell shown in fig. 4A.

Fig. 5A is a graph showing the IV characteristics of the circuit simulation results in the assumed outdoor environment.

Fig. 5B is a graph showing the IV characteristics of the circuit simulation result in the assumed indoor environment.

Fig. 6A is a diagram showing a relationship between the output of the solar cell and the series resistance component of the specific region, assuming the circuit simulation result in the outdoor environment.

Fig. 6B is a diagram showing a relationship between the output of the solar cell and the series resistance component of the specific region, assuming the circuit simulation result in the indoor environment.

Fig. 6C is a graph showing the relationship between the output of the solar cell and the series resistance component of the specific region after the circuit simulation result shown in fig. 6A and the circuit simulation result shown in fig. 6B are superimposed.

Fig. 7 is a diagram showing an example of the IV characteristics of the solar cell.

Fig. 8 is a view of a conventional solar cell as viewed from the back side.

Fig. 9 is a view of the solar cell according to the first modification of the present embodiment as viewed from the back side.

Fig. 10 is a view of the solar cell according to the second modification of the present embodiment, as viewed from the back side.

Detailed Description

Hereinafter, an example of an embodiment of the present invention will be described with reference to the drawings. In addition, the same or corresponding portions in the respective drawings are denoted by the same reference numerals. For convenience, hatching, component reference numerals, and the like may be omitted, and in this case, reference is made to other drawings.

Fig. 1 is a view of a part of a solar cell and an electronic device according to the present embodiment as viewed from the back side, and fig. 2 is a sectional view of the solar cell and the electronic device of fig. 1 taken along line II-II.

As shown in fig. 1 and 2, the electronic device of the present embodiment includes a solar cell 1 and one or more light blocking members 70. The light blocking member 70 is disposed on the light receiving surface side of the solar cell 1 (i.e., on one of the main surfaces of a semiconductor substrate (photoelectric conversion substrate) 11, which will be described later) away from the solar cell 1.

Electronic devices such as wearable devices and watches are expected to require highly designable products and products of various shapes. For example, in an electronic device such as a wearable device or a watch, a gear or an electronic component for operating the electronic device, or a light shielding member 70 such as a decorative member constituting the electronic device may be disposed on the light incident surface side of the solar cell 1, being offset from the solar cell 1.

A sealing member may be disposed between the solar cell 1 and the light blocking member 70, the sealing member being disposed on the light receiving surface side of the solar cell 1, and sealing the solar cell 1 (i.e., a semiconductor substrate (photoelectric conversion substrate) 11 described later). Examples of the sealing member include an EVA (Ethylene-Vinyl Acetate) film, an OCA (Optically Clear Adhesive) film, and glass.

Hereinafter, when viewed from the light receiving surface side or the back surface side of the solar cell 1 in plan view, the region of the solar cell 1 overlapping the light blocking member 70 (in other words, the region of the solar cell 1 corresponding to the light blocking member 70) is referred to as the specific region 60, and the region other than the specific region 60 in the solar cell 1 is referred to as the non-specific region.

(solar cell)

In the present embodiment, a back electrode type (back contact type) (back-junction type: also referred to as back junction type) solar cell is exemplified as the solar cell 1.

As a solar cell using a semiconductor substrate, there are a double-sided electrode type solar cell in which electrodes are formed on both the light receiving surface side and the back surface side, and a back electrode type solar cell in which an electrode is formed only on the back surface side. In the double-sided electrode type solar cell, since an electrode is formed on the light receiving surface side, sunlight is shielded by the electrode. On the other hand, in the back electrode type solar cell, since no electrode is formed on the light receiving surface side, the light receiving rate of sunlight is higher than that in the double-sided electrode type solar cell.

As shown in fig. 1 and 2, the back electrode type solar cell 1 includes a semiconductor substrate (photoelectric conversion substrate) 11, the semiconductor substrate 11 having two main surfaces, and the semiconductor substrate 11 having a first conductivity type region 7 and a second conductivity type region 8 on the main surfaces.

The solar cell 1 includes a passivation layer 13 and an antireflection layer 15 stacked in this order on a light-receiving surface side which is one of two main surfaces of the semiconductor substrate 11 on which light is received. The solar cell 1 further includes a passivation layer 23, a first conductive type semiconductor layer 25, and a first electrode layer 27, which are sequentially stacked on the first conductive type region 7 on the back side, which is the other main surface (one main surface) of the two main surfaces of the semiconductor substrate 11 on the opposite side of the light receiving surface. The solar cell 1 further includes a passivation layer 33, a second conductive type semiconductor layer 35, and a second electrode layer 37, which are sequentially stacked on the second conductive type region 8 on the back surface side of the semiconductor substrate 11.

< semiconductor substrate >

As the semiconductor substrate 11, a conductive type single crystal silicon substrate, for example, an n-type single crystal silicon substrate or a p-type single crystal silicon substrate is used. Thereby, high photoelectric conversion efficiency is achieved.

The semiconductor substrate 11 is preferably an n-type single crystal silicon substrate. This prolongs the carrier lifetime in the crystalline silicon substrate. In addition, in a p-type single crystal silicon substrate, B (boron) as a p-type dopant is affected by Light irradiation, and LID (Light Induced Degradation) serving as a recombination center may be caused, but LID is further suppressed in an n-type single crystal silicon substrate.

The semiconductor substrate 11 may have a pyramid-shaped fine uneven structure called a textured structure on the back surface side which is one of the two main surfaces. This improves the efficiency of collecting light that has passed through without being absorbed by the semiconductor substrate 11.

The semiconductor substrate 11 may have a pyramid-shaped fine uneven structure called a textured structure on the light receiving surface side. This reduces reflection of incident light on the light receiving surface, thereby improving the light confinement effect of the semiconductor substrate 11.

The thickness of the semiconductor substrate 11 is preferably 50 μm to 200 μm, more preferably 60 μm to 180 μm, and still more preferably 70 μm to 180 μm. By making the thickness of the semiconductor substrate 11 thin in this way, the open circuit voltage of the solar cell 1 is increased, and the material cost is reduced.

Further, as the semiconductor substrate 11, a conductive type polycrystalline silicon substrate, for example, an n-type polycrystalline silicon substrate or a p-type polycrystalline silicon substrate may be used. In this case, the back electrode type solar cell can be manufactured more inexpensively.

< anti-reflection layer >

The anti-reflection layer 15 is formed on the light-receiving surface side of the semiconductor substrate 11 with the passivation layer 13 interposed therebetween. The passivation layer 13 is formed of an intrinsic silicon-based layer. The passivation layer 13 terminates surface defects of the semiconductor substrate 11, suppressing recombination of carriers.

As the antireflection layer 15, a light-transmitting film having a refractive index of about 1.5 to 2.3 is preferably used. The material of the antireflection layer 15 is preferably SiO, SiN, SiON, or the like. The method for forming the antireflection layer 15 is not particularly limited, but a CVD (Chemical Vapor Deposition) method capable of controlling a precise film thickness is preferably used. In film formation by the CVD method, the film quality is controlled by adjusting the material gas or the film formation conditions.

In the present embodiment, since no electrode is formed on the light receiving surface side (back electrode type), the light receiving rate of sunlight is high, and the photoelectric conversion efficiency is improved.

< the first conductive type semiconductor layer and the second conductive type semiconductor layer >

The first conductive type semiconductor layer 25 is formed on the first conductive type region 7 on the back surface side of the semiconductor substrate 11 with the passivation layer 23 interposed therebetween, and the second conductive type semiconductor layer 35 is formed on the second conductive type region 8 on the back surface side of the semiconductor substrate 11 with the passivation layer 33 interposed therebetween. The first conductive type semiconductor layer 25 has a shape corresponding to a shape of a first electrode layer 27 (see fig. 1) described later, and the second conductive type semiconductor layer 35 has a shape corresponding to a shape of a second electrode layer 37 (see fig. 1) described later.

The first conductive type semiconductor layer 25 is formed of a first conductive type silicon-based layer, for example, a p-type silicon-based layer. The second conductive type semiconductor layer 35 is formed of a second conductive type silicon-based layer different from the first conductive type, for example, an n-type silicon-based layer. In addition, the first conductive type semiconductor layer 25 may be an n-type silicon-based layer, and the second conductive type semiconductor layer 35 may be a p-type silicon-based layer.

The p-type silicon layer and the n-type silicon layer are formed of an amorphous silicon layer or a microcrystalline silicon layer containing amorphous silicon and crystalline silicon. B (boron) is suitably used as the dopant impurity of the P-type silicon-based layer, and P (phosphorus) is suitably used as the dopant impurity of the n-type silicon-based layer.

The method for forming the first conductive type semiconductor layer 25 and the second conductive type semiconductor layer 35 is not particularly limited, but a CVD method is preferably used. As the material gas, for example, SiH is preferably used₄Gas, as dopant additive gas, for example, B diluted with hydrogen is preferably used₂H₆Or pH₃. In addition, in order to improve the light transmittance, for example, an impurity such as oxygen or carbon may be added in a small amount. In this case, for example, CO is introduced during CVD film formation₂Or CH₄And the like.

In addition, as another example of a method for forming the first conductive type semiconductor layer 25 and the second conductive type semiconductor layer 35, a thermal diffusion doping method, a laser doping method, or the like can be given.

In the back electrode type solar cell, light is received on the light receiving surface side, and generated carriers are collected on the back surface side, so that the first conductive type semiconductor layer 25 and the second conductive type semiconductor layer 35 are formed on the same plane. The method for forming the first conductive type semiconductor layer 25 and the second conductive type semiconductor layer 35 into a predetermined shape (patterning) in the same plane is not particularly limited, and a CVD method using a mask or an etching method using a resist, an etching solution, an etching paste, or the like may be used.

The first conductive type semiconductor layer 25 and the second conductive type semiconductor layer 35 are preferably not joined. Therefore, an insulating layer (not shown) may be provided between these layers. For example, in the case where an insulating layer is provided at the boundary portion between the p-type silicon thin film and the n-type silicon thin film, if an insulating layer of silicon oxide or the like is formed by a CVD method, the film formation process can be simplified, and reduction in process cost and improvement in yield can be achieved.

< passivation layer >

The passivation layers 23, 33 are formed of an intrinsic silicon-based layer. The passivation layers 23, 33 terminate surface defects of the semiconductor substrate 11, and suppress recombination of carriers. Thus, the output of the solar cell is improved in order to increase the lifetime of carriers.

< first electrode layer and second electrode layer >

The first electrode layer 27 is formed on the first conductive type semiconductor layer 25 in the non-specific region, and the second electrode layer 37 is formed on the second conductive type semiconductor layer 35 in the non-specific region. In addition, the first electrode layer 27H is formed on the first conductive type semiconductor layer 25 in the specific region 60, and the second electrode layer 37H is formed on the second conductive type semiconductor layer 35 in the specific region 60. The first electrode layers 27 and 27H and the second electrode layers 37 and 37H may be physically in contact with each other or may be separated from each other as long as they are not directly electrically connected. In addition, in fig. 1, an example in which the first electrode layers 27, 27H and the second electrode layers 37, 37H are physically separated is shown.

The first electrode layers 27, 27H and the second electrode layers 37, 37H may be formed by transparent electrode layers 28, 38, 28H, 38H made of a transparent conductive material. As the transparent conductive material, a transparent conductive metal oxide such as indium oxide, tin oxide, zinc oxide, titanium oxide, and a composite oxide thereof can be used. Among these, indium composite oxides containing indium oxide as a main component are also preferable. Indium oxide is particularly preferable from the viewpoint of high conductivity and transparency. Further, in order to ensure reliability or higher conductivity, a dopant is preferably added to the indium oxide. Examples of the dopant include Sn, W, Zn, Ti, Ce, Zr, Mo, Al, Ga, Ge, As, Si, and S.

As a method for forming the transparent electrode layers 28, 38, 28H, and 38H, a physical vapor deposition method such as a sputtering method, a chemical vapor deposition method (for example, a CVD method) using a reaction between an organic metal compound and oxygen or water, or the like can be used.

The first electrode layers 27, 27H and the second electrode layers 37, 37H are not limited to the transparent electrode layers 28, 38, 28H, 38H, and may include metal electrode layers 29, 39, 29H, 39H stacked on the transparent electrode layers 28, 38, 28H, 38H. That is, the first electrode layers 27 and 27H and the second electrode layers 37 and 37H may be laminated layers in which the transparent electrode layers 28, 38, 28H, and 38H and the metal electrode layers 29, 39, 29H, and 39H are laminated. In addition, one of the first electrode layer and the second electrode layer may be a laminated electrode layer, and the other may be a single-layer transparent electrode layer. The first electrode layer 27 and the second electrode layer 37 may be formed only of a metal electrode layer.

The metal electrode layers 29, 39, 29H, and 39H are formed of a metal material. As the metal material, for example, Cu, Ag, Al, and an alloy thereof can be used.

As a method for forming the metal electrode layers 29, 39, 29H, and 39H, for example, a printing method such as screen printing using Ag paste, or a plating method such as plating using Cu, or the like can be used.

< specific region >

As described above, the solar cell 1 of the present embodiment is used in combination with the light blocking member 70 that is disposed on the light incident surface side of the solar cell 1 and is offset from the solar cell 1 in an electronic device such as a wearable device or a watch.

The solar cell 1 has one or more specific regions 60 overlapping the light-shielding member 70, that is, corresponding to the light-shielding member 70, and a non-specific region other than the specific regions 60 on the main surface of the semiconductor substrate 11. The solar cell 1 of the present embodiment shown in fig. 1 has three specific regions 60.

The specific region 60 has a circular shape in a plan view of the main surface of the semiconductor substrate 11, for example. Further, the shape of the specific region 60 is not limited to this, and may be a belt shape or a polygonal shape (for example, a triangular shape or a quadrangular shape), or a more complicated shape.

In the case where a plurality of specific regions 60 are provided, the areas of the plurality of specific regions 60 may be the same or different. The area of the specific region 60 may be equal to or smaller than the area of the light blocking member 70.

Since the light shielding member 70 is offset from the specific region 60 of the solar cell 1, in an indoor environment, direct light from a light source such as a fluorescent lamp or light reflected or scattered by a component of an electronic device is obliquely irradiated to the specific region 60 at a gap between the light shielding member 70 and the specific region 60.

In an outdoor environment where sunlight is irradiated, the specific region 60 is a region where a shadow is formed mainly by the light shielding member 70, and a non-specific region other than the specific region 60 is a region where sunlight is irradiated. Therefore, in the outdoor environment, the difference between the irradiation light amount of the specific region 60 and the irradiation light amount of the non-specific region is very large.

On the other hand, in the indoor environment, since light is irradiated from various directions, the difference in the irradiation light amount between the specific region 60 and the non-specific region is small compared to that in the outdoor environment.

Therefore, in the outdoor environment, the output of the solar cell is suppressed from being reduced due to the influence of the shadow in the specific region 60, and in the indoor environment, the output of the solar cell in the specific region 60 is extracted as much as possible, whereby the power generation amount of the solar cell is improved.

In order to suppress a decrease in the output of the solar cell due to the influence of the shadow in the specific region 60 in the outdoor environment and extract the output of the solar cell in the specific region 60 as much as possible in the indoor environment, in the present embodiment, the series resistance component in the resistance in the specific region 60 is higher than the series resistance component in the resistance in the non-specific region other than the specific region 60.

Thus, in an outdoor environment where the amount of power generated in the non-specific region is large and the difference between the amount of light irradiated to the specific region 60 and the amount of light irradiated to the non-specific region is large, the influence of dark current in the specific region 60 is suppressed by a voltage drop due to the series resistance in the specific region 60, and the output drop in the non-specific region is suppressed. That is, the output of the solar cell in the outdoor environment is improved.

On the other hand, in an indoor environment, the amount of power generated by the solar cell 1 is 1/100 times or less, and is 1/1000 times or less depending on the location, compared to that in an outdoor environment, and the magnitude of the series resistance loss in the specific region 60 is relatively small, so that the output of the solar cell in the specific region 60 due to scattered light or the like in the indoor environment can be extracted to some extent. In this way, in an indoor environment, not only the power generation in the non-specific region but also the power generation in the specific region 60 can be utilized, and the output of the solar cell can be improved.

The method of increasing the series resistance component of the resistance in the specific region 60 is not particularly limited, and for example, the resistance in the film thickness direction of the passivation layer 23 and the first conductive type semiconductor layer 25, or the passivation layer 33 and the second conductive type semiconductor layer 35 may be increased. Alternatively, the contact resistance of the interface between the semiconductor substrate 11 and the passivation layer 23 and the interface between the semiconductor substrate 11 and the passivation layer 33, the contact resistance of the interface between the passivation layer 23 and the first conductive type semiconductor layer 25 and the interface between the passivation layer 33 and the second conductive type semiconductor layer 35, or the contact resistance of the interface between the first conductive type semiconductor layer 25 and the first electrode layer 27H and the interface between the second conductive type semiconductor layer 35 and the second electrode layer 37H may be increased.

As a particularly simple method, it is preferable that the resistance of the first electrode layer 27H and the second electrode layer 37H in the specific region 60 is higher than the resistance of the first electrode layer 27 and the second electrode layer 37 in the unspecified region. Hereinafter, the first electrode layer 27H and the second electrode layer 37H in the specific region 60 will be described after the first electrode layer 27 and the second electrode layer 37 in the non-specific region are described.

< electrode layer in non-specific region >

In the non-specific region, the width of the first electrode layer 27 is preferably smaller than the width of the first conductive type semiconductor layer 25, and the width of the second electrode layer 37 is preferably smaller than the width of the second conductive type semiconductor layer 35. Note that the widths of the conductive layer and the electrode layer indicate a direction perpendicular to the extending direction of each layer (however, not the thickness direction of each layer), unless otherwise specified.

In order to efficiently extract the photo carriers collected in the first and second conductive type semiconductor layers 25 and 35, the widths of the first and second electrode layers 27 and 37 are preferably as large as possible with respect to the first and second conductive type semiconductor layers 25 and 35. Therefore, the width of the first electrode layer 27 is preferably larger than 0.5 times, and more preferably larger than 0.7 times the width of the first conductive type semiconductor layer 25. Similarly, the width of the second electrode layer 37 is preferably greater than 0.5 times, and more preferably greater than 0.7 times the width of the second conductive type semiconductor layer 35.

In addition, when the insulating layer or another layer is provided at the boundary portion between the first conductive type semiconductor layer 25 and the second conductive type semiconductor layer 35 and the first electrode layer 27 and the second electrode layer 37 are separated from each other, the widths of the first electrode layer 27 and the second electrode layer 37 may be larger than the width of the first conductive type semiconductor layer 25 and the width of the second conductive type semiconductor layer 35, respectively.

On the other hand, in order to efficiently recover the photo carriers in the semiconductor substrate 11 in the first conductive type semiconductor layer 25 and the second conductive type semiconductor layer 35, the widths of the first electrode layer 27 (a first branch electrode layer 27f and a first main electrode layer 27b, which will be described later) and the second electrode layer 37 (a second branch electrode layer 37f and a second main electrode layer 37b, which will be described later) are preferably made small to some extent.

The widths of the first and second branch electrode layers 27f and 37f and the first and second conductive type semiconductor layers 25 and 35 corresponding to the respective branch electrode layers are not particularly limited as long as they are small to some extent, but are preferably in the range of 50 to 3000 μm, respectively.

On the other hand, from the viewpoint of electrical transportation, the trunk electrode layer needs to have a certain cross-sectional area in order to suppress resistance loss, and the cross-sectional area needs to be secured by the width and height (film thickness) of the trunk electrode layer. Accordingly, the widths of the first and second trunk electrode layers 27b and 37b and the first and second conductive type semiconductor layers 25 and 35 corresponding to the trunk electrode layers are preferably in the range of 50 to 5000 μm, respectively.

If the heights of the first electrode layer 27 and the second electrode layer 37 are increased, the cross-sectional area for the current flowing in the surface direction increases, and thus the series resistance decreases. However, if the height of the electrode layer is increased, stress at the interface between the semiconductor layer and the electrode layer increases, and electrode peeling may occur. Further, in the back electrode type solar cell, since the electrode is provided only on one surface, if the height of the electrode layer is increased, the stress on the front and back surfaces of the substrate becomes uneven, and deformation such as warping of the solar cell is likely to occur, and the solar cell may be damaged. Further, when the solar cell is deformed by stress at the electrode interface, defects such as misalignment and short-circuiting may occur in the modularization. Accordingly, the height of the first electrode layer 27 and the second electrode layer 37 is preferably 100 μm or less, more preferably 60 μm or less, and further preferably 30 μm or less.

The height of the electrode is the distance from the main surface of the substrate to the apex of the electrode. When there is a region in which the thickness of the substrate is locally reduced by etching or the like for forming the semiconductor layer, a reference plane parallel to the main surface of the substrate may be determined, and the distance from the reference plane to the apex of the electrode may be defined as the height of the electrode.

< electrode layer in specific region >

As described above, the resistance of the first electrode layer 27H and the second electrode layer 37H in the specific region 60 is preferably higher than the resistance of the first electrode layer 27 and the second electrode layer 37 in the non-specific region.

As a method of increasing the resistance of the first electrode layer 27H and the second electrode layer 37H in the specific region 60 to be higher than the resistance of the first electrode layer 27 and the second electrode layer 37 in the unspecified region, for example, it is conceivable to increase the resistance of the metal electrode layers 29H and 39H of the electrode layers 27H and 37H in the specific region 60 to be higher than the resistance of the metal electrode layers 29 and 39 of the electrode layers 27 and 37 in the unspecified region.

For example, as shown in fig. 2, the widths of the metal electrode layers 29H and 39H of the electrode layers 27H and 37H in the specific region 60 may be made narrower than the widths of the metal electrode layers 29 and 39 of the electrode layers 27 and 37 in the unspecified region. In other words, it is conceivable that the widths of the first electrode layer 27H and the second electrode layer 37H in the specific region 60 are narrower than the widths of the first electrode layer 27 and the second electrode layer 37 in the non-specific region.

The method of making the resistance of the metal electrode layers 29H, 39H of the electrode layers 27H, 37H in the specific region 60 larger than the resistance of the metal electrode layers 29, 39 of the electrode layers 27, 37 in the unspecified region is not limited to this, and the sectional area of the metal electrode layers 29H, 39H in the specific region 60 may be made smaller than the sectional area of the metal electrode layers 29, 39 in the unspecified region. For example, the height of the metal electrode layers 29H and 39H in the specific region 60 may be set lower than the height of the metal electrode layers 29 and 39 in the non-specific region.

Alternatively, the material of the metal electrode layers 29H and 39H in the specific region 60 may be a material having a higher resistance than the material of the metal electrode layers 29 and 39 in the unspecified region. For example, aluminum paste or copper paste is used as a material for the high-resistance metal electrode layer, and silver paste is used as a material for the low-resistance metal electrode layer.

As a method of increasing the resistance of the first electrode layer 27H and the second electrode layer 37H in the specific region 60 to be higher than the resistance of the first electrode layer 27 and the second electrode layer 37 in the non-specific region, for example, as shown in fig. 3, it is conceivable that the first electrode layer 27H and the second electrode layer 37H in the specific region 60 are formed only of the transparent electrode layers 28H and 38H without including the metal electrode layers 29H and 39H.

The resistance of the transparent electrode layers 28H and 38H in the specific region 60 may be set to be higher than the resistance of the transparent electrode layers 28 and 38 in the unspecified region. For example, the thickness of the transparent electrode layers 28H and 38H in the specific region 60 may be made thinner than the thickness of the transparent electrode layers 28 and 38 in the non-specific region, or the width of the transparent electrode layers 28H and 38H in the specific region 60 may be made narrower than the width of the transparent electrode layers 28 and 38 in the non-specific region. That is, the cross-sectional area of the transparent electrode layers 28H and 38H in the specific region 60 may be smaller than the cross-sectional area of the transparent electrode layers 28 and 38 in the non-specific region.

The width of the first conductive type semiconductor layer 25 and the width of the second conductive type semiconductor layer 35 in the specific region 60 are not particularly limited as long as the width of the first conductive type semiconductor layer 25 and the width of the second conductive type semiconductor layer 35 in the unspecified region are small to some extent, but are preferably in the range of 50 to 3000 μm, respectively.

As described above, according to the back electrode type solar cell 1 of the present embodiment, the series resistance component of the resistance in the specific region 60 overlapping with the light shielding member 70 in the electronic device has a higher resistance than the series resistance component of the resistance in the non-specific region other than the specific region 60.

Therefore, in an outdoor environment where the amount of power generation in the non-specific region is large and the difference between the amount of light irradiated to the specific region 60 and the amount of light irradiated to the non-specific region is large, the influence of the dark current in the specific region 60 is suppressed by the voltage drop due to the series resistance in the specific region 60, and the output drop in the non-specific region is suppressed. That is, the output of the solar cell in the outdoor environment is improved.

On the other hand, in an indoor environment, the amount of power generated by the solar cell 1 is 1/100 times or less as compared with that in an outdoor environment, and is 1/1000 times or less depending on the location, and the magnitude of the series resistance loss in the specific region 60 is relatively small, so that the output of the solar cell in the specific region 60 due to scattered light or the like in the indoor environment can be extracted to some extent. In this way, in an indoor environment, not only the power generation in the non-specific region but also the power generation in the specific region 60 can be utilized, and the output of the solar cell can be improved.

This can suppress the performance degradation of the solar cell caused by the specific region 60 overlapping the light blocking member 70 in the electronic device in both the outdoor and indoor environments.

< circuit simulation verification >

Here, verification is made using a circuit simulation (circuit calculation) using an equivalent circuit for an improvement in the output of the solar cell by increasing the series resistance component of the resistance in the specific region 60.

Fig. 4A is a diagram showing an equivalent circuit of a solar cell used in circuit simulation (circuit calculation). As shown in fig. 4A, as a calculation module of an equivalent circuit of a solar cell, a diode module generally used in calculation of a solar cell is used.

In this equivalent circuit, two diode modules are introduced, one diode module PV (light) representing a non-specific area of the solar cell 1 and the other diode module PV (dark) representing a specific area 60.

The parameters of the two diode modules PV (light) and PV (dark) are determined by fitting the output characteristics of the heterojunction solar cell actually fabricated using the following equations.

[ numerical formula 1]

In the above equation, j (V) on the left is the current density of PV (light) or PV (dark) in the diode module of fig. 4A, indicating the current density with respect to the applied voltage V. Fig. 4B shows an example of the current density of PV (light) or PV (dark) in the diode module of fig. 4A. As shown in FIG. 4B, the current density J (V) varies according to the applied voltage V, for example, the current density at the applied voltage V1 is J (V1).

The first term Jph on the right represents I _ p or I _ d in the diode module of fig. 4A, i.e., the photocurrent density corresponding to the photocurrent. Second item J on the right₀₁A reverse saturation current density of one diode D1_ p or D1_ D in the diode module of fig. 4A is shown. Third item J on the right₀₂A reverse saturation current density of another diode D2_ p or D2_ D in the diode module of fig. 4A is shown. The fourth term on the right hand side is represented by the series resistance Rs (i.e., Rs _ p or Rs _ d) and the parallel resistance R in the diode module of FIG. 4ALoss due to sh (i.e., Rsh _ p or Rsh _ d). Here, since the series resistance Rs and the parallel resistance Rsh use the value of each solar cell, they are multiplied by the area S of the solar cell (S is 239 (cm)²) To convert to per unit area. Further, q represents an electric quantity, k_BRepresents boltzmann's constant and T represents temperature.

The parameters in the above formula are as follows.

PV (Ming):

J₀₁(D1_p)＝7.9E－15(A/cm²)

J₀₂(D2_p)＝1.23E－8(A/cm²)

Rs_p＝0.002(Ω)

Rsh_p＝1E+6(Ω)

PV (dark):

J₀₁(D1_d)＝7.9E－15(A/cm²)

J₀₂(D2_d)＝1.23E－8(A/cm²)

Rsh_d＝1E+6(Ω)

in the circuit simulation in the outdoor environment, it is assumed that I _ p is 0.038 (a/cm) generated in PV (bright) of a non-specific area (light irradiation area)²) Assuming that I _ d is 0.00038 (a/cm) generated in PV (dark) of a specific region (shaded region)²) The photocurrent (1/100 times of I _ p of PV (bright) of the non-specific region (light irradiation region)).

On the other hand, in the circuit simulation under the indoor environment, it is assumed that, by irradiating the specific region 60 with light to some extent by the scattered light, I _ p (I _ d) is 0.00038 (a/cm) in PV (light) of the non-specific region (light irradiation region) and PV (dark) of the specific region (shaded region) 60²) A photocurrent (1/100 times of I _ p of PV (bright) of a non-specific area (light irradiation area) in an outdoor environment).

In the circuit simulation, the series resistance component Rs _ d of the specific region 60 is changed in a range of 0.002 Ω to 2000 Ω. In the circuit simulation, for the ratio S _ p of the area S _ p of the non-specific region (light irradiation region) to the area S _ d of the specific region (shaded region) 60: s _ d is 1: 3. 1: 1. 3: 1 three patterns are calculated. And, for solar electricityThe area of the pool is 8cm²、239cm²Two modes are calculated. In addition, Rs _ p, Rsh _ d use fixed values regardless of the cell area.

Fig. 5A shows an assumed outdoor environment (I _ p is 0.038 (a/cm)²)，I_d＝0.00038(A/cm²) Fig. 5B shows IV characteristics of the circuit simulation results, assuming that (I _ p — I _ d — 0.00038 (a/cm) is in an indoor environment²) IV characteristics of the circuit simulation results. In FIGS. 5A and 5B, the area of the solar cell is 239cm ²The ratio S _ p of the area S _ p of the non-specific region (light irradiation region) to the area S _ d of the specific region (shaded region) 60: s _ d is 1: 3.

according to fig. 5A, as the series resistance component Rs _ d of the specific region 60 becomes larger, the open-circuit voltage Voc increases, and the output of the solar cell also increases. As described above, if the series resistance component of the specific region 60 increases, the influence of the dark current in the specific region 60 is suppressed, and the output of the solar cell increases.

On the other hand, according to fig. 5B, as the series resistance component Rs _ d of the specific region 60 becomes smaller, the output of the solar cell increases. This is considered to be because the electric energy generated in the specific region 60 is consumed by the series resistance component Rs _ d and is hard to be taken out when the series resistance component Rs _ d is large, whereas the electric energy generated in the specific region 60 is taken out when the series resistance component Rs _ d is small.

According to fig. 5A and 5B, if the series resistance component Rs _ d of the specific region 60 is, for example, about 6.32E-1(Ω), the influence of a dark current to some extent can be suppressed in the outdoor environment (fig. 5A), and a sufficient output can be obtained even in the indoor environment (fig. 5B). Thus, it is understood that if the Rs _ d is selected appropriately, high output can be obtained both in the outdoor and indoor environments.

Next, the relationship between the output of the solar cell and the series resistance component in the specific region 60 in the outdoor environment and the indoor environment is generalized.

Fig. 6A shows an assumed outdoor environment (I _ p is 0.038 (a/cm)²)，I_d＝0.00038(A/cm²) Of circuit simulation results, sunFig. 6B shows a relationship between the output of the rechargeable battery and the series resistance component of the specific region 60, and it is assumed that the indoor environment is an environment (I _ p ═ I _ d ═ 0.00038 (a/cm)²) ) the output of the solar cell and the series resistance component of the specific region 60. Fig. 6C shows the relationship between the output of the solar cell and the series resistance component of the specific region 60, which is obtained by superimposing the circuit simulation result shown in fig. 6A and the circuit simulation result shown in fig. 6B.

In fig. 6A to 6C, the abscissa indicates the product Rs _ d × S _ d of the series resistance component Rs _ d of the specific region 60 and the area S _ d of the specific region 60, and the ordinate indicates the product Rs _ d × S _ d of 0 Ω · cm · in each solar cell²The difference Δ Power between the output of the solar cell per unit area at the time and the output of the solar cell per unit area of the values of Rs _ d × S _ d. Here, the area in the calculation of the output of the solar cell per unit area is the area of the non-specific region (light irradiation region), and is S _ p (fig. 6A) in the outdoor environment and the sum of S _ p and S _ d (fig. 6B) in the indoor environment.

In FIGS. 6A to 6C, the area of the solar cell is 8cm²、239cm²Two modes, and, for the ratio S _ p of the area S _ p of the non-specific region (light irradiation region) to the area S _ d of the specific region (shaded region) 60: s _ d is 1: 3. 1: 1. 3: 1 three modes showing the results of the circuit simulation.

According to FIG. 6A, in an outdoor environment, Rs _ d × S _ d is 1. omega. cm²In the region of a small value or less, the series resistance component in the specific region 60 is small, and therefore, the decrease in the solar cell output due to dark current cannot be suppressed, but if it exceeds 1 Ω · cm, it can be seen²On the left and right sides, the output gradually increases, and exceeds 1E + 4. omega. cm²The left and right sides are saturated. In particular, the ratio of the area (S _ p) of the non-specific region (light irradiation region) to the area (S _ d) of the specific region (shaded region) 60 is 1: 3, the ratio of the output loss due to the dark current in the specific region 60 to the others is 1: 1. 3: 1, and therefore the larger Rs _ d × S _ d proportional to the series resistance component of the resistance in the specific region 60, the more the loss due to dark current is suppressed, and the more the sun isThe more the output of the battery can be improved.

On the other hand, according to FIG. 6B, in an indoor environment, Rs _ d × S _ d is 10. omega. cm ²To the extent that the output of the solar cell in the specific region 60 can be sufficiently extracted, the output drop due to the series resistance component in the specific region 60 is small, but when Rs _ d × S _ d exceeds 10 Ω · cm²On the left and right sides, the output of the solar cell gradually decreases. This is because the output of the solar cell in the specific region 60 cannot be extracted due to the series resistance component in the specific region 60.

According to fig. 6C, there is a series resistance (dotted line portion) of the specific region 60, so that sufficient output improvement is expected in the outdoor environment and output reduction is suppressed in the indoor environment. The optimum series resistance varies slightly depending on the usage environment of the solar cell, but the product Rs _ d × S _ d of the series resistance component Rs _ d in the specific region 60 and the area S _ d of the specific region 60 is preferably 10 Ω · cm²More than 10000 omega cm and less than cm²More preferably 20. omega. cm²More than and less than 1000 omega cm²Particularly preferably 50. omega. cm²Above and below 500 omega cm²。

In addition, the product Rs _ p × S _ p of the series resistance component Rs _ p in the non-specific region and the area S _ p of the non-specific region is preferably larger than 0 Ω · cm²And less than 10 omega cm²And particularly smaller is more preferable.

The area S _ d of the specific region 60 is preferably 0.25 times (corresponding to S _ p: S _ d being 3: 1) or more and 0.95 times or less, and more preferably 0.25 times or more and 0.75 times (corresponding to S _ p: S _ d being 1: 3) or less of the sum S _ p + S _ d of the area S _ p of the non-specific region and the area S _ d of the specific region 60, which are the areas of the main surface of the semiconductor substrate 11.

The method for measuring the series resistance component of the resistance in the specific region 60 is not particularly limited, and for example, the series resistance can be calculated by Photoluminescence (PL) and Electroluminescence (EL), or the series resistance component can be easily estimated by using LIS-R2 of BT Imaging Pty Ltd. For example, when the area of the specific region 60 is large to some extent and the series resistance component is also large, IV measurement including a sufficient reverse bias range may be performed using light with an emission intensity of AM1.5 or more, and the series resistance component may be estimated from the inclination of the IV curve in two stages shown in fig. 7. In fig. 7, the inclination of the IV curve in the range of the first stage where the current is low among the two-stage IV curves corresponds to the series resistance component Rs _ p in the non-specific region, and the inclination of the IV curve in the range of the second stage where the current is high corresponds to the series resistance component Rs _ d in the specific region 60.

Here, fig. 8 is a view of a conventional back electrode type solar cell as viewed from the back surface side. The solar cell 1X shown in fig. 8 includes a first conductive type semiconductor layer 25X and a second conductive type semiconductor layer 35X on the back surface side of a semiconductor substrate 11X. The first conductive type semiconductor layer 25X has a so-called comb shape, and includes a plurality of finger portions corresponding to comb teeth and a bus portion corresponding to a support portion of the comb teeth. The bus bar portion extends in the X direction along one side portion of the semiconductor substrate 11X, and the finger portion extends from the bus bar portion in the Y direction intersecting the X direction. Similarly, the second conductive type semiconductor layer 35X has a so-called comb-like shape, and includes a plurality of finger portions corresponding to comb teeth and a bus portion corresponding to a support portion of the comb teeth. The bus bar portion extends in the X direction along the other side portion opposed to the one side portion of the semiconductor substrate 11X, and the finger portion extends in the Y direction from the bus bar portion. The finger portions of the first conductive type semiconductor layer 25X and the finger portions of the second conductive type semiconductor layer 35X are alternately arranged in the X direction. Thereby, the formation region of the first conductive type semiconductor layer 25X and the formation region of the second conductive type semiconductor layer 35X are engaged with each other. According to such a configuration, photo carriers induced in the semiconductor substrate 11X by incident light from the light receiving surface side can be efficiently recovered in each semiconductor layer.

The first conductive type semiconductor layer 25X and the second conductive type semiconductor layer 35X are provided with a first electrode layer 27X and a second electrode layer 37X for extracting the collected photo carriers to the outside. The first electrode layer 27X has a so-called comb-like shape, and includes a plurality of finger portions 27fX corresponding to comb teeth and a bus portion 27bX corresponding to a support portion of the comb teeth. The bus bar portion 27bX extends in the X direction along one side portion of the semiconductor substrate 11X, and the finger portions 27fX extend from the bus bar portion 27bX in the Y direction intersecting the X direction. Similarly, the second electrode layer 37X has a so-called comb-like shape, and includes a plurality of finger portions 37fX corresponding to comb teeth and a bus portion 37bX corresponding to a support portion of the comb teeth. The bus bar portion 37bX extends in the X direction along the other side portion facing the one side portion of the semiconductor substrate 11X, and the finger portions 37fX extend in the Y direction from the bus bar portion 37 bX. The finger portions 27fX and the finger portions 37fX are alternately arranged in the X direction.

In the conventional back electrode type solar cell 1X, when the series resistance component of the resistance of the specific region 60X overlapping the light shielding member of the electronic device is set to a high resistance (hatched portion), a part of the distal end side of the finger portion 27fX of the first electrode layer 27X or a part of the distal end side of the finger portion 37fX of the second electrode layer 37X is connected to the bus bar portion 27bX or the bus bar portion 37bX via the high resistance specific region 60X. Therefore, the carrier extraction efficiency recovered in the first electrode layer 27X and the second electrode layer 37X is lowered, and the output of the solar cell 1X is lowered.

In this regard, in the present embodiment, the first electrode layers 27 and 27H and the second electrode layers 37 and 37H in the non-specific region and the specific region 60 are formed in the following shapes. The first conductive type semiconductor layer 25 has a shape corresponding to the shape of the first electrode layers 27 and 27H, and the second conductive type semiconductor layer 35 has a shape corresponding to the shape of the second electrode layers 37 and 27H.

< dividing regions >

As shown in fig. 1, the solar cell 1 has three divided regions 50 divided into three regions on the main surface of the semiconductor substrate 11 so as to surround three specific regions 60, respectively.

By providing a single specific region 60 in the divided region 50, the low-resistance branch electrode layer in the non-specific region can be connected to the trunk electrode layer without passing through the high-resistance branch electrode layer in the specific region 60.

< shape of first electrode layer and second electrode layer in non-specific region >

Preferably, the first electrode layer 27 and the second electrode layer 37 in the non-specific region are formed so as to be distributed over the entire non-specific region on the main surface of the semiconductor substrate 11. Therefore, the effective power generation area is enlarged, and the photoelectric conversion efficiency is improved.

In each of the divisional areas 50, the first electrode layer 27 includes a plurality of first branch electrode layers 27f and a first main electrode layer 27 b. In addition, in each of the divisional areas 50, the second electrode layer 37 includes a plurality of second branch electrode layers 37f and a second trunk electrode layer 37 b.

< first Branch electrode layer and second Branch electrode layer >)

The first branch electrode layer 27f and the second branch electrode layer 37f are so-called finger electrodes, and have a shape (band shape) like a band. The first branch electrode layer 27f and the second branch electrode layer 37f may be linear or curved.

The electrode patterns of the first branch electrode layer 27f and the second branch electrode layer 37f are not particularly limited, and for example, in each of the divided regions 50, a pattern concentric with the specific region 60 is preferable in a region excluding the formation region of the specific region 60, the first trunk electrode layer 27b, and the second trunk electrode layer 37 b. In other words, the first branch electrode layer 27f and the second branch electrode layer 37f are preferably formed so that the center overlaps with the center of the specific region 60 and overlaps with the similar shape of the specific region 60. This prevents disconnection of the low-resistance branch electrode layer in the unspecific region due to the high-resistance specific region 60, and prevents resistance loss due to the high-resistance branch electrode layer in the unspecific region connected to the trunk electrode without passing through the high-resistance branch electrode layer in the specific region 60. This enables the output of the solar cell 1 in the outdoor environment to be efficiently extracted, and the output of the solar cell 1 to be improved.

Considering the local range, the first branch electrode layers 27f and the second branch electrode layers 37f are preferably arranged alternately in a direction intersecting the extending direction (for example, a direction perpendicular to a tangent line of each point) so as to be locally parallel to each other.

Any one of the first branch electrode layer 27f and the second branch electrode layer 37f surrounds the outer edge of the specific region 60. The branch electrode layer surrounding the outer edge of the specific region 60 may be the first branch electrode layer 27f or the second branch electrode layer 37 f. In the solar cell 1 of the present embodiment, a part of the second branch electrode layer 37f surrounds the outer edge of the specific region 60.

The shape of the branch electrode surrounding the outer edge of the specific region 60 may be a ring shape (closed ring shape) or an open ring shape. The shape of the ring-shaped or open-ring-shaped branch electrode may be curved or linear.

In each of the divisional areas 50, one end of the first branch electrode layer 27f is connected to the first trunk electrode layer 27b, and the other end of the first branch electrode layer 27f is separated from the second trunk electrode layer 37 b. One end of the second branch electrode layer 37f is connected to the second trunk electrode layer 37b, and the other end of the second branch electrode layer 37f is separated from the first trunk electrode layer 27 b.

< < first trunk electrode layer and second trunk electrode layer >)

The first trunk electrode layer 27b and the second trunk electrode layer 37b are so-called bus bar electrodes, and have a shape (band shape) like a tape. The first trunk electrode layer 27b and the second trunk electrode layer 37b may be linear or curved.

In each of the divisional areas 50, the first trunk electrode layer 27b includes a first frame-use trunk electrode layer 27bf and a first strip-shaped trunk electrode layer 27 bb. In addition, in each of the divisional areas 50, the second trunk electrode layer 37b includes a second frame-use trunk electrode layer 37bf and a second belt-shaped trunk electrode layer 37 bb.

< < < < first frame trunk electrode layer, second frame trunk electrode layer, and frame electrode layer > >)

The first frame trunk electrode layer 27bf and the second frame trunk electrode layer 37bf constitute a frame electrode layer 40. The frame electrode layer 40 is formed so as to surround each of the divided regions 50, in other words, so as to overlap the outer edges of the divided regions 50. The frame electrode layer 40 may have an open loop shape in which the first frame trunk electrode layer 27bf and the second frame trunk electrode layer 37bf are separated from each other, or may have a loop shape (closed loop shape) formed by either the first frame trunk electrode layer 27bf or the second frame trunk electrode layer 37 bf. The shape of the ring-shaped or ring-opened frame electrode layer 40 may be curved or linear.

The frame electrode layer 40 preferably includes both the first frame trunk electrode layer 27bf of the first electrode layer 27 and the second frame trunk electrode layer 37bf of the second electrode layer 37. For example, in fig. 1, the frame electrode layer 40 includes a second frame trunk electrode layer 37bf formed on the periphery of the semiconductor substrate 11 and a first frame trunk electrode layer 27bf formed on the boundary with the adjacent divided region. Thus, the first branch electrode layer 27f and the second branch electrode layer 37f are difficult to isolate without being electrically connected to the trunk electrode, and the output of the solar cell 1 is collected in the entire divided region 50. I.e. the output of the solar cell 1 is increased.

Further, since a part of the frame electrode layer 40 is formed at the boundary between adjacent divided regions, even if different patterns of the branch electrode layers are arranged in the respective divided regions, it is not necessary to connect the patterns of the respective branch electrode layers at the boundary. Therefore, a part of the frame electrode layer 40 is disposed at the boundary between the adjacent divided regions, and the branch electrode layer of an arbitrary pattern is connected to the frame electrode layer 40. Therefore, carriers collected by the highly arbitrary branch electrode layer are collected by the frame electrode layer 40 on the boundary, and the output of the solar cell 1 is efficiently recovered.

Here, if the width is made smaller than the trunk electrode layer and the length of the branch electrode layer having a high resistance is made longer, the resistance loss increases. In this regard, in the present embodiment, the trunk electrode layer is disposed between the adjacent divided regions 50, and the branch electrode layers are connected to the trunk electrode layer, so that the length of the branch electrode layer can be shortened as compared with the case where the trunk electrode layer is not provided, and the resistance loss can be reduced. I.e. the output of the solar cell 1 is increased.

Further, since the frame electrode layer 40 is formed also on the peripheral edge of the semiconductor substrate 11, even in the shape of the semiconductor substrate 11 having a certain degree of discretion, carriers collected by the branch electrode layers in the divided regions 50 can be collected by the frame electrode layer on the peripheral edge of the semiconductor substrate 11, and the output of the solar cell 1 can be efficiently collected. I.e. the output of the solar cell 1 is increased.

As described above, the improvement in the shape of the specific region 60 or the branch electrode layer improves the design flexibility of the shape of the solar cell and the output of the solar cell 1 efficiently in addition to the improvement in the shape design of the electronic device mounted in wearable applications (a wristwatch, an intelligent pocket watch, and a sensor).

< < < first strip-shaped stem electrode and second strip-shaped stem electrode > >)

The first band-shaped trunk electrode layer 27bb is a band-shaped extending from the first frame-use trunk electrode layer 27bf of the frame electrode layer 40 toward the specific region 60. The second strip-shaped trunk electrode layer 37bb is a strip-shaped one extending from the second frame-use trunk electrode layer 37bf of the frame electrode layer 40 toward the specific region 60. The first strip-shaped main electrode layer 27bb and the second strip-shaped main electrode layer 37bb may be linear or curved.

A plurality of first branch electrode layers 27f are connected to the first frame trunk electrode layer 27bf and the first band-shaped trunk electrode layer 27bb of the frame electrode layer 40, and a plurality of second branch electrode layers 37f are connected to the second frame trunk electrode layer 37bf and the second band-shaped trunk electrode layer 37bb of the frame electrode layer 40. This prevents disconnection of the low-resistance branch electrode layer in the unspecific region due to the high-resistance specific region 60, and prevents resistance loss due to the high-resistance branch electrode layer in the unspecific region connected to the trunk electrode without passing through the high-resistance branch electrode layer in the specific region 60. As a result, the carriers collected in the plurality of first branch electrode layers 27f and second branch electrode layers 37f are collected via the first main electrode layer 27b (frame electrode layer 40, first strip-shaped main electrode layer 27bb), that is, the output of the solar cell 1 is improved.

The back electrode type solar cell of the present embodiment is preferably used for electronic devices mainly used in low emission intensity environments, particularly wearable applications (watches, smart pocket watches, sensors), and the like. In this case, the light to be irradiated is generally weak, and the resistance loss is not as large as that of the solar cell panel. Therefore, extraction electrodes (not shown) of an anode and a cathode are formed in a part of the first trunk electrode layer 27b and the second trunk electrode layer 37b, respectively, and the collected carriers are easily extracted. As a method for forming the extraction electrode, for example, a printing method such as screen printing using Ag paste, or a plating method such as plating using Cu, or the like can be used. Alternatively, the extraction electrode may be formed by soldering or the like.

< shape of first electrode layer and second electrode layer in specific region >

Preferably, the first electrode layer 27H and the second electrode layer 37H in the specific region 60 are distributed over the entire specific region 60 on the main surface of the semiconductor substrate 11.

The first electrode layer 27H includes a plurality of first branch electrode layers 27Hf and a first trunk electrode layer 27 Hb. In addition, the second electrode layer 37H includes a plurality of second branch electrode layers 37Hf and a second trunk electrode layer 37 Hb.

< first Branch electrode layer and second Branch electrode layer >)

The first branch electrode layer 27Hf and the second branch electrode layer 37Hf are so-called finger electrodes having a shape (band shape) like a tape, similarly to the first branch electrode layer 27f and the second branch electrode layer 37f in the above-described non-specific region. The first branch electrode layer 27f and the second branch electrode layer 37f may be linear or curved.

The electrode pattern of the first branch electrode layer 27Hf and the second branch electrode layer 37Hf is not particularly limited, and is preferably a concentric circle pattern with the specific region 60, for example, similar to the first branch electrode layer 27f and the second branch electrode layer 37f in the non-specific region described above. In other words, the first branch electrode layer 27Hf and the second branch electrode layer 37Hf are preferably formed so that the center overlaps with the center of the specific region 60 and overlaps with the similar shape of the specific region 60.

Considering the local range, it is preferable that the first branch electrode layers 27Hf and the second branch electrode layers 37Hf are alternately arranged in a direction intersecting with the extending direction (for example, a direction perpendicular to a tangent line of each point) and are locally arranged in parallel.

One end of the first branch electrode layer 27Hf is connected to the first trunk electrode layer 27Hb, and the other end of the first branch electrode layer 27Hf is separated from the second trunk electrode layer 37 Hb. In addition, one end of the second branch electrode layer 37Hf is connected to the second trunk electrode layer 37Hb, and the other end of the second branch electrode layer 37Hf is separated from the first trunk electrode layer 27 Hb.

< < first trunk electrode layer and second trunk electrode layer >)

The first trunk electrode layer 27Hb and the second trunk electrode layer 37Hb are so-called bus bar electrodes, which are shaped like a tape (band shape), like the first trunk electrode layer 27b (particularly, the first band-shaped trunk electrode layer 27bb) and the second trunk electrode layer 37b (particularly, the second band-shaped trunk electrode layer 37bb) in the non-specific region described above. The first trunk electrode layer 27Hb and the second trunk electrode layer 37Hb may be linear or curved.

The first trunk electrode layer 27Hb is a band shape extending from the first band-shaped trunk electrode layer 27bb (or the first branch electrode layer 27f surrounding the specific region 60) toward the center of the specific region 60. The second trunk electrode layer 37Hb has a band shape extending from the second band-shaped trunk electrode layer 37bb (or the second branch electrode layer 37f surrounding the specific region 60) toward the center of the specific region 60.

The shapes of the first electrode layer 27 and the second electrode layer 37 in the non-specific region and the shapes of the first electrode layer 27H and the second electrode layer 37H in the specific region 60 are not limited to these. Hereinafter, two other shapes of the first electrode layer 27 and the second electrode layer 37 in the non-specific region and the first electrode layer 27H and the second electrode layer 37H in the specific region 60 are exemplified.

(first modification)

Fig. 9 is a view of the solar cell according to the first modification of the present embodiment as viewed from the back side. The solar cell 1 shown in fig. 9 is different from the present embodiment in that the shapes of the first electrode layer 27 and the second electrode layer 37 in the non-specific region and the shapes of the first electrode layer 27H and the second electrode layer 37H in the specific region 60 are different in the solar cell 1 shown in fig. 1.

< shape of first electrode layer and second electrode layer in non-specific region >

Preferably, the first electrode layer 27 and the second electrode layer 37 in the non-specific region are formed in a distributed manner in all regions except the specific region 60 on the main surface of the semiconductor substrate 11. Therefore, the effective power generation area is enlarged, and the photoelectric conversion efficiency is improved.

The first electrode layer 27 includes a plurality of first branch electrode layers 27f and three first trunk electrode layers 27 b. In addition, the second electrode layer 37 includes a plurality of second branch electrode layers 37f and three second trunk electrode layers 37 b.

< first Branch electrode layer and second Branch electrode layer >)

The first branch electrode layer 27f and the second branch electrode layer 37f are so-called finger electrodes, and have a shape (band shape) like a band. The first branch electrode layer 27f and the second branch electrode layer 37f may be linear or curved.

The electrode patterns of the first branch electrode layer 27f and the second branch electrode layer 37f are not particularly limited, and for example, a pattern concentric with the semiconductor substrate 11 is preferable in a region excluding the formation regions of the specific region 60, the first trunk electrode layer 27b, and the second trunk electrode layer 37 b. In other words, the first branch electrode layer 27f and the second branch electrode layer 37f are preferably formed so that the center overlaps the center of the semiconductor substrate 11 and overlaps the similar shape of the semiconductor substrate 11. Thus, the first branch electrode layer 27f and the second branch electrode layer 37f are distributed without a gap over the entire non-specific region in the semiconductor substrate 11, and are less likely to break at the peripheral edge of the semiconductor substrate 11.

Further, even when the semiconductor substrate 11 is warped due to the formation of the branch electrode layer, the warping is relatively uniformly generated on the entire substrate, and it is difficult to locally generate a large warping. This suppresses the occurrence of damage or the like to the solar cell.

Considering the local range, it is preferable that the first branch electrode layers 27f and the second branch electrode layers 37f are alternately arranged in a direction intersecting the extending direction (for example, a direction perpendicular to a tangent line of each point) and are locally arranged in parallel.

Between the adjacent first trunk electrode layer 27b and second trunk electrode layer 37b, one end of the first branch electrode layer 27f is connected to the first trunk electrode layer 27b, and the other end of the first branch electrode layer 27f is separated from the second trunk electrode layer 37 b. One end of the second branch electrode layer 37f is connected to the second trunk electrode layer 37b, and the other end of the second branch electrode layer 37f is separated from the first trunk electrode layer 27 b.

< < first trunk electrode layer and second trunk electrode layer >)

The first trunk electrode layer 27b and the second trunk electrode layer 37b are so-called bus bar electrodes, and have a shape (band shape) like a tape or a complicated shape in which a band is wound or connected. The first trunk electrode layer 27b and the second trunk electrode layer 37b may be linear or curved. The first trunk electrode layer 27b includes a first surrounding-shaped trunk electrode layer 27be and a first band-shaped trunk electrode layer 27 bb. In addition, the second trunk electrode layer 37b includes a second surrounding-shaped trunk electrode layer 37be and a second belt-shaped trunk electrode layer 37 bb.

< < < < first surrounding-shaped trunk electrode layer and second surrounding-shaped trunk electrode layer > >)

The first surrounding trunk electrode layer 27be and the second surrounding trunk electrode layer 37be are formed so as to surround the outer edge of the specific region 60. The first surrounding trunk electrode layer 27be surrounds a half (a part) of the outer edge of the specific region 60, and the second surrounding trunk electrode layer 37be surrounds the remaining half (the other part than the part) of the outer edge of the specific region 60. In other words, the outer edge of the one specific region 60 is surrounded by both the first surrounding trunk electrode layer 27be and the second surrounding trunk electrode layer 37 be.

The shape of the connection between the first surrounding trunk electrode layer 27be and the second surrounding trunk electrode layer 37be may be a ring shape (closed ring shape) in which the two surrounding trunk electrode layers 27be and 37be physically in contact with each other, as long as the two surrounding trunk electrode layers 27be and 37be are not electrically directly connected to each other. In addition, the two surrounding trunk electrode layers 27be and 37be may be formed into an open ring shape without physically contacting each other. The shape of the first surrounding trunk electrode layer 27be and the second surrounding trunk electrode layer 37be may be curved or linear, and the shape of the first surrounding trunk electrode layer 27be and the second surrounding trunk electrode layer 37be may be circular or polygonal.

< < < first strip-shaped trunk electrode layer and second strip-shaped trunk electrode layer > >)

The first band-shaped trunk electrode layer 27bb is a band-shaped extending radially from the first surrounding-shaped trunk electrode layer 27be with respect to the center of the semiconductor substrate 11. The second band-shaped trunk electrode layer 37bb is a band-shaped layer extending radially from the second surrounding-shaped trunk electrode layer 37be with respect to the center of the semiconductor substrate 11. The first strip-shaped trunk electrode layer 27bb and the second strip-shaped trunk electrode layer 37bb extend adjacently. The first strip-shaped main electrode layer 27bb may be linear or curved.

A plurality of first branch electrode layers 27f are connected to the first surrounding trunk electrode layer 27be and the first band-shaped trunk electrode layer 27bb, and a plurality of second branch electrode layers 37f are connected to the second surrounding trunk electrode layer 37be and the second band-shaped trunk electrode layer 37 bb. This prevents disconnection of the low-resistance branch electrode layer in the unspecific region due to the high-resistance specific region 60, and prevents resistance loss due to the high-resistance branch electrode layer which is connected to the trunk electrode layer without passing through the high-resistance branch electrode layer in the specific region 60. I.e. the output of the solar cell 1 is increased.

< shape of first electrode layer and second electrode layer in specific region >

Preferably, the first electrode layer 27H and the second electrode layer 37H in the specific region 60 are distributed over the entire specific region 60 on the main surface of the semiconductor substrate 11.

The first electrode layer 27H includes a first diverging electrode layer 27Hf, and the second electrode layer 37H includes a second diverging electrode layer 37 Hf. The first branch electrode layer 27Hf and the second branch electrode layer 37Hf are so-called finger electrodes, and have a shape (band shape) like a tape. The first branch electrode layer 27Hf and the second branch electrode layer 37Hf may be linear or curved.

Preferably, the first branch electrode layers 27Hf and the second branch electrode layers 37Hf are alternately arranged in a direction intersecting the extending direction and are arranged in parallel.

One end of the first branch electrode layer 27Hf is connected to the first surrounding trunk electrode layer 27be, and the other end of the first branch electrode layer 27Hf is separated from the second surrounding trunk electrode layer 37 be. In addition, one end of the second branch electrode layer 37Hf is connected to the second surrounding trunk electrode layer 37be, and the other end of the second branch electrode layer 37Hf is separated from the first surrounding trunk electrode layer 27 be.

(second modification)

Fig. 10 is a view of the solar cell according to the second modification of the present embodiment, as viewed from the back side. The solar cell 1 shown in fig. 10 is different from the first modification in that the solar cell 1 shown in fig. 9 differs in the shape of the first electrode layer 27 (particularly, the first trunk electrode layer 27b) and the second electrode layer 37 (particularly, the second trunk electrode layer 37b) in the unspecified region and the shape of the electrode layers 27H and 37H in the specified region 60.

< shape of first electrode layer and second electrode layer in non-specific region >

The second surrounding trunk electrode layer 37be of the second trunk electrode layer 37b in the non-specific region surrounds the entire outer edge of the specific region 60.

In this case, the first trunk electrode layer 27b may be disposed between the adjacent second trunk electrode layers 37b and may be formed only by a band-shaped trunk electrode layer similar to the first band-shaped trunk electrode layer 27bb described above. The first trunk electrode layer 27b is a band shape extending in a radial direction from the center of the semiconductor substrate 11 toward the outer edge, in other words, in a radial direction from the center of the concentric circle of the first branch electrode layer 27 f. Thus, the first trunk electrode layer 27b extends so as to intersect the first branch electrode layer 27f in a concentric circle shape. The first stem electrode layer 27b may be linear or curved.

A plurality of first branch electrode layers 27f are connected to the first trunk electrode layer 27b, and a plurality of second branch electrode layers 37f are connected to the second surrounding trunk electrode layer 37be and the second band-shaped trunk electrode layer 37 bb. This prevents disconnection of the low-resistance branch electrode layer in the unspecific region due to the high-resistance specific region 60, and prevents resistance loss due to the high-resistance branch electrode layer which is connected to the trunk electrode layer without passing through the high-resistance branch electrode layer in the specific region 60. I.e. the output of the solar cell 1 is increased.

< shape of first electrode layer and second electrode layer in specific region >

When the semiconductor substrate 11 is of the first conductivity type, the entire surface of the specific region 60 is covered with the second conductivity type semiconductor layer 35. The second electrode layer 37H is formed on the entire corresponding surface or as a comb-shaped electrode on the second conductive type semiconductor layer 35, and the first conductive type semiconductor layer 25 and the first electrode layer 27H are not formed in the specific region 60.

Thus, depending on the conductivity type of the semiconductor substrate 11, minority carriers are collected in the specific region 60, and majority carriers are collected in the non-specific region. In this way, the majority carriers generated in the specific region 60 are collected in the non-specific region, and the series resistance increases according to the distance.

For example, in the case of using an n-type semiconductor substrate, it is preferable that the specific region 60 is covered with a p-type semiconductor layer, holes generated in the specific region 60 are transported to an electrode layer in the specific region 60 via the p-type semiconductor layer in the specific region 60, and electrons generated in the specific region 60 are transported to an electrode layer in the non-specific region via an n-type semiconductor layer in the non-specific region. This increases the series resistance component in extracting carriers generated in the specific region 60, thereby improving the output of the solar cell.

(electronic apparatus)

The solar cell 1 of the present embodiment is preferably modularized for practical use. The modularity of the solar cells is carried out by a suitable method. For example, wiring, contact pins, and the like are connected to the trunk electrode layers 27b and 37b of both the anode and the cathode, or extraction electrodes (not shown) provided separately, and thereby electric extraction is possible. In addition, the back electrode type solar cell is modularized by being sealed by a sealant and a glass plate. The solar cell thus modularized can be mounted on an electronic device for wearable use (a wristwatch, an intelligent pocket watch, or a sensor).

While the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various modifications are possible. For example, although the heterojunction-type solar cell is exemplified in the above-described embodiment, the features of the present invention are not limited to the heterojunction-type solar cell, and can be applied to various solar cells such as a homojunction-type solar cell.

In addition, although the back electrode type solar cell is exemplified in the above-described embodiment, the features of the present invention are not limited to the back electrode type solar cell, and can be applied to various solar cells such as a double-sided electrode type solar cell.

In a double-sided electrode type solar cell, a passivation layer, a first conductive type semiconductor layer, and a first electrode layer are sequentially stacked on substantially the entire surface of a light receiving surface side of one main surface that receives light from one of two main surfaces of a semiconductor substrate, and a passivation layer, a second conductive type semiconductor layer, and a second electrode layer are sequentially stacked on substantially the entire surface of a back surface side that is the other main surface of the two main surfaces opposite to the light receiving surface. In this case, the series resistance component in the resistance in the specific region corresponding to the light shielding member may be higher than the series resistance component in the resistance in the non-specific region.

In the above-described embodiment, the back electrode type solar cell 1 is exemplified, and the back electrode type solar cell 1 includes the passivation layer 23, the first conductivity type semiconductor layer 25, and the first electrode layer 27, which are sequentially stacked on the first conductivity type region 7 on the back surface side of the semiconductor substrate 11, and the passivation layer 33, the second conductivity type semiconductor layer 35, and the second electrode layer 37, which are sequentially stacked on the second conductivity type region 8 other than the first conductivity type region 7 on the back surface side of the semiconductor substrate 11. However, the present invention is not limited to the solar cell 1, and may be a back electrode type solar cell in which at least a part of the first conductivity type semiconductor layer and at least a part of the second conductivity type semiconductor layer are overlapped. In this case, the first electrode layer corresponding to the first conductivity type semiconductor layer may be formed of the first branch electrode layer and the first trunk electrode layer (frame electrode layer and/or first strip-like trunk electrode layer, or first surrounding-like trunk electrode layer and/or first strip-like trunk electrode layer), and the second electrode layer corresponding to the second conductivity type semiconductor layer may be formed of the second branch electrode layer and the second trunk electrode layer (frame electrode layer and/or second strip-like trunk electrode layer, or second surrounding-like trunk electrode layer and/or second strip-like trunk electrode layer).

Description of the reference numerals

1. 1X … solar cell; 7 … a first conductivity type region; 8 … second conductivity type region; 11 … semiconductor substrate (photoelectric conversion substrate); 13. 23, 33 … passivation layer; 15 … an anti-reflective layer; 25. a 25X … first conductivity type semiconductor layer; 27. 27H, 27X … first electrode layer; 27b, 27Hb … first main electrode layers (bus bar electrodes, bus bar portions); 27bb … first strip-shaped main electrode layer; 27be … first surrounding trunk electrode layer; 27bf … first frame trunk electrode layer; 27f, 27Hf … first branch electrode layer (finger ); 28. 28H … transparent electrode layer; 29. 29H … metal electrode layer; 35. 35X … second conductive type semiconductor layer; 37. 37H, 37X … second electrode layer; 37b, 37Hb … second main electrode layers (bus bar electrodes, bus bar portions); 37bb … second strip-shaped backbone electrode layer; 37be … second surrounding trunk electrode layer; 37bf … second frame trunk electrode layer; 37f, 37Hf … second branch electrode layer (finger ); 38. 38H … transparent electrode layer; 39. 39H … metal electrode layer; 40 … frame electrode layer; 50 … dividing the region; 60 … specific area; 70 … light blocking member.