JP7300444B2 - Solar cell and electronic device equipped with the solar cell - Google Patents

Description

TECHNICAL FIELD The present invention relates to a solar cell and an electronic device equipped with the solar cell.

2. Description of the Related Art There is a demand for mounting a solar cell on electronic equipment such as wearable equipment and wristwatches used in an outdoor environment exposed to sunlight. Patent Document 1 discloses a wristwatch equipped with a solar cell as such an electronic device.
In such an electronic device, gears, electronic members, decorative members, and the like, which constitute the electronic device, may be arranged on the light incident surface side of the solar cell. In such a case, a shadow may be formed on the solar cell and the performance of the solar cell may be degraded.

In this regard, Patent Document 1 discloses that the transparent electrode is removed or the solar cell itself is removed in the portion of the solar cell that overlaps the decorative member applied to the dial (that is, the shadowed region of the solar cell). (referring to the terminology described in Patent Document 1, openings or slits provided in the transparent electrode, or through holes formed in the solar cell) to prevent electricity from flowing, and the power generation efficiency of the solar cell It is described that the decrease in

JP 2015-55578 A

Electronic devices such as wearable devices and wristwatches are used even in an indoor environment where light from a light source with relatively low illuminance such as a fluorescent lamp is illuminated. In an indoor environment, scattered light or light from multiple light sources irradiates an electronic device at various angles of incidence, and when decorative materials, etc., are placed away from the solar cell, the light incident side of the solar cell It is expected that the light will also be applied to a portion that overlaps with the arranged member.
However, like the solar cell described in Patent Document 1, in order to suppress deterioration of the performance of the solar cell in an outdoor environment, the transparent electrode or the solar cell itself is removed from the portion overlapping with the decorative member so that electricity does not flow. Then, it is expected that the light irradiated to the portion overlapping with the decorative member cannot be utilized in the indoor environment, and the performance of the solar cell in the indoor environment is degraded.

SUMMARY OF THE INVENTION An object of the present invention is to provide a solar cell that suppresses performance deterioration of the solar cell both in outdoor and indoor environments, and an electronic device equipped with the solar cell.

A solar cell according to the present invention comprises a photoelectric conversion substrate, and a first conductivity type semiconductor layer and a second conductivity type semiconductor disposed on each of both main surfaces of the photoelectric conversion substrate or on one main surface of the photoelectric conversion substrate. A solar cell comprising a layer, a first electrode layer corresponding to the first conductivity type semiconductor layer and a second electrode layer corresponding to the second conductivity type semiconductor layer, wherein the light shielding member is arranged apart from the solar cell In the solar cell used in combination with , 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 the series resistance component of the electrical resistance in the specific region is , is higher than the series resistance component of the electrical resistance in the non-specific region.

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

ADVANTAGE OF THE INVENTION According to this invention, the deterioration of the performance of a solar cell is suppressed in both outdoor and indoor environments.

It is the figure which looked at the solar cell which concerns on this embodiment, and some electronic devices from the back surface side. FIG. 2 is a cross-sectional view taken along the line II-II of part of the solar cell and the electronic device of FIG. 1; It is a partial sectional view of the solar cell concerning the modification of this embodiment. It is a figure which shows the equivalent circuit of the solar cell used by the circuit simulation. 4B is a diagram showing an example of the current density of the equivalent circuit of the solar cell shown in FIG. 4A; FIG. It is a figure which shows the IV characteristic of the circuit simulation result assuming an outdoor environment. It is a figure which shows the IV characteristic of the circuit simulation result assuming an indoor environment. FIG. 10 is a diagram showing the relationship between the output of a solar cell and the series resistance component in a specific region, as a result of a circuit simulation assuming an outdoor environment; FIG. 10 is a diagram showing the relationship between the output of a solar cell and the series resistance component in a specific region, as a result of a circuit simulation assuming an indoor environment; FIG. 6B is a diagram showing the relationship between the output of the solar cell and the series resistance component in a specific region, in which the circuit simulation result shown in FIG. 6A and the circuit simulation result shown in FIG. 6B are superimposed; It is a figure which shows an example of the IV characteristic of a solar cell. It is the figure which looked at the conventional solar cell from the back surface side. It is the figure which looked at the solar cell which concerns on the 1st modification of this embodiment from the back surface side. It is the figure which looked at the solar cell which concerns on the 2nd modification of this embodiment from the back surface side.

An example of an embodiment of the present invention will be described below with reference to the accompanying drawings. In each drawing, the same reference numerals are given to the same or corresponding parts. For the sake of convenience, hatching, member numbers, etc. may be omitted, but in such cases, other drawings shall be referred to.

FIG. 1 is a view of the solar cell and part of the electronic device according to the present embodiment viewed from the back side, and FIG. 2 is a cross-sectional view of the solar cell and part of the electronic device in FIG. 1 taken along line II-II. .
As shown in FIGS. 1 and 2, the electronic device of this embodiment includes a solar cell 1 and one or more light shielding members 70 . The light shielding member 70 is arranged on the light receiving surface side of the solar cell 1 (that is, on the side of one of the main surfaces of the semiconductor substrate (photoelectric conversion substrate) 11 to be described later), separated from the solar cell 1 .
Wearable devices and electronic devices such as wristwatches are expected to have products with a high degree of design, and products with various shapes are expected to be designed. For example, in an electronic device such as a wearable device or a wristwatch, a light shielding member 70 such as a gear or an electronic member for operating the electronic device, or a decorative member constituting the electronic device is provided on the light incident surface side of the solar cell 1. It may be arranged apart from the battery 1 .
Between the solar cell 1 and the light shielding member 70, a sealing member is arranged on the light-receiving surface side of the solar cell 1 and seals the solar cell 1 (that is, a semiconductor substrate (photoelectric conversion substrate) 11 to be described later). may have been Examples of the sealing member include EVA (Ethylene-Vinyl Acetate) film, OCA (Optically Clear Adhesive) film, and glass.
In the following, a region of solar cell 1 overlapping light shielding member 70 (in other words, a region of solar cell 1 corresponding to light shielding member 70) in plan view from the light-receiving surface side or back surface side of solar cell 1 is defined as specific region 60. , and a region other than the specific region 60 in the solar cell 1 is defined as a non-specific region.

(solar cell)
In this embodiment, as the solar cell 1, a solar cell of a back electrode type (back contact type) (also referred to as a back contact type: back junction type) is exemplified.
As solar cells using semiconductor substrates, there are double-sided electrode solar cells in which electrodes are formed on both the light-receiving side and the back side, and back electrode-type solar cells in which electrodes are formed only on the back side. In a double-sided electrode type solar cell, electrodes are formed on the light-receiving surface side, and sunlight is shielded by these electrodes. On the other hand, in the back electrode type solar cell, no electrode is formed on the light receiving surface side, so the solar cell has a higher light receiving rate than the double electrode type solar cell.

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

The solar cell 1 includes a passivation layer 13 and an antireflection layer 15 that are laminated in order on the light-receiving surface side of the light-receiving main surface, which is one of the main surfaces of the semiconductor substrate 11 . In the solar cell 1, a passivation layer 23 is laminated in order on the first conductivity 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 opposite to the light receiving surface. , a first conductivity type semiconductor layer 25 , and a first electrode layer 27 . The solar cell 1 also includes a passivation layer 33 , a second conductivity type semiconductor layer 35 , and a second electrode layer 37 that are laminated in order on the second conductivity type region 8 on the back surface side of the semiconductor substrate 11 .

<Semiconductor substrate>
As the semiconductor substrate 11, a conductivity type single crystal silicon substrate such as an n-type single crystal silicon substrate or a p-type single crystal silicon substrate is used. This realizes high photoelectric conversion efficiency.
Semiconductor substrate 11 is preferably an n-type single crystal silicon substrate. This prolongs the lifetime of carriers in the crystalline silicon substrate. In addition, in a p-type single crystal silicon substrate, LID (Light Induced Degradation), which is a recombination center, may occur due to the influence of B (boron), which is a p-type dopant, due to light irradiation. , the LID is more suppressed.

The semiconductor substrate 11 may have a pyramidal fine uneven structure called a texture structure on the back surface side, which is one of the two main surfaces. As a result, the efficiency of collecting the light that has passed through the semiconductor substrate 11 without being absorbed increases.
Further, the semiconductor substrate 11 may have a pyramid-shaped fine uneven structure called a texture structure on the light receiving surface side. As a result, the reflection of incident light on the light receiving surface is reduced, and the light confinement effect in the semiconductor substrate 11 is improved.

The thickness of the semiconductor substrate 11 is preferably 50 μm or more and 200 μm or less, more preferably 60 μm or more and 180 μm or less, and even more preferably 70 μm or more and 180 μm or less. Since the thickness of the semiconductor substrate 11 is thin as described above, the open-circuit voltage of the solar cell 1 can be improved, and the material cost can be reduced.
As the semiconductor substrate 11, a conductive polycrystalline silicon substrate such as an n-type polycrystalline silicon substrate or a p-type polycrystalline silicon substrate may be used. In this case, the back contact solar cell can be manufactured at a lower cost.

<Antireflection layer>
The antireflection 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 and suppresses recombination of carriers.
As the antireflection layer 15, a translucent film having a refractive index of about 1.5 to 2.3 is preferably used. As a material for the antireflection layer 15, SiO, SiN, SiON, or the like is preferable. Although the method for forming the antireflection layer 15 is not particularly limited, it is preferable to use a CVD (Chemical Vapor Deposition) method that enables precise film thickness control. According to the film formation by the CVD method, the film quality is controlled by controlling the material gas or the film formation conditions.

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

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

The first-conductivity-type semiconductor layer 25 is formed of a first-conductivity-type silicon-based layer, for example, a p-type silicon-based layer. The second conductivity type semiconductor layer 35 is formed of a silicon-based layer of a second conductivity type different from the first conductivity type, such as an n-type silicon-based layer. The first conductivity type semiconductor layer 25 may be an n-type silicon-based layer, and the second conductivity type semiconductor layer 35 may be a p-type silicon-based layer.
The p-type silicon-based layer and the n-type silicon-based layer are formed of an amorphous silicon layer or a microcrystalline silicon layer containing amorphous silicon and crystalline silicon. B (boron) is preferably used as the dopant impurity for the p-type silicon-based layer, and P (phosphorus) is preferably used as the dopant impurity for the n-type silicon-based layer.

Although the method of forming the first conductivity type semiconductor layer 25 and the second conductivity type semiconductor layer 35 is not particularly limited, it is preferable to use the CVD method. SiH ₄ gas, for example, is preferably used as the material gas, and hydrogen-diluted B ₂ H ₆ or PH ₃ , for example, is preferably used as the dopant addition gas. Also, in order to improve the light transmittance, a small amount of impurity such as oxygen or carbon may be added. In that case, for example, a gas such as CO ₂ or CH ₄ is introduced during CVD film formation.
Other examples of the method for forming the first conductivity type semiconductor layer 25 and the second conductivity type semiconductor layer 35 include a thermal diffusion doping method, a laser doping method, and the like.

In the back electrode type solar cell, the first conductivity type semiconductor layer 25 and the second conductivity type semiconductor layer 35 are formed in the same plane in order to receive light on the light receiving surface side and collect the generated carriers on the back surface side. . The method of forming (patterning) the first conductivity type semiconductor layer 25 and the second conductivity type semiconductor layer 35 in a predetermined shape in the same plane is not particularly limited, and a CVD method using a mask may be employed. Alternatively, an etching method using a resist, an etchant, an etching paste, or the like may be employed.

Preferably, the semiconductor layer 25 of the first conductivity type and the semiconductor layer 35 of the second conductivity type are not joined. Therefore, an insulating layer (not shown) may be provided between these layers. For example, when providing an insulating layer at the boundary between a p-type silicon thin film and an n-type silicon thin film, if an insulating layer such as silicon oxide is formed by the CVD method, the film forming process can be simplified and the process cost can be reduced. Reduction and improvement of yield can be achieved.

<Passivation layer>
The passivation layers 23 and 33 are formed of intrinsic silicon-based layers. The passivation layers 23 and 33 terminate surface defects of the semiconductor substrate 11 and suppress recombination of carriers. This improves the output of the solar cell because the life time of the carriers is improved.

<First electrode layer and second electrode layer>
The first electrode layer 27 is formed on the first conductivity type semiconductor layer 25 in the non-specific region, and the second electrode layer 37 is formed on the second conductivity type semiconductor layer 35 in the non-specific region. In addition, the first electrode layer 27H is formed on the first conductivity type semiconductor layer 25 in the specific region 60, and the second electrode layer 37H is formed on the second conductivity type semiconductor layer 35 in the specific region 60. there is The first electrode layers 27, 27H and the second electrode layers 37, 37H may be physically in contact with each other or separated from each other, as long as they are not electrically connected directly. do not have. Note that FIG. 1 shows an example in which the first electrode layers 27, 27H and the second electrode layers 37, 37H are physically separated.

The first electrode layers 27, 27H and the second electrode layers 37, 37H may be formed of transparent electrode layers 28, 38, 28H, 38H made of a transparent conductive material. As the transparent conductive material, transparent conductive metal oxides such as indium oxide, tin oxide, zinc oxide, titanium oxide and composite oxides thereof are used. Among these, an indium-based composite oxide containing indium oxide as a main component is preferable. Indium oxide is particularly preferred from the viewpoint of high electrical conductivity and transparency. Additionally, dopants are preferably added to the indium oxide to ensure reliability or higher conductivity. Dopants include Sn, W, Zn, Ti, Ce, Zr, Mo, Al, Ga, Ge, As, Si, or S, for example.
Methods for forming such transparent electrode layers 28, 38, 28H, 38H include a physical vapor deposition method such as a sputtering method, or a chemical vapor deposition method using a reaction between an organometallic compound and oxygen or water (for example, CVD method) and the like are 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. It may have electrode layers 29, 39, 29H, 39H. That is, even if the laminated first electrode layers 27, 27H and the second electrode layers 37, 37H in which the transparent electrode layers 28, 38, 28H, 38H and the metal electrode layers 29, 39, 29H, 39H are laminated, good. Further, 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. Also, the first electrode layer 27 and the second electrode layer 37 may be formed only from a metal electrode layer.
The metal electrode layers 29, 39, 29H, 39H are made of metal material. For example, Cu, Ag, Al, and alloys thereof are used as the metal material.
As a method of forming the metal electrode layers 29, 39, 29H, 39H, for example, a printing method such as screen printing using Ag paste, or a plating method such as electrolytic plating using Cu, or the like is used.

<Specific area>
As described above, the solar cell 1 of the present embodiment can be combined with the light shielding member 70 arranged away from the solar cell 1 on the light incident surface side of the solar cell 1 in an electronic device such as a wearable device or a wristwatch. Used.
Solar cell 1 has, on the main surface of semiconductor substrate 11 , one or a plurality of specific regions 60 overlapping light shielding member 70 , that is, corresponding to light shielding member 70 , and non-specific regions other than specific regions 60 . The solar cell 1 of this embodiment shown in FIG. 1 has three specific regions 60 .
The specific region 60 has, for example, a circular shape in plan view of the main surface of the semiconductor substrate 11 . Note that the shape of the specific region 60 is not limited to this, and may be a strip shape, a polygonal shape (for example, a triangular shape or a quadrangular shape), or a more complicated shape.
When there are a plurality of specific regions 60, the areas of the plurality of specific regions 60 may be the same or different. Also, the area of the specific region 60 may be less than or equal to the area of the light blocking member 70 .

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

In an outdoor environment where sunlight is irradiated, the specific region 60 is a region where shadows are mainly formed by the light shielding member 70, and the non-specific regions other than the specific region 60 are regions irradiated with sunlight. . Therefore, in an outdoor environment, the difference between the amount of irradiation light on the specific area 60 and the amount of irradiation light on the non-specific area is very large.
On the other hand, in an indoor environment, light is emitted from various directions, so the difference in the amount of illumination light between the specific region 60 and the non-specific region is smaller than in the outdoor environment.
For this reason, in an outdoor environment, while suppressing a decrease in the output of the solar cell due to the influence of the shadow in the specific region 60, in an indoor environment, the output of the solar cell in the specific region 60 is extracted as much as possible. Increases battery power output.

In the present embodiment, in order to extract as much solar cell output as possible in the specific region 60 in an indoor environment while suppressing a decrease in solar cell output due to the influence of shadows in the specific region 60 in an outdoor environment, A series resistance component of the electrical resistance is higher than a series resistance component of the electrical resistance in the non-specific regions other than the specific region 60 .
As a result, in an outdoor environment in which the amount of power generated in the non-specific area is large and the difference between the amount of irradiation light in the specific area 60 and the amount of irradiation light in the non-specific area is large, the voltage drop due to the series resistance in the specific area 60 causes the specific area 60 The influence of the dark current is suppressed, and the decrease in output in the non-specific area is suppressed. That is, the output of the solar cell is improved in an outdoor environment.
On the other hand, in an indoor environment, the amount of power generated by the solar cell 1 is 1/100 times or less that in an outdoor environment, and depending on the location, it is often 1/1000 times or less. The amount of loss is relatively small, and the output of the solar cell in the specific region 60 due to scattered light or the like in an indoor environment can be extracted to some extent. As a result, in an indoor environment, power generation in the specific region 60 can be used in addition to power generation in the non-specific region, and the output of the solar cell is improved.

Although the method for increasing the series resistance component of the electrical resistance in the specific region 60 is not particularly limited, for example, the passivation layer 23 and the first conductivity type semiconductor layer 25, or the passivation layer 33 and the second conductivity type semiconductor layer 35 The electrical resistance in the thickness direction may be increased. Alternatively, the contact resistance at 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 interface between the passivation layer 23 and the first conductivity type semiconductor layer 25, and the passivation layer 33 and the second Contact resistance at the interface with the conductivity type semiconductor layer 35, or contact at the interface between the first conductivity type semiconductor layer 25 and the first electrode layer 27H and the interface between the second conductivity type semiconductor layer 35 and the second electrode layer 37H You can increase the resistance.
As a particularly simple method, it is preferable to increase the electrical resistance of the first electrode layer 27H and the second electrode layer 37H in the specific region 60 compared to the electrical resistance of the first electrode layer 27 and the second electrode layer 37 in the non-specific region. . Hereinafter, the electrical resistance of 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, it is preferable that the width of the first electrode layer 27 is smaller than the width of the semiconductor layer 25 of the first conductivity type, and the width of the second electrode layer 37 is smaller than the width of the semiconductor layer 35 of the second conductivity type. The widths of the conductive layers and the electrode layers refer to directions perpendicular to the extending directions of the layers (but not the thickness directions of the layers), unless otherwise specified.

In order to efficiently take out the photocarriers recovered by the first conductivity type semiconductor layer 25 and the second conductivity type semiconductor layer 35, the width of the first electrode layer 27 and the second electrode layer 37 should be set to the width of the first conductivity type semiconductor layer. 25 and second-conductivity-type semiconductor layer 35 as large as possible. Therefore, the width of the first electrode layer 27 is preferably greater than 0.5 times the width of the first conductivity type semiconductor layer 25, and more preferably greater than 0.7 times. Similarly, the width of the second electrode layer 37 is preferably greater than 0.5 times the width of the second conductivity type semiconductor layer 35, and more preferably greater than 0.7 times.
An insulating layer or other layers are provided at the boundary between the semiconductor layer 25 of the first conductivity type and the semiconductor layer 35 of the second conductivity type to separate the first electrode layer 27 and the second electrode layer 37 from each other. In some cases, the widths of the first electrode layer 27 and the second electrode layer 37 may be larger than the widths of the first conductivity type semiconductor layer 25 and the second conductivity type semiconductor layer 35, respectively.

On the other hand, in order to efficiently collect photocarriers in the semiconductor substrate 11 with the first conductivity type semiconductor layer 25 and the second conductivity type semiconductor layer 35, the first electrode layer 27 (first branch electrode layer 27f and first It is preferable that the widths of the trunk electrode layer 27b) and the second electrode layer 37 (the second branch electrode layer 37f and the second trunk electrode layer 37b to be described later) are somewhat small.
The widths of the first branched electrode layer 27f, the second branched electrode layer 37f, and the first conductivity type semiconductor layer 25 and the second conductivity type semiconductor layer 35 corresponding to each of the branched electrode layers are not particularly limited as long as they are relatively small. , respectively in the range of 50 to 3000 μm.
On the other hand, from the viewpoint of electrical transport, in order to suppress electrical resistance loss, the trunk electrode layer must have a certain cross-sectional area, and the width and height (film thickness) of the trunk electrode layer must ensure the cross-sectional area. There is As a result, the widths of the first trunk electrode layer 27b, the second trunk electrode layer 37b, and the first conductivity type semiconductor layer 25 and the second conductivity type semiconductor layer 35 corresponding to each of the trunk electrode layers are 50 to 50 mm. A range of 5000 μm is preferred.

If the heights of the first electrode layer 27 and the second electrode layer 37 are increased, the cross-sectional area with respect to the current flowing in the plane direction is increased, thereby reducing the series resistance. However, when the height of the electrode layer is increased, the stress at the interface between the semiconductor layer and the electrode layer increases, which may cause electrode peeling. Furthermore, in the back electrode type solar cell, since the electrode is provided only on one side, if the height of the electrode layer increases, the stress on the front and back of the substrate becomes unbalanced, and deformation such as warping of the solar cell easily occurs. Battery may be damaged. Further, if the solar cell is deformed due to the stress at the electrode interface, problems such as misalignment or short circuit may occur during 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 even more preferably 30 μm or less.
The height of the electrode is the distance from the main surface of the substrate to the top of the electrode. If there is a region where the thickness of the substrate is partially reduced due to etching or the like for forming the semiconductor layer, a reference plane parallel to the main surface of the substrate is determined, and the distance from the reference plane to the apex of the electrode is determined. can be defined as the height of the electrode.

<Electrode layer in specific region>
As described above, the electrical resistance of the first electrode layer 27H and the second electrode layer 37H in the specific region 60 is preferably higher than the electrical resistance of the first electrode layer 27 and the second electrode layer 37 in the non-specific region.
As a method of increasing the electrical resistance of the first electrode layer 27H and the second electrode layer 37H in the specific region 60 compared to the electrical resistance of the first electrode layer 27 and the second electrode layer 37 in the non-specific region, for example, the specific region It is conceivable that the electrical resistance of the metal electrode layers 29H, 39H of the electrode layers 27H, 37H in 60 is made higher than the electrical resistance of the metal electrode layers 29, 39 of the electrode layers 27, 37 in the non-specific region.
For example, as shown in FIG. 2, the width of the metal electrode layers 29H, 39H of the electrode layers 27H, 37H in the specific region 60 is made narrower than the width of the metal electrode layers 29, 39 of the electrode layers 27, 37 in the non-specific region. You may In other words, the width of the first electrode layer 27H and the second electrode layer 37H in the specific region 60 can be narrower than the width of the first electrode layer 27 and the second electrode layer 37 in the non-specific region.

The method of making the electrical resistance of the metal electrode layers 29H, 39H of the electrode layers 27H, 37H in the specific region 60 higher than the electrical resistance of the metal electrode layers 29, 39 of the electrode layers 27, 37 in the non-specific region is limited to this. First, the cross-sectional area of the metal electrode layers 29H, 39H in the specific region 60 may be smaller than the cross-sectional area of the metal electrode layers 29, 39 in the non-specific region. For example, the height of the metal electrode layers 29H, 39H in the specific region 60 may be lower than the height of the metal electrode layers 29, 39 in the non-specific region.
Alternatively, the material of the metal electrode layers 29H, 39H in the specific region 60 may be a material with higher resistance than the material of the metal electrode layers 29, 39 in the non-specific region. For example, materials for the metal electrode layer with high resistance include aluminum paste and copper paste, and materials for the metal electrode layer with low resistance include silver paste.

Further, as a method of increasing the electrical resistance of the first electrode layer 27H and the second electrode layer 37H in the specific region 60 compared to the electrical 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.
Furthermore, the electrical resistance of the transparent electrode layers 28H, 38H in the specific region 60 may be made larger than the electrical resistance of the transparent electrode layers 28, 38 in the non-specific region. For example, the film thickness of the transparent electrode layers 28H, 38H in the specific region 60 may be thinner than the film thickness of the transparent electrode layers 28, 38 in the non-specific region. The width may be narrower than the width of the transparent electrode layers 28, 38 in the non-specific regions. That is, the cross-sectional area of the transparent electrode layers 28H, 38H in the specific region 60 may be smaller than the cross-sectional area of the transparent electrode layers 28, 38 in the non-specific region.

The width of the first conductivity type semiconductor layer 25 and the width of the second conductivity type semiconductor layer 35 in the specific region 60 are the same as the width of the first conductivity type semiconductor layer 25 and the width of the second conductivity type semiconductor layer 35 in the non-specific region. Similar to the width, it is not particularly limited as long as it is small to some extent, but it is preferable that each range is from 50 to 3000 μm.

As described above, according to the back electrode type solar cell 1 of the present embodiment, the series resistance component of the electrical resistance in the specific region 60 overlapping the light shielding member 70 in the electronic device is It has a higher resistance than the series resistance component of the electrical resistance of the region.
Therefore, in an outdoor environment in which the amount of power generated in the non-specific area is large and the difference between the amount of light emitted to the specific area 60 and the amount of light emitted to the non-specific area is large, the voltage drop due to the series resistance in the specific area 60 causes the voltage drop in the specific area 60. The influence of dark current is suppressed, and the decrease in output in the non-specific area is suppressed. That is, the output of the solar cell is improved in an outdoor environment.
On the other hand, in an indoor environment, the amount of power generated by the solar cell 1 is often less than 1/100 times that in an outdoor environment, and is often less than 1/1000 times depending on the location. The amount of loss is relatively small, and the output of the solar cell in the specific region 60 due to scattered light or the like in an indoor environment can be extracted to some extent. As a result, in an indoor environment, power generation in the specific region 60 can be used in addition to power generation in the non-specific region, and the output of the solar cell is improved.
As a result, deterioration in the performance of the solar cell due to the specific region 60 overlapping the light shielding member 70 in the electronic device is suppressed in both outdoor and indoor environments.

上記式において、左辺のＪ（Ｖ）は、図４Ａの２ダイオードモデルにおけるＰＶ（ｐｈｏｔｏ）またはＰＶ（ｄａｒｋ）の電流密度であって、印加電圧Ｖに対する電流密度を表す。図４Ｂに、図４Ａの２ダイオードモデルにおけるＰＶ（ｐｈｏｔｏ）またはＰＶ（ｄａｒｋ）の電流密度の一例を示す。図４Ｂに示すように、電流密度Ｊ（Ｖ）は印加電圧Ｖに応じて変化し、例えば印加電圧Ｖ１における電流密度はＪ（Ｖ１）となる。
右辺の第１項のＪｐｈは、図４Ａの２ダイオードモデルにおけるＩ＿ｐまたはＩ＿ｄ、すなわち光電流に対応する光電流密度を表す。右辺の第２項のＪ_０１は、図４Ａの２ダイオードモデルにおける一方のダイオードＤ１＿ｐまたはＤ１＿ｄの逆方向飽和電流密度を表す。右辺の第３項のＪ_０２は、図４Ａの２ダイオードモデルにおける他方のダイオードＤ２＿ｐまたはＤ２＿ｄの逆方向飽和電流密度を表す。右辺の第４項は、図４Ａの２ダイオードモデルにおける直列抵抗Ｒｓ（すなわち、Ｒｓ＿ｐまたはＲｓ＿ｄ）および並列抵抗Ｒｓｈ（すなわち、Ｒｓｈ＿ｐまたはＲｓｈ＿ｄ）による損失を表す。ここで、直列抵抗Ｒｓおよび並列抵抗Ｒｓｈは太陽電池当たりの値を用いているため、単位面積当たりに換算するため太陽電池の面積Ｓを掛けてある（Ｓ＝２３９（ｃｍ^２））。なお、ｑは電気素量、ｋ_Ｂはボルツマン定数、Ｔは温度を表す。
上記式における各パラメータは以下の通りである。
ＰＶ（ｐｈｏｔｏ）：
Ｊ_０１（Ｄ１＿ｐ）＝７．９Ｅ－１５（Ａ／ｃｍ^２）
Ｊ_０２（Ｄ２＿ｐ）＝１．２３Ｅ－８（Ａ／ｃｍ^２）
Ｒｓ＿ｐ＝０．００２（Ω）
Ｒｓｈ＿ｐ＝１Ｅ＋６（Ω）
ＰＶ（ｄａｒｋ）：
Ｊ_０１（Ｄ１＿ｄ）＝７．９Ｅ－１５（Ａ／ｃｍ^２）
Ｊ_０２（Ｄ２＿ｄ）＝１．２３Ｅ－８（Ａ／ｃｍ^２）
Ｒｓｈ＿ｄ＝１Ｅ＋６（Ω）<Circuit simulation verification>
Here, the output improvement of the solar cell by increasing the series resistance component of the electrical resistance in the specific region 60 will be verified using a circuit simulation (circuit calculation) using an equivalent circuit.
FIG. 4A is a diagram showing an equivalent circuit of a solar cell used in circuit simulation (circuit calculation). As shown in FIG. 4A, a two-diode model, which is commonly used in solar cell calculations, was used as a calculation model for an equivalent circuit of a solar cell.
This equivalent circuit introduces two two-diode models, one two-diode model PV (photo) represents the non-specific region of the solar cell 1, and the other two-diode model PV (dark) represents the specific region 60. show.
Each parameter of these two-diode models PV(photo) and PV(dark) was determined by fitting the output characteristics of an actually manufactured heterojunction solar cell using the following equations.

In the above equation, J(V) on the left side is the current density of PV(photo) or PV(dark) in the two-diode model of FIG. FIG. 4B shows an example of PV(photo) or PV(dark) current density in the two-diode model of FIG. 4A. As shown in FIG. 4B, the current density J(V) changes according to the applied voltage V. For example, the current density at the applied voltage V1 is J(V1).
Jph in the first term on the right side represents I_p or I_d in the two-diode model of FIG. 4A, that is, the photocurrent density corresponding to the photocurrent. J ₀₁ in the second term on the right side represents the reverse saturation current density of one diode D1_p or D1_d in the two-diode model of FIG. 4A. _J02 in the third term on the right side represents the reverse saturation current density of the other diode D2_p or D2_d in the two-diode model of FIG. 4A. The fourth term on the right side represents the loss due to series resistance Rs (ie, Rs_p or Rs_d) and parallel resistance Rsh (ie, Rsh_p or Rsh_d) in the two-diode model of FIG. 4A. Here, since values per solar cell are used for the series resistance Rs and the parallel resistance Rsh, they are multiplied by the solar cell area S (S=239 (cm ² )) in order to convert to per unit area. Here, q is the elementary charge, _kB is the Boltzmann constant, and T is the temperature.
Each parameter in the above formula is as follows.
PV (photo):
J ₀₁ (D1_p) = 7.9E-15 (A/cm ² )
J ₀₂ (D2_p) = 1.23E-8 (A/cm ² )
Rs_p = 0.002 (Ω)
Rsh_p = 1E + 6 (Ω)
PV (dark):
J ₀₁ (D1_d)=7.9E−15 (A/cm ² )
J ₀₂ (D2_d) = 1.23E-8 (A/cm ² )
Rsh_d = 1E + 6 (Ω)

In the circuit simulation under an outdoor environment, it is assumed that a photocurrent of I_p=0.038 (A/cm ² ) is generated in the PV (photo) of the non-specific area (light irradiation area), and the PV of the specific area (shadow area) It was assumed that a photocurrent of I_d=0.00038 (A/cm ² ) was generated in (dark) (1/100 times I_p of PV (photo) in the non-specific region (light irradiation region)).
On the other hand, in a circuit simulation under an indoor environment, the specific region 60 is also irradiated with a certain amount of light due to scattered light. It was assumed that a photocurrent of I_p = I_d = 0.00038 (A/cm ² ) was generated in (dark) (1/100 times I_p of PV (photo) in a non-specific area (light irradiation area) under an outdoor environment ).
Also, in the circuit simulation, the series resistance component Rs_d of the specific region 60 was changed in the range of 0.002Ω to 2000Ω. Also, in the circuit simulation, three patterns in which the ratio S_p:S_d of the area S_p of the non-specific region (light irradiation region) and the area S_d of the specific region (shadow region) 60 is 1:3, 1:1, and 3:1 Calculated. Further, calculations were made for two patterns of solar cell areas of 8 cm ² and 239 cm ² . Rs_p, Rsh_p, and Rsh_d are fixed values regardless of the cell area.

FIG. 5A shows IV characteristics of circuit simulation results assuming an outdoor environment (I_p=0.038 (A/cm ² ), I_d=0.00038 (A/cm ² )), and FIG. 5B shows an indoor environment. FIG. 10 shows IV characteristics of circuit simulation results assuming the lower (I_p=I_d=0.00038 (A/cm ² )). 5A and 5B, the area of the solar cell is 239 cm ² , and the ratio S_p:S_d between the area S_p of the non-specific region (light irradiation region) and the area S_d of the specific region (shadow region) 60 is 1:3. be.
According to FIG. 5A, as the series resistance component Rs_d of the specific region 60 increases, the open-circuit voltage Voc increases, and the output of the solar cell also increases. As described above, when 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 is improved.
On the other hand, according to FIG. 5B, the output of the solar cell improves as the series resistance component Rs_d of the specific region 60 decreases. This is because when the series resistance component Rs_d is large, the electrical energy generated in the specific region 60 is consumed by the series resistance component Rs_d and is difficult to extract, whereas when the series resistance component Rs_d is small, the specific region 60 This is thought to be due to the extraction of the electrical energy generated in
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 dark current can be suppressed to some extent in an outdoor environment (FIG. 5A), and , a sufficient output can be obtained even in an indoor environment (Fig. 5B). Thus, it can be seen that high output can be obtained in both outdoor and indoor environments by selecting an appropriate Rs_d.

Next, the relationship between the output of the solar cell and the series resistance component in the specific region 60 under such outdoor and indoor environments will be generalized.
FIG. 6A shows the series of the output of the solar cell and the specific region 60 of the circuit simulation result assuming an outdoor environment (I_p=0.038 (A/cm ² ), I_d=0.00038 (A/cm ² )). FIG. 6B shows the output of the solar cell and the series resistance component of the specific region 60 in the circuit simulation results assuming an indoor environment (I_p=I_d=0.00038 (A/cm ² )). indicates a relationship with FIG. 6C shows the relationship between the output of the solar cell and the series resistance component of the specific region 60 by superimposing the circuit simulation result shown in FIG. 6A and the circuit simulation result shown in FIG. 6B.
6A to 6C, the horizontal axis is 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 vertical axis is Rs_d×S_d=0Ω·cm in each solar cell. ² and the difference ΔPower between the output of the solar cell per unit area at each value 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 area (light irradiation area), which is S_p under the outdoor environment (FIG. 6A), and S_p and S_d under the indoor environment. sum (Fig. 6B).
6A to 6C, for two patterns with solar cell areas of 8 cm ² and 239 cm ² , and the ratio S_p between the area S_p of the non-specific region (light irradiation region) and the area S_d of the specific region (shadow region) 60 : The results of circuit simulation are shown for three patterns of 1:3, 1:1, and 3:1 of S_d.

According to FIG. 6A, in an outdoor environment, in a small region where Rs_d×S_d is about 1 Ω cm ² or less, the series resistance component under the specific region 60 is small, so it is possible to suppress the decrease in solar cell output due to dark current. However, when the resistance exceeds about 1 Ω·cm ² , the output gradually increases, and when it exceeds about 1E+4 Ω·cm ² , the output saturates. In particular, when the ratio of the area (S_p) of the non-specific region (light irradiation region) and the area (S_d) of the specific region (shadow region) 60 is 1:3, the output loss due to the dark current in the specific region 60 is ratios of 1:1 and 3:1, the larger Rs_d×S_d, which is proportional to the series resistance component of the electrical resistance in the specific region 60, the more the loss due to dark current is suppressed, and the output of the solar cell increases. improves.
On the other hand, according to FIG. 6B, in an indoor environment, when Rs_d×S_d is about 10 Ω cm ² or less, the output of the solar cell in the specific region 60 can be sufficiently extracted, so the series resistance component in the specific region 60 Although the decrease in output is small, when Rs_d×S_d exceeds about 10 Ω·cm ² , 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. FIG.

According to FIG. 6C, there is a series resistance in the specific region 60 (broken line portion) where a sufficient increase in output can be expected in an outdoor environment and a decrease in output is suppressed in an indoor environment. Although the optimum series resistance varies slightly depending on the usage environment of the solar cell, 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 10 Ω·cm ² or more and less than 10000 Ω·cm ² . It is preferably 20 Ω·cm ² or more and less than 1000 Ω·cm ² , and particularly preferably 50 Ω·cm ² or more and less than 500 Ω·cm ² .
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 greater than 0 Ω·cm ² and less than 10 Ω·cm ² , particularly preferably as small as possible. .
The area S_d of the specific region 60 is 0.25 times the sum S_p+S_d of the area of the main surface of the semiconductor substrate 11, that is, the area S_p of the non-specific region and the area S_d of the specific region 60 (S_p:S_d=3:1 (equivalent to S_p:S_d=1:3), preferably 0.95 times or less, and more preferably 0.25 times or more and 0.75 times or less (equivalent to S_p:S_d=1:3).

The method for measuring the series resistance component of the electrical resistance in such a specific region 60 is not particularly limited. The resistance may be calculated, and the series resistance component can be easily estimated by using LIS-R2 from BT Imaging Pty Ltd. Further, 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 is performed using light with an illuminance of AM 1.5 or higher. The series resistance component may be roughly estimated from the slope of the IV curve with two stages as shown. In FIG. 7, among such two-stage IV curves, the slope of the IV curve in the low current range in the first stage corresponds to the series resistance component Rs_p in the non-specific region, and the slope of the IV curve in the high current range in the second stage corresponds to corresponds to the series resistance component Rs_d of the specific region 60, the series resistance component may be estimated from these gradients.

Here, FIG. 8 is a view of a conventional back electrode type solar cell viewed from the back side. A solar cell 1X shown in FIG. 8 has a first conductivity type semiconductor layer 25X and a second conductivity type semiconductor layer 35X on the back surface side of a semiconductor substrate 11X. The first-conductivity-type semiconductor layer 25X has a so-called comb shape, and includes a plurality of finger portions corresponding to comb teeth and busbar portions corresponding to support portions of the comb teeth. The busbar portion extends in the X direction along one side of the semiconductor substrate 11X, and the finger portions extend in the Y direction intersecting the X direction from the busbar portion. Similarly, the second conductivity type semiconductor layer 35X has a so-called comb shape, and has a plurality of finger portions corresponding to comb teeth and busbar portions corresponding to support portions of the comb teeth. The busbar portion extends in the X direction along one side portion of the semiconductor substrate 11X that faces the other side portion, and the finger portion extends in the Y direction from the busbar portion. The finger portions of the first conductivity type semiconductor layer 25X and the finger portions of the second conductivity type semiconductor layer 35X are alternately arranged in the X direction. As a result, the formation region of the first conductivity type semiconductor layer 25X and the formation region of the second conductivity type semiconductor layer 35X mesh with each other. With such a structure, photocarriers induced in the semiconductor substrate 11X by incident light from the light-receiving surface side can be efficiently recovered in each semiconductor layer.

A first electrode layer 27X and a second electrode layer 37X are provided on the first conductivity type semiconductor layer 25X and the second conductivity type semiconductor layer 35X for extracting recovered photocarriers to the outside. The first electrode layer 27X has a so-called comb shape, and includes a plurality of finger portions 27fX corresponding to comb teeth and busbar portions 27bX corresponding to support portions of the comb teeth. The busbar portion 27bX extends in the X direction along one side of the semiconductor substrate 11X, and the finger portions 27fX extend in the Y direction intersecting the X direction from the busbar portion 27bX. Similarly, the second electrode layer 37X has a so-called comb shape, and includes a plurality of finger portions 37fX corresponding to comb teeth and busbar portions 37bX corresponding to support portions of the comb teeth. The busbar portion 37bX extends in the X direction along one side portion of the semiconductor substrate 11X opposite to the other side portion, and the finger portion 37fX extends in the Y direction from the busbar portion 37bX. The finger portions 27fX and the finger portions 37fX are alternately arranged in the X direction.

In such a conventional back electrode type solar cell 1X, if the series resistance component of the electrical resistance of the specific region 60X overlapping with the light shielding member of the electronic device is made high (hatched portion), the finger portions 27fX of the first electrode layer 27X or a portion of the tip side of the finger portion 37fX of the second electrode layer 37X is connected to the busbar portion 27bX or the busbar portion 37bX via the high resistance specific region 60X. Therefore, the extraction efficiency of carriers recovered by the first electrode layer 27X and the second electrode layer 37X is lowered, and the output of the solar cell 1X is lowered.

Regarding this point, in the present embodiment, the shapes of the first electrode layers 27, 27H and the second electrode layers 37, 37H in the non-specific region and the specific region 60 are as follows. The first conductivity type semiconductor layer 25 has a shape corresponding to the shape of the first electrode layers 27 and 27H, and the second conductivity type semiconductor layer 35 has a shape corresponding to the shape of the second electrode layers 37 and 27H. .

<Division area>
As shown in FIG. 1 , solar cell 1 has three divided regions 50 divided into three regions so as to surround three specific regions 60 on the main surface of semiconductor substrate 11 .
By providing a single specific region 60 in the partitioned region 50 , the low-resistance branch electrode layer in the non-specific region can be connected to the trunk electrode layer without the high-resistance branch electrode layer in the specific region 60 .

<Shape of first electrode layer and second electrode layer in non-specific region>
It is preferable that the first electrode layer 27 and the second electrode layer 37 in the non-specific region are distributed over the entire non-specific region on the main surface of the semiconductor substrate 11 . This increases the effective power generation area and improves the photoelectric conversion efficiency.
In each segmented region 50, the first electrode layer 27 includes a plurality of first branch electrode layers 27f and a first trunk electrode layer 27b. Also, in each segmented region 50, the second electrode layer 37 includes a plurality of second branch electrode layers 37f and a second trunk electrode layer 37b.

<<First Branched Electrode Layer and Second Branched Electrode Layer>>
The first branched electrode layer 27f and the second branched electrode layer 37f are so-called finger electrodes and have a strip-like shape (strip shape). The shape of the first branched electrode layer 27f and the second branched electrode layer 37f may be linear or curved.
Although the electrode patterns of the first branched electrode layer 27f and the second branched electrode layer 37f are not particularly limited, for example, in each partitioned region 50, the specific region 60, the first trunk electrode layer 27b and the second trunk electrode layer 37b are formed. It is preferable that the pattern is concentric with the specific region 60 in the region excluding the region. In other words, the first branched electrode layer 27f and the second branched electrode layer 37f are preferably formed so that their centers overlap the center of the specific region 60 and overlap similar shapes of the specific region 60 . As a result, disconnection of the low-resistance branch electrode layers in the non-specific region caused by the high-resistance specific region 60 is prevented, and the branch electrode layers in the non-specific region do not pass through the high-resistance branch electrode layers in the specific region 60. is connected to the trunk electrode, preventing resistance loss due to high-resistance branch electrodes. As a result, the output of the solar cell 1 can be efficiently extracted in an outdoor environment, and the output of the solar cell 1 is improved.

Considering the local range, the first branched electrode layers 27f and the second branched electrode layers 37f are arranged alternately in a direction intersecting the extending direction (for example, a direction perpendicular to the tangent line at each point). Local parallel alignment is preferred.

A portion of either the first branched electrode layer 27 f or the second branched electrode layer 37 f 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 37f. In the solar cell 1 of this embodiment, part of the second branched electrode layer 37f surrounds the outer edge of the specific region 60 .
The shape of the branch electrodes surrounding the outer edge of the specific region 60 may be annular (closed annular) or open annular. The shape of the ring-shaped or open ring-shaped branch electrode may be curved or linear.

In each segmented region 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 37b. . 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 27b.

<<First Stem Electrode Layer and Second Stem Electrode Layer>>
The first trunk electrode layer 27b and the second trunk electrode layer 37b are so-called busbar electrodes and have a strip-like shape (strip shape). The shape of the first trunk electrode layer 27b and the second trunk electrode layer 37b may be linear or curved.
In each segmented region 50, the first stem electrode layer 27b includes a first frame stem electrode layer 27bf and a first strip-shaped stem electrode layer 27bb. Also, in each sectioned region 50, the second stem electrode layer 37b includes a second frame stem electrode layer 37bf and a second strip-shaped stem electrode layer 37bb.

<<<First Frame Stem Electrode Layer, Second Frame Stem Electrode Layer, and Frame Electrode Layer>>>
The first frame main electrode layer 27bf and the second frame main electrode layer 37bf constitute a frame electrode layer 40 . The frame electrode layer 40 is formed so as to surround each partitioned region 50 , in other words, overlap the outer edge of the partitioned region 50 . The shape of the frame electrode layer 40 may be an open ring in which the first frame stem electrode layer 27bf and the second frame stem electrode layer 37bf are separated from each other, or the shape of the first frame stem electrode layer 27bf or the second frame stem electrode layer 37bf may be an open ring. Either of the two-frame trunk electrode layers 37bf may form a ring (closed ring). The shape of the annular or open annular frame electrode layer 40 may be curved or linear.

The frame electrode layer 40 preferably has both the first frame main electrode layer 27bf of the first electrode layer 27 and the second frame main electrode layer 37bf of the second electrode layer 37 . For example, in FIG. 1, the frame electrode layer 40 consists of the second frame main electrode layer 37bf formed on the peripheral edge of the semiconductor substrate 11 and the first frame main electrode layer 27bf formed on the boundary between the adjacent partitioned regions. and As a result, the first branched electrode layer 27f and the second branched electrode layer 37f are not electrically connected to the trunk electrode and are less likely to be isolated, and the output of the solar cell 1 in the entire divided region 50 is recovered. That is, the output of the solar cell 1 is improved.

In addition, since a part of the frame electrode layer 40 is formed at the boundary between adjacent segmented regions, even if different branch electrode layer patterns are arranged in the respective segmented regions, the pattern of each branch electrode layer at the boundary can be reduced. do not need to be connected. Therefore, by arranging a part of the frame electrode layer 40 on the boundary between the adjacent segmented regions, the branch electrode layer of any pattern is connected to the frame electrode layer 40 . Therefore, the carriers collected by the highly arbitrary branch electrode layers are collected by the frame electrode layer 40 on the boundary, and the output of the solar cell 1 is efficiently collected.

Here, if the length of the branch electrode layer, which is narrower than the trunk electrode layer and has a higher electric resistance, is increased, the resistance loss increases. In this regard, in the present embodiment, by arranging the trunk electrode layer between the adjacent segmented regions 50 and connecting the branch electrode layer to the trunk electrode layer, the number of branch electrode layers is reduced compared to when there is no trunk electrode layer. The length can be shortened and electrical resistance loss is reduced. That is, the output of the solar cell 1 is improved.

In addition, since the frame electrode layer 40 is also formed at the periphery of the semiconductor substrate 11, even if the shape of the semiconductor substrate 11 is highly arbitrary to some extent, the carriers collected by the branch electrode layers in the partitioned region 50 can be transferred to the semiconductor substrate. 11 can be recovered by the frame electrode layer on the periphery, and the output of the solar cell 1 can be efficiently recovered. That is, the output of the solar cell 1 is improved.

As described above, the arbitrariness of the shape of the specific region 60 or the branch electrode layer is increased, and the arbitrariness of the shape design of the solar cell is increased when it is mounted on an electronic device for wearable applications (wristwatch or smart watch, sensor), and The output of the solar cell 1 is efficiently improved.

<<<first strip-shaped stem electrode and second strip-shaped stem electrode>>>
The first strip-shaped stem electrode layer 27bb has a strip shape extending from the first frame stem electrode layer 27bf of the frame electrode layer 40 toward the specific region 60 . The second strip-shaped stem electrode layer 37bb has a strip shape extending from the second frame stem electrode layer 37bf of the frame electrode layer 40 toward the specific region 60 . The first strip-shaped stem electrode layer 27bb and the second strip-shaped stem electrode layer 37bb may be straight or curved.

A plurality of first branch electrode layers 27f are connected to the first frame stem electrode layer 27bf and the first strip-shaped stem electrode layers 27bb of the frame electrode layer 40, and the second frame stem electrode layers 37bf and A plurality of second branch electrode layers 37f are connected to the second strip-shaped trunk electrode layer 37bb. As a result, disconnection of the low-resistance branch electrode layers in the non-specific region caused by the high-resistance specific region 60 is prevented, and the branch electrode layers in the non-specific region do not pass through the high-resistance branch electrode layers in the specific region 60. is connected to the trunk electrode, preventing resistance loss due to high-resistance branch electrodes. As a result, carriers recovered from the plurality of first branch electrode layers 27f and second branch electrode layers 37f are recovered via the first trunk electrode layer 27b (frame electrode layer 40, first strip-shaped trunk 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 in electronic devices that are mainly used in low-illumination environments, such as wearable applications (wristwatches, smartwatches, sensors). In this case, the light emitted is usually weak, and the electrical resistance loss is not as large as that of the solar cell panel. Therefore, by forming anode and cathode extraction electrodes (not shown) on parts of the first trunk electrode layer 27b and the second trunk electrode layer 37b, respectively, the recovered carriers can be 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 electrolytic plating using Cu, or the like is used. Alternatively, the extraction electrode may be formed by solder or the like.

<Shape of first electrode layer and second electrode layer in specific region>
The first electrode layer 27</b>H and the second electrode layer 37</b>H in the specific region 60 are preferably formed 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 first trunk electrode layers 27Hb. Also, the second electrode layer 37H includes a plurality of second branch electrode layers 37Hf and second trunk electrode layers 37Hb.

<<First Branched Electrode Layer and Second Branched Electrode Layer>>
The first branched electrode layer 27Hf and the second branched electrode layer 37Hf are so-called finger electrodes, similar to the first branched electrode layer 27f and the second branched electrode layer 37f in the non-specific region described above, and have a band-like shape ( band). The shape of the first branched electrode layer 27f and the second branched electrode layer 37f may be linear or curved.
The electrode patterns of the first branched electrode layer 27Hf and the second branched electrode layer 37Hf are not particularly limited. It is preferable that the pattern is concentric with the . In other words, the first branched electrode layer 27Hf and the second branched electrode layer 37Hf are preferably formed so that their centers overlap the center of the specific region 60 and overlap similar shapes of the specific region 60 .
Considering the local range, the first branched electrode layers 27Hf and the second branched electrode layers 37Hf are arranged alternately in a direction intersecting the extending direction (for example, a direction perpendicular to the tangent line at each point). Local parallel alignment is preferred.
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 37Hb. 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 27Hb.

<<First Stem Electrode Layer and Second Stem Electrode Layer>>
The first trunk electrode layer 27Hb and the second trunk electrode layer 37Hb are the first trunk electrode layer 27b (in particular, the first strip-shaped trunk electrode layer 27bb) and the second trunk electrode layer 37b (in particular, the second trunk electrode layer 27bb) in the non-specific region described above. Like the strip-shaped stem electrode layer 37bb), it is a so-called busbar electrode and has a strip-like shape (strip shape). The shape of the first trunk electrode layer 27Hb and the second trunk electrode layer 37Hb may be linear or curved.
The first trunk electrode layer 27Hb has a strip shape extending toward the center of the specific region 60 from the first strip-like trunk electrode layer 27bb (or the first branch electrode layer 27f surrounding the specific region 60). The second trunk electrode layer 37Hb has a strip shape extending from the second strip-shaped trunk electrode layer 37bb (or the second branch electrode layer 37f surrounding the specified region 60) toward the center of the specified region 60. As shown in FIG.

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. 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 below.

(First modification)
FIG. 9 is a diagram of a solar cell according to a first modified example of the present embodiment, viewed from the back side. Solar cell 1 shown in FIG. 9 is different from solar cell 1 shown in FIG. This embodiment differs from the present embodiment in that the shape of the electrode layer 37H is different.

<Shape of first electrode layer and second electrode layer in non-specific region>
It is preferable that the first electrode layer 27 and the second electrode layer 37 in the non-specific region be distributed over the entire main surface of the semiconductor substrate 11 except for the specific region 60 . This increases the effective power generation area and improves the photoelectric conversion efficiency.
The first electrode layer 27 includes a plurality of first branch electrode layers 27f and three first trunk electrode layers 27b. Also, the second electrode layer 37 includes a plurality of second branch electrode layers 37f and three second trunk electrode layers 37b.

<<First Branched Electrode Layer and Second Branched Electrode Layer>>
The first branched electrode layer 27f and the second branched electrode layer 37f are so-called finger electrodes and have a strip-like shape (strip shape). The shape of the first branched electrode layer 27f and the second branched 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. The pattern is preferably concentric with the semiconductor substrate 11 . In other words, the first branched electrode layer 27f and the second branched electrode layer 37f are preferably formed so that their centers overlap the center of the semiconductor substrate 11 and overlap similar shapes of the semiconductor substrate 11 . As a result, the first branched electrode layer 27f and the second branched electrode layer 37f are distributed without gaps over the entire non-specific region in the semiconductor substrate 11, and are less likely to be separated at the periphery of the semiconductor substrate 11. FIG.
Furthermore, since the branched electrode layers have such a shape, even if the semiconductor substrate 11 is warped due to the formation of the branched electrode layers, the warpage is generated relatively uniformly over the entire substrate and locally Large warpage is less likely to occur. As a result, the occurrence of breakage or the like of the solar cell is suppressed.

Considering the local range, the first branched electrode layers 27f and the second branched electrode layers 37f are arranged alternately in a direction intersecting the extending direction (for example, a direction perpendicular to the tangent line at each point). Local parallel alignment is preferred.

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 connected to the first branch electrode layer 27f. The end is separated from the second trunk electrode layer 37b. 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 27b.

<<First Stem Electrode Layer and Second Stem Electrode Layer>>
The first trunk electrode layer 27b and the second trunk electrode layer 37b are so-called busbar electrodes, and have a strip-like shape (strip shape) or a complex shape in which strips are wound or connected. The shape of the first trunk electrode layer 27b and the second trunk electrode layer 37b may be linear or curved. The first stem electrode layer 27b includes a first surrounding stem electrode layer 27be and a first strip-shaped stem electrode layer 27bb. The second stem electrode layer 37b includes a second surrounding stem electrode layer 37be and a second strip-shaped stem electrode layer 37bb.

<<<First Surrounding Stem Electrode Layer and Second Surrounding Stem Electrode Layer>>>
The first surrounding stem electrode layer 27be and the second surrounding stem electrode layer 37be are formed to surround the outer edge of the specific region 60. As shown in FIG. The first surrounding stem electrode layer 27be surrounds half (part) of the outer edge of the specific region 60, and the second surrounding stem electrode layer 37be surrounds the other half (part other than the part) of the outer edge of the specific region 60. ). In other words, the outer edge of one specific region 60 is surrounded by both the first surrounding stem electrode layer 27be and the second surrounding stem electrode layer 37be.
If the first enclosing stem electrode layer 27be and the second enclosing stem electrode layer 37be are connected to each other, the enclosing stem electrode layers 27be and 37be can may be in physical contact (closed ring). Also, the two encircling stem electrode layers 27be and 37be may be physically out of contact with each other to form an open ring. The shape of the first surrounding stem electrode layer 27be and the second surrounding stem electrode layer 37be may be curved or straight. The shape of the stem electrode layer 37be may be circular or polygonal.

<<<first strip-shaped stem electrode layer and second strip-shaped stem electrode layer>>>
The first strip-shaped stem electrode layer 27bb has a strip shape radially extending from the first surrounding stem electrode layer 27be toward the center of the semiconductor substrate 11 . The second strip-shaped stem electrode layer 37bb has a strip-like shape radially extending from the second surrounding stem electrode layer 37be toward the center of the semiconductor substrate 11 . The first strip-shaped stem electrode layer 27bb and the second strip-shaped stem electrode layer 37bb extend side by side. The shape of the first strip-shaped stem electrode layer 27bb may be linear or curved.
A plurality of first branch electrode layers 27f are connected to the first surrounding stem electrode layer 27be and the first strip-shaped stem electrode layer 27bb, and the second surrounding stem electrode layer 37be and the second strip-shaped stem electrode layer 37bb are connected to A plurality of second branch electrode layers 37f are connected. This prevents the high-resistance specific region 60 from disconnecting the low-resistance branch electrode layer in the non-specific region, so that the branch electrode layer in the non-specific region does not pass through the high-resistance branch electrode layer in the specific region 60 . It is connected to the electrode layer and prevents the resistance loss due to the high-resistance branch electrode. That is, the output of the solar cell 1 is improved.

<Shape of first electrode layer and second electrode layer in specific region>
The first electrode layer 27</b>H and the second electrode layer 37</b>H in the specific region 60 are preferably formed distributed over the entire specific region 60 on the main surface of the semiconductor substrate 11 .
The first electrode layer 27H includes first branch electrode layers 27Hf, and the second electrode layer 37H includes second branch electrode layers 37Hf. The first branched electrode layer 27Hf and the second branched electrode layer 37Hf are so-called finger electrodes and have a strip-like shape (strip shape). The shape of the first branched electrode layer 27Hf and the second branched electrode layer 37Hf may be linear or curved.
The first branched electrode layers 27Hf and the second branched electrode layers 37Hf are preferably arranged in parallel by being alternately arranged in a direction intersecting the extending direction.
One end of the first branch electrode layer 27Hf is connected to the first surrounding stem electrode layer 27be, and the other end of the first branch electrode layer 27Hf is separated from the second surrounding stem electrode layer 37be. One end of the second branch electrode layer 37Hf is connected to the second surrounding stem electrode layer 37be, and the other end of the second branch electrode layer 37Hf is separated from the first surrounding stem electrode layer 27be. .

(Second modification)
FIG. 10 is a view of a solar cell according to a second modified example of this embodiment, viewed from the back side. Solar cell 1 shown in FIG. 10 is similar to solar cell 1 shown in FIG. It differs from the first modification in that the shape of the layer 37b) and the shape of the electrode layers 27H, 37H in the specific region 60 are different.

<Shape of first electrode layer and second electrode layer in non-specific region>
The second surrounding stem electrode layer 37be of the second stem electrode layer 37b in the non-specified region surrounds the entire outer edge of the specified region 60 .
In this case, the first stem electrode layer 27b may be arranged between the adjacent second stem electrode layers 37b and may be composed only of strip-shaped stem electrode layers similar to the above-described first strip-shaped stem electrode layers 27bb. The first trunk electrode layer 27b is strip-shaped extending along the radial direction from the center of the semiconductor substrate 11 toward the outer edge, in other words, along the radial direction from the center of the concentric circles of the first branch electrode layers 27f. As a result, the first trunk electrode layer 27b extends to cross the concentric first branch electrode layers 27f. The shape of 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 strip-shaped trunk electrode layer 37bb. be done. This prevents the high-resistance specific region 60 from disconnecting the low-resistance branch electrode layer in the non-specific region, so that the branch electrode layer in the non-specific region does not pass through the high-resistance branch electrode layer in the specific region 60 . It is connected to the electrode layer and prevents the resistance loss due to the high-resistance branch electrode. That is, the output of the solar cell 1 is improved.

<Shape of first electrode layer and second electrode layer in specific region>
When the semiconductor substrate 11 is of the first conductivity type, the specific region 60 is entirely covered with the second conductivity type semiconductor layer 35 . Furthermore, on the second conductivity type semiconductor layer 35, a second electrode layer 37H is formed on the corresponding entire surface or as a comb electrode. Layer 27H is not formed.
As a result, minority carriers are recovered in the specific region 60 and majority carriers are recovered in the non-specific region, depending on the conductivity type of the semiconductor substrate 11 . By recovering the majority carriers generated in the specific region 60 in the non-specific region in this way, the series resistance increases according to the distance.
For example, when using an n-type semiconductor substrate, the specific region 60 is preferably covered with a p-type semiconductor layer, and holes generated in the specific region 60 pass through the p-type semiconductor layer in the specific region 60. The electrons generated in the specific region 60 are transported to the electrode layer in the non-specific region via the n-type semiconductor layer in the non-specific region. As a result, the series resistance component in taking out the carriers generated in the specific region 60 is increased, and the output of the solar cell is improved.

(Electronics)
It is preferable that the solar cell 1 of this embodiment be modularized for practical use. Modularization of the solar cell is performed by an appropriate method. For example, electricity can be extracted by connecting wires, contact pins, or the like to the main electrode layers 27b and 37b of both the anode and the cathode, or to extraction electrodes (not shown) provided on each. Also, the back electrode type solar cell is modularized by being sealed with a sealant and a glass plate. Solar cells that are modularized in this way can be mounted in electronic devices for wearable applications (wristwatches or smartwatches, sensors).

Although 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, in the above-described embodiments, heterojunction solar cells were exemplified, but the features of the present invention are not limited to heterojunction solar cells, and can be applied to various solar cells such as homojunction solar cells. is.

In addition, in the above-described embodiments, the back electrode type solar cell was exemplified, but 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 double-sided electrode type solar cells. is.
In a double-sided electrode type solar cell, a passivation layer, a first conductivity type semiconductor layer, and a first electrode are provided on substantially the entire light-receiving surface side of the light-receiving main surface, which is one of the main surfaces of the semiconductor substrate. Layers are laminated in order, and a passivation layer, a second conductivity type semiconductor layer, and a second electrode layer are laminated in order on substantially the entire rear surface side, which is the other main surface opposite to the light-receiving surface, of the two main surfaces of the semiconductor substrate. be done. Even in this case, the series resistance component of the electrical resistance in the specific region corresponding to the light shielding member may be made higher than the series resistance component of the electrical resistance in the non-specific region.

Further, in the above-described embodiment, the passivation layer 23, the first conductivity type semiconductor layer 25 and the first electrode layer 27 which are laminated in order on the first conductivity type region 7 on the back side of the semiconductor substrate 11, and the back surface of the semiconductor substrate 11 1 illustrates a back contact solar cell 1 including a passivation layer 33, a second conductivity type semiconductor layer 35 and a second electrode layer 37 which are laminated in order on a second conductivity type region 8 excluding a first conductivity type region 7 on the side. bottom. However, the present invention is not limited to the solar cell 1 as described above, but may be a back electrode type solar cell in which at least a portion of the first conductivity type semiconductor layer and at least a portion of the second conductivity type semiconductor layer overlap. I don't mind. In this case, the first branch electrode layer and the first trunk electrode layer (the frame electrode layer and/or the first belt-like trunk electrode layer, or the first surrounding trunk electrode layer) are the first electrode layers corresponding to the first conductivity type semiconductor layers. electrode layer and/or first belt-like trunk electrode layer), and the second electrode layer corresponding to the second conductivity type semiconductor layer is the above-described second branch electrode layer and second trunk electrode layer (frame electrode layer and/or a second strip-shaped stem electrode layer, or a second surrounding stem electrode layer and/or a second strip-shaped stem electrode layer).

1, 1X solar cell 7 first conductivity type region 8 second conductivity type region 11 semiconductor substrate (photoelectric conversion substrate)
13, 23, 33 passivation layer 15 antireflection layer 25, 25X first conductivity type semiconductor layer 27, 27H, 27X first electrode layer 27b, 27Hb first trunk electrode layer (busbar electrode, busbar portion)
27bb First strip-shaped stem electrode layer 27be First surrounding stem electrode layer 27bf First frame stem electrode layer 27f, 27Hf First branch electrode layer (finger electrodes, finger portions)
28, 28H transparent electrode layer 29, 29H metal electrode layer 35, 35X second conductivity type semiconductor layer 37, 37H, 37X second electrode layer 37b, 37Hb second trunk electrode layer (busbar electrode, busbar portion)
37bb Second strip-shaped stem electrode layer 37be Second surrounding stem electrode layer 37bf Second frame stem electrode layer 37f, 37Hf Second branch electrode layer (finger electrodes, finger portions)
38, 38H transparent electrode layer 39, 39H metal electrode layer 40 frame electrode layer 50 division region 60 specific region 70 light shielding member

Claims (12)

a photoelectric conversion substrate; a semiconductor layer of a first conductivity type and a semiconductor layer of a second conductivity type; A solar cell comprising a first electrode layer corresponding to a conductivity type semiconductor layer and a second electrode layer corresponding to the second conductivity type semiconductor layer, in combination with a light shielding member arranged apart from the solar cell In the solar cell used,
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,
A series resistance component of the electrical resistance in the specific region is higher than a series resistance component of the electrical resistance in the non-specific region,
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·cm ² or more and less than 10000 Ω·cm ² .
solar cell. 2. The solar cell according to claim 1 , wherein a 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 greater than 0 Ω·cm ² and less than 10 Ω·cm ² . The solar cell according to claim 1 or 2 , wherein the area S_d of the specific region is 0.25 to 0.95 times the area of the main surface of the photoelectric conversion substrate. 4. The cross-sectional area of the first electrode layer or the second electrode layer in the specific region is smaller than the cross-sectional area of the first electrode layer or the second electrode layer in the non-specific region. 1. The solar cell according to claim 1. 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;
The solar cell according to any one of claims 1-3 . The solar cell is a back electrode type solar cell, and includes the first conductivity type semiconductor layer and the first conductivity type semiconductor layer disposed on the other main surface side opposite to the one main surface of the photoelectric conversion substrate. 6. The device according to any one of claims 1 to 5 , comprising a two-conductivity-type semiconductor layer, and said first electrode layer corresponding to said first-conductivity-type semiconductor layer and said second electrode layer corresponding to said second-conductivity-type semiconductor layer. 2. The solar cell according to item 1. 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,
The solar cell according to claim 6 . Having a plurality of partitioned regions obtained by partitioning the main surface of the photoelectric conversion substrate into a plurality of regions so as to surround the plurality of specific regions,
In each of the plurality of segmented regions,
Each of the first electrode layer and the second electrode layer has a plurality of strip-shaped branch electrode layers and a trunk electrode layer to which one end of the plurality of branch electrode layers is connected,
a portion of the plurality of branch electrode layers of the first electrode layer or the second electrode layer surrounds at least a portion of an outer edge of the specific region;
the stem electrode layers of the first electrode layer and the second electrode layer have a frame electrode layer surrounding the segmented regions;
The solar cell according to claim 6 . Each of the first electrode layer and the second electrode layer has a plurality of strip-shaped branch electrode layers and a trunk electrode layer to which one end of the plurality of branch electrode layers is connected,
At least one stem electrode layer of the first electrode layer and the second electrode layer has a surrounding stem electrode layer surrounding the outer edge of the specific region, and a strip-shaped stem electrode layer extending from the surrounding stem electrode layer,
The solar cell according to claim 6 . A solar cell according to any one of claims 1 to 9 ,
one or more light shielding members arranged away from the solar cell on one main surface side of the main surfaces of the photoelectric conversion substrate in the solar cell;
An electronic device. 11. The sealing member according to claim 10 , wherein a sealing member is arranged between the solar cell and the light shielding member and is arranged on the one main surface side of the photoelectric conversion substrate to seal the photoelectric conversion substrate. Electronics. 12. The electronic device according to claim 10 , wherein said light shielding member is a member for operating said electronic device.

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