Solar cell and method for manufacturing solar cell

Abstract

To provide a see-through type solar cell with a high photoelectric conversion efficiency at an inexpensive price.SOLUTION: A solar cell 1 according to an embodiment of the present invention, comprises: a semiconductor substrate 10 that is formed in a plate like, and includes a plurality of translucent openings penetrated to a thickness direction; a first semiconductor layer 20 that is laminated on a light reception side of the semiconductor substrate 10; a second semiconductor layer 30 that is laminated on a back surface side of the semiconductor substrate 10; a front surface electrode 40 that is laminated onto the first semiconductor layer 20, and includes a plurality of finger electrodes 41 arranged in parallel each other; a back surface electrode 50 that is laminated on the second semiconductor layer 30; and a plurality of line-shaped compensation electrodes 60 that is laminated over the first semiconductor layer 20 and each of the finger electrodes 41, and is arranged so as to be crossed to each of the finger electrodes 41 in parallel each other.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a solar cell and a method for manufacturing a solar cell. [Background technology]

[0002] The use of solar cells as a clean energy source is becoming more widespread. General solar cells are not installed on windows or the like in order to block light. Therefore, see-through solar cells with openings that transmit light are also being considered. For example, Patent Document 1 discloses a solar cell in which a semiconductor substrate is formed with a p-type semiconductor film laminated on an n-type semiconductor base material that generates carriers when light is incident, forming multiple openings in the semiconductor substrate to form a p-n junction that collects carriers, and finger electrodes are arranged on the light-receiving surface of the semiconductor substrate to avoid the openings. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2002-299672 A Summary of the Invention [Problem to be solved by the invention]

[0004] When an opening is formed in an existing solar cell to make it see-through, the finger electrodes may be cut, which may result in a decrease in photoelectric conversion efficiency. Therefore, in order to provide a highly efficient see-through solar cell, it is necessary to design it differently from existing solar cells, which tends to be expensive. Therefore, the present invention aims to provide an inexpensive see-through solar cell with high photoelectric conversion efficiency. [Means for solving the problem]

[0005] A solar cell according to one embodiment of the present invention comprises a semiconductor substrate formed in a plate shape and having a plurality of light-transmitting openings penetrating in a thickness direction, a first semiconductor layer stacked on the light-receiving surface side of the semiconductor substrate, a second semiconductor layer stacked on the back surface side of the semiconductor substrate, a front surface electrode stacked on the first semiconductor layer and having a plurality of finger electrodes arranged parallel to each other, a back surface electrode stacked on the second semiconductor layer, and a plurality of linear compensation electrodes stacked across the first semiconductor layer and the finger electrodes and arranged parallel to each other and intersecting the finger electrodes.

[0006] In the above-mentioned solar cell, the pitch of the compensation electrodes may be not less than 1.2 times and not more than 5.0 times the pitch of the finger electrodes.

[0007] In the above-mentioned solar cell, the compensation electrode may be perpendicular to the finger electrodes.

[0008] A solar cell manufacturing method according to one embodiment of the present invention includes a step of stacking a plurality of linear compensation electrodes on a primary solar cell product comprising a plate-shaped semiconductor substrate, a first semiconductor layer stacked on the light-receiving surface side of the semiconductor substrate, a second semiconductor layer stacked on the back surface side of the semiconductor substrate, a surface electrode stacked on the first semiconductor layer and having a plurality of finger electrodes arranged parallel to each other, and a back surface electrode stacked on the second semiconductor layer, the compensation electrodes being stacked across the first semiconductor layer and the finger electrodes, so as to be parallel to each other and to intersect with the finger electrodes, and a step of forming a plurality of light-transmitting openings in the primary solar cell product that penetrate the semiconductor substrate in the thickness direction. Effect of the Invention

[0009] According to the present invention, it is possible to provide a see-through type solar cell which is inexpensive and has high photoelectric conversion efficiency. [Brief description of the drawings]

[0010] [Figure 1] 1 is a schematic plan view of a solar cell according to one embodiment of the present invention. [Diagram 2]2 is a schematic cross-sectional view of the solar cell shown in FIG. 1 taken along line AA. [Diagram 3] 1 is a flowchart showing the steps of a solar cell manufacturing method according to one embodiment of the present invention. [Figure 4] 1 is a schematic cross-sectional view of a primary solar cell product prepared in a solar cell manufacturing method according to one embodiment of the present invention. [Diagram 5] 1 is a schematic cross-sectional view showing a step in a solar cell manufacturing method according to one embodiment of the present invention. [Figure 6] 4 is a graph showing the relationship between the pitch of the compensation electrodes and the output of the solar cell according to the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Hereinafter, each embodiment of the present invention will be described with reference to the attached drawings. In each drawing, the same or corresponding parts are denoted by the same reference numerals. For simplification, illustrations and reference numerals of members may be omitted, in which case, other drawings shall be referred to. For convenience, the shapes and dimensions of various members in the drawings have been adjusted to make them easy to see.

[0012] Fig. 1 is a schematic plan view of a solar cell 1 according to a first embodiment of the present invention. Fig. 2 is a schematic cross-sectional view of the solar cell 1. The solar cell 1 includes a semiconductor substrate 10 formed in a plate shape, a first semiconductor layer 20 laminated on the light-receiving surface side of the semiconductor substrate 10, a second semiconductor layer 30 laminated on the back surface side (the side opposite to the light-receiving surface) of the semiconductor substrate 10, a front surface electrode 40 laminated on the first semiconductor layer 20, a back surface electrode 50 laminated on the second semiconductor layer 30, and a plurality of compensation electrodes 60 laminated across the first semiconductor layer 20 and the front surface electrode 40.

[0013] The semiconductor substrate 10 functions as a photoelectric conversion substrate that absorbs incident light and generates photocarriers (electrons and holes). The semiconductor substrate 10 may have a pyramidal fine uneven structure called a texture structure in order to improve the incidence rate of light on the light receiving surface.

[0014] The semiconductor substrate 10 can be made of a crystalline silicon material such as single crystal silicon or polycrystalline silicon. It may also be made of other semiconductor materials such as gallium arsenide (GaAs). The semiconductor substrate 10 can be, for example, an n-type semiconductor substrate in which a crystalline silicon material is doped with an n-type dopant. An example of the n-type dopant is phosphorus (P). By using crystalline silicon as the material for the semiconductor substrate 10, a relatively small dark current can be obtained, and a relatively high output (stable output regardless of illuminance) can be obtained even when the intensity of the incident light is low.

[0015] The semiconductor substrate 10 has a plurality of light-transmitting openings 11 penetrating in the thickness direction. The light-transmitting openings 11 allow light to pass through and reach the back side of the solar cell 1. The shape of the light-transmitting openings 11 in a plan view is typically circular, but may be any shape, such as an ellipse or a polygon.

[0016] The light-transmitting openings 11 are preferably formed so as to be dispersed over substantially the entire semiconductor substrate 10 in order to admit light evenly, but may not be provided in specific regions, such as the periphery of the semiconductor substrate 10 or a strip-shaped region that crosses the semiconductor substrate 10, in order to ensure the strength of the semiconductor substrate 10. The light-transmitting openings 11 are preferably arranged regularly in order to admit light evenly and to improve the aesthetic appearance. For example, a row of a plurality of light-transmitting openings 11 arranged at equal intervals can be arranged at regular intervals.

[0017] The area ratio of the light-transmitting openings 11 in the semiconductor substrate 10, i.e., the aperture ratio of the semiconductor substrate 10, can be, for example, from 3% to 50%, and preferably from 5% to 30%. This allows sufficient light to pass through the solar cell 1, and enables relatively large electric power to be obtained.

[0018] The average diameter (equivalent circle diameter) of the light-transmitting openings 11 can be, for example, 0.5 mm to 10 mm, and preferably 1 mm to 5 mm. This allows sufficient light to be collected while increasing the photoelectric conversion efficiency of the solar cell 1. The pitch (center-to-center distance) of the light-transmitting openings 11 can be, for example, 2 times to 5 times the average diameter of the light-transmitting openings 11.

[0019] The first semiconductor layer 20 and the second semiconductor layer 30 collect charges of opposite polarities by attracting carriers of opposite polarities from inside the semiconductor substrate 10. Specifically, when the semiconductor substrate 10 is an n-type, the first semiconductor layer 20 may be formed of a p-type semiconductor, and the second semiconductor layer 30 may be formed of an n-type semiconductor.

[0020] The first semiconductor layer 20 and the second semiconductor layer 30 may be formed of, for example, an amorphous silicon material containing a dopant that imparts a desired conductivity type. An example of a p-type dopant may be boron (B), and an example of an n-type dopant may be phosphorus (P), as discussed above.

[0021] The front electrode 40 and the back electrode 50 extract, as electric charges, carriers attracted by the first semiconductor layer 20 and the second semiconductor layer 30. The front electrode 40 and the back electrode 50 are made of a material having electrical conductivity, and are preferably mainly made of a metal having low electrical resistance. The front electrode 40 and the back electrode 50 may have a multi-layer structure.

[0022] The front surface electrode 40 includes a plurality of finger electrodes 41 arranged parallel to one another and a bus bar electrode 42 connecting the plurality of finger electrodes 41. Meanwhile, the back surface electrode 50 may be laminated on substantially the entire surface except for the light-transmitting opening 11. Here, "parallel to one another" means that the average angle difference in all possible combinations of two electrodes selected from the whole is 10° or less, preferably 5° or less, and more preferably 2° or less.

[0023] In order to minimize the area and increase the amount of incident light, the finger electrodes 41 are preferably formed with a minimum width that ensures conductivity and are disposed at equal intervals. Although it depends on the material and the formation method, the width of the finger electrodes 41 can be, for example, 30 μm or more and 200 μm or less. If the pitch of the finger electrodes 41 is increased, the total area of ​​the finger electrodes 41 can be reduced and the amount of incident light can be increased, but the loss increases because carriers generated inside the semiconductor substrate 10 recombine before reaching the finger electrodes 41. For this reason, the pitch of the finger electrodes 41 is selected so as to comprehensively maximize the photoelectric conversion efficiency in consideration of the loss due to light blocking (shadow loss) and the loss due to carrier recombination. A specific pitch of the finger electrodes 41 can be, for example, 1 mm or more and 3 mm or less.

[0024] Busbar electrode 42 is desired to flow the current collected from each finger electrode 41 without loss, and can also be used as a connection terminal for connecting solar cell 1 to the outside. For this reason, busbar electrode 42 has a width larger than that of finger electrode 41. In particular, when a plurality of solar cells 1 are modularized by arranging their ends overlapping each other, by arranging busbar electrode 42 on the back side of solar cell 1 on the front side, it is possible to prevent a decrease in output even if the area of ​​busbar electrode 42 is increased. For this reason, busbar electrode 42 is preferably arranged along the side edge of solar cell 1 so as to connect the ends of the plurality of finger electrodes 41. The width of busbar electrode 42 can be, for example, 0.5 mm or more and 2 mm or less.

[0025] The compensation electrodes 60 are arranged parallel to each other and cross the finger electrodes 41. The compensation electrode 60 connects the finger electrodes 41, and even if the light-transmitting opening 11 overlaps any one of the finger electrodes 41 and the finger electrode 41 is cut, the charge from the cut finger electrode 41 can be diverted to the adjacent finger electrode 41 via the compensation electrode 60 and finally transmitted to the bus bar electrode 42. The compensation electrode 60 is preferably perpendicular to the finger electrodes 41 so that the adjacent finger electrodes 41 can be connected at the shortest distance to reduce electrical resistance. Note that "perpendicular" means that the average angle at all intersections between the finger electrodes 41 and the compensation electrode 60 is 80° to 100°, preferably 85° to 95°, and more preferably 88° to 92°.

[0026] Similar to the finger electrodes 41, the compensation electrodes 60 are preferably formed with the minimum width required to ensure conductivity and arranged at equal intervals in order to minimize the area and maximize the amount of incident light. Similar to the finger electrodes 41, the width of the compensation electrodes 60 can be, for example, 30 μm or more and 200 μm or less. However, since the compensation electrodes 60 are laminated so as to straddle the first semiconductor layer 20 and the finger electrodes 41 and overcome the step, they can be formed with a width slightly larger than that of the finger electrodes 41.

[0027] The lower limit of the pitch of the compensation electrodes 60 is preferably 1.2 times, and more preferably 2.0 times, the pitch of the finger electrodes 41. Meanwhile, the upper limit of the pitch of the compensation electrodes 60 is preferably 5.0 times, and more preferably 4.0 times, the pitch of the finger electrodes 41. By setting the pitch of the compensation electrodes 60 to the lower limit or more, it is possible to reduce a decrease in output caused by a decrease in the amount of incident light by the compensation electrodes 60. Furthermore, by setting the pitch of the compensation electrodes 60 to the upper limit or less, when the light-transmitting opening 11 cuts a finger electrode 41, charges are collected by bypassing the adjacent finger electrodes 41, thereby suppressing a decrease in output.

[0028] In this way, since the solar cell 1 has the compensation electrode 60 that intersects with the finger electrode 41, there is no need to precisely adjust the positional relationship between the finger electrode 41 and the light-transmitting opening 11 during design and manufacturing, and therefore the solar cell 1 can be manufactured inexpensively, yet has a relatively high photoelectric conversion efficiency.

[0029] The solar cell 1 can be manufactured by an embodiment of a solar cell manufacturing method according to the present invention, shown in Fig. 3. The solar cell manufacturing method of this embodiment includes a solar cell primary product preparation step (step S1), a compensation electrode lamination step (step S2), and a light-transmitting opening formation step (step S3).

[0030] 4, in the solar cell product preparation process of step S1, a solar cell primary product P is prepared, which includes a plate-shaped semiconductor substrate 10, a first semiconductor layer 20 laminated on the light-receiving surface side of the semiconductor substrate 10, a second semiconductor layer 30 laminated on the back surface side of the semiconductor substrate 10, a front surface electrode 40 laminated on the first semiconductor layer 20 and having a plurality of finger electrodes 41 arranged parallel to each other, and a back surface electrode 50 laminated on the second semiconductor layer 30. In other words, as the solar cell primary product P, an existing solar cell without a light-transmitting opening can be used.

[0031] 5, in the compensation electrode lamination step of step S2, a plurality of linear compensation electrodes 60 are laminated on the solar cell primary product P so as to straddle the first semiconductor layer 20 and the finger electrodes 41, be parallel to each other and intersect with the finger electrodes 41. The compensation electrodes 60 can be formed, for example, by printing and firing a conductive paste or the like. The compensation electrodes 60 may also be laminated using a conductive pattern formation method such as a subtractive method or a semi-additive method.

[0032] In the light-transmitting opening forming step S3, a plurality of light-transmitting openings 11 penetrating the semiconductor substrate 10 in the thickness direction are formed in the solar cell primary product P. This results in the solar cell 1 shown in Fig. 1. The light-transmitting openings 11 can be formed by laser processing, etching processing, or the like, or a combination of a plurality of these. The light-transmitting opening forming step may be performed prior to the compensation electrode lamination step, provided that it does not interfere with the compensation electrode lamination step.

[0033] In this way, according to the solar cell manufacturing method of this embodiment, a light-transmitting opening 11 can be formed in an existing solar cell P to convert it into a see-through type solar cell 1, thereby reducing design costs and enabling the mass production effect to result in relatively inexpensive manufacture of the see-through type solar cell 1.

[0034] Although the embodiments of the present invention have been described above, the present invention is not limited to the above-mentioned embodiments, and various modifications and variations are possible. The solar cell according to the present invention may further include additional components such as a passivation layer, an anti-reflection film, etc. Furthermore, the front electrode, the back electrode, and the compensation electrode may have a structure. EXAMPLES

[0035] The present invention will be described in more detail below with reference to examples, although the present invention is not limited to these examples.

[0036] A simulation was performed to create a see-through solar cell by forming compensation electrodes with different pitches perpendicular to the finger electrodes on a solar cell with a finger electrode pitch of 1.5 mm, and forming light-transmitting openings with a diameter of 2.5 mm in each electrode at a pitch of 6 mm, with a row spacing of 6 mm and a half-period offset for each row, and the maximum output of each solar cell was confirmed.

[0037] The relationship between the ratio of the pitch of the compensation electrodes to the pitch of the finger electrodes and the maximum output confirmed by the simulation is shown in Figure 6. The maximum output of the solar cell before forming the compensation electrodes and the light-transmitting openings is 0.792 W.

[0038] These results confirmed that by setting the pitch of the compensation electrodes to be between 1.2 and 5.0 times the pitch of the finger electrodes, it is possible to reduce the output reduction (shadow loss) caused by the compensation electrodes blocking light, while improving the efficiency of charge recovery via the compensation electrodes from the finger electrodes cut by the light-transmitting openings, thereby obtaining a relatively high output. [Explanation of symbols]

[0039] 1 Solar cell 10. Semiconductor Substrate 11 Translucent aperture 20 First semiconductor layer 30 Second semiconductor layer 40 surface electrode 41 Finger Electrode 42 Busbar electrode 50 Back electrode 60 compensation electrode

Claims

1. a semiconductor substrate formed in a plate shape and having a plurality of light-transmitting openings penetrating in a thickness direction; A first semiconductor layer laminated on a light receiving surface side of the semiconductor substrate; A second semiconductor layer laminated on the back surface side of the semiconductor substrate; a surface electrode having a plurality of finger electrodes disposed parallel to each other and stacked on the first semiconductor layer; A back electrode laminated on the second semiconductor layer; a plurality of linear compensation electrodes stacked across the first semiconductor layer and the finger electrodes and arranged parallel to each other and intersecting with the finger electrodes; Equipped with an area ratio of the light-transmitting opening is 3% or more and 50% or less; The average diameter of the light-transmitting opening is 0.5 mm or more and 10 mm or less, The pitch of the finger electrodes is 1 mm or more and 3 mm or less, A solar cell, wherein the pitch of the compensation electrodes is 1.2 times or more and 5.0 times or less the pitch of the finger electrodes.

2. The solar cell of claim 1 , wherein the compensation electrode is perpendicular to the finger electrodes.

3. a step of stacking a plurality of linear compensation electrodes on a primary solar cell product including a plate-shaped semiconductor substrate, a first semiconductor layer stacked on a light receiving surface side of the semiconductor substrate, a second semiconductor layer stacked on a back surface side of the semiconductor substrate, a front surface electrode stacked on the first semiconductor layer and having a plurality of finger electrodes arranged parallel to each other, and a back surface electrode stacked on the second semiconductor layer, the compensation electrodes being stacked across the first semiconductor layer and the finger electrodes, so as to be parallel to each other and to intersect with the finger electrodes; forming a plurality of light-transmitting openings penetrating the solar cell primary product in a thickness direction of the semiconductor substrate; Equipped with an area ratio of the light-transmitting opening is 3% or more and 50% or less; The average diameter of the light-transmitting opening is 0.5 mm or more and 10 mm or less, The pitch of the finger electrodes is 1 mm or more and 3 mm or less, A method for manufacturing a solar cell, wherein the pitch of the compensation electrodes is 1.2 times or more and 5.0 times or less the pitch of the finger electrodes.

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