TWI636577B - Solar cell and module comprising the same - Google Patents

Abstract

A solar cell and a module thereof, comprising: a substrate having an opposite light receiving surface and a back surface; a passivation layer on the back surface and having an opening portion; and a passivation layer on the passivation layer and passing through the opening The portion contacts the back electrode of the back surface. The opening portion has a first opening pattern extending along a circumference of the substrate and being annular, and a second opening pattern surrounded by the first opening pattern and having a plurality of sub-openings, the first opening pattern and The distance from the periphery of the substrate is less than 5 mm. By disposing the first opening pattern on the periphery of the second opening pattern, and the first opening pattern is disposed adjacent to the periphery of the substrate, the conductive contact area between the back surface electrode and the substrate can be improved, thereby improving the current collecting effect. With photoelectric conversion efficiency.

Description

Solar cell and its module

The invention relates to a solar cell and a module thereof, in particular to a twin solar cell and a module thereof.

Referring to FIGS. 1 and 2, a known twin solar cell mainly comprises: a substrate 91 having an opposite light receiving surface 911 and a back surface 912, a front surface electrode 92 on the light receiving surface 911, and a plurality of the front surface 912. a local back surface field (LBSF) 93, a passivation layer 94 on the back surface 912 and having a plurality of openings 941, and a passivation layer 94 on the passivation layer 94 and contact through the plurality of openings 941 The back surface electrode 95 of the back surface 912.

The passivation layer 94 is used to fill and reduce surface defects of the substrate 91, thereby reducing the recombination rate of the carrier at the back surface 912 of the substrate 91 to improve the conversion efficiency of the battery. The plurality of partial back surface electric fields 93 are respectively located at the back surface 912 corresponding to the plurality of openings 941. The carrier concentration of the partial back surface electric field 93 is greater than the carrier concentration of the substrate 91, which can improve the carrier collection efficiency and photoelectric conversion. effectiveness. Such a battery having a passivation layer 94 and a partial back surface electric field 93 is called a PERC (Passivated Emitter and Rear Contact Solar Cell), and has a higher conversion efficiency than a conventional battery in which the passivation layer 94 is not provided.

The area of the back surface electrode 95 of the PERC battery contacting the back surface 912 of the substrate 91 corresponds to the area of the plurality of openings 941 of the passivation layer 94. Since the area of the plurality of openings 941 is limited, the back surface electrode 95 is The back surface 912 has a small contact area, which causes the series resistance (Rs) of the battery to be too large, and the current collection effect is not good. Moreover, according to the article IEEE FORUM OF PHOTOVOLTAICS, VOL.1, NO.1, JULY 2011, "Evaluation of Series Resistance Losses in Screen-Printed Solar Cells With Local Rear Contacts", the four corners 913 of the back surface 912 of the battery are easier. The problem of high impedance occurs, that is, the Redge mentioned in the journal is high, and the smaller the area of the back surface electrode 95 that passes through the plurality of openings 941 and contacts the back surface 912, the more significant the above-mentioned high Redge phenomenon, which may result in The Fill Factor drops and affects the conversion efficiency of the battery, so the known PERC solar cells need to be improved.

Accordingly, it is an object of the present invention to provide a solar cell and a module thereof which can reduce the series resistance of a battery and improve the photoelectric conversion efficiency.

Therefore, the solar cell of the present invention comprises: a substrate having an opposite light receiving surface and a back surface, a front electrode on the light receiving surface, a passivation layer on the back surface and having an opening portion, and a The back surface electrode of the back surface of the substrate is contacted through the opening on the passivation layer. The opening portion has a first opening pattern extending along a circumference of the substrate and being annular, and a second opening pattern surrounded by the first opening pattern and having a plurality of sub-openings, the first opening pattern and The distance from the periphery of the substrate is less than 5 mm.

Another solar cell provided by the present invention comprises: a substrate, a front electrode, a passivation layer, and a back electrode. The substrate is a single crystal ruthenium The plate has an opposite light receiving surface and a back surface, four spaced long sides, and four short sides arranged in a staggered manner with the four long sides. The front electrode is located on the light receiving surface. The passivation layer is on the back surface and has an opening. The back electrode is located on the passivation layer and contacts the back surface of the substrate via the opening.

The opening portion includes a first opening pattern and a second opening pattern, the first opening pattern includes four first linear openings respectively adjacent to the four short sides of the substrate, each of the first lines The distance between any portion of the opening and the corresponding short side is less than 8 mm, the second opening pattern includes a plurality of sub-openings, and the shortest distance of each of the short sides of each of the four short sides is greater than 8 mm .

The solar cell module of the present invention comprises: a first plate and a second plate disposed oppositely, a plurality of solar cells as described above and arranged between the first plate and the second plate, and a package. The encapsulant is located between the first plate and the second plate and is wrapped around the plurality of solar cells.

The effect of the present invention is that the first opening pattern is disposed on the periphery of the second opening pattern, and the first opening pattern is disposed adjacent to the circumference or the four corners of the substrate, thereby improving the conductivity between the back surface electrode and the substrate Contact area to reduce the series resistance of the battery, improve current collection and improve photoelectric conversion efficiency.

The foregoing and other technical contents, features, and effects of the present invention will be described in the following detailed description of the eleven preferred embodiments with reference to the drawings. Can be clearly presented. Before the present invention is described in detail, it is noted that in the following description, similar elements are denoted by the same reference numerals.

Referring to FIG. 3, FIG. 4, the first preferred embodiment of the solar cell module of the present invention comprises: a first plate 1 and a second plate 2 disposed opposite each other, and a plurality of arrays arranged on the first plate 1 The solar cell 3 between the second plate 2 and at least one of the first plate 1 and the second plate 2 are wrapped around the plurality of solar cells 3.

The first plate 1 and the second plate 2 are not particularly limited in implementation, and a glass or plastic plate may be used, and the plate on one side of the light receiving surface of the battery must be permeable to light. The material of the encapsulant 4 is, for example, a light transmissive ethylene vinyl acetate copolymer (EVA), or other related materials that can be used for solar cell module packaging.

The plurality of solar cells 3 are electrically connected through ribbons not shown. The structures of the plurality of solar cells 3 are the same, and only one of them will be described below as an example.

The solar cell 3 includes a substrate 31, a front electrode 32, a plurality of partial back surface electric fields 33, a passivation layer 34, and a back surface electrode 35.

The substrate 31 has an opposite light receiving surface 311 and a back surface 312. An emitter layer 313 may be disposed on the inner side of the light receiving surface 311, and an antireflection layer (not shown) may be disposed on the emitter layer 313. The substrate 31 is, for example, a germanium substrate, and one of the substrate 31 and the emitter layer 313 is an n-type semiconductor, and the other is a p-type semiconductor, thereby forming a pn junction. In this embodiment, a single crystal germanium substrate is taken as an example. Therefore, the four sides of the substrate 31 are cut so that the substrate 31 is similar to an octagon, and the four short sides 316 of the substrate 31 are curved, but the present invention is implemented. A polycrystalline germanium substrate can also be used, and the polycrystalline germanium substrate exhibits a quadrangular shape. The material of the anti-reflection layer such as tantalum nitride (SiN _x ) can be used to reduce light reflection to increase the amount of light incident.

The front surface electrode 32 is located on the light receiving surface 311 and cooperates with the back surface electrode 35 for conducting electric energy of the battery. Since the front surface electrode 32 is not a modification of the present invention, it will not be described here.

The plurality of partial back surface electric fields 33 are located at the back surface 312 of the substrate 31. The partial back surface electric field 33 of the present embodiment is a p-type semiconductor formed of an aluminum-bismuth (Al-Si) mixed material, and the conductive form thereof and the substrate 31 The same and the carrier concentration is greater than the carrier concentration of the substrate 31, and the electric field of the partial back surface electric field 33 blocks the movement of electrons toward the back surface 312, so that electrons are collected in the emitter layer 313 to lift the carrier. Collect efficiency and conversion efficiency.

The passivation layer 34 is located on the back surface 312 for filling and reducing surface defects of the substrate 31, thereby reducing the recombination rate of the carrier at the back surface 312, and improving the open circuit voltage, short circuit current and conversion efficiency of the battery. The material of the passivation layer 34 is, for example, an oxide, a nitride, or a composite of an oxide and a nitride.

The passivation layer 34 has an opening portion 36 having a first opening pattern 37 extending along the circumference of the substrate 31 and being annular, and a plurality of sub-openings surrounded by the first opening pattern 37. a second opening pattern 38 of 381. The first opening pattern 37 of the present embodiment is a continuous and closed annular opening 371 having an extended shape identical to the peripheral shape of the substrate 31. The plurality of sub-openings 381 of the second opening pattern 38 are linear openings parallel to each other, and the plurality of sub-openings 381 are along a The first direction 51 extends and is spaced apart along a second direction 52 that is perpendicular to the first direction 51. The width w1 of the first opening pattern 37 and the width w2 of the plurality of sub-openings 381 may be the same or different. Preferably, the total area of the first opening pattern 37 and the second opening pattern 38 is between 0.5% and 20% of the area of the back surface 312, and a sufficiently large area of the passivation layer 34 can be retained in the area. In order to provide a good passivation effect, it is also possible to form a back electrode 35 having a sufficient area to provide good electrical properties. Although the two ends of each sub-opening 381 of the present embodiment are not connected to the first opening pattern 37, they may be connected during implementation.

It is to be noted that the region where the uniformity of the coating of the passivation layer 34 is poor in the range of 5 mm from the periphery of the substrate 31 to the periphery of the substrate 31 is also an anti-reflection layer (SiN) on the light-receiving surface 311 of the substrate 31. The region of _x ) which is easy to be plated, so that the passivation effect of the passivation layer 34 in the range is limited, so that the first opening pattern 37 is disposed on the passivation layer 34 in the range, and the effect on the passivation layer 34 is not Preferably, the distance d1 between the first opening pattern 37 and the periphery of the substrate 31 is less than 5 mm, so that the series resistance and the lifting filling can be reduced without damaging the quality of the passivation layer 34 and less affecting the open circuit voltage. Factor (Fill Factor). It should be noted that the distance between each part of the first opening pattern 37 and the periphery of the substrate 31 is not necessarily the same, but the distance of each part is less than 5 mm.

The back surface electrode 35 is located on the passivation layer 34 and contacts the back surface 312 of the substrate 31 via the opening portion 36. The back surface electrode 35 includes a plurality of first conductive portions 351 respectively filled in the annular opening 371 of the first opening pattern 37 and the plurality of sub- openings 381, and a surface on the passivation layer 34. The second conductive portions 352 of the plurality of first conductive portions 351 are connected to each other. In fact, the back electrode 35 may further include at least one bus electrode extending in the second direction 52, but since the bus electrode is not a modification of the present invention, it will not be described. Further, since the peripheral edge of the back surface electrode 35 of the present embodiment extends substantially along the peripheral edge shape of the substrate 31, the peripheral edge of the back surface electrode 35 includes a plurality of straight segments and a plurality of arc segments.

In summary, the back surface electrode 35 can simultaneously pass through the holes of the first opening pattern 37 and the second opening pattern 38 by the cooperation design of the first opening pattern 37 and the second opening pattern 38. Contacting the back surface 312 of the substrate 31 further increases the conductive contact area of the back surface electrode 35 and the back surface 312, thereby reducing the series resistance of the battery, improving current collection efficiency and increasing the fill factor, and effectively improving the photoelectric conversion efficiency of the battery. The first opening pattern 37 is disposed adjacent to and along the circumference of the substrate 31, thereby improving the conductive contact area between the surface of the peripheral portion of the substrate 31 and the back surface electrode 35, thereby reducing the high impedance of the edge portion of the conventional battery. problem.

Referring to FIG. 6, a second preferred embodiment of the solar cell module of the present invention is substantially the same as that of the first preferred embodiment, except that the first opening pattern 37 of the solar cell 3 of the present embodiment includes a plurality of spaced island openings 372, wherein the plurality of island openings 372 are arranged such that the first opening pattern 37 is integrally formed with a broken line and a discontinuous annular opening, and the dotted annular opening means The plurality of island-shaped openings 372 are spaced apart along the circumference of the substrate 31 such that the first opening pattern 37 as a whole can surround the plurality of sub-openings 381 of the second opening pattern 38. Among them, the island-shaped master In order to distinguish from the continuous uninterrupted opening pattern of the first preferred embodiment, the island shape may be circular, semi-circular, polygonal, square or other shape.

Referring to Figure 7, a third preferred embodiment of the solar cell module of the present invention is substantially identical in construction to the first preferred embodiment. The peripheral edge of the substrate 31 of the solar cell 3 includes two first side edges 314 opposite and extending along the first direction 51, and two opposite and located between the two first side edges 314 along the The second side 315 of the second direction extension 52 is connected between each of the first side edges 314 and each of the second side edges 315 through a short side 316. The difference between the embodiment and the first preferred embodiment is that the first opening pattern 37 has two first pattern portions 373 adjacent to the two first side edges 314, and two adjacent to the first opening portion 314. The second pattern portion 374 of the two second side edges 315. The two first pattern portions 373 are respectively a linear opening 375 extending continuously in the first direction 51. The two second pattern portions 374 are dotted-shaped openings, each of the second pattern portions 374 includes a plurality of spaced island-shaped openings 376, and each of the second pattern portions 374 may extend corresponding to the plurality of short sides 316. That is, at least one island-shaped opening 376 may be disposed at each short side 316.

It should be noted that, when a polycrystalline germanium substrate is used, there is no design of the plurality of short sides 316, and the first side 314 is directly connected to the second side 315.

Referring to FIG. 8, a fourth preferred embodiment of the solar cell module of the present invention is substantially the same as the structure of the third preferred embodiment, and the difference is that the second pattern portion of the first opening pattern 37 of the embodiment is 374 includes several rooms Each of the connection openings 377 is connected to the end of the two adjacent sub-openings 381 of the second opening pattern 38, or is connected to the end of the linear opening 375 of the first pattern portion 373 and adjacent thereto. The end of the child opening 381. The plurality of connection openings 377 are spaced apart and actually correspond to the form of island openings.

Referring to FIG. 9, the fifth preferred embodiment of the solar cell module of the present invention is substantially the same as the structure of the first preferred embodiment, and the difference is that the plurality of sub-openings of the second opening pattern 38 of the embodiment 381 is an island-shaped opening, and the positions of the plurality of sub-openings 381 correspond to each other. The island shape may be circular, semi-circular, polygonal, square or other shape.

Referring to FIG. 10, the sixth preferred embodiment of the solar cell module of the present invention is substantially the same as the structure of the fifth preferred embodiment, except that the positions of the plurality of sub-openings 381 of the present embodiment are staggered.

Referring to FIG. 11, a seventh preferred embodiment of the solar cell module of the present invention is substantially the same as the first preferred embodiment, except that the second opening pattern 38 includes a plurality of along the first In addition to the sub-opening 381 extending in the direction 51, a plurality of sub-openings 382 extending along the second direction 52 are further included, and the plurality of sub-openings 381 and the plurality of sub-openings 382 are arranged in a crisscross manner to form a grid shape. Moreover, the first opening pattern 37 of the embodiment connects the plurality of sub-openings 381, 382, thereby forming the back electrode 35 to form a continuous conductive network, which can further improve the current collecting effect.

Referring to FIG. 12, the eighth preferred embodiment of the solar cell module of the present invention is substantially the same as the structure of the first preferred embodiment, except that the width w1 of the first opening pattern 37 of the embodiment is greater than The second opening The width w2 of the plurality of sub-openings 381 of the mouth pattern 38. Moreover, the first opening pattern 37 of the embodiment is connected to the plurality of sub-openings 381, and the conductive contact area between the back surface electrode (not shown) and the substrate 31 is increased by the above design, and a continuous conductive mesh can be formed. The road helps to improve current collection and photoelectric conversion efficiency. The boundary of the back surface electrode of the present embodiment extends substantially along the peripheral edge shape of the first opening pattern 37, and the back surface electrode can completely cover the first opening pattern 37 and the second opening pattern 38.

It should be noted that the first opening pattern of the first to eighth preferred embodiments partially extends in a curved shape corresponding to the four short sides of the substrate, so that the portions of the first opening pattern and the substrate The distance between the circumferences is less than 5mm. The partial periphery of the back electrode also has an arc shape corresponding to the four short sides. However, the present invention is not limited to the above design, and will be described below by way of other embodiments.

Referring to FIG. 13, a ninth preferred embodiment of the solar cell module of the present invention is substantially the same as that of the first preferred embodiment. The substrate 31 of the present embodiment is also a single crystal germanium substrate, and the periphery of the substrate 31 has Four spaced apart and linearly extending long sides 317, and four short sides 316 that are staggered with the four long sides 317 and extend in an arc. Two of the long sides 317 extend along the first direction 51 and are opposite to the second direction 52. The other two long sides 317 extend along the second direction 52 and are opposite along the first direction 51. The four short The side edges 316 are respectively connected between any two adjacent long side edges 317, and the four short side edges 316 are not parallel to the first direction 51 and the second direction 52.

The opening portion 36 of the passivation layer 34 of the present embodiment also includes a first opening The mouth pattern 37 and a second opening pattern 38. The main difference between this embodiment and the first preferred embodiment is that the first opening pattern 37 of the embodiment includes four first linear openings 378 adjacent to the four short sides 316 of the substrate 31, respectively. The distance between any portion of each first linear opening 378 and the corresponding short side 316 is less than 8 mm. Of course, the distance between the different portions of the first linear opening 378 and the corresponding short side 316 is not It must be the same, but the distance of each part is always less than 8mm. For example, d2, d3, and d4 indicated in Figure 13 are less than 8mm. The reason why the embodiment is set to 8 mm is that since the first linear opening 378 extends in a straight line, the distance between the short side edges 316 extending from the arc portion is large, and exceeds the setting of the first preferred embodiment. 5mm.

The shortest distance between each sub-opening 381 of the second opening pattern 38 and any short side 316 of the four short sides 316 is greater than 8 mm. Of course, the shortest distance of each sub-opening 381 may be different (eg, Figure 13 shows that some of the shortest distances are d5, d6, d7), but the above is mainly used to indicate that each sub-opening 381 is within the range enclosed by the four first linear openings 378, so each sub- The opening 381 is farther from the periphery of the substrate 31 than each of the first linear openings 378.

Furthermore, the distance between any portion of each of the first linear openings 378 of the present invention and the corresponding short sides 316 may be less than 5 mm. The shortest distance between each of the sub-openings 381 of the second opening pattern 38 and any of the short sides 316 of the four short sides 316 is greater than 5 mm. Preferably, the total area of the first opening pattern 37 and the second opening pattern 38 accounts for 0.5%-20% of the back surface area of the substrate 31.

In this embodiment, the four first linear openings 378 are respectively disposed on the four short sides 316 of the substrate 31, thereby increasing the contact conductive area between the back surface electrode 35 and the substrate 31, thereby improving the single crystal germanium. The battery is prone to high impedance at the four corners of the battery, thereby improving current collection and photoelectric conversion efficiency.

It is to be noted that the width w3 of the first linear opening 378 of the first opening pattern 37 and the width w2 of the plurality of sub-openings 381 of the second opening pattern 38 may be the same or different, wherein the first linear opening The width w3 of 378 is increased and larger than the width w2 of the plurality of sub-openings 381, which helps to reduce the high impedance problem at the four corners of the battery. In addition, the plurality of sub-openings 381 of the embodiment may be island-shaped openings as shown in FIG. 9 or FIG. 10, or may be grid-like as shown in FIG. Or it can be designed for other purposes.

Another difference between this embodiment and the first preferred embodiment is that the peripheral edge of the back surface electrode 35 of the present embodiment extends in a straight line at a portion corresponding to the four short side edges 316 of the substrate 31. The back electrode 35 of the embodiment and the plurality of first linear openings 378 do not conform to the arc of the four short sides 316, but have a linearly extending design, which is advantageous with respect to the first preferred embodiment. To simplify the process. However, the partial periphery of the back surface electrode 35 of the present embodiment may actually extend in an arc conforming to the four short side edges 316.

Referring to FIG. 14, a tenth preferred embodiment of the solar cell module of the present invention is substantially the same as the structure of the ninth preferred embodiment, and the difference is that the plurality of sub-opening patterns 38 of the embodiment are The opening 381 has a long extension length, and wherein the plurality of sub-openings 381 are connected to the first opening The first linear opening 378 of the case 37 can increase the contact conductive area between the back surface electrode 35 and the substrate 31, thereby improving the current collecting effect and the photoelectric conversion efficiency.

Referring to FIG. 15, an eleventh preferred embodiment of the solar cell module of the present invention is substantially the same as the structure of the tenth preferred embodiment. The difference is that the first opening pattern 37 further includes two along the first a second linear opening 379 extending in a direction 51 and opposite the second direction 52, and the two second linear openings 379 respectively extending along two of the four long sides 317 of the substrate 31, The distance d7 of each of the second linear openings 379 and the corresponding long side 317 is less than 5 mm.

In addition, the width w3 of each of the first linear openings 378 is greater than the width w4 of each of the second linear openings 379, and the width w3 of each of the first linear openings 378 is also greater than the width w2 of the plurality of sub-openings 381, thereby It can raise the electrode contact area at the four corners of the battery to reduce the high impedance problem at the four corners of the battery, thereby improving the current collecting effect. However, in implementation, the width w3 of each of the first linear openings 378 may also be equal to or smaller than the width w4 of each of the second linear openings 379.

As can be seen from the above description, the spirit of the present invention mainly lies in that the first opening pattern 37 is disposed on the periphery of the second opening pattern 38, and the first opening pattern 37 is disposed adjacent to the circumference or the four corners of the substrate 31, thereby being The conductive contact area between the back electrode 35 and the substrate 31 improves the current collecting effect and the photoelectric conversion efficiency. As for the design of the shape, width, and connection relationship of the first opening pattern 37 and the second opening pattern 38, there are many types.

The above is only the preferred embodiment of the present invention, and the scope of the invention is not limited thereto, that is, the simple equivalent changes and modifications made by the scope of the invention and the description of the invention are All remain within the scope of the invention patent.

1‧‧‧ first plate

2‧‧‧Second plate

3‧‧‧Solar battery

31‧‧‧Substrate

311‧‧‧Stained surface

312‧‧‧ back

313‧‧ ‧ emitter layer

314‧‧‧ first side

315‧‧‧ second side

316‧‧‧ Short side

317‧‧‧Long side

32‧‧‧ front electrode

33‧‧‧Partial back surface electric field

34‧‧‧ Passivation layer

35‧‧‧Back electrode

351‧‧‧First Conductive Department

352‧‧‧Second Conductive Department

36‧‧‧ openings

37‧‧‧First opening pattern

371‧‧‧Aperture opening

372‧‧‧ island opening

373‧‧‧First Pattern Department

374‧‧‧Second Pattern Department

375‧‧‧Linear opening

376‧‧‧ island opening

377‧‧‧Connecting opening

378‧‧‧First line opening

379‧‧‧Second wire opening

38‧‧‧Second opening pattern

381‧‧‧ child opening

382‧‧‧ child opening

4‧‧‧Package

51‧‧‧First direction

52‧‧‧second direction

D1~d7‧‧‧distance

W1~w4‧‧‧Width

1 is a schematic rear view of a known solar cell, in which a plurality of openings are indicated by dot-like regions for easy identification; FIG. 2 is a partial cross-sectional view taken along line AA of FIG. 1; FIG. A schematic cross-sectional view of a first preferred embodiment of a solar cell module; FIG. 4 is a schematic rear view of a solar cell of the first preferred embodiment, mainly illustrating a pattern design of an opening of a passivation layer, and The opening portion is indicated by a dot-like area for easy identification; the imaginary line in the figure indicates a back electrode; FIG. 5 is a partial cross-sectional view taken along line BB of FIG. 4; and FIG. 6 is a second of the solar cell module of the present invention. FIG. 7 is a schematic rear view of a solar cell according to a third preferred embodiment of the solar cell module of the present invention; FIG. 8 is a fourth embodiment of the solar cell module of the present invention. FIG. 9 is a schematic rear view of a solar cell according to a fifth preferred embodiment of the solar cell module of the present invention; FIG. 10 is a solar energy of the present invention; a sixth preferred embodiment of the battery module FIG. 11 is a schematic rear view of a solar cell according to a seventh preferred embodiment of the solar cell module of the present invention; and FIG. 12 is an eighth preferred embodiment of the solar cell module of the present invention. FIG. 13 is a schematic rear view of a solar cell according to a ninth preferred embodiment of the solar cell module of the present invention; and FIG. 14 is a tenth preferred embodiment of the solar cell module of the present invention. A rear view of a solar cell; and FIG. 15 is a schematic rear view of a solar cell according to an eleventh preferred embodiment of the solar cell module of the present invention.

Claims (14)

A solar cell comprising: a substrate having an opposite light receiving surface and a back surface; a front electrode on the light receiving surface; a passivation layer on the back surface and having an opening; and a back electrode located at the And contacting the back surface of the substrate through the opening portion; wherein the opening portion has a first opening pattern extending along a circumference of the substrate and being annular, and a number surrounded by the first opening pattern and having a number a second opening pattern of the sub-opening, the first opening pattern having a distance from the periphery of the substrate of less than 5 mm. The solar cell according to claim 1, wherein the first opening pattern is a ring-shaped annular opening. The solar cell of claim 1, wherein the periphery of the substrate comprises two opposite first sides, and two opposite sides located between the two first sides, The first opening pattern has two first pattern portions respectively adjacent to the two first side edges, and two second pattern portions respectively adjacent to the two second side edges, the two first pattern portions being straight lines An opening, the two second pattern portions are dotted openings. The solar cell according to claim 1, wherein the plurality of sub-openings of the second opening pattern are linear openings parallel to each other. According to the solar cell of claim 4, wherein The width of the first opening pattern is greater than the width of the plurality of sub-openings of the second opening pattern. The solar cell of claim 1, wherein the plurality of sub-openings of the second opening pattern are island-shaped openings. A solar cell comprising: a substrate, a single crystal germanium substrate having opposite light receiving surfaces and a back surface, four spaced long sides, and four short sides interleaved with the four long sides a front surface electrode on the light receiving surface; a passivation layer on the back surface and having an opening; and a back surface electrode on the passivation layer and contacting the back surface of the substrate via the opening portion; wherein the opening The portion includes a first opening pattern and a second opening pattern, the first opening pattern including four first linear openings respectively adjacent to the four short sides of the substrate, and each of the first linear openings The distance between the portion and the corresponding short side is less than 8 mm, and the second opening pattern includes a plurality of sub-openings, and the shortest distance of each of the short sides of each of the four short sides is greater than 8 mm. The solar cell of claim 7, wherein the distance between any portion of each of the first linear openings and the corresponding short side is less than 5 mm, each of the sub-openings and the four short sides The shortest distance of any short side is greater than 5mm. The solar cell of claim 7, wherein the first opening pattern further comprises two opposite and four respectively along the substrate A second linear opening extending in two of the long sides, each second linear opening having a distance of less than 5 mm from the corresponding long side. The solar cell of claim 7, wherein the first opening pattern further comprises two second linear openings that are opposite and respectively extend along two of the four long sides of the substrate, Moreover, the width of each of the first linear openings is greater than the width of each of the second linear openings. The solar cell according to claim 7, wherein the plurality of sub-openings of the second opening pattern are linear openings parallel to each other. The solar cell of claim 11, wherein a width of the first linear opening of the first opening pattern is greater than a width of the plurality of sub-openings of the second opening pattern. The solar cell of claim 7, wherein the plurality of sub-openings of the second opening pattern are island-shaped openings. A solar cell module comprising: a first plate and a second plate disposed opposite to each other; and a solar cell according to any one of claims 1 to 13 arranged on the first plate And the second plate; and a packaging material between the first plate and the second plate, and wrapped around the plurality of solar cells.