CN106449834A - Back surface gate line structure of double-sided PERC solar cell piece - Google Patents

Abstract

The invention discloses a double-sided PERC solar cell rear grid line structure; it includes several rows of back electrodes and grid line parts, the back electrode includes several sub-electrode segments, and the symmetrical center line of two adjacent sub-electrode segments is set as A Line, the main grid part is arranged between the end of the sub-electrode segment and the adjacent A line, the symmetrical center line of the two adjacent back electrodes is set as the B line, and the intersection point of the A line and the B line is set as the C point, An auxiliary part is provided between the end of the sub-electrode segment and the adjacent point C; the setting of the auxiliary part enables the point far away from the sub-electrode segment to collect current through the auxiliary part, and the collected current can be directly transmitted to the back On the electrode, the problem of being transmitted to the back electrode by the main grid part as an intermediary is avoided. The double-sided PERC solar cell back grid line structure of the present invention increases the output current of the solar cell module and improves the output of the solar cell module. power.

Description

A double-sided PERC solar cell rear grid structure

technical field

The invention relates to the technical field of solar cells, in particular to a grid line structure on the back of a double-sided PERC solar cell.

Background technique

Conventional fossil fuels are being exhausted day by day. Among all sustainable energy sources, solar energy is undoubtedly one of the cleanest, most common and most potential alternative energy sources. Among all solar cells, silicon solar cells are one of the most widely used solar cells. This is due to the extremely abundant reserves of silicon materials in the earth's crust. At the same time, silicon solar cells have excellent electrical properties compared to other types of solar cells. properties and mechanical properties.

PERC cells (Passivated emitter rear contact solar cells), that is, passivated emitter rear contact solar cells. In the prior art, the back grid line structure of double-sided PERC solar cells includes a back electrode (silver grid line) and a local back electric field (aluminum grid line). When the solar cell module is working, the current generated in the silicon material is collected by the aluminum grid wire and then converged to the silver back electrode, and then flows into the next solar cell through the soldering strip. As shown in FIG. 4 , the number of back electrodes in the prior art is the number of busbars of the cell, the shape of the back electrodes is strips or segmented strips, and the shape of the aluminum back electric field is strips. The existing strip-shaped back electrode consumes a lot of silver paste and has a high cost. When the segmented strip-shaped back electrode is used, since the welding strip and the aluminum cannot form a good contact, after welding, it is far away from the silver back electrode. It is more difficult to collect the current, which leads to the blackening of the component EL and the increase of the series resistance.

Contents of the invention

The object of the present invention is to provide a double-sided PERC solar cell rear grid line structure, which increases the output current of the solar cell assembly and improves the output power of the solar cell assembly.

For reaching this purpose, the present invention adopts following technical scheme:

A grid line structure on the back of a double-sided PERC solar cell, including several columns of back electrodes and grid line parts, the back electrode includes a number of sub-electrode segments arranged at intervals along the interconnection direction, and in the same column of back electrodes, two adjacent sub-electrodes The symmetrical center line of the segment is set as line A, and the line A is perpendicular to the back electrode. A main gate part is arranged between the end of the sub-electrode segment and the adjacent line A, and two adjacent sub-electrode segments pass through the gap between them. The two busbars are electrically connected, the symmetrical center line of two adjacent rows of back electrodes is set as line B, line B is parallel to the back electrode, the intersection point of line A and line B is set as point C, and the end of the sub-electrode segment An auxiliary part is provided between the part and the adjacent point C. The setting of the auxiliary part enables the point away from the sub-electrode segment to collect current through the auxiliary part, and the collected current can be directly transmitted to the back electrode, avoiding the problem of the main grid part as an intermediary and then transmitted to the back electrode .

The interconnection direction refers to the direction in which the batteries in the battery string are electrically connected.

Preferably, several columns of back electrodes are parallel to each other. Further preferably, the back electrode is parallel to one side of the double-sided PERC solar cell sheet.

Preferably, the lengths of the rear electrodes in several columns are equal.

Wherein, the width of the auxiliary part gradually decreases from the end of the sub-electrode segment to the direction of point C.

Wherein, the centerline of the busbar part and the centerline of the back electrode are parallel to each other.

Preferably, the busbar part is provided with a coverage area overlapping with the sub-electrode segments, and the height of the coverage area along the interconnection direction is 0.05-5 mm. Further preferably, the height of the footprint along the interconnection direction is 0.1-2 mm.

Wherein, the busbar part is a linear structure with equal width.

Wherein, the width of the main gate part gradually decreases from the end of the sub-electrode segment to the direction of the A line. The current density at the end of the main grid part far away from the sub-electrode segment is small, and the current density at the end of the main grid part close to the sub-electrode segment is relatively large, and the width of the main grid part gradually decreases from the end of the sub-electrode segment to the direction of the A line. Small, that is, the width of the main gate part matches the current density, which solves the problem of current transmission and avoids the phenomenon of EL blackening.

Wherein, the width of the sub-electrode segment is smaller than or equal to the width of the main gate portion.

Wherein, a sub-gate part is arranged between the two main grid parts at two ends of the sub-electrode segment, and the sub-gate part is located outside the sub-electrode segment.

Wherein, the width of the sub-electrode segment is larger than the width of the main grid part, the intersection point of the extension line of the side line perpendicular to the interconnection direction of the sub-electrode segment and the outer side line of the adjacent auxiliary part is set as point D, and the width of the sub-electrode segment is smaller than the corresponding The length between two adjacent D points.

Wherein, the width of the sub-electrode segment is smaller than the maximum width of the main gate portion.

Preferably, the line width of the busbar portion is 2mm˜10mm. Further preferably, the line width of the busbar part is 2.5mm˜5mm.

Preferably, the line width of the end of the busbar part close to the sub-electrode segment is 3mm-10mm, and the line width of the end of the busbar part away from the sub-electrode segment is 0.05mm-5mm. Further preferably, the line width of the end of the busbar portion close to the sub-electrode segment is 3 mm to 6 mm, and the line width of the end of the bus bar portion away from the sub-electrode segment is 0.1 mm to 3 mm.

Preferably, the line width of the grid line part is 0.05mm-0.5mm. Further preferably, the line width of the grid line portion is 0.1 mm˜0.4 mm.

Preferably, the line width of the end of the auxiliary part close to the sub-electrode segment is 2 mm to 10 mm, and the line width of the end of the auxiliary part away from the sub-electrode segment is 0.05 mm to 1 mm. Further preferably, the line width of the end of the auxiliary part close to the sub-electrode segment is 3 mm to 5 mm, and the line width of the end of the auxiliary part away from the sub-electrode segment is 0.1 mm to 0.6 mm.

Preferably, the total area of the back electrodes is 0.1%-3% of the total area of the back surfaces of the double-sided PERC solar cells. Further preferably, the total area of the back electrode is 0.2%-2% of the total area of the back of the double-sided PERC solar cell.

Wherein, the back electrode is back silver, and the main gate part, the auxiliary part and the grid line part are all back aluminum.

Beneficial effects of the present invention: a double-sided PERC solar cell back grid line structure, including several columns of back electrodes and grid line parts, the back electrodes include several sub-electrode segments arranged at intervals along the interconnection direction, in the same column of back electrodes, The symmetrical center line of two adjacent sub-electrode segments is set as A line, and the A line is perpendicular to the back electrode. The segments are electrically connected through the two busbars between them, the symmetrical center line of two adjacent columns of back electrodes is set as line B, line B is parallel to the back electrode, and the intersection point of line A and line B is set as point C , an auxiliary part is provided between the end of the sub-electrode segment and the adjacent point C. The setting of the auxiliary part enables the point away from the sub-electrode segment to collect current through the auxiliary part, and the collected current can be directly transmitted to the back electrode, avoiding the problem of the main grid part as an intermediary and then transmitted to the back electrode According to the present invention, the double-sided PERC solar cell rear grid line structure increases the output current of the solar cell module and improves the output power of the solar cell module.

Description of drawings

FIG. 1 is a schematic structural diagram of Embodiment 1 of the present invention.

Fig. 2 is a schematic structural diagram of Embodiment 2 of the present invention.

Fig. 3 is a schematic structural diagram of Embodiment 3 of the present invention.

Fig. 4 is a schematic structural diagram of Comparative Example 1 of the present invention.

The reference signs are as follows:

1-grid line part; 2-sub-electrode segment; 3-main grid part; 31-coverage area; 4-auxiliary part; 5-sub-gate part.

detailed description

The technical solution of the present invention will be further described below with reference to FIG. 1 to FIG. 4 and through specific embodiments.

Embodiment one

As shown in Figure 1, a grid line structure on the back of a double-sided PERC solar cell, Figure 1 is a schematic diagram of a unit cell, including several rows of back electrodes and grid line parts 1, and the back electrodes include several grid lines arranged at intervals along the interconnection direction In the sub-electrode segment 2, in the same row of back electrodes, the symmetrical centerlines of two adjacent sub-electrode segments 2 are set as A line, and the A line is perpendicular to the back electrode, and the end of the sub-electrode segment 2 is connected to the adjacent A line. A main grid portion 3 is arranged between them, and two adjacent sub-electrode segments 2 are electrically connected through the two main grid portions 3 between them. The symmetrical center line of two adjacent columns of back electrodes is set as the B line, and the B line and the The back electrodes are parallel, the intersection of A line and B line is set as point C, and an auxiliary part 4 is arranged between the end of the sub-electrode segment 2 and the adjacent point C.

In this embodiment, several columns of back electrodes are parallel to each other, and the back electrodes are parallel to one side of the double-sided PERC solar cell sheet. In other embodiments, several rows of back electrodes may also be offset, and may not be parallel to the sides of the double-sided PERC solar cells.

In this embodiment, the lengths of the rear electrodes in several rows are equal. In other embodiments, back electrodes with different lengths can also be set as required.

In this embodiment, the width of the auxiliary portion 4 gradually decreases from the end of the sub-electrode segment 2 toward the point C.

In this embodiment, the centerline of the busbar part 3 and the centerline of the back electrode are parallel to each other.

In this embodiment, the busbar portion 3 is provided with a coverage area 31 overlapping with the sub-electrode segments 2 , and the height of the coverage area 31 along the interconnection direction is 1 mm. In other embodiments, the height of the coverage area 31 along the interconnection direction can be selected as required. For example, the height of the coverage area 31 along the interconnection direction may be 0.05mm, 0.1mm, 0.5mm, 1.5mm, 2mm, 3mm, 4mm or 5mm.

In this embodiment, the main gate portion 3 is a linear structure with equal width. The width of the sub-electrode segment 2 is less than or equal to the width of the main grid part 3 , and a sub-gate part 5 is arranged between the two main grid parts 3 at both ends of the sub-electrode segment 2 , and the sub-gate part 5 is located outside the sub-electrode segment 2 .

In this embodiment, the line width of the busbar part 3 is 3 mm. In other embodiments, the line width of the main gate portion 3 can be selected as required. For example, the line width of the busbar portion 3 may be 2mm, 2.5mm, 4mm, 5mm, 8mm or 10mm, etc. FIG.

In this embodiment, the line width of the gate line portion 1 is 0.3 mm. In other embodiments, the line width of the gate line portion 1 can be selected as required. For example, the line width of the grid line part 1 may be 0.05 mm, 0.1 mm, 0.2 mm, 0.4 mm or 0.5 mm, etc. FIG.

In this embodiment, the line width of the end of the auxiliary part 4 close to the sub-electrode segment 2 is 3 mm, and the line width of the end of the auxiliary part 4 away from the sub-electrode segment 2 is 0.3 mm. In other embodiments, the line widths of the ends of the auxiliary part 4 close to and far from the sub-electrode segment 2 can be selected according to needs. For example, the line width of the end of the auxiliary part 4 close to the sub-electrode segment 2 can be 2 mm, 4 mm, 5 mm, 6 mm, 8 mm or 10 mm; the line width of the end of the auxiliary part 4 away from the sub-electrode segment 2 can be 0.05 mm, 0.1 mm, 0.2mm, 0.4mm, 0.6mm, 0.8mm or 1mm etc.

In this embodiment, the total area of the back electrodes is 1% of the total area of the back of the double-sided PERC solar cells. In other embodiments, the percentage of the total area of the back electrodes to the total area of the back of the double-sided PERC solar cell can be selected according to needs. For example, the total area of the back electrodes may be 0.1%, 0.2%, 0.5%, 2% or 3% of the total area of the backside of the double-sided PERC solar cell.

In this embodiment, the back electrode is back silver, and the main grid part 3 , auxiliary part 4 and grid line part 1 are all back aluminum. In other embodiments, the back electrode, the main grid portion 3 and the grid line portion 1 can be selected from other materials as required.

Embodiment two

As shown in Figure 2, a grid line structure on the back of a double-sided PERC solar cell, Figure 2 is a schematic diagram of a unit cell, including several columns of back electrodes and grid line parts 1, and the back electrodes include several grid lines arranged at intervals along the interconnection direction In the sub-electrode segment 2, in the same row of back electrodes, the symmetrical centerlines of two adjacent sub-electrode segments 2 are set as A line, and the A line is perpendicular to the back electrode, and the end of the sub-electrode segment 2 is connected to the adjacent A line. A main grid portion 3 is arranged between them, and two adjacent sub-electrode segments 2 are electrically connected through the two main grid portions 3 between them. The symmetrical center line of two adjacent columns of back electrodes is set as the B line, and the B line and the The back electrodes are parallel, the intersection of A line and B line is set as point C, and an auxiliary part 4 is arranged between the end of the sub-electrode segment 2 and the adjacent point C.

In this embodiment, several columns of back electrodes are parallel to each other, and the back electrodes are parallel to one side of the double-sided PERC solar cell sheet. In other embodiments, several rows of back electrodes may also be offset, and may not be parallel to the sides of the double-sided PERC solar cells.

In this embodiment, the lengths of the rear electrodes in several rows are equal. In other embodiments, back electrodes with different lengths can also be set as required.

In this embodiment, the width of the auxiliary portion 4 gradually decreases from the end of the sub-electrode segment 2 toward the point C.

In this embodiment, the centerline of the busbar part 3 and the centerline of the back electrode are parallel to each other.

In this embodiment, the busbar portion 3 is provided with a coverage area 31 overlapping with the sub-electrode segments 2 , and the height of the coverage area 31 along the interconnection direction is 1 mm. In other embodiments, the height of the coverage area 31 along the interconnection direction can be selected as required. For example, the height of the coverage area 31 along the interconnection direction may be 0.05mm, 0.1mm, 0.5mm, 1.5mm, 2mm, 3mm, 4mm or 5mm.

In this embodiment, the main gate portion 3 is a linear structure with equal width. The width of the sub-electrode segment 2 is greater than the width of the main grid part 3, the intersection of the extension line of the side line perpendicular to the interconnection direction of the sub-electrode segment 2 and the outer side line of the adjacent auxiliary part 4 is set as point D, and the sub-electrode segment 2 The width is smaller than the length between two adjacent D points.

In this embodiment, the line width of the busbar portion 3 is 2 mm˜10 mm. In this embodiment, the line width of the busbar portion 3 is 3 mm. In other embodiments, the line width of the main gate portion 3 can be selected as required. For example, the line width of the busbar portion 3 may be 2mm, 2.5mm, 4mm, 5mm, 8mm or 10mm, etc. FIG.

In this embodiment, the line width of the gate line portion 1 is 0.3 mm. In other embodiments, the line width of the gate line portion 1 can be selected as required. For example, the line width of the grid line part 1 may be 0.05 mm, 0.1 mm, 0.2 mm, 0.4 mm or 0.5 mm, etc. FIG.

In this embodiment, the line width of the end of the auxiliary part 4 close to the sub-electrode segment 2 is 3 mm, and the line width of the end of the auxiliary part 4 away from the sub-electrode segment 2 is 0.3 mm. In other embodiments, the line widths of the ends of the auxiliary part 4 close to and far from the sub-electrode segment 2 can be selected according to needs. For example, the line width of the end of the auxiliary part 4 close to the sub-electrode segment 2 can be 2 mm, 4 mm, 5 mm, 6 mm, 8 mm or 10 mm; the line width of the end of the auxiliary part 4 away from the sub-electrode segment 2 can be 0.05 mm, 0.1 mm, 0.2mm, 0.4mm, 0.6mm, 0.8mm or 1mm etc.

In this embodiment, the total area of the back electrodes is 1.5% of the total area of the back surfaces of the double-sided PERC solar cells. In other embodiments, the percentage of the total area of the back electrodes to the total area of the back of the double-sided PERC solar cell can be selected according to needs. For example, the total area of the back electrodes may be 0.1%, 0.2%, 0.5%, 2% or 3% of the total area of the backside of the double-sided PERC solar cell.

In this embodiment, the back electrode is back silver, and the main grid part 3 , auxiliary part 4 and grid line part 1 are all back aluminum. In other embodiments, the back electrode, the main grid portion 3 and the grid line portion 1 can be selected from other materials as required.

Embodiment Three

As shown in Figure 3, a grid line structure on the back of a double-sided PERC solar cell, Figure 3 is a schematic diagram of a unit cell, including several rows of back electrodes and grid line parts 1, and the back electrodes include several grid lines arranged at intervals along the interconnection direction In the sub-electrode segment 2, in the same row of back electrodes, the symmetrical centerlines of two adjacent sub-electrode segments 2 are set as A line, and the A line is perpendicular to the back electrode, and the end of the sub-electrode segment 2 is connected to the adjacent A line. A main grid portion 3 is arranged between them, and two adjacent sub-electrode segments 2 are electrically connected through the two main grid portions 3 between them. The symmetrical center line of two adjacent columns of back electrodes is set as the B line, and the B line and the The back electrodes are parallel, the intersection of A line and B line is set as point C, and an auxiliary part 4 is arranged between the end of the sub-electrode segment 2 and the adjacent point C.

In this embodiment, several columns of back electrodes are parallel to each other, and the back electrodes are parallel to one side of the double-sided PERC solar cell sheet. In other embodiments, several rows of back electrodes may also be offset, and may not be parallel to the sides of the double-sided PERC solar cells.

In this embodiment, the lengths of the rear electrodes in several rows are equal. In other embodiments, back electrodes with different lengths can also be set as required.

In this embodiment, the width of the auxiliary portion 4 gradually decreases from the end of the sub-electrode segment 2 toward the point C.

In this embodiment, the centerline of the busbar part 3 and the centerline of the back electrode are parallel to each other.

In this embodiment, the busbar portion 3 is provided with a coverage area 31 overlapping with the sub-electrode segments 2 , and the height of the coverage area 31 along the interconnection direction is 1 mm. In other embodiments, the height of the coverage area 31 along the interconnection direction can be selected as required. For example, the height of the coverage area 31 along the interconnection direction may be 0.05mm, 0.1mm, 0.5mm, 1.5mm, 2mm, 3mm, 4mm or 5mm.

In this embodiment, the width of the main gate portion 3 gradually decreases from the end of the sub-electrode segment 2 to the direction of the A line. The width of the sub-electrode segment 2 is smaller than the maximum width of the main grid part 3 , and a sub-gate part 5 is arranged between the two main grid parts 3 at both ends of the sub-electrode segment 2 , and the sub-gate part 5 is located outside the sub-electrode segment 2 .

In this embodiment, the line width of the end of the busbar part 3 close to the sub-electrode segment 2 is 5 mm, and the line width of the end of the busbar part 3 away from the sub-electrode segment 2 is 2 mm. In other embodiments, the line widths of the ends of the main gate portion 3 close to and far from the sub-electrode segments 2 can be selected according to requirements. For example, the line width of the end of the busbar part 3 close to the sub-electrode segment 2 can be 3 mm, 4 mm, 6 mm, 8 mm or 10 mm, etc., and the line width of the end of the bus bar part 3 away from the sub-electrode segment 2 can be 0.05 mm, 0.1 mm , 1mm, 3mm, 4mm or 5mm, etc.

In this embodiment, the line width of the gate line portion 1 is 0.3 mm. In other embodiments, the line width of the gate line portion 1 can be selected as required. For example, the line width of the grid line part 1 may be 0.05 mm, 0.1 mm, 0.2 mm, 0.4 mm or 0.5 mm, etc. FIG.

In this embodiment, the line width of the end of the auxiliary part 4 close to the sub-electrode segment 2 is 3 mm, and the line width of the end of the auxiliary part 4 away from the sub-electrode segment 2 is 0.3 mm. In other embodiments, the line widths of the ends of the auxiliary part 4 close to and far from the sub-electrode segment 2 can be selected according to needs. For example, the line width of the end of the auxiliary part 4 close to the sub-electrode segment 2 can be 2 mm, 4 mm, 5 mm, 6 mm, 8 mm or 10 mm; the line width of the end of the auxiliary part 4 away from the sub-electrode segment 2 can be 0.05 mm, 0.1 mm, 0.2mm, 0.4mm, 0.6mm, 0.8mm or 1mm etc.

In this embodiment, the total area of the back electrodes is 1% of the total area of the back of the double-sided PERC solar cells. In other embodiments, the percentage of the total area of the back electrodes to the total area of the back of the double-sided PERC solar cell can be selected according to needs. For example, the total area of the back electrodes may be 0.1%, 0.2%, 0.5%, 2% or 3% of the total area of the backside of the double-sided PERC solar cell.

In this embodiment, the back electrode is back silver, and the main grid part 3 , auxiliary part 4 and grid line part 1 are all back aluminum. In other embodiments, the back electrode, the main grid portion 3 and the grid line portion 1 can be selected from other materials as required.

Comparative example one

As shown in FIG. 4 , it is a grid line structure on the back side of a double-sided PERC solar cell in the prior art, and FIG. 4 is a schematic diagram of a unit cell. The only difference between Comparative Example 1 and Example 1 is that Comparative Example 1 is not provided with the auxiliary part 4 in Example 1, and the others are the same as Example 1.

The output powers of the three embodiments of the present invention were compared with those of Comparative Example 1, and the test results are shown in Table 1.

Table 1

Pmax(W) Embodiment one 298.5 Embodiment two 297.5 Embodiment Three 299.0 Comparative example one 296.0

It can be seen from Table 1 that, compared with the existing double-sided PERC solar battery, the output power of the double-sided PERC solar battery of the present invention is significantly improved.

The above content is only a preferred embodiment of the present invention. For those of ordinary skill in the art, according to the idea of the present invention, there will be changes in the specific implementation and application scope. limits.

Claims (14)

1. A double-sided PERC solar cell back grid line structure, comprising several rows of back electrodes and grid line parts (1), is characterized in that, the back electrode comprises several sub-electrode sections (2) arranged at intervals along the interconnection direction ), in the same row of the back electrodes, the symmetrical centerlines of the two adjacent sub-electrode segments (2) are set as line A, and the line A is perpendicular to the back electrode, and the sub-electrode segments ( 2) and the adjacent A line is provided with a main grid part (3), and the two adjacent sub-electrode segments (2) pass through the two main grid parts between them (3) Electrically connected, the symmetric center line of the two adjacent columns of the back electrodes is set as the B line, the B line is parallel to the back electrode, and the intersection point of the A line and the B line is set as C point, an auxiliary part (4) is provided between the end of the sub-electrode segment (2) and the adjacent point C. 2. The double-sided PERC solar cell back grid line structure according to claim 1, characterized in that, the width of the auxiliary part (4) is from the end of the sub-electrode segment (2) to the point C direction gradually decreases. 3. The double-sided PERC solar cell back grid structure according to claim 1, characterized in that the center line of the main grid part (3) and the center line of the back electrode are parallel to each other. 4. The double-sided PERC solar cell back grid line structure according to claim 1, characterized in that, the main grid part (3) is provided with a coverage area (31) overlapping with the sub-electrode segment (2) ), the height of the coverage area (31) along the interconnection direction is 0.05-5mm. 5 . The back grid line structure of double-sided PERC solar cells according to any one of claims 1 to 4 , characterized in that the main grid part ( 3 ) is a linear structure with equal width. 6 . 6. The double-sided PERC solar cell back grid line structure according to any one of claims 1 to 4, characterized in that, the width of the main grid part (3) is from the end of the sub-electrode segment (2) The portion gradually decreases toward the direction of the A line. 7. The double-sided PERC solar cell back grid line structure according to claim 5, characterized in that the width of the sub-electrode segment (2) is less than or equal to the width of the main grid portion (3). 8. The double-sided PERC solar cell back grid line structure according to claim 7, characterized in that a sub-grid is arranged between the two main grid parts (3) at both ends of the sub-electrode segment (2) part (5), the sub-gate part (5) is located outside the sub-electrode segment (2). 9. The double-sided PERC solar cell back grid wire structure according to claim 5, characterized in that, the width of the sub-electrode segment (2) is greater than the width of the main grid part (3), and the sub-electrode The intersection of the extension line of the sideline perpendicular to the interconnection direction of the segment (2) and the sideline outside the adjacent auxiliary part (4) is set as point D, and the width of the sub-electrode segment (2) is smaller than that of the two adjacent The length between the D points. 10. The double-sided PERC solar cell back grid line structure according to claim 6, characterized in that the width of the sub-electrode segment (2) is smaller than the maximum width of the main grid part (3). 11. The double-sided PERC solar cell back grid line structure according to claim 5, characterized in that, the line width of the main grid part (3) is 2mm-10mm. 12. The double-sided PERC solar cell back grid line structure according to claim 6, characterized in that, the line width of the end of the main grid part (3) close to the sub-electrode segment (2) is 3 mm to 10 mm , the line width of the end of the busbar portion (3) away from the sub-electrode segment (2) is 0.05mm˜0.5mm. 13. The double-sided PERC solar cell back grid wire structure according to claim 1, characterized in that the line width of the auxiliary part (4) near the end of the sub-electrode segment (2) is 2 mm to 10 mm, The line segment of the auxiliary part (4) away from the end of the sub-electrode segment (2) is 0.05mm-1mm. 14. The back grid line structure of double-sided PERC solar cells according to claim 1, characterized in that, the back electrode is back silver, and the main grid part (3), the auxiliary part (4) and the The grid lines (1) are all aluminum backs.