Back contact photovoltaic cell and photovoltaic module

Abstract

The utility model relates to the photovoltaic field, and discloses a back contact photovoltaic cell piece and a photovoltaic module. The electrode structure comprises additional main grid lines, connecting grid lines, first thin grid lines, second thin grid lines, first main grid lines and second main grid lines, wherein the first thin grid lines and the second thin grid lines are alternately distributed in the first direction, and the first main grid lines and the second main grid lines are alternately distributed in the second direction. The additional main grid lines are located at the edge of the battery piece in the second direction, the edge main grid lines adjacent to the additional main grid lines comprise grid line segments distributed at intervals in the first direction, and the polarity of the edge main grid lines is opposite to that of the additional main grid lines; the edge main grid line is a first main grid line or a second main grid line; one end of the connecting grid line is electrically connected with the additional main grid line and penetrates through the interval area between the adjacent grid line segments, and the other end of the connecting grid line is electrically connected with the main grid line which is closest to the additional main grid line and has the same polarity with the additional main grid line; the thin grid lines which are located between the additional main grid lines and the edge main grid lines and have opposite polarity with the edge main grid lines are electrically connected with the additional main grid lines. The conversion efficiency of the battery is improved.

Description

Technical Field

[0001] The present application relates to the photovoltaic field, and in particular to a back-contact photovoltaic cell and a photovoltaic module. Background Art

[0002] Photovoltaic cells can convert light energy into electrical energy. When the photovoltaic cells are exposed to light, the substrate absorbs photons to generate electron-hole pairs. The hole pairs are separated under the action of the built-in electric field of the PN junction, and are led out through the emitter and back field of the photovoltaic cell, and are finally collected by the electrodes arranged on the substrate and transmitted to the outside.

[0003] The emitter and base of the back-contact photovoltaic cell are both arranged on the back, and the positive and negative fine grid lines are distributed in a forked finger shape and are electrically connected to the main grid lines of the same polarity. The current is transmitted from the fine grid lines to the main grid lines, and then conducted out by welding the welding points and welding strips. Since the outermost welding points of the back-contact photovoltaic cell need to be kept at a certain distance from the edge of the cell, the fine grid lines with opposite polarity to the outermost main grid lines between the outermost welding points and the edge of the cell cannot be connected to the main grid lines with the same polarity, and thus the current in the area where the fine grid lines with opposite polarity to the outermost main grid lines between the outermost welding points and the edge of the cell are located cannot be collected, resulting in low efficiency of the back-contact photovoltaic cell.

[0004] Therefore, how to improve the efficiency of back-contact photovoltaic cells should be a technical problem that needs to be solved urgently by technical personnel in this field. Utility Model Content

[0005] The purpose of this application is to provide a back-contact photovoltaic cell and photovoltaic module to improve cell efficiency.

[0006] In order to solve the above technical problems, the present application provides a back-contact photovoltaic cell sheet, including an electrode structure;

[0007] The electrode structure includes additional main grid lines, connecting grid lines, first fine grid lines and second fine grid lines alternately distributed along a first direction, and first main grid lines and second main grid lines alternately distributed along a second direction, wherein the first direction is perpendicular to the second direction;

[0008] The additional main grid line is located at the edge of the back-contact photovoltaic cell in the second direction, the edge main grid line adjacent to the additional main grid line includes grid line segments spaced apart along the first direction, the edge main grid line has opposite polarity to the additional main grid line; the edge main grid line is the first main grid line or the second main grid line;

[0009] One end of the connecting grid line is electrically connected to the additional main grid line and passes through the spacing area between adjacent grid line segments, and the other end is electrically connected to the main grid line closest to the additional main grid line and having the same polarity;

[0010] A thin gate line located between the additional main gate line and the edge main gate line and having a polarity opposite to that of the edge main gate line is electrically connected to the additional main gate line.

[0011] As an implementable embodiment, it also includes:

[0012] An insulating portion covers the connecting gate line, wherein the covering area of ​​the insulating portion includes an area between adjacent gate line segments.

[0013] As an implementation method, the width of the additional main grid line ranges from 0.2 mm to 1 mm.

[0014] As an implementation method, the distance between adjacent gate line segments ranges from 0.5 mm to 3 mm.

[0015] As an implementation method, the width of the connecting grid lines ranges from 0.2 mm to 1 mm.

[0016] As an implementable embodiment, it also includes:

[0017] Passivation layers located on the front and back of the back contact photovoltaic cell.

[0018] As an implementable embodiment, it also includes:

[0019] The anti-reflection layer is located on the surface of the passivation layer on the front side of the back contact photovoltaic cell.

[0020] As an implementation method, the anti-reflection layer includes a stack of a silicon nitride layer and a silicon oxide layer.

[0021] As an implementable embodiment, it also includes:

[0022] An auxiliary connection portion, wherein the auxiliary connection portion is located between a welding point on the first main grid line and the first thin grid line, and / or the auxiliary connection portion is located between a welding point on the second main grid line and the second thin grid line.

[0023] The present application also provides a photovoltaic module, which includes any one of the above-mentioned back-contact photovoltaic cells.

[0024] A back-contact photovoltaic cell provided in the present application comprises an electrode structure; the electrode structure comprises an additional main grid line, a connecting grid line, a first fine grid line and a second fine grid line alternately distributed along a first direction, and a first main grid line and a second main grid line alternately distributed along a second direction, wherein the first direction is perpendicular to the second direction; the additional main grid line is located at the edge of the back-contact photovoltaic cell in the second direction, and the edge main grid line adjacent to the additional main grid line comprises grid line segments spaced apart along the first direction, and the edge main grid line has an opposite polarity to the additional main grid line; the edge main grid line is the first main grid line or the second main grid line; one end of the connecting grid line is electrically connected to the additional main grid line and passes through the spacing area between adjacent grid line segments, and the other end is electrically connected to the main grid line closest to the additional main grid line and having the same polarity; the fine grid line located between the additional main grid line and the edge main grid line and having an opposite polarity to the edge main grid line is electrically connected to the additional main grid line.

[0025] It can be seen that in the back-contact photovoltaic cell of the present application, the electrode structure includes, in addition to the first main grid line, the second main grid line, the first thin grid line, and the second thin grid line, an additional main grid line and a connecting grid line. The additional main grid line is located at the edge of the cell, and the thin grid line between the additional main grid line and the edge main grid line and with the opposite polarity to the edge main grid line is electrically connected to the additional main grid line, that is, the current in the area where the thin grid line between the additional main grid line and the edge main grid line and with the opposite polarity to the edge main grid line is located can be collected and aggregated to the additional main grid line. The connecting grid line connects the additional main grid line with the main grid line that is closest to the additional main grid line and has the same polarity, so the current on the additional main grid line is transmitted to the main grid line that is closest to the additional main grid line and has the same polarity through the connecting grid line, and then transported to the outside of the battery. Since the current in the area where the thin grid line between the additional main grid line and the edge main grid line and with the opposite polarity to the edge main grid line is located can be collected, the conversion efficiency of the battery is improved.

[0026] In addition, the present application also provides a photovoltaic module having the above advantages. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the embodiments of the present application or the technical solutions of the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0028] Figure 1 It is a schematic diagram of the back structure of a back-contact photovoltaic cell in the related art;

[0029] Figure 2A schematic diagram of a back contact photovoltaic cell surface structure provided in an embodiment of the present application Figure 1 ;

[0030] Figure 3 A schematic diagram of a back contact photovoltaic cell surface structure provided in an embodiment of the present application Figure 2 ;

[0031] In the figure, 1. positive fine grid line, 2. negative fine grid line, 3. negative main grid line, 4. positive main grid line, 5. first fine grid line, 6. second fine grid line, 7. grid line segment, 8. second main grid line, 9. additional main grid line, 10. connecting grid line, 11. auxiliary connecting part, 12. welding point, 13. insulating part. DETAILED DESCRIPTION

[0032] In order to enable those skilled in the art to better understand the present application, the present application is further described in detail below in conjunction with the accompanying drawings and specific implementation methods. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in the field without making creative work are within the scope of protection of the present application.

[0033] In the following description, many specific details are set forth to facilitate a full understanding of the present invention, but the present invention may also be implemented in other ways different from those described herein, and those skilled in the art may make similar generalizations without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0034] In the related art, the back structure of the back contact photovoltaic cell is as follows: Figure 1 As shown, positive electrode fine grid lines 1, negative electrode fine grid lines 2, positive electrode main grid lines 4 and negative electrode main grid lines 3 are provided.

[0035] The outermost welding point of the back-contact photovoltaic cell needs to maintain a certain distance from the edge of the cell, so that the fine grid line with opposite polarity to the outermost main grid line between the outermost welding point and the edge of the cell cannot be connected to the main grid line with the same polarity. As a result, the current in the area where the fine grid line with opposite polarity to the outermost main grid line between the outermost welding point and the edge of the cell is located cannot be collected, resulting in low efficiency of the back-contact photovoltaic cell.

[0036] In view of this, the present application provides a back contact photovoltaic cell, please refer to Figure 2 , including an electrode structure;

[0037] The electrode structure includes an additional main grid line 9, a connecting grid line 10, first fine grid lines 5 and second fine grid lines 6 alternately distributed along a first direction, and first main grid lines and second main grid lines 8 alternately distributed along a second direction, wherein the first direction is perpendicular to the second direction;

[0038] The additional main grid line 9 is located at the edge of the back contact photovoltaic cell in the second direction, the edge main grid line adjacent to the additional main grid line 9 includes grid line segments 7 spaced apart along the first direction, and the edge main grid line has opposite polarity to the additional main grid line 9; the edge main grid line is the first main grid line or the second main grid line 8;

[0039] One end of the connecting grid line 10 is electrically connected to the additional main grid line 9 and passes through the spacing area between the adjacent grid line segments 7, and the other end is electrically connected to the main grid line closest to the additional main grid line 9 and having the same polarity;

[0040] The thin gate line located between the additional main gate line 9 and the edge main gate line and having a polarity opposite to that of the edge main gate line is electrically connected to the additional main gate line 9 .

[0041] It should be noted that the back contact photovoltaic cell also includes a substrate, a tunneling oxide layer and a doped polysilicon layer located on the back of the substrate. The doping type of the doped polysilicon layer is opposite to that of the substrate. The substrate can be a P-type substrate or an N-type substrate, and correspondingly, the doped polysilicon layer is an N-type doped polysilicon layer or a P-type doped polysilicon layer.

[0042] In order to improve the light absorption efficiency of the back-contact photovoltaic cell and improve the cell efficiency, as an implementation method, the front side of the substrate is a velvet surface formed by texturing.

[0043] The function of the additional main grid line 9 is to collect carriers on the thin grid lines between the additional main grid line 9 and the edge main grid lines and having opposite polarity to the edge main grid lines. The polarity of the additional main grid line 9 is opposite to the polarity of the adjacent edge main grid lines. For example, when the edge main grid line adjacent to the additional main grid line 9 is a positive main grid line, that is, the grid line segment 7 is a positive main grid line, the additional main grid line 9 is a negative main grid line; when the edge main grid line adjacent to the additional main grid line 9 is a negative main grid line, the additional main grid line 9 is a positive main grid line.

[0044] The width of the additional busbar line 9 is in the range of 0.2 mm to 1 mm. For example, the width of the additional busbar line 9 can be 0.2 mm, 0.4 mm, 0.6 mm, 0.8 mm, 1 mm, etc.

[0045] The width of the additional main grid line 9 is related to the width between the additional main grid line 9 and the edge main grid line. The width between the additional main grid line 9 and the edge main grid line is usually about 10 mm, that is, the thin grid line between the additional main grid line 9 and the edge main grid line and with the opposite polarity to the edge main grid line needs to collect the carriers in this area. If the width of the additional main grid line 9 is set too narrow, it will affect the collection of carriers in this area. If the width of the additional main grid line 9 is set too wide, it will consume more grid line raw materials and increase the production cost.

[0046] In one implementation of the present application, the distance between adjacent gate line segments 7 ranges from 0.5 mm to 3 mm, for example, the distance between the gate line segments 7 can be 0.5 mm, 1 mm, 1.5 mm, 2 mm, 25 mm, 3 mm, etc. If the distance between the gate line segments 7 is too large or too small, it will affect the area ratio of the P region and the N region in the back contact photovoltaic cell, thereby affecting the efficiency of the back contact photovoltaic cell.

[0047] The function of the connecting grid line 10 is to transmit the current collected on the additional main grid line 9 to the main grid line which is closest to the additional main grid line 9 and has the same polarity as the additional main grid line 9 .

[0048] As an implementation method, the width of the connecting grid line 10 ranges from 0.2 mm to 1 mm. For example, the width of the connecting grid line 10 can be 0.2 mm, 0.4 mm, 0.6 mm, 0.8 mm, 1 mm, etc.

[0049] The current on the connecting grid line 10 is the same as that on the additional main grid line 9 , and the width of the connecting grid line 10 may be equal to the width of the additional main grid line 9 .

[0050] It should be pointed out that the polarities of the first thin gate line 5 , the second thin gate line 6 , the first main gate line and the second main gate line 8 are not limited in the present application.

[0051] In one possible implementation of the present application, the first thin gate line 5 is a positive thin gate line, the first main gate line is a positive main gate line, the second thin gate line 6 is a negative thin gate line, and the second main gate line 8 is a negative main gate line.

[0052] Please refer to Figure 2 When the first fine grid line 5 is a positive fine grid line, the first main grid line is a positive main grid line, the second fine grid line 6 is a negative fine grid line, and the second main grid line 8 is a negative main grid line, the additional main grid line 9 is a negative type grid line, and the edge main grid line adjacent to the additional main grid line 9 is a positive main grid line.

[0053] In another possible implementation of the present application, the first thin gate line 5 is a positive thin gate line, the first main gate line is a positive main gate line, the second thin gate line 6 is a negative thin gate line, and the second main gate line 8 is a negative main gate line.

[0054] Please refer to Figure 2 When the first fine grid line 5 is a negative fine grid line, the first main grid line is a negative main grid line, the second fine grid line 6 is a positive fine grid line, and the second main grid line 8 is a positive main grid line, the additional main grid line 9 is a positive type grid line, and the edge main grid line adjacent to the additional main grid line 9 is a negative main grid line.

[0055] The back electrode structure of the back contact photovoltaic cell is designed to be bilaterally symmetrical. Figure 2 Only the left part of the electrode structure is shown, and the right side is symmetrical to the left side.

[0056] The first main grid line and the second main grid line 8 respectively include a welding point 12, the first fine grid line 5 corresponding to the welding point 12 on the first main grid line is connected to the welding point 12, and the second fine grid line 6 corresponding to the welding point 12 on the second main grid line 8 is connected to the welding point 12. The first fine grid line 5 and the second fine grid line 6 are printed, and in order to ensure that the fine grid line is electrically connected to the welding point 12 on the main grid line with the same polarity, in one embodiment of the present application, it also includes:

[0057] The auxiliary connection part 11 is located between the welding point 12 on the first main grid line and the first thin grid line 5, and / or the auxiliary connection part 11 is located between the welding point 12 on the second main grid line 8 and the second thin grid line 6.

[0058] In the back-contact photovoltaic cell of this embodiment, the electrode structure includes, in addition to the first main grid line, the second main grid line 8, the first thin grid line 5, and the second thin grid line 6, an additional main grid line 9 and a connecting grid line 10. The additional main grid line 9 is located at the edge of the cell, and the thin grid lines between the additional main grid line 9 and the edge main grid lines and with opposite polarity to the edge main grid lines are electrically connected to the additional main grid line 9, that is, the current in the area where the thin grid lines between the additional main grid line 9 and the edge main grid lines and with opposite polarity to the edge main grid lines are located can be collected and aggregated to the additional main grid line 9. The connecting grid line 10 connects the additional main grid line 9 with the main grid lines closest to the additional main grid line 9 and with the same polarity, so the current on the additional main grid line 9 is transmitted to the main grid lines closest to the additional main grid line 9 and with the same polarity through the connecting grid line 10, and then transmitted to the outside of the battery. Since the current in the area where the thin grid lines between the additional main grid line 9 and the edge main grid lines and with opposite polarity to the edge main grid lines are located can be collected, the conversion efficiency of the battery is improved.

[0059] Please refer to Figure 3 Based on the above embodiments, in one embodiment of the present application, the back contact photovoltaic cell further comprises:

[0060] The insulating portion 13 covers the connecting gate line 10 , and the covering area of ​​the insulating portion 13 includes the area between the adjacent gate line segments 7 .

[0061] The insulating portion 13 may be insulating glue.

[0062] The covering area of ​​the insulating portion 13 may be only the area where the connecting gate line 10 is located between adjacent gate line segments 7 , or may be larger than the area where the connecting gate line 10 is located between adjacent gate line segments 7 .

[0063] By providing the insulating portion 13 on the connecting grid line 10, it is possible to prevent the connecting grid line 10 from being connected to the grid line segment 7 with opposite polarity when welding the welding strip, thereby preventing a short circuit from occurring and affecting the battery efficiency.

[0064] Based on the above embodiments, in one embodiment of the present application, please refer to Figure 3 , the back contact photovoltaic cell also includes:

[0065] Passivation layers are located on the front and back of the back-contact photovoltaic cell to improve the efficiency of the back-contact photovoltaic cell.

[0066] The front passivation layer is located on the surface of the substrate, and the front passivation layer can be an aluminum oxide layer; the back passivation layer is located on the surface of the doped polysilicon layer, and the back passivation layer can be a stack of an aluminum oxide layer, a silicon nitride layer and a silicon oxide layer, wherein the aluminum oxide layer is located on the surface of the doped polysilicon layer, the silicon nitride layer is located on the surface of the aluminum oxide layer, and the silicon oxide layer is located on the surface of the silicon nitride layer.

[0067] In order to reduce the reflection of incident light and improve the efficiency of the back-contact photovoltaic cell, based on the above embodiment, in one embodiment of the present application, the back-contact photovoltaic cell further includes:

[0068] The anti-reflection layer is located on the surface of the passivation layer on the front side of the back contact photovoltaic cell.

[0069] As an implementation method, the anti-reflection layer includes a stack of a silicon nitride layer and a silicon oxide layer, wherein the silicon nitride layer is located on the surface of the front passivation layer, and the silicon oxide layer is located on the surface of the silicon nitride layer.

[0070] The following is an introduction to the manufacturing process of the back-contact photovoltaic cell in this application using a specific case.

[0071] Step 1: Select a P-type single crystal silicon wafer as a substrate, with a resistivity of 0.5-3Ω·cm and a thickness of 150±10um, and pre-clean the silicon wafer to remove the damaged layer;

[0072] Step 2: using LPCVD (low pressure chemical vapor deposition) equipment to deposit a tunnel oxide layer on the back of the silicon wafer;

[0073] Step 3, diffusing phosphorus on both sides of the silicon wafer;

[0074] Step 4: Make and graph the mark points on the back;

[0075] Step 5, polishing the silicon wafer to form a P region, exposing the P region silicon substrate;

[0076] Step 6: Perform double-sided tubular thermal oxidation annealing on the silicon wafer to form a protective layer to protect the back side pattern;

[0077] Step 7: Use a chain acid etching process to remove the front oxide layer of the silicon wafer using an HF solution to expose the silicon substrate for subsequent texturing;

[0078] Step 8: groove-type velveting to form a velvet surface;

[0079] Step 9: Use ALD (atomic layer deposition) equipment to prepare double-sided aluminum oxide on the front and back sides of the silicon wafer;

[0080] Step 10: Use PECVD (plasma enhanced chemical vapor deposition) equipment to perform double-sided silicon nitride passivation, first depositing the front side and then the back side;

[0081] Step 11, using nanosecond pulse laser to open holes in some areas;

[0082] Step 12: Printing paste, prepared as Figure 2 Metal electrode structure of the figure shown.

[0083] The present application also provides a photovoltaic module, which includes the back-contact photovoltaic cell sheet described in any of the above embodiments.

[0084] A plurality of back-contact photovoltaic cells are connected in series to form a cell string, and a plurality of cell strings form a cell layer. A photovoltaic module includes a back substrate, a back adhesive film layer, a cell layer, a front adhesive film layer and a front substrate stacked in sequence from bottom to top.

[0085] The various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referenced to each other.

[0086] The above is a detailed introduction to the back-contact photovoltaic cell and photovoltaic module provided by the present application. Specific examples are used in this article to illustrate the principles and implementation methods of the present application. The description of the above embodiments is only used to help understand the scheme and core ideas of the present application. It should be pointed out that for ordinary technicians in this technical field, without departing from the principles of the present application, several improvements and modifications can be made to the present application, and these improvements and modifications also fall within the scope of protection of the present application.

Claims

1. A back contact photovoltaic cell, characterized in that: including an electrode structure; The electrode structure includes additional main grid lines, connecting grid lines, first fine grid lines and second fine grid lines alternately distributed along a first direction, and first main grid lines and second main grid lines alternately distributed along a second direction, wherein the first direction is perpendicular to the second direction; The additional main grid line is located at the edge of the back-contact photovoltaic cell in the second direction, the edge main grid line adjacent to the additional main grid line includes grid line segments spaced apart along the first direction, the edge main grid line has opposite polarity to the additional main grid line; the edge main grid line is the first main grid line or the second main grid line; One end of the connecting grid line is electrically connected to the additional main grid line and passes through the spacing area between adjacent grid line segments, and the other end is electrically connected to the main grid line closest to the additional main grid line and having the same polarity; A thin gate line located between the additional main gate line and the edge main gate line and having a polarity opposite to that of the edge main gate line is electrically connected to the additional main gate line.

2. The back contact photovoltaic cell according to claim 1, characterized in that: Also includes: An insulating portion covers the connecting gate line, wherein the covering area of ​​the insulating portion includes an area between adjacent gate line segments.

3. The back contact photovoltaic cell according to claim 1, characterized in that: The width of the additional main grid line ranges from 0.2 mm to 1 mm.

4. The back contact photovoltaic cell according to claim 1, characterized in that: The distance between adjacent grid line segments ranges from 0.5 mm to 3 mm.

5. The back contact photovoltaic cell according to claim 1, characterized in that: The width of the connecting grid line ranges from 0.2 mm to 1 mm.

6. The back contact photovoltaic cell according to claim 1, characterized in that: Also includes: Passivation layers located on the front and back of the back contact photovoltaic cell.

7. The back contact photovoltaic cell according to claim 6, characterized in that: Also includes: The anti-reflection layer is located on the surface of the passivation layer on the front side of the back contact photovoltaic cell.

8. The back contact photovoltaic cell according to claim 7, characterized in that: The anti-reflection layer includes a stacked layer of a silicon nitride layer and a silicon oxide layer.

9. The back contact photovoltaic cell according to any one of claims 1 to 8, characterized in that: Also includes: An auxiliary connection portion, wherein the auxiliary connection portion is located between a welding point on the first main grid line and the first thin grid line, and / or the auxiliary connection portion is located between a welding point on the second main grid line and the second thin grid line.

10. A photovoltaic module, characterized in that: The photovoltaic module comprises the back-contact photovoltaic cell sheet according to any one of claims 1 to 9.

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