MAIN-GATE-FREE AND HIGH-EFFICIENCY BACK-CONTACT SOLAR CELL MODULE, MAIN-GATE-FREE AND HIGH-EFFICIENCY BACK-CONTACT ASSEMBLY, AND PREPARATION PROCESS THEREOF

Abstract

The present application relates to the field of solar cells, and in particular to a main-gate-free and high-efficiency back-contact solar cell module, assembly, and a preparation process thereof. The main-gate-free and high-efficiency back-contact solar cell module comprises solar cells and an electrical connection layer, a backlight side of the solar cells having P-electrodes connected to a P-type doping layer and N-electrodes connected to an N-type doping layer, wherein the electrical connection layer comprises a number of small conductive gate lines, part of which are connected to the P-electrodes on the backlight side of the solar cells while the other part of which are connected to the N-electrodes on the backlight side of the solar cells; and, the small conductive gate lines are of a multi-section structure. The present application has the following beneficial effects: the usage of silver paste is decreased, and the cost is reduced; moreover. The arrangement of small conductive gate lines in a multi-section structure reduces the series resistance and the transmission distance of a filling factor, so that the efficiency is improved and the stress on the cells from the small conductive gate lines can be effectively reduced.

Claims

1. A main-gate-free and high-efficiency back-contact solar cell module, comprising solar cells and an electrical connection layer, a backlight side of the solar cells having P-electrodes connected to a P-type doping layer and N-electrodes connected to an N-type doping layer, wherein the electrical connection layer comprises a number of small conductive gate lines, part of which are connected to the P-electrodes on the backlight side of the solar cells while the other part of which are connected to the N-electrodes on the backlight side of the solar cells; and the small conductive gate lines are of a multi-section structure.

2. The main-gate-free and high-efficiency back-contact solar cell module according to claim 1, wherein the small conductive gate lines are interdigitally arranged in parallel.

3. The main-gate-free and high-efficiency back-contact solar cell module according to claim 1, wherein an insulating medium capable of preventing the electrodes from turning on is provided between the P-electrodes and the N-electrodes of the solar cells, between the electrodes in the doping layers of the cells and the small conductive gate lines or between the small conductive gate lines.

4. The main-gate-free and high-efficiency back-contact solar cell module according to claim 1, wherein the P-electrodes are dotted P-electrodes or linear P-electrodes, and the N-electrodes are dotted N-electrodes or linear N-electrodes; and, there are 2 to 17 dotted or linear electrodes interconnected by each conductive gate line.

5. The main-gate-free and high-efficiency back-contact solar cell module according to claim 4, wherein the diameter of the dotted P-electrodes is 0.2 mm to 1.5 mm, the distance between two adjacent dotted P-electrodes connected to a same small conductive gate line is 0.7 mm to 10 mm, and the width of the linear P-electrodes is 0.4 mm to 1.5 mm; the diameter of the dotted N-electrodes is 0.2 mm to 1.5 mm, the distance between two adjacent dotted N-electrodes connected on a same small conductive gate line is 0.7 mm to 10 mm, and the width of the linear N-electrodes is 0.4 mm to 1.5 mm; and, the total number of the dotted P-electrodes and the dotted N-electrodes is 1000 to 40000.

6. The main-gate-free and high-efficiency back-contact solar cell module according to claim 4, wherein the dotted electrodes or linear electrodes are made of any one of sliver paste, conductive adhesive, conductive polymeric material or tin solder.

7. The main-gate-free and high-efficiency back-contact solar cell module according to claim 1, wherein the small conductive gate lines are made of sintered silver paste or leads, and each of the small conductive gate lines has a width of 10 μm to 300 μm and a width-to-height ratio of 1:0.01 to 1:1.

8. The main-gate-free and high-efficiency back-contact solar cell module according to claim 4, wherein there are 2, 3, 5, 7, 9, 11, 13, 15 or 17 dotted or linear electrodes interconnected by each conductive gate line.

9. The main-gate-free and high-efficiency back-contact solar cell module according to any one of claims 1 to 8, wherein leads are provided in the electrical connection layer; the leads connect a number of small conductive gate lines connected to the P-electrodes or connect the P-electrodes; and the leads connect a number of small conductive gate lines connected to the N-electrodes or connect the N-electrodes.

10. The main-gate-free and high-efficiency back-contact solar cell module according to claim 9, wherein the leads are vertically connected to a center line of the number of small conductive gate lines.

11. The main-gate-free and high-efficiency back-contact solar cell module according to claim 9, wherein the leads and the small conductive gate lines form “”-shaped structures or comb-finger structures, which are arranged crosswise.

12. The main-gate-free and high-efficiency back-contact solar cell module according to claim 9, wherein the surfaces of the leads are plated with anti-oxidation plating material or coated with a conductive adhesive; the anti-oxidation plating material is any one of tin, tin-lead alloy, tin-bismuth alloy or tin-lead-silver alloy; the plating layer or conductive adhesive layer of the leads has a thickness of 5 μm to 50 μm; the conductive adhesive is a low-resistivity conductive adhesive that uses a conductive particle and a polymeric binder as main components; the conductive particle in the conductive adhesive is any one or more of gold, silver, copper, gold-plated nickel, silver-plated nickel or silver-plated copper, the shape of the conductive particles are any one of a spherical shape, a flake shape, an olivary shape or an acicular shape, and the particle size of the conductive particle is 0.01 μm to 5 μm; and, the polymeric binder in the conductive adhesive is any one or more of epoxy resin, polyurethane resin, acrylic resin or organic silicon resin, and the binder is thermosetting or photocureable.

13. The main-gate-free and high-efficiency back-contact solar cell module according to claim 9, wherein the electrical connection layer is provided with P-busbar electrodes and N-busbar electrodes, which are arranged on two sides of the electrical connection layer; and, the surface of the busbar electrodes has a concavo-convex shape.

14. The main-gate-free and high-efficiency back-contact solar cell module according to claim 3, wherein the insulating medium is a thermoplastic resin or a thermosetting resin, and the resin is any one or more of polyimide, polycaprolactam, polyolefin resin, epoxy resin, polyurethane resin, acrylic resin and organic silicon resin.

15. A main-gate-free and high-efficiency back-contact solar cell assembly, comprising fronting material, packaging material, a solar cell layer, packaging material and backing material, which are connected from top to bottom, wherein the solar cell layer comprises a number of solar cell modules, and the solar cell modules refer to the solar cell module according to any one of claims 1 to 14.

16. The main-gate-free and high-efficiency back-contact solar cell assembly according to claim 15, wherein the solar cell modules in the solar cell layer are connected via busbars arranged on two sides of an electrical connection layer.

17. The main-gate-free and high-efficiency back-contact solar cell assembly according to any one of claims 15 to 16, wherein the number of solar cells in the solar cell assembly is 1 to 120.

18. A method for preparing a main-gate-free and high-efficiency back-contact solar cell assembly, comprising the following steps: Step 1: connecting solar cell modules in series to form a solar cell layer, an electrical connection layer on a backlight side of each of the solar cell modules having a number of small conductive gate lines connected to P-electrodes and a number of small conductive gate lines connected to N-electrodes, the small conductive gate lines being of a multi-section structure; electrically connecting a number of leads to electrodes or small conductive gate lines of a first solar cell, and aligning a second solar cell with the first solar cell so that P-electrodes on the second solar cell and N-electrodes on the first solar cell are on a same lead; and, electrically connecting the leads to electrodes or small conductive gate lines of the second solar cell, and repeating the above operations to form a series connection structure, so as to form a solar cell layer; and Step 2: successively stacking and laminating fronting material, packaging material, the solar cell layer, packaging material and backing material to obtain a solar cell assembly.

19. The method for preparing a main-gate-free and high-efficiency back-contact solar cell assembly according to 18, wherein a solar cell string is prepared in accordance with the Step 1, and the solar cell string comprises at least one solar cell; and, busbar electrodes are arranged on two sides of the solar cell string, and the busbar electrodes are connected in series to form a solar cell layer.

20. The method for preparing a main-gate-free and high-efficiency back-contact solar cell assembly according to any one of claims 18 to 19, wherein a process for preparing the small conductive gate lines is as follows: printing silver paste on the solar cells in segments by screen printing, drying small gate lines of the solar cells having silver paste electrodes printed thereon, and sintering as a whole to obtain a solar cell module with a number of small conductive gate lines.

21. The method for preparing a main-gate-free and high-efficiency back-contact solar cell assembly according to any one of claims 18 to 19, wherein parameters for the laminating operation are set according to the vulcanizing properties of the packaging material; and, the packaging material is EVA and the parameters for the laminating operation are as follows: laminating 9 to 35 min at 120° C. to 180° C.

22. The method for preparing a main-gate-free and high-efficiency back-contact solar cell assembly according to any one of claims 18 to 19, wherein the solar cells and the leads in the Step 1 are electrically connected by coating conductive adhesive on a P-type doping layer and an N-type doping layer on the cells by screen printing; the conductive adhesive, when heated, can be solidified to form the P-electrodes and the N-electrodes; and, when heated, the leads and the P-electrodes or the N-electrodes come into Ohm contact by the conductive adhesive, and in this way, the leads and the cells are electrically connected; the solar cells and the leads are also electrically connected by plating low-melting-point material on the leads by a plating process; when heated, the leads and the P-type doping layer or the N-type doping layer are welded by the melting of the low-melting-point material to form the P-electrodes and the N-electrodes, and in this way the leads and the solar cells are electrically connected; and the low-melting-point material is any one of tin solder, tin-lead alloy, tin-bismuth alloy or tin-lead-silver alloy; and the solar cells and the leads can also be electrically connected by laser welding.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0052] FIG. 1 is a schematic view of the back side of a first dotted main-gate-free and high-efficiency back-contact solar cell (Embodiment 1);

[0053] FIG. 2 is a schematic view of the back side of a second dotted main-gate-free and high-efficiency back-contact solar cell (Embodiment 1);

[0054] FIG. 3 is a cross-sectional view of a lead (FIG. 3a is a cross-sectional view of a lead having a single material layer, FIG. 3b is a cross-sectional view of a lead having two material layers and FIG. 3c is a cross-sectional view of a lead having three material layers);

[0055] FIG. 4 is a schematic view of the series connection of dotted main-gate-free and high-efficiency back-contact solar cells (Embodiment 1);

[0056] FIG. 5 is a schematic view of the back side of a third dotted main-gate-free and high-efficiency back-contact solar cell (Embodiment 2);

[0057] FIG. 6 is a schematic view of the back side of a fourth dotted main-gate-free and high-efficiency back-contact solar cell (Embodiment 2);

[0058] FIG. 7 is a schematic view of the series connection of dotted main-gate-free and high-efficiency back-contact solar cells (Embodiment 2);

[0059] FIG. 8 is a schematic view of the back side of a linear main-gate-free and high-efficiency back-contact solar cell; and

[0060] FIG. 9 is a schematic view of a main-gate-free and high-efficiency back-contact solar cell assembly,

[0061] in which:

[0062] 1: solar cell; 2: dotted P-electrode; 21: linear P-electrode; 3: dotted N-electrode; 31: linear N-electrode; 4: small conductive gate lines between P-electrodes; 5: small conductive gate lines between N-electrodes; 6: insulating medium; 7: lead; 71: metal material such as copper, aluminum or steel; 72: metal material different from 1, such as aluminum or steel; 73: tin, tin-lead, tin-bismuth, or tin-lead-silver alloy solder; 8: first solar cell; 81: second solar cell; 9: third solar cell; 91: fourth solar cell; 10: P-busbar electrode; and, 11: N-busbar electrode.

DETAILED DESCRIPTION

[0063] The present application will be described below in detail by embodiments with references to the accompanying drawings. It is to be noted that the described embodiments are merely for understanding the present application and not intended to limit the present application.

Embodiment 1

[0064] Referring to FIGS. 1, 2 and 4, a main-gate-free and high-efficiency back-contact solar cell module is provided, comprising solar cells 1 and an electrical connection layer, a backlight side of the solar cells 1 having P-electrodes connected to a P-type doping layer and N-electrodes connected to an N-type doping layer, wherein the electrical connection layer comprises a number of small conductive gate lines, part of which are connected to the P-electrodes on the backlight side of the solar cells 1 while the other part of which are connected to the N-electrodes on the backlight side of the solar cells 1; and the small conductive gate lines are of a multi-section structure.

[0065] FIG. 1 shows a first main-gate-free and high-efficiency back-contact solar cell 8, wherein there are 15 rows of dotted P-electrodes 2 and 16 dotted P-electrodes 2 in each row, total 240 dotted P-electrodes 2; and, there are 16 rows of dotted N-electrodes 3 and 16 dotted N-electrodes 3 in each row, total 256 dotted N-electrodes 3. The diameter of the dotted P-electrodes 2 is 0.2 mm to 1.5 mm, and the distance between two adjacent dotted P-electrodes 2 connected to a same small conductive gate line is 0.7 mm to 10 mm. The diameter of the dotted N-electrodes 3 is 0.2 mm to 1.5 mm, and the distance between two adjacent dotted N-electrodes 3 connected to a same small conductive gate line is 0.7 mm to 10 mm. In this embodiment, preferably, the diameter of the dotted P-electrodes 2 is 0.9 mm, and the distance between two adjacent dotted P-electrodes 2 connected to a same small conductive gate line is 10 mm; and, the diameter of the dotted N-electrodes 3 is 0.8 mm, the distance between two adjacent dotted N-electrodes 3 connected to a same small conductive gate line is 10 mm, and the center distance between a connection line of the dotted P-electrodes 2 and a connection line of the dotted N-electrodes 3 is 10 mm. The small conductive gate lines are interdigitally arranged in parallel. The number of dotted electrodes interconnected by each conductive gate line may be 2, 3, 5, 7, 9, 11, 13, 15 or 17, preferably 5 in this embodiment. Every five dotted P-electrodes 2 are connected by the small conductive gate lines. The small conductive gate lines are made of sintered silver paste or leads, preferably sintered silver paste in this embodiment. Each of the small conductive gate lines has a width of 10 μm to 300 μm and a width-to-height ratio of 1:0.01 to 1:1. In this embodiment, preferably, each of the small conductive gate lines has a width of 30 μm. Three leftmost dotted N-electrodes 3 are connected by a small conductive gate line which is made of sintered silver paste and has a width of 30 μm. Five middle dotted N-electrodes 3 are also connected by a same small conductive gate line. Three rightmost dotted N-electrodes 3 are also connected by a same small conductive gate line. The conversion efficiency of the cell is 23.2%.

[0066] FIG. 2 shows a second main-gate-free and high-efficiency back-contact solar cell 81, wherein there are 15 rows of dotted N-electrodes 3 and 16 dotted N-electrodes 3 in each row, total 240 dotted N-electrodes 3; and, there are 16 rows of dotted P-electrodes 2 and 16 dotted P-electrodes 2 in each row, total 256 dotted P-electrodes 2. The diameter of the dotted P-electrodes 2 is 0.2 mm to 1.5 mm, and the distance between two adjacent dotted P-electrodes 2 connected to a same small conductive gate line is 0.7 mm to 10 mm. The diameter of the dotted N-electrodes 3 is 0.2 mm to 1.5 mm, and the distance between two adjacent dotted N-electrodes 3 connected to a same small conductive gate line is 0.7 mm to 10 mm. In this embodiment, preferably, the diameter of the dotted P-electrodes 2 is 0.9 mm, and the distance between two adjacent dotted P-electrodes 2 connected to a same small conductive gate line is 10 mm; and, the diameter of the dotted N-electrodes 3 is 0.8 mm, and the distance between two adjacent dotted N-electrodes 3 connected to a same small conductive gate line is 10 mm, and the center distance between a connection line of the dotted P-electrodes 2 and a connection line of the dotted N-electrodes 3 is 10 mm. The small conductive gate lines are interdigitally arranged in parallel. The number of dotted electrodes interconnected by each conductive gate line may be 2, 3, 5, 7, 9, 11, 13, 15 or 17, preferably 5 in this embodiment. Every five dotted N-electrodes 3 are connected by the small conductive gate lines. The small conductive gate lines are made of sintered silver paste or leads, preferably sintered silver paste in this embodiment. Each of the small conductive gate lines has a width of 10 μm to 300 μm and a width-to-height ratio of 1:0.01 to 1:1. In this embodiment, preferably, each of the small conductive gate lines has a width of 30 μm. Three leftmost dotted P-electrodes 2 are connected by a small conductive gate line which is made of sintered silver paste and has a width of 30 μm. Five middle dotted P-electrodes 2 are also connected by a same small conductive gate line. Three rightmost dotted P-electrodes 2 are also connected by a same small conductive gate line. The conversion efficiency of the cell is 23.4%. In this embodiment, since numerous dotted electrodes on the backlight side of the solar cell 1 are centralized properly, the difficulty of series connection between cells is reduced, and it is advantageous for industrial production.

[0067] FIG. 4 shows a back schematic view of the series connection of dotted main-gate-free and high-efficiency back-contact solar cells. Leads 7 are further provided on an electrical connection layer of the main-gate-free and high-efficiency back-contact solar cell module. The leads 7 connect a number of small conductive gate lines connected to the P-electrodes or connect the P-electrodes, and the leads 7 connect a number of small conductive gate lines connected to the N-electrodes or connect the N-electrodes. A number of adjacent dotted P-electrodes 2 or dotted N-electrodes 3 converge the current by the small conductive gate lines, and the collected current is exported by the leads 7. Preferably, the leads 7 are vertically connected to a center line of the number of small conductive gate lines. The leads 7 and the small conductive gate lines form “”-shaped structures or comb-finger structures, which are arranged crosswise. In the implementations of this embodiment, the amount of silver paste is reduced, and the cost is reduced. Moreover, the arrangement of small conductive gate lines in a multi-section structure reduces the series resistance and the transmission distance of the filling factor, so that the efficiency is improved and the stress on the cells from the leads 7 can be effectively reduced. In the present application, due to the presence of multiple “”-shaped structures, the stress is dispersed. Consequently, the stress on the cells from the leads 7 is reduced, and it is advantages for the thinning of cell silicon wafers.

[0068] Preferably, an insulating medium 6 capable of preventing the electrodes from turning on is provided between the P-electrodes and the N-electrodes on the backlight side of the solar cells 1, between the electrodes in the doping layers of the cells and the small conductive gate lines, between the small conductive gate lines or at junctions of the small conductive gate lines and the leads. The insulating medium 6 is a thermoplastic resin or a thermosetting resin. The resin is any one or two of polyimide, polycaprolactam, polyolefin resin, epoxy resin, polyurethane resin, acrylic resin and organic silicon resin. This resin, on one hand, can isolate the electrodes in the emitter region and the electrodes in the base region, and on the other hand, can bond the back-contact solar cells 1 and the packaging material together during the laminating operation.

[0069] In this embodiment, the leads 7 may be any one of FIG. 3. FIG. 3a shows a cross-sectional view of a lead having a single material layer, FIG. 3b shows a cross-sectional view of a lead having two material layers, and FIG. 3c shows a cross-sectional view of a lead having three material layers. The leads used in this embodiment are plated leads 7 having three structural layers, including an innermost layer of leads having a diameter of 0.8 mm, an intermediate copper layer having a thickness of 0.2 mm, and an outermost tin-plated layer having a thickness of 0.3 mm. The plated leads have a circular cross-section and a diameter of 1.3 mm.

[0070] Preferably, the surfaces of the leads 7 are plated with anti-oxidation plating material or coated with a conductive adhesive. The anti-oxidation plating material is any one of tin, tin-lead alloy, tin-bismuth alloy or tin-lead-silver alloy. The plating layer or conductive adhesive layer of the leads 7 has a thickness of 5 μm to 50 μm. The conductive adhesive is a low-resistivity conductive adhesive that uses a conductive particle and a polymeric binder as main components. The conductive particle in the conductive adhesive is any one or more of gold, silver, copper, gold-plated nickel, silver-plated nickel or silver-plated copper. The shape of the conductive particles is any one of a spherical shape, a flake shape, an olivary shape or an acicular shape, and the particle size of the conductive particle is 0.01 μm to 5 μm. The polymeric binder in the conductive adhesive is any one or two of epoxy resin, polyurethane resin, acrylic resin or organic silicon resin, and the binder is thermosetting or photocureable.

[0071] This embodiment further provides a main-gate-free and high-efficiency back-contact solar cell assembly, comprising fronting material, packaging material, a solar cell layer, packaging material and backing material, which are connected from top to bottom, wherein the solar cell layer comprises a number of solar cell modules, and the solar cell modules refer to the solar cell module according to the above embodiment.

[0072] A preparation method of the main-gate-free and high-efficiency back-contact solar cell assembly may be realized in the following ways. Firstly, solar cells 1 comprising a number of multi-section small gate lines are connected in series, then guided out by a group of P-busbar electrodes 10 and N-busbar electrodes 11, and laminated to obtain a solar cell assembly. Secondly, a solar cell electrical connection layer comprising of multi-section small gate lines and leads 7are formed on a single cell; leads 7 connected to the N-electrodes are connected to N-busbar electrodes 11, and leads 7 connected to the P-electrodes are connected to P-busbar electrodes 10; and, the busbar electrodes are connected in series and then laminated to obtain a solar cell assembly. Thirdly, multi-section small gate lines and leads 7 are formed on at least two cells to form a solar cell string comprising of multiple solar cells; leads 7 connected to the N-electrodes are connected to N-busbar electrodes 11, and leads 7 connected to the P-electrodes are connected to P-busbar electrodes 10; and, the busbar electrodes of the solar cell string are connected in series and then laminated to obtain a solar cell assembly. The specific process is as follows.

[0073] A method for preparing a main-gate-free and high-efficiency back-contact solar cell assembly is provided, comprising the following steps.

[0074] Step 1: Solar cell modules are connected in series to form a solar cell layer, an electrical connection layer on a backlight side of each of the solar cell modules having a number of small conductive gate lines connected to P-electrodes and a number of small conductive gate lines connected to N-electrodes, and the small conductive gate lines being of a multi-section structure; a number of leads 7 are electrically connected to P-electrodes or small conductive gate lines connected to the P-electrodes in a first solar cell 8, and a second solar cell 81 is aligned with the first solar cell 8 so that P-electrodes on the second solar cell 81 and N-electrodes on the first solar cell 8 are on a same lead 7; the leads 7 are electrically connected to N-electrodes or small conductive gate lines connected to the N-electrodes in the second solar cell 81 so that the second solar cell 81 and the first solar cell 8 are connected in series; and, the first solar cell 8 is placed, the leads 7 are electrically connected to the first solar cell 8, the above operations are repeated to form a series connection structure, so as to form a solar cell layer.

[0075] In this embodiment, the connection is realized by welding. In this embodiment, the leads 7 plated with low-melting-point material are used. The low-melting-point material is any one of tin solder, tin-lead alloy, tin-bismuth alloy or tin-lead-silver alloy. The plating process is any one of hot dip coating, electroplating or chemical plating, preferably tin solder electroplating in this embodiment. When heated, the leads 7 and the P-type doping layer or the N-type doping layer are welded by the melting of the low-melting-point material to form the P-electrodes and the N-electrodes, and in this way, the leads 7 and the solar cells are electrically connected. The temperature for welding is 300° C. to 400° C., preferably 300° C. in this embodiment. In the welding process, a heating pad can be used on the front side of the cell, in order to prevent the cell from breaking or hidden-cracking due to a big temperature difference on the two sides of the cell. The temperature of the heating pad is controlled at 40° C. to 80° C., preferably 70° C. in this embodiment. The heating way is any one or more of infrared radiation, heating by resistance wires or heating by hot wind, and the heating temperature is 150° C. to 500° C., preferably 300° C. in this embodiment. A process for preparing the small conductive gate lines is as follows: printing silver paste on the solar cells in segments by screen printing, drying small gate lines of the solar cells having silver paste electrodes printed thereon, and sintering as a whole to obtain a solar cell module with a number of small conductive gate lines.

[0076] In this embodiment, the connection may also be realized in the following way. The solar cells and the leads 7 in the Step 1 are electrically connected by coating conductive adhesive on a P-type doping layer and an N-type doping layer on the cells by screen printing; the conductive adhesive, when heated, can be solidified to form the P-electrodes and the N-electrodes; and, when heated, the leads 7 and the P-electrodes or the N-electrodes come into Ohm contact by the conductive adhesive, and in this way, the leads 7 and the cells are electrically connected.

[0077] The solar cells and the leads 7 can also be electrically connected by laser welding.

[0078] Step 2: The manufactured solar cell layers are connected in series by using conventional and general busbars having a cross-sectional area of 5×0.22 mm. The number of the solar cells is selected as desired. In this embodiment, 32 solar cells are selected. Glass, EVA, the solar cell layer, EVA and backing material are successively stacked, and the appearance inspection is performed, wherein the well-stacked module is put into a laminating press for lamination, and parameters for the laminating operation are set according to the vulcanizing properties of the EVA, usually, laminating for 16 min at 145° C. At last, a metal frame and a terminal box are mounted on the laminated module, and then power test and appearance inspection are performed. Hence, the solar cell assembly is obtained.

[0079] The above back-contact assembly having 32 solar cells has the following power parameters:

[0080] open-circuit voltage: Uoc (V) 22.52;

[0081] short-circuit current: Isc (A) 9.33;

[0082] working voltage: Ump (V) 17.35;

[0083] working current: Imp (A) 9.22;

[0084] maximum power: Pmax (W) 159.97; and

[0085] filling factor: 76.13%.

[0086] A method for preparing a main-gate-free and high-efficiency back-contact solar cell assembly is provided, comprising the following steps.

[0087] Step 1: Solar cell modules are connected in series to form a solar cell layer, an electrical connection layer on a backlight side of each of the solar cell modules having a number of small conductive gate lines connected to P-electrodes and a number of small conductive gate lines connected to N-electrodes, and the small conductive gate lines being of a multi-section structure; a number of parallel leads 7 are straightened and then electrically connected to P-electrodes or small conductive gate lines connected to the P-electrodes in a first solar cell 8, and a second solar cell 81 is aligned with the first solar cell 8 so that P-electrodes on the second solar cell 81 and N-electrodes on the first solar cell 8 are on a same lead 7; the leads 7 are electrically connected to N-electrodes or small conductive gate lines connected to the N-electrodes in the second solar cell 81 so that the second solar cell 81 and the first solar cell 8 are connected in series; the first solar cell 8 is placed, the leads 7 are electrically connected to the first solar cell 8, and the above operations are repeated to form a series connection structure of 10 solar cells; N-busbar electrodes 11 and P-busbar electrodes 10 are provided on two sides of the solar cell string; and, the P-busbar electrodes 10 and the N-busbar electrodes 11 are connected in series to form a solar cell layer.

[0088] Step 2: A back-contact solar cell is manufactured, having six strings of solar cells, each string having ten solar cells, total sixty solar cells. Glass, EVA, the solar cell layers, EVA and backing material are successively stacked, and the appearance inspection is performed, wherein the well-stacked module is put into a laminating press for lamination, and parameters for the laminating operation are set according to the vulcanizing properties of the EVA, usually, laminating for 35 min at 120° C. At last, a metal frame and a terminal box are mounted on the laminated module, and then power test and appearance inspection are performed. Hence, a cell assembly is obtained.

[0089] The above back-contact assembly having 60 solar cells has the following power parameters:

[0090] open-circuit voltage: Uoc (V) 41.81;

[0091] short-circuit current: Isc (A) 9.31;

[0092] working voltage: Ump (V) 32.97;

[0093] working current: Imp (A) 9.12;

[0094] maximum power: Pmax (W) 300.68; and

[0095] filling factor: 77.26%.

Embodiment 2

[0096] Referring to FIGS. 5, 6 and 7, a main-gate-free and high-efficiency back-contact solar cell module is provided, comprising at least one solar cell 1, an electrical connection layer comprising of leads 7 and small conductive gate lines. A backlight side of a silicon substrate of the solar cell 1 has P-electrodes connected to a P-type doping layer and N-electrodes connected to an N-type doping layer. The electrical connection layer on the backlight side of the solar cell 1 is provided with a number of small conductive gate lines connected to the P-electrodes and a number of small conductive gate lines connected to the N-electrodes. The small conductive gate lines are of a multi-section structure. An insulating medium 6 capable of preventing the small conductive gate lines and the leads 7 from turning on is provided at junctions of the small conductive gate lines and the leads 7.

[0097] FIG. 5 shows a third main-gate-free and high-efficiency back-contact solar cell 9, wherein there are 15 rows of dotted P-electrodes 2 and 15 dotted P-electrodes 2 in each row, total 225 dotted P-electrodes 2; and, there are 15 rows of dotted N-electrodes 3 and 15 dotted N-electrodes 3, total 225 dotted N-electrodes 3. The diameter of the dotted P-electrodes 2 is 0.2 mm to 1.5 mm, and the distance between two adjacent dotted P-electrodes 2 connected to a same small conductive gate line is 0.7 mm to 10 mm. The diameter of the dotted N-electrodes 3 is 0.2 mm to 1.5 mm, and the distance between two adjacent dotted N-electrodes 3 connected to a same small conductive gate line is 0.7 mm to 10 mm. In this embodiment, preferably, the diameter of the dotted P-electrodes 2 is 1.5 mm, and the distance between two adjacent dotted P-electrodes 2 connected to a same small conductive gate line is 5 mm; and, the diameter of the dotted N-electrodes 3 is 1.5 mm, the distance between two adjacent dotted N-electrodes 3 connected to a same small conductive gate line is 5 mm, and the center distance between a connection line of the dotted P-electrodes 2 and a connection line between the dotted N-electrodes 3 is 5 mm. The small conductive gate lines are interdigitally arranged in parallel. The number of dotted electrodes interconnected by each conductive gate line may be 2, 3, 5, 7, 9, 11, 13, 15 or 17, preferably 3, 5 or 7 in this embodiment. Every five dotted P-electrodes 2 are connected by the small conductive gate lines. The small conductive gate lines are made of sintered silver paste or leads, preferably small conductive gate lines in this embodiment. Each of the small conductive gate lines has a width of 10 μm to 300 μm and a width-to-height ratio of 1:0.01 to 1:1. In this embodiment, preferably, each of the small conductive gate lines has a width of 300 μm. Seven leftmost dotted N-electrodes 3 are connected by a small conductive gate line which is made of sintered silver paste and has a width of 300 μm. Five middle dotted N-electrodes 3 are also connected by a same small conductive gate line. Three rightmost dotted N-electrodes 3 are also connected by a same small conductive gate line. An insulating medium 6 is further provided on the cell, and the conversion efficiency of the cell is 23.2%.

[0098] FIG. 6 shows a fourth main-gate-free and high-efficiency back-contact solar cell 91, wherein there are 15 rows of dotted P-electrodes 2 and 15 dotted P-electrodes 2 in each row, total 225 dotted P-electrodes 2; and, there are 15 rows of dotted N-electrodes 3 and 15 dotted N-electrodes 3, total 225 dotted N-electrodes 3. The diameter of the dotted P-electrodes 2 is 0.2 mm to 1.5 mm, and the distance between two adjacent dotted P-electrodes 2 connected to a same small conductive gate line is 0.7 mm to 10 mm. The diameter of the dotted N-electrodes 3 is 0.2 mm to 1.5 mm, and the distance between two adjacent dotted N-electrodes 3 connected to a same small conductive gate line is 0.7 mm to 10 mm. In this embodiment, preferably, the diameter of the dotted P-electrodes 2 is 1.5 mm, and the distance between two adjacent dotted P-electrodes 2 connected to a same small conductive gate line is 5 mm; and, the diameter of the dotted N-electrodes 3 is 1.5 mm, the distance between two adjacent dotted N-electrodes 3 connected to a same small conductive gate line is 5 mm, and the center distance between a connection line of the dotted P-electrodes 2 and a connection line between the dotted N-electrodes 3 is 5 mm. The small conductive gate lines are interdigitally arranged in parallel. The number of dotted electrodes interconnected by each conductive gate line may be 2, 3, 5, 7, 9, 11, 13, 15 or 17, preferably 3, 5 or 7 in this embodiment. Every five dotted N-electrodes 3 are connected by the small conductive gate lines. The small conductive gate lines are made of sintered silver paste or leads, preferably small conductive gate lines in this embodiment. Each of the small conductive gate lines has a width of 10 μm to 300 μm and a width-to-height ratio of 1:0.01 to 1:1. In this embodiment, preferably, each of the small conductive gate lines has a width of 300 μm. Seven leftmost dotted P-electrodes 2 are connected by a small conductive gate line which is made of sintered silver paste and has a width of 300 μm. Five middle dotted P-electrodes 2 are also connected by a same small conductive gate line. Three rightmost dotted P-electrodes 2 are also connected by a same small conductive gate line. An insulating medium 6 is further provided on the cell, and the conversion efficiency of the cell is 23.2%.

[0099] FIG. 7 shows a back schematic view of the series connection of dotted main-gate-free and high-efficiency back-contact solar cells. Leads 7 are further provided on an electrical connection layer of the main-gate-free and high-efficiency back-contact solar cell module. The leads 7 connect a number of small conductive gate lines connected to the P-electrodes or connect the P-electrodes, and the leads 7 connect a number of small conductive gate lines connected to the N-electrodes or connect the N-electrodes. A number of adjacent dotted P-electrodes 2 or dotted N-electrodes 3 converge the current by the small conductive gate lines, and the collected current is exported by the leads 7. Preferably, the leads 7 are vertically connected to a center line of the number of small conductive gate lines. The leads 7 and the small conductive gate lines form “”-shaped structures or comb-finger structures, which are arranged crosswise. The junctions of the small conductive gate lines and the leads 7 are electrically insulated by the insulating medium 6.

[0100] This embodiment further provides a main-gate-free and high-efficiency back-contact solar cell assembly, comprising fronting material, packaging material, a solar cell layer, packaging material and backing material, which are connected from top to bottom, wherein the solar cell layer comprises a number of solar cell modules, and the solar cell module refer to the above solar cell module.

[0101] A method for preparing a main-gate-free and high-efficiency back-contact solar cell assembly is provided, comprising the following steps.

[0102] Step 1: Solar cell modules are connected in series to form a solar cell layer, an electrical connection layer on a backlight side of each of the solar cell modules having a number of small conductive gate lines connected to P-electrodes and a number of small conductive gate lines connected to N-electrodes, and the small conductive gate lines being of a multi-section structure; a number of leads 7 are electrically connected to P-electrodes or small conductive gate lines connected to the P-electrodes in a third solar cell 9, and a fourth solar cell 91 is aligned with the third solar cell 9 so that P-electrodes on the fourth solar cell 91 and N-electrodes on the third solar cell 9 are on a same lead 7; the leads 7 are electrically connected to N-electrodes or small conductive gate lines connected to the N-electrodes in the fourth solar cell 91 so that the fourth solar cell 91 and the third solar cell 9 are connected in series; and, the third solar cell 9 is placed, the leads 7 are electrically connected to the third solar cell 9, the above operations are repeated to form a series connection structure, so as to form a solar cell layer.

[0103] In this embodiment, the connection is realized by welding. In this embodiment, the leads 7 plated with low-melting-point material are used. The low-melting-point material is any one of tin solder, tin-lead alloy, tin-bismuth alloy or tin-lead-silver alloy. The plating process is any one of hot dip coating, electroplating or chemical plating, preferably tin solder electroplating in this embodiment. When heated, the leads 7 and the P-type doping layer or the N-type doping layer are welded by the melting of the low-melting-point material to form the P-electrodes and the N-electrodes, and in this way the leads 7 and the solar cells are electrically connected. The temperature for welding is 300° C. to 400° C., preferably 350° C. in this embodiment. In the welding process, a heating pad can be used on the front side of the cell, in order to prevent the cell from breaking or hidden-cracking due to a big temperature difference on the two sides of the cell. The temperature of the heating pad is controlled at 40° C. to 80° C., preferably 40° C. in this embodiment. The heating way is any one or more of infrared radiation, heating by resistance wires or heating by hot wind, and the heating temperature is 150° C. to 500° C., preferably 150° C. in this embodiment. A process for preparing the small conductive gate lines is as follows: printing silver paste on the solar cells in segments by screen printing, drying small gate lines of the solar cells having silver paste electrodes printed thereon, and sintering as a whole to obtain a solar cell module with a number of small conductive gate lines. The small conductive gate lines connect three, five or seven points, as shown in FIG. 7.

[0104] Step 2: The manufactured solar cell layers are connected in series by using conventional and general busbars having a cross-sectional area of 5×0.22 mm. The number of the solar cells is selected as desired. In this embodiment, 32 solar cells are selected. Glass, EVA, the solar cell layer, EVA and backing material are successively stacked, and the appearance inspection is performed, wherein the well-stacked module is put into a laminating press for lamination, and parameters for the laminating operation are set according to the vulcanizing properties of the EVA, usually, laminating for 9 min at 180° C. At last, a metal frame and a terminal box are mounted on the laminated module, and then power test and appearance inspection are performed. Hence, a solar cell assembly is obtained, as shown in FIG. 9.

[0105] The above back-contact assembly having 32 solar cells has the following power parameters:

[0106] open-circuit voltage: Uoc (V) 22.25;

[0107] short-circuit current: Isc (A) 9.25;

[0108] working voltage: Ump (V) 17.27;

[0109] working current: Imp (A) 9.08;

[0110] maximum power: Pmax (W) 156.78; and

[0111] filling factor: 76.18%.

[0112] Similarly, the dotted electrodes of the solar cells in this embodiment can be replaced with linear electrodes. A main difference lies in that junctions of the small conductive gate lines and the linear electrodes need to be insulated by an insulating medium 6. FIG. 8 shows a main-gate-free and high-efficiency back-contact solar cell, wherein there are 10 rows of linear P-electrodes 21 and 10 rows of linear N-electrodes 31. The width of the linear P-electrodes 21 is 0.4 mm to 1.5 mm, and the width of the linear N-electrodes 31 is 0.4 mm to 1.5 mm. The small conductive gate lines are interdigitally arranged in parallel. The number of linear electrodes interconnected by each conductive gate line may be 2, 3, 5, 7, 9, 11, 13, 15 or 17, preferably 2, 3 or 5 in this embodiment. Every five linear N-electrodes 31 are connected by the small conductive gate lines. The small conductive gate lines are made of sintered silver paste or leads 7, preferably small conductive gate lines in this embodiment. Each of the small conductive gate lines has a width of 10 μm to 300 μm and a width-to-height ratio of 1:0.01 to 1:1. In this embodiment, preferably, each of the small conductive gate lines has a width of 300 μm. Three leftmost linear P-electrodes 21 are connected by a small conductive gate line which is made of sintered silver paste and has a width of 30 μm. Five middle linear P-electrodes 21 are also connected by a same small conductive gate line. Two rightmost linear P-electrodes 21 are also connected by a same small conductive gate line. An insulating medium 6 is further provided on the cell, and the conversion efficiency of the cell is 23.2%.

[0113] In another embodiment, a structure having both dotted electrodes and linear electrodes may also be adopted. The principle thereof is similar to the above embodiments and will not be repeated here.

[0114] It can be known from the experiment parameters in the embodiments that a solar cell assembly formed by the back-contact solar cell modules produced by the present application can obtain a high filling factor. Accordingly, the power generation efficiency of the assembly is improved. The short-circuiting between P-electrodes and N-electrodes can be effectively prevented. The present application also has the advantages of hidden-cracking resistance, high efficiency, high stability, simple preparation process and greatly reduced cost.

[0115] In the embodiments of the present application, the distinction between the main-gate-free and high-efficiency back-contact solar cells (the first solar cell and the second solar cell in Embodiment 1, and the third solar cell and the fourth solar cell in Embodiment 2) is merely for ease of description, and the distinction between the cells forming the electrode structures of two back-contact solar cell doping layers is not limited in sequence. The distinction is for easily understanding the embodiments of the present application, and not intended to limit the protection scope of the present application. The first solar cell may also be called a primary cell, and the second solar cell may also be called a secondary cell. In Embodiment 1, there are total X−1 rows of P-electrodes (Y P-electrodes in each row) and X rows of N-electrodes (Y N-electrodes in each row) in the first solar cell, and total X−1 rows of N-electrodes (Y N-electrodes in each row) and X rows of P-electrodes (Y P-electrodes in each row) in the second solar cell, where both X and Y are integers greater than 2.

[0116] Finally, it should be noted that the forgoing embodiments are merely for describing the technical solutions of the present application, and not intended to limit the protection scope of the present application. Although the present application has been described above in detail by the preferred embodiments, it should be understood by a person of ordinary skill in the art that modifications or equivalent replacements may be made to the technical solutions of the present application without departing from the essence and scope of the technical solutions of the present application.