CN106876494A - The back electrode structure and battery of p-type PERC double-sided solar batteries - Google Patents

Abstract

The invention discloses a back electrode structure. The back electrode structure comprises at least one back silver main grid and a plurality of mutually parallel aluminum grid lines, the aluminum grid lines and the back silver main grid are vertically connected; the aluminum grid lines An overlapping connection area is formed between the back silver main grid and the back silver main grid, and the overlapping connection area surrounds the back silver main grid; in the overlapping connection area, the aluminum grid line covers the back silver main grid. Correspondingly, the present invention also discloses a P-type PERC double-sided solar cell using the above-mentioned back electrode structure. The invention has the advantages of simple structure, low cost, good conductivity and high photoelectric conversion efficiency of the battery.

Description

Back electrode structure and cell of P-type PERC bifacial solar cell

technical field

The present invention relates to the field of solar cells, in particular to a back electrode structure of a P-type PERC double-sided solar cell and a battery adopting the above back electrode structure.

Background technique

Solar cell power generation is the use of solar cells to directly convert sunlight energy into electrical energy. Because it is a green product, it will not cause environmental pollution, and it is a renewable resource. Therefore, in today's energy shortage situation, solar cells are an effective A new type of energy with broad development prospects.

The production process of P-type PERC double-sided solar cells includes: texturing, diffusion, etching, rear passivation layer deposition, PECVD back coating, front PECVD coating, screen printing, sintering, and annealing. In the process of converting light energy into electrical energy in a solar cell, the photogenerated carriers generated inside need to be collected and extracted through external printed electrodes, and then connected to an external circuit to deliver current. The above screen printing process is further subdivided into back electrode printing and positive electrode printing of solar cells. Back electrode printing is divided into silver main grid electrode printing and aluminum sub grid electrode printing. The positive electrode paste and the back electrode paste are printed on the front surface of the crystalline silicon solar cell and are sintered to collect current. The design of the back electrode pattern determines the current collection effect and light-receiving area of the back passivation battery, thus affecting the photoelectric conversion efficiency of the battery. Therefore, it is necessary to propose a new back electrode that can improve the conductivity of the electrode, reduce the shading area, and improve The photoelectric conversion efficiency of the battery.

Contents of the invention

The technical problem to be solved by the present invention is to provide a back electrode structure of a P-type PERC double-sided solar cell, which has a simple structure, low cost, good conductivity, and high photoelectric conversion efficiency of the cell.

The technical problem to be solved by the present invention is also to provide a P-type PERC double-sided solar cell, which has good conductivity, high photoelectric conversion efficiency, and high photoelectric conversion efficiency of the battery.

In order to solve the above technical problems, the present invention provides a back electrode structure of a P-type PERC double-sided solar cell, the back electrode structure includes at least one back silver main grid and a plurality of aluminum grid lines parallel to each other, the aluminum grid The line is vertically connected to the back silver busbar;

An overlapping connection area is formed between the aluminum grid lines and the back silver main grid, and the overlapping connection area surrounds the back silver main grid;

In the overlapping connection area, the aluminum grid lines cover the back silver busbar.

As a preferred manner of the above solution, the back electrode structure includes at least two back silver busbars, and the back silver busbars are parallel to each other.

As a preferred mode of the above solution, the number of the back silver busbars is 2-8, and the width of the back silver busbars is 0.5-5 mm.

As a preferred mode of the above solution, the number of the aluminum grid lines is 20-300, and the width of the aluminum grid lines is 30-500 microns.

As a preferred mode of the above solution, the width of the overlapping connection area between the back silver main grid and the aluminum grid line is 0.05-2 mm.

Correspondingly, the present invention also provides a P-type PERC double-sided solar cell, comprising a back silver main grid, an aluminum grid line, a back passivation layer, a P-type silicon, an N-type emitter, a front passivation layer and a front silver electrode. After the passivation layer on the back side is laser-grooved, several parallel laser grooved areas are formed, and at least one set of laser grooved units is arranged in each laser grooved area; the aluminum grid lines are arranged in one-to-one correspondence with the laser grooved areas, The aluminum grid line is connected to the P-type silicon through a laser grooved area, and the aluminum grid line is vertically connected to the back silver busbar;

An overlapping connection area is formed between the aluminum grid lines and the back silver main grid, and the overlapping connection area surrounds the back silver main grid;

In the overlapping connection area, the aluminum grid lines cover the back silver busbar.

As a preferred mode of the above solution, the aluminum grid line is parallel to the laser grooved area,

At least 2 sets of laser grooving units are arranged in each laser grooving area, and the distance between adjacent two groups of parallel laser grooving units is 5-300 μm;

The width of the laser grooved area is 10-500 μm; the width of the aluminum grid line located below the laser grooved area is larger than the width of the laser grooved area, and the width of the aluminum grid line is 30-550 μm.

As a preferred mode of the above solution, the aluminum grid line is perpendicular to the laser grooved area,

The distance between the laser grooving units is 0.5-50mm.

As a preferred form of the above solution, the pattern of the laser grooved unit is a line, a circle, an ellipse, a triangle, a quadrangle, a pentagon, a hexagon, a cross or a star.

The aluminum grid lines may also be in the shape of curves, arcs, waves, etc.

As a preferred mode of the above solution, the pattern of the laser grooving unit is a continuous straight line or a dotted line composed of multiple line segments;

When the pattern of the laser groove unit is a dotted line composed of multiple line segments, the lengths of the line segments are the same or different.

Implement the present invention, have following beneficial effect:

The invention provides a back electrode structure of a P-type PERC double-sided solar cell, which can replace the effect of the all-aluminum back electric field in the existing single-sided solar cell structure, and also has the function of a current-carrying conductor, and is suitable for installation in a P-type The back side of the PERC bifacial solar cell serves as the back electrode. Specifically, the back electrode structure includes at least one back silver main grid and a plurality of aluminum grid lines parallel to each other, and the aluminum grid line and the back silver main grid are vertically connected; an overlapping connection area is formed between the aluminum grid line and the back silver main grid, The overlapping connection area surrounds the back silver busbar, which can ensure good contact between the aluminum grid lines and the back silver busbar, and ensure the current collection effect of the back electrode, thereby ensuring the photoelectric conversion efficiency of the solar cell. In the overlapping connection area, the aluminum grid lines cover the back silver main grid, which can improve the conductivity of the back electrode structure and improve the current collection effect of the back electrode, thereby ensuring the photoelectric conversion efficiency of the solar cell.

The present invention also provides a P-type PERC double-sided solar cell adopting the above-mentioned back electrode structure, which is provided with a plurality of parallel aluminum grid lines on the back of the cell, which not only replaces the all-aluminum back electric field in the existing single-sided solar cell, but also realizes The function of back light absorption is also used as a sub-gate structure in the back silver electrode to conduct electrons. The production of P-type PERCP-type PERC double-sided solar cells of the present invention can save the amount of silver paste and aluminum paste, reduce production costs, and realize double-sided absorption of light energy, significantly expand the application range of solar cells and improve photoelectric conversion efficiency.

Description of drawings

Fig. 1 is the structural representation of the back electrode structure of a kind of P-type PERC bifacial solar cell of the present invention;

Fig. 2 is the sectional view of A-A shown in Fig. 1;

Fig. 3 is a schematic structural view of the P-type PERC bifacial solar cell shown in Fig. 1;

FIG. 4 is a schematic diagram of the rear structure of the P-type PERC bifacial solar cell shown in FIG. 3 .

detailed description

In order to make the object, technical solution and advantages of the present invention clearer, the present invention will be further described in detail below in conjunction with the accompanying drawings.

In recent years, with the in-depth research of scientists and technicians, a PERC solar cell with rear passivation has been discovered, which can further improve the photoelectric conversion efficiency of the cell. However, the aluminum oxide film and silicon nitride film on the back are insulating layers and cannot conduct electrons. Therefore, the conventional method is to open a groove on the silicon nitride under the gate line. When printing the gate line, the silver paste can be filled into the groove area. Form ohmic contact with P-type silicon to realize the conductive function.

Existing PERC single-sided solar cells have an all-aluminum back electric field covering the entire back of the silicon wafer on the back of the cell. The effect of the all-aluminum back electric field is to increase the open circuit voltage Voc and short circuit current Jsc, forcing minority carriers away from the surface , the minority carrier recombination rate is reduced, thereby improving the cell efficiency as a whole. However, since the electric field of the all-aluminum back does not transmit light, the back of the solar cell with the all-aluminum back electric field cannot absorb light energy, only the front can absorb light energy, and its photoelectric conversion efficiency is difficult to be greatly improved.

For this reason, the present invention proposes a new back electrode, which can replace the effect of the all-aluminum back electric field in the existing single-sided solar cell structure, and also has the function of a current-carrying conductor, and is suitable for installation in P-type PERC double-sided solar cells. The back of the battery serves as the back electrode.

As shown in Figures 1 and 2, the present invention provides a back electrode structure of a P-type PERC double-sided solar cell. The back electrode structure includes at least one back silver main grid 1 and a plurality of parallel aluminum grid lines 2, The aluminum grid lines 2 are vertically connected to the back silver main grid 1 ; an overlapping connection area 12 is formed between the aluminum grid lines 2 and the back silver main grid 1 . Refer to the dotted line box shown in Figure 1 for details of the overlapping connection area 12, which surrounds the back silver busbar 1, which can ensure good contact between the aluminum grid lines and the back silver busbar, and ensure the current collection effect of the back electrode. , so as to ensure the photoelectric conversion efficiency of the solar cell. The aluminum grid lines 2 and the back silver main grid 1 form a plurality of light-receiving regions 10 on the silicon wafer, so that the back side of the solar cell absorbs solar energy.

In the overlapping connection area 12, the aluminum grid lines 2 cover the back silver main grid 1, which can improve the conductivity of the back electrode structure and improve the current collection effect of the back electrode, thereby ensuring the photoelectric conversion efficiency of the solar cell.

The width of the overlapping connection area 12 of the back silver busbar 1 and the aluminum grid line 2 is 0.1-2 mm, specifically 0.1 mm, 0.5 mm, 1.0 mm, 1.5 mm, 2.0 mm, but not limited thereto. The width of the overlapping connection area 12 is 0.1-2 mm, which does not affect the welding of the back silver busbar 1 and the soldering strips when packaging components.

Preferably, the back electrode structure includes at least two back silver main grids 1 , and the back silver main grids 1 are parallel to each other. The number of the back silver busbars 1 is 2-8, and the width of the back silver busbars 1 is 0.5-5 mm.

The number of the aluminum grid lines is 20-300, and the width of the aluminum grid lines is 30-500 microns.

Correspondingly, the present invention also provides a P-type PERC double-sided solar cell adopting the above-mentioned back electrode structure, as shown in FIG. 5. N-type emitter 6, front passivation layer 7 and positive silver electrode 8, wherein, the back passivation layer includes a back silicon nitride film 3, a back aluminum oxide film 4, and the front passivation layer 7 can be a front nitriding Silicon film, but not limited thereto.

The silicon nitride film 3 on the back side and the aluminum oxide film 4 on the back side are laser-grooved to form 30-500 groups of laser grooved areas 9 arranged in parallel, and 1-50 groups of laser grooved units are arranged in each laser grooved area; The aluminum grid lines 2 are provided in one-to-one correspondence with the laser grooved areas 9 , and the aluminum grid lines 2 are connected to the P-type silicon 5 through the laser grooved areas 9 ; the aluminum grid lines 2 are vertically connected to the back silver main grid 1 .

The present invention improves the existing single-sided PERC solar cell, no longer has an all-aluminum back electric field, but turns it into a lot of aluminum grid lines 2, adopts laser slotting technology on the back side of the silicon nitride film 3 and the back side The aluminum oxide film 4 is provided with laser grooved areas 9, and the aluminum grid lines 2 are printed on these parallel laser grooved areas 9, so as to form local contact with the P-type silicon 5, and the densely arranged parallel aluminum grid lines 2 It can not only increase the open circuit voltage Voc and short circuit current Jsc, reduce the recombination rate of minority carriers, and improve the photoelectric conversion efficiency of the battery, but also can replace the all-aluminum back electric field of the existing single-sided battery structure, and the aluminum grid line 2 does not The backside of the silicon wafer is completely covered, and sunlight can be projected into the silicon wafer from between the aluminum grid lines 2, so that the backside of the silicon wafer absorbs light energy and greatly improves the photoelectric conversion efficiency of the cell.

Preferably, the number of aluminum grid lines 2 is 30-500 corresponding to the number of laser grooved areas, more preferably, the number of aluminum grid lines 2 is 80-220.

As shown in Figure 4, it is the backside of the silicon wafer. The aluminum grid line 2 is vertically connected to the back silver busbar 1, and the back silver busbar 1 is a continuous straight gate. Since the silicon nitride film 3 and the aluminum oxide film 4 on the back are provided with Laser groove area 9, when aluminum paste is printed to form aluminum grid line 2, the aluminum paste is filled into laser groove area 9, so that aluminum grid line 2 forms local contact with P-type silicon 5, and electrons can be transmitted to aluminum grid line 2, The back silver main grid 1 intersecting with the aluminum grid line 2 collects the electrons on the aluminum grid line 2, so it can be seen that the aluminum grid line 2 of the present invention can improve the open circuit voltage Voc and short circuit current Jsc, and reduce the minority carrier The recombination rate and the role of electron transmission can replace the electric field of the all-aluminum back in the existing single-sided solar cells, which not only reduces the amount of silver paste and aluminum paste, reduces production costs, but also realizes double-sided absorption of light energy, which significantly expands the solar cell. Application scope and improvement of photoelectric conversion efficiency.

The aluminum grid lines and the laser grooved area can be parallel or perpendicular.

When the aluminum grid line is parallel to the laser grooved area, more than 2 sets of laser grooved units are arranged in the laser grooved area, and the distance between adjacent two groups of laser grooved units arranged in parallel is 5-300 μm.

The width of the laser grooved area 9 in the present invention is 10-500 μm; the width of the aluminum grid lines 2 located below the laser grooved area 9 is larger than the width of the laser grooved area 9, and the width of the aluminum grid lines 2 is 30-550 μm. Select a larger value such as 500 μm for the width of the above-mentioned aluminum grid line 2, and select a smaller value such as 40 μm for the width of the laser grooved area 9, so that multiple groups of laser grooved areas 9 can be arranged side by side on the same aluminum grid line 2 to ensure that the aluminum The gate line 2 has a sufficient contact area with the P-type silicon 5 .

When the aluminum grid line is perpendicular to the laser grooved area, the distance between the laser grooved units is 0.5-50 mm.

Further, each group of laser grooving units includes at least 1 laser grooving unit, and the patterns of the laser grooving units are lines, circles, ellipses, triangles, quadrilaterals, pentagons, hexagons, crosses or stars shape. Preferably, the pattern of the laser grooving unit is a continuous straight line or a dotted line composed of multiple line segments; when the pattern of the laser grooving unit is a dotted line composed of multiple line segments, the lengths of the line segments are the same or different .

Therefore, the P-type PERC double-sided solar cell of the present invention is provided with a plurality of aluminum grid lines 2 arranged in parallel, which not only replaces the all-aluminum back electric field in the existing single-sided solar cell to improve the photoelectric conversion efficiency of the cell, but also replaces the rear The sub-gate structure in the silver electrode is used to conduct electrons. The production of P-type PERCP-type PERC double-sided solar cells of the present invention can save the amount of silver paste and aluminum paste, reduce production costs, and realize double-sided absorption of light energy, significantly expand the application range of solar cells and improve photoelectric conversion efficiency.

Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than limit the protection scope of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that The technical solution of the present invention can be modified or equivalently replaced without departing from the spirit and scope of the technical solution of the present invention.

Claims (10)

1. a kind of back electrode structure of p-type PERC double-sided solar batteries, it is characterised in that the back electrode structure is included at least One silver-colored main grid of the back of the body and a plurality of alum gate line being parallel to each other, the alum gate line and the silver-colored main grid of the back of the body are vertically connected；

The region for overlapping connection is formed between the alum gate line and the silver-colored main grid of the back of the body, the region of the overlap connection is centered around the back of the body The surrounding of silver-colored main grid；

Overlapping the region of connection, the silver-colored main grid of the alum gate line covering back of the body.

2. back electrode structure as claimed in claim 1, it is characterised in that the back electrode structure includes that at least two back of the body silver are main Grid, are parallel to each other between the back of the body silver main grid.

3. back electrode structure as claimed in claim 2, it is characterised in that the quantity of the back of the body silver main grid is 2-8 roots, the back of the body silver The width of main grid is 0.5-5mm.

4. back electrode structure as claimed in claim 1, it is characterised in that the quantity of the alum gate line is 20-300 roots, the aluminium The width of grid line is 30-500 microns.

5. back electrode structure as claimed in claim 1, it is characterised in that the back of the body silver main grid and alum gate line overlap join domain Width is 0.05-2mm.

6. a kind of p-type PERC double-sided solar batteries, it is characterised in that including the silver-colored main grid of the back of the body, alum gate line, backside passivation layer, p-type Silicon, N-type emitter stage, front passivation layer and positive silver electrode, the backside passivation layer are parallel by forming several after lbg The lbg area of setting, sets at least 1 group lbg unit in each lbg area；Alum gate line and lbg area one One is correspondingly arranged, and the alum gate line is connected by lbg area with P-type silicon, and main grid is vertical is connected with back of the body silver for the alum gate line；

The region for overlapping connection is formed between the alum gate line and the silver-colored main grid of the back of the body, the region of the overlap connection is centered around the back of the body The surrounding of silver-colored main grid；

Overlapping the region of connection, the silver-colored main grid of the alum gate line covering back of the body.

7. p-type PERC double-sided solar batteries as claimed in claim 6, it is characterised in that the alum gate line and lbg area It is parallel,

In each lbg area set at least 2 groups lbg units, the lbg unit that two adjacent groups be arranged in parallel it Between spacing be 5-300 μm；

The width in the lbg area is 10-500 μm；The width of the alum gate line below lbg area is opened more than laser The width in groove area, the width of alum gate line is 30-550 μm.

8. p-type PERC double-sided solar batteries as claimed in claim 6, it is characterised in that the alum gate line and lbg area Vertically,

Spacing between the lbg unit is 0.5-50mm.

9. p-type PERC double-sided solar batteries as claimed in claim 6, it is characterised in that the pattern of the lbg unit It is lines, circle, ellipse, triangle, quadrangle, pentagon, hexagon, cross or star.

10. p-type PERC double-sided solar batteries as claimed in claim 9, it is characterised in that the pattern of the lbg unit It is a continuous straight line or the dotted line of multiple line segment compositions；

When the dotted line that the pattern of the lbg unit is multiple line segment compositions, the length of the line segment is identical or different.