CN105826408A - Local back surface field N type solar cell, preparation method, assembly and system - Google Patents

Abstract

The invention relates to a local back surface field N-type solar cell, a preparation method, an assembly and a system. The preparation method of the local back surface field N-type solar cell of the present invention comprises the following steps: respectively doping the front and rear surfaces of the N-type crystalline silicon substrate, growing barrier layers on the front and rear surfaces of the silicon substrate, and then printing acid-resistant solar cells on the back surface of the silicon substrate. The slurry forms the mask of the sub-gate pattern; then immerses in an acidic solution to remove the barrier layer in the area not covered by the mask; immerses in an alkaline solution to remove the mask, and etches other areas while retaining n+ heavily doped under the mask area; dip again into the acidic solution to remove the remaining barrier layer on the front and rear surfaces of the silicon substrate. The beneficial effects are: since the back sub-gate is only in contact with the local n+ heavily doped region, the contact resistance is low; other regions are non-doped regions, so the Auger recombination is low; the front sub-gate is formed by setting metal wires, which greatly Reduce the silver paste consumption of the battery, thereby reducing the production cost of the battery sheet.

Description

Partial back surface field N-type solar cell, preparation method, component, and system

technical field

The invention relates to the technical field of solar cells, in particular to a local back surface field N-type solar cell, a preparation method, an assembly, and a system.

Background technique

A solar cell is a semiconductor device that converts solar energy into electricity. At present, the mainstream products in the industry are P-type crystalline silicon solar cells. The battery process is simple, but it has a light-induced decay effect, that is, the efficiency of the battery will gradually decay with time, which is mainly due to the combination of boron atoms doped into the P-type silicon substrate and oxygen atoms in the substrate. Produces boron-oxygen pair results. Studies have shown that the boron-oxygen pair acts as a carrier trap, reducing the minority carrier lifetime, which leads to the attenuation of the photoelectric conversion efficiency of the battery. Compared with P-type crystalline silicon solar cells, N-type crystalline silicon solar cells have the advantages of small light-induced attenuation, good resistance to metal impurity pollution, and long minority carrier diffusion length, and because the positive and negative electrodes of N-type crystalline silicon solar cells can be It is made into a conventional H-shaped grid electrode structure, so not only the front side of the battery can absorb light, but the back surface can also absorb reflected and scattered light to generate additional electricity.

Common N-type crystalline silicon solar cells have a p+/n/n+ structure, in which the front surface of the cell is doped with p+ type, and the back surface is doped with n+ type. In order to reduce the contact resistance between the back electrode and the n+ doped region, it is desirable that the n+ layer be heavily doped. In order to improve the open-circuit voltage and short-circuit current of the battery, we need to reduce heavy doping to bring about high Auger recombination. At this time, we hope that the n+ layer is lightly doped. The prior art cannot well solve the contradiction between the fill factor brought by the n+ type doped layer on the back surface and the open circuit voltage and short circuit current. In addition, the p+ doped region on the front surface generally uses aluminum-doped silver paste to make electrodes, and the price of aluminum-doped silver paste is generally relatively expensive, which leads to a high proportion of silver-containing paste in battery manufacturing costs.

Contents of the invention

The object of the present invention is to overcome the deficiencies of the prior art, and provide a local back surface field N-type solar cell, a preparation method, an assembly, and a system. The partial back surface field N-type solar cell provided by the present invention and the local back surface field N-type solar cell obtained by the preparation method thereof can better solve the problem of the fill factor brought by the back surface n+ type doped layer and the open circuit voltage and short circuit current. contradictions between. By setting the metal wire to form the front sub-grid, the silver paste consumption of the battery is greatly reduced while ensuring that the resistance of the metal wire sub-grid line does not increase, thereby reducing the production cost of the battery sheet.

A kind of preparation method of local back surface field N-type solar cell provided by the invention, its technical scheme is:

A method for preparing a local back surface field N-type solar cell, comprising the following steps:

(1), doping the N-type crystalline silicon substrate, and then preparing a barrier layer on the front surface and the back surface of the N-type crystalline silicon substrate, the thickness of the back barrier layer is less than the thickness of the front barrier layer;

(2), printing acid-resistant slurry on the back surface of the N-type crystalline silicon substrate after step (1) and drying to form a mask of the sub-grid pattern;

(3) Immerse the N-type crystalline silicon substrate treated in step (2) in an acid solution to remove the back barrier layer in the area not covered by the mask, but the front barrier layer is required not to be removed by the acid solution, but the thickness will be reduced accordingly Thin;

(4), immerse the N-type crystalline silicon substrate treated in step (3) in an alkaline solution to remove the mask, and the alkaline solution simultaneously removes the n+ heavily doped regions not covered by the mask, and retains the n+ covered by the mask A heavily doped region, thereby forming a locally n+ heavily doped back surface;

(5), immersing the N-type crystalline silicon substrate in the acidic solution again to remove the residual barrier layer on the front surface and the back surface;

(6), prepare a passivation anti-reflection film on the front surface of the N-type crystalline silicon substrate processed in step (5) and prepare a passivation film on the back surface, and then use metal paste printing on the back surface of the N-type crystalline silicon substrate The back electrode, the back sub-gate of the back electrode is connected to the local n+ heavily doped region; a metal wire is used on the front surface of the N-type crystalline silicon substrate to prepare the front electrode in ohmic contact with the p+ doped region, and the local back field is completed after sintering Fabrication of N-type solar cells.

Wherein, in step (6), the method for preparing the front electrode is: attaching the metal wire with aluminum-doped silver paste on the front surface of the N-type crystalline silicon substrate, after drying and sintering, the metal wire is mixed with p+ The impurity region forms an ohmic contact.

Wherein, in step (6), the method for preparing the front electrode is: use aluminum-doped silver paste to print segmented sub-grids on the front surface of the N-type crystalline silicon substrate; then lay metal wires on the segmented sub-grids; An ohmic contact is formed among the segment sub-gate, the metal wire and the p+ doped region.

Wherein, in step (6), the method for preparing the front electrode is: use aluminum-doped silver paste on the front surface of the N-type crystalline silicon substrate to print the segmented sub-gate, and then perform sintering treatment; The heat-sensitive conductive layer is printed on the segmented auxiliary grid; then the metal wire coated with the heat-sensitive conductive material is laid on the heat-sensitive conductive layer, and the N-type crystalline silicon substrate on which the metal wire coated with the heat-sensitive conductive material is laid is heated. The ohmic contact is formed among the metal wire plated with the thermally sensitive conductive material, the thermally sensitive conductive layer, the p+ doped region and the segmented sub-gate.

Wherein, the heat-sensitive conductive layer is a solder paste conductive layer, and the metal wire coated with a heat-sensitive conductive material is any one of tin-clad copper wire, silver-clad copper wire, tin-clad aluminum wire or tin-clad steel wire; The solder paste contains any one of tin, tin-lead alloy, tin-bismuth alloy or tin-lead-silver alloy.

Wherein, the way of heating the N-type crystalline silicon substrate is infrared heating, and the heating reflow peak temperature is 183-250 degrees Celsius.

Wherein, the method for doping the N-type crystalline silicon substrate in step (1) includes the following steps:

S1. Select an N-type crystalline silicon substrate, and perform texturing treatment on the front surface of the N-type crystalline silicon substrate; the resistivity of the N-type crystalline silicon substrate is 0.5-15Ω·cm;

S2. Put the N-type crystalline silicon substrate treated in step S1 into an industrial diffusion furnace to perform boron diffusion on the textured surface to form a p+ doped region on the front surface. The boron source is boron tribromide, and the diffusion temperature is 900-1000 ℃, the time is 60-180 minutes; the square resistance value after boron diffusion is 40-100Ω/sqr;

S3. Put the boron-diffused N-type crystalline silicon substrate into an etching cleaning machine to remove the boron diffusion layer on the back surface and the borosilicate glass layer on the front surface;

S4. Using an ion implanter to implant phosphorus on the back surface of the N-type crystalline silicon substrate processed in step S3 and perform annealing treatment to form an n+ heavily doped region on the back surface, the square resistance of the n+ heavily doped region is 10-40Ω/sqr ; The annealing peak temperature is 700-950°C, the annealing time is 30-200min, and the ambient gas source is N ₂ and O ₂ .

Wherein, the barrier layer is a _SiO2 layer or a _SiNx layer, the thickness of the front barrier layer is 200-300nm, and the thickness of the back barrier layer is 50-100nm.

Wherein, in the step (2), the width of the mask of the sub-grid pattern is 20-100um, parallel to each other, and the distance is 1-2mm.

Wherein, the acidic solution in step (3) is in the 5-20% HF solution, the time for the N-type crystalline silicon substrate to be immersed in the 5-20% HF solution is 0.5-5 minutes, and the N-type crystalline silicon substrate is taken out and used Ionized water cleaning.

Wherein, the alkaline solution in step (4) is 10-30% KOH solution, 10-30% NaOH solution, 10-30% tetramethylammonium hydroxide solution or 10-30% ethylene glycol Amine solution; the temperature of the alkaline solution is 50-90°C, the reaction time for the N-type crystalline silicon substrate immersed in the alkaline solution is 0.5-5 minutes, and the N-type crystalline silicon substrate is taken out and cleaned with deionized water.

Wherein, the acid solution in step (5) is in 5-20% HF solution, the time for the N-type crystalline silicon substrate to be immersed in the 5-20% HF solution is 2-5 minutes, and the N-type crystalline silicon substrate is taken out and used Ionized water cleaning.

Wherein, in step (6), the method for preparing the back electrode on the back surface of the N-type crystalline silicon substrate is: use silver paste to print the back electrode of the H-type grid line on the back surface of the N-type crystalline silicon substrate and dry it, wherein The width of the main grid on the back is 0.5-3mm, 3-6 grids are arranged at equal intervals, and the width of the auxiliary grid on the back is 20-100um.

The present invention also provides a local back surface field N-type solar cell, comprising an N-type crystalline silicon substrate, the front surface of the N-type crystalline silicon substrate includes a p+ doped region from inside to outside and a passivation antireflection on the front surface film; the back surface of the N-type crystalline silicon substrate includes a local n+ heavily doped region and a passivation film on the back surface in sequence from the inside to the outside; the N-type crystalline silicon substrate also includes a back electrode arranged on the back surface, so The back electrode includes a back main gate and a back sub-gate, the back sub-gate is connected to the local n+ heavily doped region, and the front electrode includes a metal wire in ohmic contact with the p+ doped region.

Wherein, the metal wire is electrically connected to the p+ doped region through a silver-aluminum alloy material.

Wherein, the front electrode includes a segmented sub-gate, and the metal wire is electrically connected to the p+ doped region through the segmented sub-gate.

Wherein, the front electrode includes a segmented sub-gate and a heat-sensitive conductive layer disposed on the segmented sub-gate, and the segmented sub-gate is electrically connected to the p+ doped region; the metal wire is connected to the heat-sensitive conductive layer. layer electrical connection.

Wherein, the segmented sub-grid is a silver-aluminum alloy segmented sub-grid; the heat-sensitive conductive layer is a solder paste conductive layer, and the metal wire is a metal wire coated with a heat-sensitive conductive material.

The present invention also provides a local back surface field N-type solar cell assembly, comprising front layer material, encapsulation material, local back surface field N-type solar cell, encapsulation material, and back layer material arranged sequentially from top to bottom. The partial back surface field N-type solar cell is the aforementioned partial back surface field N-type solar cell.

The present invention also provides a local back surface field N-type solar cell system, comprising more than one local back surface field N-type solar cell components connected in series, the local back surface field N-type solar cell component is the above-mentioned partial back surface field N-type solar cell system Surface field N-type solar cell module.

Implementation of the present invention comprises following technical effect:

The technical effects of the present invention are mainly reflected in: 1. After a series of operations such as setting barrier layer, acid-resistant slurry mask, acid corrosion and alkali corrosion, etc., the present invention can form local n+ heavy In the doped region, during subsequent metallization, the sub-gate metal paste only contacts the local n+ heavily doped region. Since the sub-gate is only in contact with the local n+ heavily doped region, the contact resistance is low and the fill factor is high; at the same time, the region not in contact with the sub-gate is a non-doped region, so the Auger recombination is low and the open circuit voltage is high. However, using the prior art, if the local n+ doped doped layer on the back is heavily doped, the open circuit voltage is low although the contact resistance is low; if the n+ doped region on the back is lightly doped, the open circuit voltage is high but the contact resistance High fill factor is poor. It can be seen that the n-type solar cell prepared according to the above method can overcome the contradiction between the open circuit voltage and the fill factor in the prior art, so it has a higher photoelectric conversion efficiency. 2. The metallization of the p+ doped area on the front surface abandons the conventional method of printing aluminum-doped silver paste to make the main grid and the sub-grid, and forms the sub-grid by setting metal wires, while ensuring that the resistance of the metal wire sub-grid line does not increase , greatly reducing the silver paste consumption of the battery, thereby reducing the production cost of the battery sheet.

Description of drawings

FIG. 1 is a schematic cross-sectional view of a cell structure after step 1 of a method for preparing a partial back surface field N-type solar cell according to an embodiment of the present invention.

FIG. 2 is a schematic cross-sectional view of a cell structure after step 4 of a method for preparing a partial back surface field N-type solar cell according to an embodiment of the present invention.

3 is a schematic cross-sectional view of a cell structure after step five of a method for preparing a partial back surface field N-type solar cell according to an embodiment of the present invention.

FIG. 4 is a schematic cross-sectional view of a cell structure after step six of a method for preparing a partial back surface field N-type solar cell according to an embodiment of the present invention.

5 is a schematic cross-sectional view of a cell structure after step 7 of a method for preparing a partial back surface field N-type solar cell according to an embodiment of the present invention.

FIG. 6 is a schematic cross-sectional view of a cell structure after step eight of a method for manufacturing a partial back surface field N-type solar cell according to an embodiment of the present invention.

7 is a schematic cross-sectional view of a cell structure after step 9 of a method for preparing a partial back surface field N-type solar cell according to an embodiment of the present invention.

FIG. 8 is a schematic cross-sectional view of a cell structure after step ten of a method for preparing a partial back surface field N-type solar cell according to an embodiment of the present invention.

9 is a schematic cross-sectional view of a cell structure after step eleven of a method for preparing a partial back surface field N-type solar cell according to an embodiment of the present invention.

FIG. 10 is a schematic diagram of a metal wire adhered with silver paste after step 12 (a) of the preparation method of a partial back surface field N-type solar cell according to Embodiment 1 of the present invention.

11 is a schematic cross-sectional view of the cell structure after step 12 (b) of the method for preparing a partial back surface field N-type solar cell according to Embodiment 1 of the present invention.

12 is a schematic cross-sectional view of the cell structure after step 12 (a) of the method for preparing a partial back surface field N-type solar cell according to Embodiment 2 of the present invention.

13 is a schematic cross-sectional view of the cell structure after step 12 (b) of the method for preparing a partial back surface field N-type solar cell according to Embodiment 2 of the present invention.

FIG. 14 is a schematic cross-sectional view of the cell structure after step 12 (a) of the method for preparing a partial back surface field N-type solar cell according to Embodiment 3 of the present invention.

15 is a schematic cross-sectional view of the cell structure after step 12 (b) of the method for preparing a partial back surface field N-type solar cell according to Embodiment 3 of the present invention.

16 is a schematic cross-sectional view of the cell structure after step 12 (c) of the method for preparing a local back surface field N-type solar cell according to Embodiment 3 of the present invention.

FIG. 17 is a schematic diagram of discontinuous line-shaped segmented sub-gates in Step 12 of a method for preparing a partial back surface field N-type solar cell according to Embodiment 2 and Embodiment 3 of the present invention.

FIG. 18 is a schematic diagram of discontinuous dot-shaped segmented sub-grids in Step 12 of a method for preparing a partial back surface field N-type solar cell according to Embodiment 2 and Embodiment 3 of the present invention.

FIG. 19 is a schematic diagram of discontinuous dot-shaped segmented sub-grids arranged in dislocations in Step 12 of a method for preparing a partial back surface field N-type solar cell according to Embodiment 2 and Embodiment 3 of the present invention.

detailed description

The present invention will be described in detail below in conjunction with the embodiments and the accompanying drawings. It should be noted that the described embodiments are only intended to facilitate the understanding of the present invention, rather than limiting it in any way.

Example 1

Referring to Fig. 1 to Fig. 11, the preparation method of a partial back surface field N-type solar cell provided in this embodiment includes the following steps:

(1), select the N-type crystalline silicon substrate 10 of 156mm * 156mm, and do texture processing to the front surface of the N-type crystalline silicon substrate 10; The resistivity of the N-type crystalline silicon substrate 10 is 0.5～15Ω·cm, preferably 1 ~5Ω·cm; the thickness of the N-type crystalline silicon substrate 10 is 50-300 μm, preferably 80-200 μm; the battery structure after this step is shown in FIG. 1 .

(2), put the N-type crystalline silicon substrate 10 processed in step (1) into an industrial diffusion furnace to carry out boron diffusion on the suede surface to form the p+ doped region 12 on the front surface, and the boron source adopts boron tribromide, The diffusion temperature is 900-1000° C., and the time is 60-180 minutes. The square resistance after boron diffusion is 40-100Ω/sqr, preferably 50-70Ω/sqr.

(3) Put the boron-diffused N-type crystalline silicon substrate 10 into an etching cleaning machine, and remove the boron diffusion layer on the back surface and the borosilicate glass layer on the front surface.

(4), use an ion implanter to implant phosphorus into the back surface of the N-type crystalline silicon substrate 10 processed in step (3) and perform annealing to form the n+ heavily doped region 16 on the back surface, and the square resistance of the n+ heavily doped region 16 10-40Ω/sqr. The annealing peak temperature is 700-950°C, preferably 850-900°C, the annealing time is 30-200min, preferably 60-200min, and the ambient gas source is preferably N ₂ and O ₂ . The structure of the battery after this step is shown in FIG. 2 .

(5) A barrier layer is grown on the front surface and the back surface of the N-type crystalline silicon substrate 10 treated in step (4). The barrier layer can be a SiO ₂ layer or a SiN _x layer, and this embodiment uses a SiO ₂ layer as a specific example. The specific method is to put the N-type crystalline silicon substrate 10 into PECVD (Plasma Enhanced Chemical Vapor Deposition) equipment, grow a SiO2 layer 13 with a thickness of 200-300nm on the front surface, and grow a _SiO2 layer 13 with a thickness of 50-100nm on the back surface. _SiO2 layer 17. The structure of the battery after this step is shown in FIG. 3 .

(6) Print the acid-resistant paste 40 on the back surface of the N-type crystalline silicon substrate 10 after the treatment in step (5), and dry it to form a mask. The pattern after ink passing is sub-grid structure, the sub-grid lines are 50-200um in width, 154mm in length, parallel to each other, with a distance of 1-2mm, preferably 1.55mm, and a total of 100 sub-grid lines are arranged. The battery structure after completing this step is shown in FIG. 4 .

(7) Immerse the N-type crystalline silicon substrate 10 treated in step (6) in 5-20% HF solution, take it out after 0.5-5 minutes and clean it with deionized water. At this time, the SiO ₂ in the area not covered by the mask on the back surface is removed by HF, while most of the SiO ₂ on the front surface is still not removed. The battery structure after this step is shown in FIG. 5 .

(8), immerse the N-type crystalline silicon substrate 10 treated in step (7) in 10-30% by weight of lye, the working temperature is 50-90°C, react for 0.5-5 minutes, take it out and clean it with deionized water . At this time, the regions on the back surface not covered by the mask will react with the alkali solution because there is no protection of SiO ₂ , and the n+ heavily doped regions in these regions are removed. At the same time, the residual mask will also be removed by lye. The area covered by the mask is the local n+ heavily doped region 161; note that in this step, the p+ doped region 12 on the front surface and the sub-gate-shaped local n+ heavily doped region 161 on the back surface are covered with SiO ₂ membrane, and will not react with lye. The lye can be KOH, NaOH, tetramethylammonium hydroxide or ethylenediamine solution. The structure of the battery after this step is shown in FIG. 6 .

(9) Immerse the N-type crystalline silicon substrate 10 treated in step (8) in a 5-20% HF solution, take it out after 2-5 minutes and clean it with deionized water. At this time, the remaining SiO ₂ layers on the front surface and the back surface are all removed. The battery structure after completing this step is shown in FIG. 7 .

(10), passivation anti-reflection film 14 and passivation film 18 are set on the front surface and back surface of N-type crystalline silicon substrate 10 after step (9) process, wherein the passivation anti-reflection film 14 of front surface is SiO ₂ One or more of SiN _x and Al ₂ O ₃ dielectric films, and the passivation film 18 on the back surface is a composite dielectric film composed of SiO ₂ and SiN _x dielectric films. The thickness of the passivation anti-reflection film 14 on the front surface is 70-110 nm; the thickness of the passivation film 18 on the back surface is not less than 20 nm. The battery structure after completing this step is shown in FIG. 8 .

(11) Use silver paste to print electrodes on the back surface of the N-type crystalline silicon substrate 10 and dry them. The electrode pattern is an H-type grid line, wherein the back main grid 22 has a line width of 0.5-3mm and a length of 154mm, and is arranged at equal intervals 3-6 wires, 28 wires on the back side are 20-100um wide, 154mm long, parallel to each other, with a spacing of 1.55mm, and a total of 100 wires are installed. Make sure that the printed rear sub-gate 28 falls within the local n+ heavily doped region 161 . The battery structure after completing this step is shown in FIG. 9 .

(12), complete the metallization of the front surface of the N-type crystalline silicon substrate 10, the process includes the following steps:

(a) As shown in Figure 10, the aluminum-doped silver paste 24 that can form ohmic contact with the p+ doped region 12 is adhered on one side of the metal wire 26, and the aluminum-doped silver paste 24 that is adhered on the metal wire 26 can Attached discontinuously on the metal wire, also can be attached on the metal wire continuously; The cross-sectional shape of the metal wire 26 can be circular, and its diameter is 40-80um; The cross-sectional shape of the metal wire 26 can also be square or triangle. Metal wire 26 may be copper wire, silver-clad copper wire or other alloy wires.

(b), as shown in Figure 11, a plurality of metal wires 26 coated with aluminum-doped silver paste 24 are attached in parallel to the front surface of the N-type crystalline silicon substrate 10 at equal intervals and dried, and the distance between the wires 26 is The spacing is 1-3mm;

(c) The N-type crystalline silicon substrate 10 after step (b) is placed in a sintering furnace for sintering, and the peak temperature of sintering is not higher than 900°C. So far, the preparation of the local n+ N-type battery is completed.

Example 2

Referring to Fig. 1 to Fig. 9, Fig. 12 and Fig. 13 and Fig. 17 to Fig. 19, a method for preparing a partial back surface field N-type solar cell in this embodiment includes the following steps:

Steps (1)-(11) are the same as those in Embodiment 1, and will not be repeated here.

(12), complete the metallization of the front surface of the N-type crystalline silicon substrate 10, the process includes the following steps:

(a) As shown in FIG. 12 , the segmented sub-gate 27 is printed on the front surface of the N-type crystalline silicon substrate 10 using an aluminum-doped silver paste that can form an ohmic contact with the p+ doped region 12 . The length of the segmented sub-grid 27 is less than or equal to the side length of the cell, which is 154 mm in this embodiment, and preferably the segmented sub-grids are parallel to each other. The segmented sub-gate 27 may be composed of discontinuous lines, and each line is 30-300 microns long and 30-300 microns wide. In this embodiment, the segmented auxiliary grid 27 is composed of discontinuous dots, and the diameter of the dots is 30-300 microns. The pattern shape of the segmented sub-gate 27 in this embodiment can be discontinuous dots (as shown in FIG. 18 ), discontinuous lines (as shown in FIG. 17 ) or discontinuous dots arranged in dislocation (as shown in FIG. 19 ).

(b) As shown in FIG. 13 , metal wires 26 are laid one by one on the segmented auxiliary grids 27 to form continuous auxiliary grid lines. The cross section of the metal wire 26 can be circular with a diameter of 40-80um; the cross section shape of the metal wire 26 can also be square or triangular. The metal wire 26 can be copper wire, silver-clad copper wire or other alloy wire, with a length of 154 mm and a diameter of 40-80 microns. When laying, be sure to make the metal wire 26 contact the aluminum-doped silver paste layer on the segment sub-grid 27 .

(c) The N-type crystalline silicon substrate 10 after step (b) is placed in a sintering furnace for sintering, and the sintering temperature is not higher than 900°C. So far, the preparation of the local n+ N-type battery is completed.

Example 3

Referring to Fig. 1 to Fig. 9, Fig. 14 to Fig. 16 and Fig. 17 to Fig. 19, a method for preparing a partial back surface field N-type solar cell in this embodiment includes the following steps:

Steps (1)-(11) are the same as those in Embodiment 1, and will not be repeated here.

(12), complete the metallization of the front surface of the N-type crystalline silicon substrate 10, the process includes the following steps:

(a) As shown in FIG. 14 , the segmented sub-gate 27 is printed and sintered on the front surface of the N-type crystalline silicon substrate 10 using an aluminum-doped silver paste that can form an ohmic contact with the p+ doped region 12 . The length of the segmented sub-grid 27 is less than or equal to the side length of the cell, which is 154 mm in this embodiment, and preferably the segmented sub-grids are parallel to each other. The segmented sub-gate 27 may be composed of discontinuous lines, and each line is 30-300 microns long and 30-300 microns wide. The segmented sub-grid 27 can also be composed of discontinuous dots, and the diameter of the dots is 30-300 microns. The sintering temperature is not higher than 900°C. The pattern shape of the segmented sub-gate 27 in this embodiment can be discontinuous dots (as shown in FIG. 18 ), discontinuous lines (as shown in FIG. 17 ) or discontinuous dots arranged in dislocation (as shown in FIG. 19 ).

(b) As shown in FIG. 15 , place the N-type crystalline silicon substrate 10 treated in step (a) on a printing machine, and print the solder paste conductive layer 29 with solder paste. The overink pattern of the solder paste conductive layer 29 can be discontinuous lines, each line is 40-300 microns long and 40-300 microns wide. The over-ink pattern of the solder paste conductive layer 29 can also be discontinuous dots with a diameter of 40-300 microns. Make sure that the conductive layer 29 of solder paste after ink is positioned on the segmented sub-gate 27 during printing.

(c) As shown in FIG. 16 , the metal wires 26 are laid one by one correspondingly on the solder paste conductive layer 29 to form continuous sub-grid lines. The cross section of the metal wire 26 can be circular with a diameter of 40-80um; the cross section shape of the metal wire 26 can also be square or triangular. The metal wire 26 can be copper wire, silver-clad copper wire or other alloy wire, with a length of 154 mm and a diameter of 40-80 microns. Be sure to make the metal wire 26 contact the conductive layer 29 of solder paste when laying.

(d) Heating the N-type crystalline silicon substrate 10 after step (c), so that the metal wire 26 , the conductive layer of solder paste 29 and the segmented sub-gate 27 form an ohmic contact. The heating method adopts infrared heating, and the peak reflow temperature is 183-250 degrees. So far, the preparation of the local n+ N-type battery is completed.

In this embodiment, a local n+ heavily doped region can be formed on the back of N-type crystalline silicon after a series of operations such as setting a barrier layer, an acid-resistant slurry mask, acid corrosion, and alkali corrosion. The gate metal paste only contacts the local n+ heavily doped regions. Since the sub-gate is only in contact with the local n+ heavily doped region, the contact resistance is low and the fill factor is high; at the same time, the region not in contact with the sub-gate is a non-doped region, so the Auger recombination is low and the open circuit voltage is high. However, using the existing technology, if the local n+ doped region on the back is heavily doped, although the contact resistance is low, the open circuit voltage is also low; if the n+ doped region on the back is lightly doped, although the open circuit voltage is high, the contact resistance is high. Factor difference. It can be seen that the n-type solar cell prepared according to the above method can overcome the contradiction between the open circuit voltage and the fill factor in the prior art, so it has a higher photoelectric conversion efficiency. 2. The metallization of the p+ doped area on the front surface abandons the conventional method of printing aluminum-doped silver paste to make the main grid and the sub-grid, and forms the sub-grid by setting metal wires, while ensuring that the resistance of the metal wire sub-grid line does not increase , greatly reducing the silver paste consumption of the battery, thereby reducing the production cost of the battery sheet.

Referring to Figures 9 to 19, this embodiment also provides a partial back surface field N-type solar cell, which includes an N-type crystalline silicon substrate 10, and the front surface of the N-type crystalline silicon substrate 10 includes sequentially from the inside to the outside. The p+ doped region 12 and the passivation anti-reflection film 14 on the front surface; the back surface of the N-type crystalline silicon substrate 10 includes a local n+ heavily doped region 161 and a rear surface passivation film 18 from inside to outside; the N-type crystalline silicon substrate 10 also includes a back electrode arranged on the back surface, the back electrode includes a back main gate 22 and a back sub-gate 28, the back sub-gate 28 is connected to the local n+ heavily doped region 161, and the front electrode includes an ohmic contact with the p+ doped region 12 wire 26. In the above-mentioned partial back surface field N-type solar cell, since the back sub-gate is only in contact with the local n+ heavily doped region 161, the contact resistance is low and the fill factor is high; meanwhile, the region not in contact with the back sub-gate is a non-doped region , so the Auger recombination is low and the open circuit voltage is high. However, using the existing technology, if the local n+ doped region on the back is heavily doped, although the contact resistance is low, the open circuit voltage is also low; if the n+ doped region on the back is lightly doped, although the open circuit voltage is high, the contact resistance is high. Factor difference. It can be seen that the N-type solar cell of this embodiment can overcome the contradiction between the open circuit voltage and the fill factor in the prior art, so it has a higher photoelectric conversion efficiency. The metallization of the p+ doped region on the front surface abandons the conventional method of printing aluminum-doped silver paste to make the main grid and the sub-grid, and forms the sub-grid by setting the metal wire. Under the condition that the resistance of the metal wire sub-grid line does not increase, it is extremely Greatly reduce the silver paste consumption of the battery, thereby reducing the production cost of the battery sheet.

In this embodiment, the connection mode between the metal wire and the p+ doped region is that the metal wire is electrically connected to the p+ doped region 12 through a silver aluminum alloy material; It is electrically connected to the p+ doped region 12; or the front electrode includes a segmented sub-gate 27 and a heat-sensitive conductive layer arranged on the segmented sub-gate 27, and the segmented sub-gate is electrically connected to the p+ doped region 12; the metal wire 26 is connected to the thermal The sensitive conductive layer is electrically connected. The segmented sub-grid 27 is a silver-aluminum alloy segmented sub-grid; the heat-sensitive conductive layer is a solder paste conductive layer 29, and the metal wire is a metal wire coated with a heat-sensitive conductive material. The segmented sub-gate 27 may be composed of discontinuous lines, and each line is 30-300 microns long and 30-300 microns wide. The segmented sub-grid may be composed of discontinuous dots, and the diameter of the dots is 30-300 microns. The pattern shape of the segmented sub-gate can be discontinuous dots (as shown in FIG. 18 ), discontinuous lines (as shown in FIG. 17 ), or discontinuous dots arranged in dislocation (as shown in FIG. 19 ). The metal wire is one of copper wire, tin-clad copper wire, silver-clad copper wire, tin-clad aluminum wire or tin-clad steel wire. The passivation anti-reflection film 14 is one or more of SiO ₂ , SiN _x or Al ₂ O ₃ dielectric films, and the passivation film 18 is a composite dielectric film composed of SiO ₂ and SiN _x dielectric films; the passivation anti-reflection film 14 The thickness of the passivation film 18 is not less than 20 nm. The back busbar 22 is a silver back busbar, and the back sub-bar 28 is a silver back sub-bar.

This embodiment also provides a local back surface field N-type solar cell assembly, including a front layer material connected from top to bottom, an encapsulation material, a local back surface field N-type solar cell, an encapsulation material, a back layer material, and a local back surface field N-type solar cell assembly. The surface field N-type solar cell is the aforementioned local back surface field N-type solar cell. The structure and working principle of the local back surface field N-type solar cell assembly in this embodiment use technologies known in the art, and the improvement of the local back surface field N-type solar cell assembly provided by the present invention only involves the above-mentioned local back surface field N Type solar cells, do not make changes to other parts. Therefore, this description only details the partial back surface field N-type solar cell and its preparation method, and does not repeat the details of other components and working principles of the partial back surface field N-type solar cell module here. Those skilled in the art can realize the local back surface field N-type solar cell module of the present invention on the basis of the content described in this specification.

This embodiment also provides a local back surface field N-type solar cell system, including one or more than one local back surface field N-type solar cell components in series, and the local back surface field N-type solar cell component is one of the above-mentioned Partial back surface field N-type solar cell module. The structure and working principle of the local back surface field N-type solar cell system in this embodiment use technologies known in the art, and the improvement of the local back surface field N-type solar cell system provided by the present invention only involves the above-mentioned local back surface field N Type solar cells, do not make changes to other parts. Therefore, this description only details the partial back surface field N-type solar cell and its preparation method, and other components and working principles of the partial back surface field N-type solar cell system will not be repeated here. Those skilled in the art can realize the local back surface field N-type solar cell system of the present invention on the basis of the content described in this specification.

Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than limiting 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 , the technical solution of the present invention may be modified or equivalently replaced without departing from the spirit and scope of the technical solution of the present invention.

Claims (20)

1. A preparation method for a local back surface field N-type solar cell, characterized in that: comprising the following steps: (1), doping the N-type crystalline silicon substrate, and then preparing a barrier layer on the front surface and the back surface of the N-type crystalline silicon substrate, the thickness of the back barrier layer is less than the thickness of the front barrier layer; (2), printing acid-resistant slurry on the back surface of the N-type crystalline silicon substrate after step (1) and drying to form a mask of the sub-grid pattern; (3) Immerse the N-type crystalline silicon substrate treated in step (2) in an acid solution to remove the back barrier layer in the area not covered by the mask, but the front barrier layer is required not to be removed by the acid solution, but the thickness will be reduced accordingly Thin; (4), immerse the N-type crystalline silicon substrate treated in step (3) in an alkaline solution to remove the mask, and the alkaline solution simultaneously removes the n+ heavily doped regions not covered by the mask, and retains the n+ covered by the mask A heavily doped region, thereby forming a locally n+ heavily doped back surface; (5), immersing the N-type crystalline silicon substrate in the acidic solution again to remove the residual barrier layer on the front surface and the back surface; (6), prepare a passivation anti-reflection film on the front surface of the N-type crystalline silicon substrate processed in step (5) and prepare a passivation film on the back surface, and then use metal paste printing on the back surface of the N-type crystalline silicon substrate The back electrode, the back sub-gate of the back electrode is connected to the local n+ heavily doped region; a metal wire is used on the front surface of the N-type crystalline silicon substrate to prepare the front electrode in ohmic contact with the p+ doped region, and the local back field is completed after sintering Fabrication of N-type solar cells. 2. the preparation method of a kind of local back surface field N-type solar cell according to claim 1 is characterized in that: in step (6), the method for preparing front electrode is: the metal that is attached with aluminum-doped silver paste The wire is attached to the front surface of the N-type crystalline silicon substrate, and after drying and sintering, the metal wire forms an ohmic contact with the p+ doped region. 3. The preparation method of a kind of partial back surface field N-type solar cell according to claim 1, is characterized in that: in step (6), the method for preparing front electrode is: use on the front surface of N-type crystalline silicon substrate Aluminum-doped silver paste is used to print segmented sub-grids; then metal wires are laid on the segmented sub-grids, and ohmic contact is formed between the sintered segmented sub-grids, metal wires and p+ doped regions. 4. the preparation method of a kind of local back surface field N-type solar cell according to claim 1 is characterized in that: in step (6), the method for preparing front electrode is: use on the front surface of N-type crystalline silicon substrate Aluminum-doped silver paste is used to print segmented sub-grids, and then sintered; a heat-sensitive conductive layer is printed on the segmented sub-grids of the sintered N-type crystalline silicon substrate; Heat the N-type crystalline silicon substrate on which the metal wire coated with the thermally sensitive conductive material is laid, so that the metal wire coated with the thermally sensitive conductive material, the thermally sensitive conductive layer, the p+ doped region and the segmented sub-gate Ohmic contact is formed between the four. 5. The preparation method of a local back surface field N-type solar cell according to claim 4, characterized in that: the heat-sensitive conductive layer is a solder paste conductive layer, and the metal wire coated with a heat-sensitive conductive material It is any one of tin-clad copper wire, silver-clad copper wire, tin-clad aluminum wire or tin-clad steel wire; the solder paste contains any one of tin, tin-lead alloy, tin-bismuth alloy or tin-lead-silver alloy. 6. the preparation method of a kind of local back surface field N-type solar cell according to claim 4, is characterized in that: the mode that N-type crystalline silicon substrate is heated is to adopt the mode of infrared heating, and the reflux peak temperature of heating is 183-250 degrees Celsius. 7. the preparation method of a kind of local back surface field N-type solar cell according to claim 1, is characterized in that: the method for carrying out doping treatment to N-type crystalline silicon substrate in step (1) comprises the following steps: S1. Select an N-type crystalline silicon substrate, and perform texturing treatment on the front surface of the N-type crystalline silicon substrate; the resistivity of the N-type crystalline silicon substrate is 0.5-15Ω·cm; S2. Put the N-type crystalline silicon substrate treated in step S1 into an industrial diffusion furnace to perform boron diffusion on the textured surface to form a p+ doped region on the front surface. The boron source is boron tribromide, and the diffusion temperature is 900-1000 ℃, the time is 60-180 minutes; the square resistance value after boron diffusion is 40-100Ω/sqr; S3. Put the boron-diffused N-type crystalline silicon substrate into an etching cleaning machine to remove the boron diffusion layer on the back surface and the borosilicate glass layer on the front surface; S4. Using an ion implanter to implant phosphorus on the back surface of the N-type crystalline silicon substrate processed in step S3 and perform annealing treatment to form an n+ heavily doped region on the back surface, the square resistance of the n+ heavily doped region is 10-40Ω/sqr ; The annealing peak temperature is 700-950°C, the annealing time is 30-200min, and the ambient gas source is N ₂ and O ₂ . 8. according to the preparation method of the _arbitrary described a kind of local back surface field N-type solar cell of claim 1-7, it is characterized in that: described barrier layer is SiO Layer or _SiNx layer, the thickness of front barrier layer is 200-300nm, the thickness of the back barrier layer is 50-100nm. 9. the preparation method of a kind of local back surface field N-type solar cell according to claim 1, is characterized in that: the width of the mask of sub-grid pattern in step (2) is 20-100um, parallel to each other, spacing 1-2mm. 10. The preparation method of a local back surface field N-type solar cell according to claim 1, characterized in that: the acidic solution in step (3) is 5-20% HF solution, the N-type crystalline silicon substrate The immersion time in 5-20% HF solution is 0.5-5 minutes, and the N-type crystalline silicon substrate is taken out and cleaned with deionized water. 11. A method for preparing a partial back surface field N-type solar cell according to claim 1, characterized in that: the alkaline solution in step (4) is 10-30% KOH solution, 10-30% % NaOH solution, 10-30% tetramethylammonium hydroxide solution or 10-30% ethylenediamine solution; the temperature of the alkaline solution is 50-90°C, and the N-type crystalline silicon substrate is immersed in the alkaline solution The reaction time is 0.5-5 minutes, and the N-type crystalline silicon substrate is taken out and washed with deionized water. 12. The preparation method of a local back surface field N-type solar cell according to claim 1, characterized in that: the acidic solution in step (5) is 5-20% HF solution, N-type crystalline silicon substrate The immersion time in 5-20% HF solution is 2-5 minutes, and the N-type crystalline silicon substrate is taken out and cleaned with deionized water. 13. The preparation method of a local back surface field N-type solar cell according to claim 1, characterized in that: in step (6), the method for preparing the back electrode on the back surface of the N-type crystalline silicon substrate is: The back surface of the N-type crystalline silicon substrate is printed with silver paste on the back electrode of the H-type grid line and dried, wherein the width of the main grid on the back is 0.5-3mm, and 3-6 grids are arranged at equal intervals, and the width of the auxiliary grids on the back is 20-100um. 14. A local back surface field N-type solar cell, comprising an N-type crystalline silicon substrate, the front surface of the N-type crystalline silicon substrate includes a p+ doped region and a passivation anti-reflection film on the front surface sequentially from the inside to the outside; The back surface of the N-type crystalline silicon substrate includes local n+ heavily doped regions and a passivation film on the back surface sequentially from the inside to the outside; it is characterized in that: the N-type crystalline silicon substrate also includes a back electrode arranged on the back surface, The back electrode includes a back main gate and a back sub-gate, the back sub-gate is connected to the local n+ heavily doped region, and the front electrode includes a metal wire in ohmic contact with the p+ doped region. 15 . The local back surface field N-type solar cell according to claim 14 , wherein the metal wire is electrically connected to the p+ doped region through a silver-aluminum alloy material. 16. A partial back surface field N-type solar cell according to claim 14, characterized in that: the front electrode comprises a segmented sub-gate, and the metal wire connects with the p+ doped region through the segmented sub-gate electrical connection. 17. A partial back surface field N-type solar cell according to claim 14, characterized in that: the front electrode comprises a segmented sub-grid and a heat-sensitive conductive layer arranged on the segmented sub-grid, and the segmented sub-grid The sub-gate is electrically connected to the p+ doped region; the metal wire is electrically connected to the heat-sensitive conductive layer. 18. A partial back surface field N-type solar cell according to claim 17, characterized in that: the segmented sub-grid is a silver-aluminum alloy segmented sub-grid; the heat-sensitive conductive layer is a solder paste conductive layer , the metal wire is a metal wire coated with a heat-sensitive conductive material. 19. A local back surface field N-type solar cell assembly, comprising front layer material, encapsulation material, local back surface field N-type solar cell, encapsulation material, and back layer material arranged sequentially from top to bottom, characterized in that: The local back surface field N-type solar cell is a partial back surface field N-type solar cell according to any one of claims 14-18. 20. A partial back surface field N-type solar cell system, comprising more than one partial back surface field N-type solar cell components connected in series, characterized in that: said partial back surface field N-type solar cell components are the ones described in claim 19 A local back surface field N-type solar cell module.