A method for preparing a selective emitter of an N-type crystalline silicon solar cell

Abstract

The present application provides a method for preparing a selective emitter of an N-type crystalline silicon solar cell, wherein after texturing the crystalline silicon wafer, the intended heavily doped area on the surface of the crystalline silicon is subjected to laser bombardment to obtain the intended heavily doped area after bombardment, and the dirt that may exist on the surface of the crystalline silicon is cleaned; the cleaned crystalline silicon is then placed in a diffusion furnace, and the crystalline silicon is subjected to through-source junction making in the diffusion furnace, and finally a heavily doped junction is formed in the intended heavily doped area on the surface of the crystalline silicon, and a lightly doped junction is formed in other junction areas on the surface of the crystalline silicon. Compared with the existing selective emitter preparation technology, the present invention application provides a method for preparing a boron-doped selective emitter for an N-type battery, which can simplify the process flow, and only requires a simple chemical cleaning treatment to carry out the subsequent process.

Description

Technical Field

[0001] The present application belongs to the technical field of solar cells, and specifically, relates to a method for preparing a selective emitter of an N-type crystalline silicon solar cell, and more specifically, to a method for preparing a selective emitter (SE). Background Art

[0002] The characteristic of selectively doped solar cells is that a selectively doped structure is prepared on a silicon wafer, so that the metal electrode contact area of ​​the solar cell is heavily doped with impurities to reduce the contact resistance and metal recombination of the cell; at the same time, light doping is performed in the non-metallic electrode area to reduce surface Auger recombination, increase the carrier collection rate, improve the short-wave response, improve the passivation effect, increase the opening voltage, and thus improve the electrical performance of the solar cell.

[0003] N-type high-efficiency battery technology is the next generation product after PERC batteries. The battery production capacity layout in 2022 has exceeded 60GW, and the market prospects are broad. The implementation of selective emitter technology on N-type batteries can bring significant efficiency improvements, which is of great significance.

[0004] Compared with the phosphorus-doped SE structure on P-type silicon wafers, it is very difficult to realize the boron-doped SE structure on N-type silicon wafers. (1) The atomic radius of boron is 0.082nm, the atomic radius of silicon is 0.118nm, and the mismatch ratio is 0.75. The lattice tension generated during the diffusion process leads to dislocation formation, which reduces the diffusion rate. (2) The maximum solid solubility of boron in silicon is about 5E+20cm-3. The solid solubility of boron is lower, the doping difficulty is higher, and higher energy is required. Therefore, it is difficult to use a laser doping method similar to phosphorus SE (first diffuse phosphorus, use the surface phosphorus silicon glass layer as the doping source, and then perform laser doping) to prepare a boron SE structure (first diffuse boron, use the surface borosilicate glass layer as the doping source, and then perform laser doping). Once the laser energy is too high, it will cause large laser damage in the local area, increasing the recombination of the area. If the laser energy is too low, it is difficult for the laser to dope the boron in the borosilicate glass layer into the P+ layer, and the heavily doped area cannot form an effective selective emitter structure, resulting in difficulty in reducing the contact resistance.

[0005] In order to solve the difficulty of realizing the boron SE structure on N-type cells, various patents have mentioned a variety of methods: (1) first diffuse to form a borosilicate glass layer, then locally dope it with a laser, and then perform a high-temperature oxidation annealing step after cleaning; (2) first diffuse to form a borosilicate glass layer, then locally groove it with a laser, and then perform a second high-temperature diffusion after cleaning. Both methods require two high-temperature equipment steps, which increases the number of steps.

[0006] There is also a type of boron source printing method, which has a complicated process and uneven doping under high-temperature advancement conditions. At the same time, the printing of the boron source is prone to pollution, and it is not an acceptable solution at present.

[0007] Patent No. CN113314627A proposes a new method for realizing the phosphorus SE structure of PERC cells, but this method still has some obvious defects. Summary of the invention

[0008] In view of the defects of the above-mentioned method, the present invention application proposes a method for preparing a selective emitter of an N-type crystalline silicon solar cell, which can be applicable to all N-type high-efficiency battery technologies, simplifies the preparation method of the boron SE structure, and can effectively meet the different concentration requirements of the lightly doped area and the heavily doped area, thereby significantly improving the conversion efficiency of the N-type battery.

[0009] The present invention is achieved by the following steps:

[0010] S1, texturing the surface of the N-type silicon wafer;

[0011] S2, bombarding the proposed heavily doped area on the surface of the N-type silicon wafer to obtain the bombarded proposed heavily doped area;

[0012] S3, pickling to remove possible dirt on the surface of the N-type silicon wafer after bombardment treatment;

[0013] S4, and then put the N-type silicon wafer cleaned in S3 into a diffusion furnace, and perform a through-source junction process on the crystalline silicon in the diffusion furnace, and finally form a heavily doped junction in the intended heavily doped area on the surface of the crystalline silicon, and form a lightly doped junction in other junction areas on the surface of the crystalline silicon.

[0014] The principle of the present invention is that the diffusion of boron atoms is almost entirely carried out through a self-interstitial mechanism. Self-interstitial diffusion comes from the collision of silicon self-interstitial atoms with displaced boron atoms, causing them to move to an interstitial position. Then the interstitial boron atom will collide with another silicon atom at the silicon lattice, causing it to move to a self-interstitial position, and the interstitial boron atom occupies this lattice position. Self-interstitial atomic diffusion requires the existence of vacancies or gaps, and the diffusion rate depends on the concentration of silicon self-interstitial atoms. Therefore, only by breaking enough silicon lattice bonds and forming enough vacancies and gaps can the diffusion rate of boron atoms be accelerated.

[0015] The breaking of crystal bonds is a high-energy driven process. The present invention bombards the quasi-heavy doping area on the N-type silicon wafer with a high-energy laser, causing a large number of silicon crystal bonds to break there, increasing the concentration of vacancies and self-interstitial atoms in the silicon wafer, and further helping to accelerate the diffusion of boron atoms. By utilizing this difference in diffusion rate, a high-concentration heavy doping can be formed in the laser-processed area on the surface of the silicon wafer through only one diffusion, and a low-concentration shallow doping can be formed in the non-laser-processed area. The crystal bond breakage caused by laser bombardment can also be annealed and repaired in the subsequent high-temperature diffusion process.

[0016] Furthermore, the bombardment treatment method is: forming damage on the surface of the N-type silicon wafer by laser beam marking.

[0017] Furthermore, the laser used for the bombardment treatment is a sub-nanosecond, picosecond or femtosecond laser, with a pulse width of 100fs-1ns and an instantaneous peak power of 50KW-500MW.

[0018] The special laser process used in this application bombards N-type silicon wafers, and the effect to be achieved is to only break the silicon crystal bonds without producing other adverse effects. The nanosecond laser pulse time is too long, and the thermal effect phenomenon is obvious, which will form thermal melt damage on the surface of the silicon wafer. The thermal melt damage must be removed by alkali washing. The thermal melt damage will seriously increase the surface recombination and affect the light trapping effect and the absorption of light. On the other hand, the instantaneous peak power of the nanosecond laser cannot be too low, otherwise it is difficult to break enough silicon crystal bonds, and it will not have a significant effect on increasing the diffusion rate of boron atoms.

[0019] Furthermore, the laser wavelength of the bombardment treatment is 355nm-532nm. The shorter the laser wavelength, the higher the energy of a single photon, and the more conducive it is to breaking the silicon crystal bond. The laser wavelength mentioned in the patent number CN113314627A is 1064nm, which is infrared light. The infrared thermal effect is obvious, which will cause thermal ablation on the surface of the silicon wafer and cause a high recombination rate on the surface of the silicon wafer.

[0020] Furthermore, the N-type silicon wafer is cleaned in a low-concentration alkaline solution for 5-15 seconds after being treated with laser bombardment, thereby reducing the consumption of chemicals.

[0021] Furthermore, after the S1 texturing step, the surface of the crystalline silicon wafer is subjected to oxidation treatment, and after the oxidation treatment, the area to be heavily doped on the surface of the crystalline silicon is subjected to laser bombardment treatment.

[0022] Furthermore, the N-type silicon wafer after laser bombardment must be pickled before entering the diffusion tube to remove possible dirt on the surface. The diffusion tube is a high-temperature device and it is necessary to ensure that no impurities are introduced. If the cleanliness can be controlled, this cleaning step can be omitted.

[0023] Furthermore, the surface texturing treatment in step S1 is not only texturing, but also acid polishing or alkaline polishing required by other battery technologies.

[0024] Furthermore, the selective emitter formation method proposed in the present application can be used in any N-type battery structure to form a boron-doped selective emitter structure.

[0025] After adopting the above technical solution, the beneficial effects of the present invention are:

[0026] Compared with the existing selective emitter preparation technology, the present invention provides a method for preparing a boron-doped selective emitter for an N-type battery, which can simplify the process flow and can be used for subsequent processes after washing in a low-concentration alkaline solution for 5-15 seconds. Only one laser process is required and only one high-temperature diffusion is required to achieve a boron-doped selective emitter. It can effectively improve electrical performance and has the significant effects of high mass production feasibility and low unit watt cost. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0028] The structures, proportions, sizes, etc. illustrated in the drawings of this specification are only used to match the contents disclosed in the specification so as to facilitate understanding and reading by persons familiar with this technology. They are not used to limit the conditions under which this application can be implemented, and therefore have no substantive technical significance. Any structural modification, change in proportion or adjustment of size, without affecting the effects and purposes that can be achieved by this application, should still fall within the scope of the technical contents disclosed in this application.

[0029] Figure 1 This is the microscopic texture of the silicon wafer surface that has not been treated by laser blasting in Example 1 of the present application.

[0030] Figure 2 This is the concentration doping curve of Example 2 of the present application after gas phase diffusion.

[0031] Figure 3 This is a schematic diagram of a typical process flow of Example 1 of the present application.

[0032] Figure 4 This is a typical process flow diagram of Example 3 of this application. DETAILED DESCRIPTION

[0033] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the embodiments in the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.

[0034] The present application proposes a method for preparing a selective emitter of an N-type crystalline silicon solar cell, wherein the surface of an N-type silicon wafer is textured. The typical textured structure is not treated by laser bombardment, and the microscopic texture of the surface of the silicon wafer is as follows: Figure 1 As shown in the figure; the N-type silicon wafer surface is subjected to laser beam bombardment treatment to obtain the bombarded heavily doped area, and the velvet structure of the silicon wafer surface is almost undamaged after the laser bombardment treatment. The laser used for the bombardment treatment is a sub-nanosecond, picosecond or femtosecond laser with a pulse width of 100fs-1ns, and the instantaneous peak power of the laser is 50KW-500MW; after rapid cleaning with low-concentration alkali solution for 5-15s, the dirt that may be generated on the surface of the N-type silicon wafer after the laser bombardment treatment is removed by acid washing; the cleaned N-type crystalline silicon wafer is placed in a high-temperature diffusion furnace, and a through-source bonding process is performed on the crystalline silicon in the high-temperature diffusion furnace. Usually, the boron source is a liquid source such as BCl3, boron tribromide or a gaseous source such as trimethylborane, and the carrier gas is N 2 Gases such as silicon dioxide and silicon iodine will eventually form heavily doped junctions in the heavily doped areas on the surface of the crystalline silicon, while lightly doped junctions are formed in other junction areas on the surface of the crystalline silicon. After cleaning the borosilicate glass layer formed by the diffusion, the subsequent processes can be carried out to complete the production of solar cells.

[0035] Optionally, the method of crystalline silicon knotting is to coat the entire surface of the crystalline silicon after laser bombardment with a boron source, and then drive the boron source into the crystalline silicon surface by laser doping to complete the knotting process. The main components of the coated boron source include boric acid and tributyl borate or boron tribromide or nano silicon boron slurry, and the boron source is in solid or liquid form; when the boron source is nano silicon boron slurry, the method of depositing the boron source in the heavily doped area on the surface of the crystalline silicon is screen printing or laser transfer, and the laser transfer is to place the boron slurry of the material to be transferred in the transfer sheet, and transfer and deposit it on the surface of the crystalline silicon wafer under the action of laser irradiation.

[0036] Optionally, after the texturing step, the surface of the crystalline silicon wafer is oxidized, and after the oxidation, the area to be heavily doped on the surface of the crystalline silicon is laser bombarded, and then cleaned and bonded.

[0037] Example 1

[0038] The preparation process of an N-type Topcon solar cell with a boron-doped selective emitter is as follows: Figure 3 As shown, the details are as follows:

[0039] (1) Select an N-type single crystal silicon wafer with a resistivity of 0.5-1 ohm*cm, a thickness of 160 μm, and a size of 182 mm*182 mm. Use alkaline texturing to remove the damaged layer and texturing in a texturing tank to form a pyramid texture surface with a height of 0.5 μm-5 μm.

[0040] (2) The surface of the N-type single crystal silicon substrate 101 and the proposed heavily doped region 111 are laser bombarded using a picosecond laser with a laser wavelength of 355-532nm, a laser instantaneous peak power of 200-20000KW, a laser light output frequency of 200KHZ, and a laser scanning speed of 18m / s to obtain the bombarded proposed heavily doped region 111. The pattern of the proposed heavily doped region is consistent with the metal gate line, consisting of 160 lines with a width of 90μm.

[0041] (3) After rapid cleaning with low-concentration alkali solution for 5-15 seconds, the silicon wafer treated by laser bombardment is cleaned with a 5% HF solution to ensure that the silicon wafer is clean before entering the high-temperature diffusion tube to avoid contamination of the high-temperature diffusion tube.

[0042] (4) The cleaned N-type single crystal silicon 101 is placed in a high-temperature diffusion furnace, and a through-source bonding process is performed on the crystalline silicon in the high-temperature diffusion furnace. The boron source is BCl 3 , liquid sources such as boron tribromide or gaseous sources such as trimethylborane, and the carrier gas is N 2 The reaction temperature is 800-1000℃, the whole diffusion process time is 1-5 hours, and a heavily doped P++ junction 121 is formed in the heavily doped area on the surface of the N-type silicon wafer, and a lightly doped P+ junction 122 is formed in other junction areas on the surface of the N-type silicon wafer. + The surface concentration of junction 121 is about 2 -6 E19cm -3 The junction depth is about 0.6-1.2μm, the square resistance is 60-120ohm, and the surface concentration of the lightly doped P+ junction 122 is about 0.5 -2 E19cm -3 The junction depth is 0.3-1.0μm and the square resistance is 120-220ohm. The lattice defects generated during the laser bombardment process are also repaired in the high-temperature diffusion step.

[0043] (5) Use wet alkaline polishing process to remove the P+ layer on the back and edge of the silicon wafer, and polish the back of the silicon wafer.

[0044] (6) forming an extremely thin tunnel oxide layer 102 and a doped amorphous silicon layer 103 on the alkali polished surface by LPCVD or PECVD, wherein the thickness of the tunnel oxide layer 102 is 0.5-5 nm, and the thickness of the doped amorphous silicon layer 103 is 50-200 nm;

[0045] (7) placing the substrate 101 in an oxidation tube for a thermal annealing process at 700-950° C. for 30-60 min;

[0046] (8) Using wet equipment to remove the front amorphous silicon coating;

[0047] (9) Atomic layer deposition or plasma enhanced chemical vapor deposition is used to sequentially deposit an AlOx passivation layer 131, a single-layer or multi-layer SiNx anti-reflection layer, i.e., a passivation layer and an anti-reflection layer 132 on the front side of the N-type silicon wafer to form a passivation anti-reflection stacked structure, wherein the aluminum oxide (AlOx) layer is deposited using TMA and O 2 or N 2 O mixed gas, the reaction temperature is 200-350 ° C; the silicon nitride (SiNx) layer is deposited using SiH 4 and NH 3 The reaction temperature is 300-550℃;

[0048] (10) A single or multi-layer SiNx passivation anti-reflection layer 104 is formed on the back of the N-type silicon wafer by using a plasma enhanced chemical vapor deposition method, and a silicon nitride (SiNx) layer is deposited by using SiH 4 and NH 3 The reaction temperature is 300-550℃;

[0049] (11) forming a back electrode and a back electric field on the back of the battery by screen printing or laser transfer, and drying;

[0050] (12) A positive electrode is formed on the front side of the battery by screen printing or laser transfer, and then dried and sintered to prepare a complete electrode for the solar cell (not shown).

[0051] Example 2

[0052] This embodiment is the same as embodiment 1, except that in step (2), a picosecond laser is used, the laser wavelength is 355nm, the laser instantaneous peak power is 1000KW, the laser light frequency is 200KHZ, and the laser scanning speed is 18m / s. The silicon wafer with selective emitter is completed, and the doping concentration of the heavily doped area and the lightly doped area is tested. The test results are as follows: Figure 2 The peak surface concentration of the heavily doped region of the boron selective emitter prepared in Example 2 is 1.71E19 cm -3 The peak surface concentration of the lightly doped region is 1.28E19cm -3 The surface doping concentration of the heavily doped area is significantly different from that of the lightly doped area, which enables the preparation of a selective emitter structure. Through a series of subsequent laser parameter optimizations and diffusion process optimizations, a more ideal selective emitter structure can be achieved to meet the technical requirements of a variety of high-efficiency batteries.

[0053] Example 3

[0054] Compared with Example 1, in Example 3, after the texturing step, the surface of the crystalline silicon wafer is oxidized, and the oxide film layer is SiO2 The layer is laser-bombarded on the surface of the crystalline silicon in the area to be heavily doped, and then a boron source is deposited, followed by laser doping and subsequent solar cell manufacturing processes.

[0055] As a typical non-limiting method for preparing solar cells, the process of preparing solar cells from N-type crystalline silicon wafers in this embodiment is as follows: Figure 4 As shown, the details are as follows:

[0056] (1) An N-type single crystal silicon wafer with a resistivity of 0.5-1 ohm*cm, a thickness of 160 μm, and a size of 210 mm*210 mm is selected, and an N-type single crystal silicon substrate 201 is placed in a texturing tank to remove the damaged layer and texturing to form a pyramid texture surface with a height of 0.5 μm-5 μm; then the texturing single crystal silicon substrate is placed in a high-temperature mixture of concentrated nitric acid and sulfuric acid to form a thin layer of SiO 2 Layer 202, or thermally oxidized in a high temperature furnace to form SiO 2 Layer 202;

[0057] (2) laser bombarding the proposed heavily doped region 211 on the surface of the N-type single crystal silicon substrate 201, using a picosecond laser, with a laser wavelength of 355-532nm, a laser instantaneous peak power of 200-20000KW, a laser light frequency of 200KHZ, and a laser scanning speed of 18m / s, to obtain the bombarded proposed heavily doped region 211, the pattern of which is consistent with the metal gate line, consisting of 160 lines with a width of 90μm. The laser bombardment of the N-type silicon wafer surface destroys the silicon-crystal bond and introduces an amorphous layer on the silicon surface to a certain extent;

[0058] (3) After simple chemical cleaning, the single crystal silicon substrate 201 treated by laser blasting is cleaned with a 5% HF solution, and a boron source is deposited on the single crystal silicon substrate 201. The main components of the deposited boron source include boric acid and tributyl borate or boron tribromide or nano-silicon boron slurry, etc. The boron source can be applied to the surface of the single crystal silicon substrate by spraying, spin coating or other coating methods, and dried and solidified if necessary;

[0059] (4) After a boron source is deposited on the surface of the single crystal silicon substrate, a heavily doped region 221 and a lightly doped region 222 are formed on the surface of the substrate by laser doping. The laser wavelength used is 355 to 532 nm, the laser power is 20 to 1000 W, the frequency is 5 to 50 MHz, the scanning speed is 5 to 50 m / s, and the spot size is 20 to 1000 um.

[0060] (5) using a cleaning solution of 5% HF solution, alkali or an alkaline aqueous solution of NaOH, KOH or TMAH with a concentration range of 10-50wt% to clean off the boron source on the substrate surface that has not formed effective doping and the surface damage caused by the laser doping process; etching away the P+ layer at the edge of the single crystal silicon wafer, and polishing the back of the silicon wafer;

[0061] (6) forming an extremely thin tunnel oxide layer 206 and a doped amorphous silicon layer 208 on the polished surface of the back side of the silicon wafer by LPCVD or PECVD, wherein the thickness of the tunnel oxide layer 206 is 0.5-5 nm, and the thickness of the doped amorphous silicon layer 208 is 50-200 nm;

[0062] (7) placing the substrate 201 in an oxidation tube for a thermal annealing process at 700-950° C. for 30-60 min;

[0063] (8) Using wet equipment to remove the front amorphous silicon coating;

[0064] (9) A passivation layer 231 of AlOx and a single-layer or multi-layer SiNx anti-reflection layer are sequentially deposited on the front side of the N-type silicon wafer by atomic layer deposition or plasma enhanced chemical vapor deposition, so as to form a passivation anti-reflection stacked structure including the passivation layer 231 and the anti-reflection layer 232, wherein the aluminum oxide (AlOx) layer is deposited by TMA and O 2 or N 2 O mixed gas, the reaction temperature is 200-350 ° C; the silicon nitride (SiNx) layer is deposited using SiH 4 and NH 3 The reaction temperature is 300-550℃;

[0065] (10) A single or multi-layer SiNx passivation anti-reflection layer (not shown) is formed on the back of the N-type silicon wafer by plasma enhanced chemical vapor deposition, and a SiH 4 and NH 3 The reaction temperature is 300-550℃;

[0066] (11) forming a back electrode and a back electric field on the back of the battery by screen printing or laser transfer, and drying;

[0067] (12) A positive electrode is formed on the front side of the battery by screen printing or laser transfer, and then dried and sintered to prepare a complete electrode for the solar cell (not shown).

[0068] Optionally, the method of crystalline silicon knotting is to coat the entire surface of the crystalline silicon after laser bombardment with a boron source, and then drive the boron source into the crystalline silicon surface by laser doping to complete the knotting process. The main components of the coated boron source include boric acid and tributyl borate or boron tribromide or nano silicon boron slurry, and the boron source is in solid or liquid form; when the boron source is nano silicon boron slurry, the method of depositing the boron source in the heavily doped area on the surface of the crystalline silicon is screen printing or laser transfer, and the laser transfer is to place the boron slurry of the material to be transferred in the transfer sheet, and transfer and deposit it on the surface of the crystalline silicon wafer under the action of laser irradiation.

[0069] Example 4

[0070] Compared with Example 1, in this embodiment, the cleaning solution after laser bombardment treatment can use an alkaline solution instead of a 5% HF solution, and the alkaline solution includes an aqueous solution of NaOH or KOH or TMAH with a concentration range of 10-50wt%, and the alkaline solution is corroded for 100-600s at 25-70°C; further, a mixed solution including polydimethylsiloxane and trimethylammonium bromide is added to the alkaline corrosion solution, which can shorten the alkaline corrosion time to 10-500s at a temperature range of 25-70°C, and can improve the cleaning ability of the silicon surface layer after laser bombardment, effectively clean the dirt on the surface of the crystalline silicon, and obtain a cleaner surface.

[0071] For example, if the etching solution is 40wt% KOH, the etching temperature is 70℃, and the etching time is 7min, the objects to be cleaned in the bombardment area can be cleaned. If the etching solution is 30wt% KOH, and the additive PDMS+trimethylammonium bromide mixed solution is added at about 5‰, the etching temperature is 50℃, and the etching time is reduced to 4min, the objects to be cleaned in the bombardment area can be cleaned.

[0072] In contrast, the etching solution is 20wt% KOH, and the additive PDMS+trimethylammonium bromide mixed solution is added at about 5‰, the etching temperature is 70℃, and the etching time is reduced to 6min, and the objects to be cleaned in the bombardment treatment area can be cleaned. It can be seen that after adding the additive, the corrosion rate increases and the corrosion time becomes shorter. Adding the additive can enhance the corrosion ability and surface cleaning ability of the alkali solution after bombarding the silicon substrate surface.

[0073] In this specification, each embodiment is described in a progressive, parallel, or progressive and parallel manner. Each embodiment focuses on the differences from other embodiments, and the same or similar parts between the embodiments can be referred to each other. For the device disclosed in the embodiment, since it corresponds to the method disclosed in the embodiment, the description is relatively simple, and the relevant parts can be referred to the method part.

[0074] It should be noted that in the description of the present application, it should be understood that the terms "upper", "lower", "top", "bottom", "inside", "outside" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the drawings, which are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present application. When a component is considered to be "connected" to another component, it may be directly connected to the other component or there may be a centrally arranged component at the same time.

[0075] It should also be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "comprises", "comprising" or any other variants thereof are intended to cover non-exclusive inclusion, so that an article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such article or device. In the absence of further restrictions, the elements defined by the sentence "comprising a ..." do not exclude the existence of other identical elements in the article or device including the above elements.

[0076] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present application. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to the embodiments shown herein, but will conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for preparing a selective emitter of an N-type crystalline silicon solar cell, characterized in that: The steps include: S1, texturing the surface of the N-type silicon wafer; S2, laser bombarding the proposed heavily doped area on the surface of the N-type silicon wafer to obtain the proposed heavily doped area after laser bombardment; the laser for the laser bombardment treatment is a sub-nanosecond, picosecond or femtosecond laser, with a pulse width of 100fs-1ns, and the instantaneous peak power of the laser is 50KW-500MW; S3, pickling to remove possible dirt on the surface of the N-type silicon wafer after bombardment treatment; S4, and then put the N-type silicon wafer cleaned in S3 into a diffusion furnace, and perform a through-source junction process on the crystalline silicon in the diffusion furnace, and finally form a heavily doped junction in the intended heavily doped area on the surface of the N-type silicon wafer, and form a lightly doped junction in other junction areas on the surface of the crystalline silicon.

2. The method for preparing a selective emitter of an N-type crystalline silicon solar cell according to claim 1, characterized in that: After the step of texturing the surface of the N-type silicon wafer in S1, the surface of the N-type silicon wafer is oxidized, and after the oxidation, the heavily doped region on the surface of the N-type silicon wafer is laser bombarded.

3. A method for preparing a selective emitter of an N-type crystalline silicon solar cell according to claim 1 or 2, characterized in that: The laser wavelength of the laser bombardment treatment is 355nm-532nm.

4. The method for preparing a selective emitter of an N-type crystalline silicon solar cell according to claim 1, characterized in that: After laser blasting and before pickling, the surface is quickly cleaned in a low concentration alkali solution for 5-15 seconds.

5. The method for preparing a selective emitter of an N-type crystalline silicon solar cell according to claim 1, characterized in that: The boron source of the through-source bonding process is a liquid source such as BCl3, boron tribromide or a gaseous source such as trimethylborane, and the carrier gas is a gas such as N2.

6. A method for preparing a selective emitter of an N-type crystalline silicon solar cell, characterized in that: The steps include: S1, texturing the surface of the N-type silicon wafer; S2, laser bombarding the proposed heavily doped area on the surface of the N-type silicon wafer to obtain the proposed heavily doped area after laser bombardment; the laser for the laser bombardment treatment is a sub-nanosecond, picosecond or femtosecond laser, with a pulse width of 100fs-1ns, and the instantaneous peak power of the laser is 50KW-500MW; S3, pickling to remove possible dirt on the surface of the N-type silicon wafer after bombardment treatment; S4. Coating the surface of the N-type silicon wafer cleaned in S3 with a boron source and then performing laser doping. The main components of the boron source include boric acid and tributyl borate or boron tribromide or nano-silicon boron slurry. The boron source is in solid or liquid form. Finally, a heavily doped junction is formed in the intended heavily doped area on the crystalline silicon surface, and a lightly doped junction is formed in other junction areas on the crystalline silicon surface.

7. The method for preparing a selective emitter of an N-type crystalline silicon solar cell according to claim 6, characterized in that: The laser parameters of the laser doping include: laser wavelength of 355-1064nm, laser power of 20-1000W, frequency of 5-50MHz, scanning speed of 5-50m / s, and spot size of 20-1000μm.

8. The method for preparing a selective emitter of an N-type crystalline silicon solar cell according to claim 6, characterized in that: The boron source that does not form effective doping on the substrate surface and the surface damage caused by the laser doping process are cleaned off. The cleaning liquid is 5% HF solution, alkali or NaOH or KOH or TMAH alkaline aqueous solution with a concentration range of 10-50wt%.

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