阅读说明：本技术 一种n型太阳能电池及制造方法 (N-type solar cell and manufacturing method thereof ) 是由 曹育红 张胜军 许佳平 符黎明 于 2021-08-27 设计创作，主要内容包括：本发明公开了一种N型太阳能电池及制造方法,所述制造方法包括以下步骤：提供N型硅片；通过硼扩散在N型硅片的正面形成硼扩散层；在所述硼扩散层的表面沉积Al-(2)O-(3)钝化膜；对Al-(2)O-(3)钝化膜进行局部开窗处理。本发明采用新型激光工艺或者腐蚀浆料刻蚀的方式对Al-(2)O-(3)钝化膜进行局部开窗处理,解决了N型太阳能电池正面的Al-(2)O-(3)钝化膜在烧结过程中难以烧穿的问题,不仅保证了硼发射极表面烧结峰值温度的稳定性,避免了由于氧化铝膜厚度的波动导致硼发射极烧结工艺的波动,有利于生产的连贯性,提高了生产效率,而且最终也提高了N型太阳能电池的综合电性能,大大降低了因Al-(2)O-(3)钝化膜未烧穿或者过烧导致的电性能异常现象的发生。(The invention discloses an N-type solar cell and a manufacturing method thereof, wherein the manufacturing method comprises the following steps: providing an N-type silicon wafer; forming a boron diffusion layer on the front surface of the N-type silicon wafer through boron diffusion; depositing Al on the surface of the boron diffusion layer 2 O 3 A passivation film; for Al 2 O 3 And carrying out local windowing treatment on the passivation film. The invention adopts a novel laser process or a corrosion slurry etching mode to carry out Al treatment 2 O 3 The passivation film is subjected to local windowing treatment, so that Al on the front surface of the N-type solar cell is solved 2 O 3 The problem that the passivation film is difficult to burn through in the sintering process is solved, the stability of the sintering peak temperature on the surface of the boron emitter is ensured, the fluctuation of the sintering process of the boron emitter caused by the fluctuation of the thickness of the alumina film is avoided, the production continuity is facilitated, the production efficiency is improved, the comprehensive electrical property of the N-type solar cell is finally improved, and the problem that the sintering process is difficult to burn through due to Al is greatly reduced 2 O 3 The abnormal phenomenon of electrical property caused by non-burn-through or over-burn of the passivation film.)

1. A method for manufacturing an N-type solar cell, comprising the steps of:

providing an N-type silicon wafer;

forming a boron diffusion layer on the front surface of the N-type silicon wafer through boron diffusion;

depositing Al on the surface of the boron diffusion layer₂O₃A passivation film;

for Al₂O₃And carrying out local windowing treatment on the passivation film.

2. The method for manufacturing the N-type solar cell according to claim 1, wherein the Al is etched by a novel laser process or etching slurry₂O₃And carrying out local windowing treatment on the passivation film.

3. The method for manufacturing an N-type solar cell according to claim 2, wherein Al is subjected to a novel laser process₂O₃When the passivation film is subjected to local windowing treatment, the wavelength of the laser is 532nm, and the power is 10-20W.

4. The method of claim 2, wherein the pattern of the partial windowing process is consistent with the pattern of the front side electrode of the cell.

5. The method of claim 4, wherein the depth of the pattern of the partial windowing and Al is determined by the method₂O₃The thickness of the passivation film is kept consistent.

6. The method for manufacturing an N-type solar cell according to claim 1, wherein the Al is₂O₃The thickness of the passivation film is 4-8 nm.

7. The method for manufacturing an N-type solar cell according to claim 1, wherein Al is added₂O₃After the passivation film is subjected to local windowing treatment, the passivation film is also includedAl₂O₃And depositing a silicon nitride film on the passivation film.

8. The method for manufacturing an N-type solar cell according to claim 1, wherein the thickness of the silicon nitride film is 70 to 80 nm.

9. The method of manufacturing an N-type solar cell according to claim 1, characterized in that it comprises, but is not limited to, the following steps:

(1) removing a damage layer and texturing on the silicon wafer;

(2) b diffusion, forming a boron diffusion layer and a BSG layer on the front side of the silicon wafer, and removing the boron diffusion layer on the back side and the side of the silicon wafer after the boron diffusion is finished;

(3) phosphorus diffusion, namely forming a heavily doped layer and a PSG layer on the back of the silicon wafer, and removing the PSG layer and the phosphorus diffusion layer on the side surface of the N-type silicon wafer after the phosphorus diffusion is finished;

(4) depositing Al with the thickness of 4-8 nm on the front surface of the silicon wafer₂O₃A passivation film;

(5) al on the front side of the silicon wafer by adopting a novel laser process or etching slurry₂O₃Carrying out local windowing treatment on the passivation film;

(6) depositing silicon nitride films with the thickness of 70-80 nm on the front side and the back side of the silicon wafer respectively;

(7) and respectively printing a positive electrode and a back electrode on the front side and the back side of the silicon wafer, and sintering to obtain the N-type solar cell.

10. An N-type solar cell produced by the method for producing an N-type solar cell according to any one of claims 1 to 9.

Technical Field

The invention relates to the technical field of solar cells, in particular to an N-type solar cell and a preparation method thereof.

Background

The N-type crystalline silicon solar cell has become a key development direction of a new generation of high-efficiency solar cell due to the advantages of long minority carrier lifetime, insensitivity to metal impurities, good weak light effect, low temperature coefficient, no photothermal induced attenuation caused by B-O recombination and the like, and is also more and more concerned by the industry. The mature N typeThe crystalline silicon solar cell mainly comprises N-PERT, N-PERL, N-TOPCon, N-IBC, HIT and other structures. These cells all use a boron doped layer as the emitter (P) of the cell⁺Layer) due to Al₂O₃The interface of the passivation film and the silicon contains high-density negative charges, the repulsion effect on minority electrons can be enhanced, and field passivation is formed, so that Al with the thickness of 5-8 nm is mainly adopted in the industry₂O₃SiN with passivation film overlapping thickness of 70-80 nm_xThe film acts as a passivating antireflective film for the boron emitter. However, when Al is used₂O₃After the passivation film is used as a passivation film, great difficulty is brought to the subsequent printing and sintering process of the battery.

From the aspect of work function matching, the printing paste on the side of the boron emitter generally adopts Ag-Al paste, and the paste has strong ablation capacity on silicon nitride, is easy to penetrate through the silicon nitride, but has strong ablation capacity on Al₂O₃The ablation ability of the passivation film is weak and it is against Al₂O₃The thickness of the passivation film is sensitive and thus the optimum sintering temperature fluctuates greatly during sintering, which is very disadvantageous for production. To ensure burning through of Al₂O₃Passivation film and overlying SiN_xThe film is generally sintered at a high temperature, but if the sintering temperature is too high, the overburning phenomenon is easy to occur, and the battery efficiency is influenced. Meanwhile, when the sintering peak temperature is slightly fluctuated and lowered, the Ag-Al slurry in a partial region is difficult to burn through Al₂O₃The passivation film cannot form a good ohmic contact with the silicon substrate, so that the requirement for temperature fluctuation of sintering furnace equipment is very high, but the temperature control accuracy of the conventional sintering furnace cannot meet the requirement. The current sintering process window is narrow and often ends up affecting cell performance due to temperature fluctuations.

However, if the boron emitter adopts the existing PERC battery manufacturing method, Al is directly treated₂O₃Passivation film and overlying SiN_xThe Ag-Al slurry is printed after the film is perforated, so that excessive Ag-Al slurry is inevitably generated during sintering and enters the boron emitter, metal recombination is aggravated, even the boron emitter is burnt through, and the battery is greatly influencedAnd (4) performance.

None of the above methods well solves the problems encountered in the sintering process of the conventional boron emitter, and therefore, a novel method for manufacturing a boron emitter suitable for an N-type crystalline silicon solar cell needs to be provided to solve the problem of sintering stability of the conventional boron emitter.

Disclosure of Invention

The invention provides an N-type solar cell and a manufacturing method thereof, which can greatly solve the problem that the sintering temperature window of the surface of the N-type solar cell with a boron emitter is narrow, improve the stability of a sintering process and further improve the conversion efficiency of the cell.

According to a first aspect of the present invention, there is provided a method of manufacturing an N-type solar cell, comprising the steps of:

providing an N-type silicon wafer;

forming a boron diffusion layer on the front surface of the N-type silicon wafer through boron diffusion;

depositing Al on the surface of the boron diffusion layer₂O₃A passivation film;

for Al₂O₃And carrying out local windowing treatment on the passivation film.

Preferably, Al is etched by adopting a novel laser process or corrosion slurry₂O₃And carrying out local windowing treatment on the passivation film.

Preferably, Al is treated by adopting a novel laser process mode₂O₃When the passivation film is subjected to local windowing treatment, the wavelength of the laser is 532nm, and the power is 10-20W.

Preferably, the pattern of the partial windowing process is consistent with the electrode pattern on the front side of the cell.

Preferably, the pattern depth of the partial windowing treatment and Al₂O₃The thickness of the passivation film is kept consistent.

Preferably, the Al is₂O₃The thickness of the passivation film is 4-8 nm.

Preferably, for Al₂O₃After the passivation film is subjected to local windowing treatment, Al is added₂O₃And depositing a silicon nitride film on the passivation film.

Preferably, the thickness of the silicon nitride film is 70-80 nm.

Preferably, the method for manufacturing the N-type solar cell includes, but is not limited to, the following steps:

(1) removing a damage layer and texturing on the silicon wafer;

(2) b diffusion, forming a boron diffusion layer and a BSG layer on the front side of the silicon wafer, and removing the boron diffusion layer on the back side and the side of the silicon wafer after the boron diffusion is finished;

(3) phosphorus diffusion, namely forming a heavily doped layer and a PSG layer on the back of the silicon wafer, and removing the PSG layer and the phosphorus diffusion layer on the side surface of the silicon wafer after the phosphorus diffusion is finished;

(4) depositing Al with the thickness of 4-8 nm on the front surface of the silicon wafer₂O₃A passivation film;

(5) al on the front side of the silicon wafer by adopting a novel laser process or etching slurry₂O₃Carrying out local windowing treatment on the passivation film;

(6) depositing silicon nitride films with the thickness of 70-80 nm on the front side and the back side of the silicon wafer respectively;

(7) and respectively printing a positive electrode and a back electrode on the front side and the back side of the silicon wafer, and sintering to obtain the N-type solar cell.

According to one embodiment of the method, the thickness of Al on the surface of the boron emitter is 4-8 nm₂O₃Passivating the film, firstly adopting a novel laser process to Al₂O₃The passivation film is subjected to local windowing, the graph of the local windowing is consistent with the electrode graph on the surface of the boron emitter, and the laser windowing depth is equal to that of the Al₂O₃The thickness of the passive film is consistent, and Al is added after the windowing is finished₂O₃And a silicon nitride film with the thickness of about 70-80 nm is deposited on the surface of the passivation film, so that the Ag-Al slurry printed on the front surface of the silicon wafer with the boron emitter can be contacted with the silicon substrate only by burning through the silicon nitride film in the sintering process. In the sintering process, the Ag-Al slurry can not burn through the boron emitter due to the blocking of the silicon nitride film, so that the stability of the battery performance is improved.

Using laser to treat Al₂O₃During the local windowing of the passivation film due to Al₂O₃The difference between the passivation film and the silicon wafer substrate in the properties such as the refractive index of the material is large, so that laser with proper wavelength needs to be selected to selectively apply energy mainly to Al₂O₃On the passivation film, due to Al₂O₃The thickness of the passive film is thinner, so that lower power is required to enable Al to be obtained₂O₃The invention provides a novel laser process, which ensures Al by setting proper laser wavelength and laser power₂O₃The boron emitter of the silicon chip substrate is not affected when the passivation film is windowed, and the integrity of the boron emitter is ensured.

Alternatively, Al may be used₂O₃Printing corrosion slurry on the surface of the passive film to etch Al₂O₃The purpose of local windowing is realized by the passivation film, the graph of the local windowing is consistent with the electrode graph on the surface of the boron emitter, and the laser windowing depth is equal to that of Al₂O₃The thickness of the passive film is consistent, and Al is added after the windowing is finished₂O₃And a silicon nitride film with the thickness of about 70-80 nm is deposited on the surface of the passivation film, so that the Ag-Al slurry printed on the front surface of the silicon wafer with the boron emitter can be contacted with the silicon substrate only by burning through the silicon nitride film in the sintering process. In the sintering process, the Ag-Al slurry can not burn through the boron emitter due to the blocking of the silicon nitride film, so that the stability of the battery performance is improved.

According to a second aspect of the present invention, an N-type solar cell is provided, which is manufactured using the above-described method for manufacturing an N-type solar cell.

In summary, compared with the prior art, the invention has the following significant advantages:

the invention adopts a novel laser process or a corrosion slurry etching mode to carry out Al treatment on the front surface of the silicon wafer₂O₃The passivation film is subjected to local windowing treatment, so that Al on the front surface of the N-type solar cell is solved₂O₃The problem that the passive film is difficult to burn through in the sintering process is solved, so that the sintering temperature window of the side of the battery with the boron emitter is widened, and the surface of the boron emitter is ensuredThe stability of the sintering peak temperature avoids the fluctuation of the boron emitter sintering process caused by the fluctuation of the thickness of the alumina film, is beneficial to the production continuity, improves the production efficiency, finally improves the comprehensive electrical property of the N-type solar cell, and greatly reduces the influence of Al on the overall electrical property of the N-type solar cell₂O₃The abnormal phenomenon of electrical property caused by the non-burn-through or the burn-through of the passivation film occurs.

Detailed Description

The technical solution of the present invention will be further described with reference to the following examples.

In the existing application, one surface of the N-type solar cell having the boron diffusion layer is a boron emitter, the boron emitter is located on the front surface of the N-type solar cell, and an Ag — Al paste is usually printed to manufacture an electrode.

Example 1

A method of manufacturing an N-type solar cell, comprising, but not limited to, the steps of:

(1) and removing a damage layer and texturing the silicon wafer.

Taking an N-type silicon wafer with the thickness of 150-200 mu m and the resistivity of 1-10 ohm cm, firstly placing the N-type silicon wafer in a KOH solution with the mass fraction of 0.5-2.0%, reacting for 100-200 s at 40-80 ℃, removing an original damage layer caused in the cutting process of the silicon wafer, then placing the N-type silicon wafer in a mixed solution of KOH with the mass fraction of 0.5-2.5% and a texturing additive with the volume fraction of 0.5-1.5%, performing double-sided texturing for 350-500 s at 50-85 ℃, cleaning and drying.

(2) And B, boron diffusion, namely forming a boron diffusion layer and a BSG layer on the front side of the silicon wafer, and removing the boron diffusion layer on the back side and the side surface of the silicon wafer after the boron diffusion is finished.

Inserting the textured N-type silicon wafer double-sided lamination into a quartz boat, placing the quartz boat in a furnace tube for high-temperature boron diffusion, and forming a boron diffusion layer and a BSG layer on the front side of the silicon wafer, wherein the diffusion sheet resistance of the boron diffusion layer is controlled to be 60-100 ohm/sq, and the surface boron atom concentration of the boron diffusion layer is 1E 19-4E 19cm^-3The junction depth is 0.5-1 um, and the thickness of the BSG layer on the boron diffusion layer is controlled to be 30-60 nm; the main process of boron diffusion in this example is as follows: pre-oxidizing the silicon wafer for 400-800 s at 820-870 ℃; introducing a boron source at 820-870 ℃ for carrying out pre-deposition for 800-1500 s; high temperature propulsion 2000 at 900-4000 s; and carrying out oxidation promotion at 950-1000 ℃, and reducing the surface concentration of the boron diffusion layer through high-temperature oxidation while forming a BSG layer.

The single-side acid washing method of the chain type etching machine is characterized in that the belt speed is set to be 0.4-0.8 m/min, the silicon wafer is subjected to HF solution with the mass fraction of 3-6% to remove BSG layers on the back and the side of the silicon wafer, then mixed solution consisting of KOH aqueous solution with the mass fraction of 5-10% and alkali polishing additives with the volume fraction of 0.5-5% is subjected to alkali polishing on the side and the back of the silicon wafer for 200-400 s at the temperature of 50-80 ℃, the polishing depth is 3-8 microns, the BSG layer on the front of the silicon wafer is retained while the boron diffusion layer on the back and the side is removed, and the silicon wafer is washed by acid and water and then dried.

(3) Phosphorus is diffused to form N on the back of the silicon chip⁺Heavily doped layer and PSG layer, removing N on the side surface of the silicon wafer after phosphorus diffusion⁺Heavily doped layer and PSG layer.

Inserting the silicon wafer double-sided lamination (boron diffusion layer face to face) with polished back and side into quartz boat, placing in furnace tube for POCl₃Diffusing to form N on the back of the silicon wafer⁺Heavily doped and PSG layers, N⁺The diffusion sheet resistance of the heavily doped layer is controlled to be 20-80 ohm/sq, N⁺The surface phosphorus atom concentration of the heavily doped layer is 1E 19-5E 19cm^-3The junction depth is 0.2-0.5 um, N⁺Controlling the thickness of the PSG layer on the heavily doped layer to be 2-7 nm; in the embodiment, the phosphorus diffusion is carried out in three steps of pre-deposition, propulsion and post-oxidation, wherein the pre-deposition temperature is 800-830 ℃, the deposition time is 800-1200 s, the propulsion temperature is 830-870 ℃, the deposition time is 300-1000 s, and the post-oxidation temperature is 750-820 ℃, and the deposition time is 500-1000 s.

The single-side acid washing method of the chain type etching machine is utilized, the belt speed is set to be 1.5-3.5 m/min, the front side of a silicon wafer is downwards arranged on a chain type roller, a water film is fully paved on the back side of the silicon wafer upwards to protect a back side PSG layer, the liquid level of the HF solution is contacted with the bottom of the roller of the etching machine through the HF solution with the mass concentration of 0.5-2%, the HF solution is contacted with the front side BSG layer of the silicon wafer and a side PSG layer through the roller rotating belt liquid, and the thickness of the front side BSG layer is far larger than that of the side PSG layer, so that the front side PSG layer of the silicon wafer is completely removed while the front side PSG layer of the silicon wafer is completely removed through adjusting the HF acid solution concentration and the roller belt speedReserving a BSG layer of the surface, wherein the thickness is about 15-45 nm; then, the silicon wafer is subjected to a mixed solution consisting of 5-10% by mass of KOH aqueous solution and 0.5-5% by volume of alkali polishing additive, and N on the side surface of the silicon wafer is treated at 40-75 DEG C⁺Etching the heavily doped layer for 100-400 s, and controlling the etching depth to be 1.5-5 um; wherein the alkali polishing additive has the functions of slowing or blocking the reaction rate of the alkali solution with the front surface BSG layer and the back surface PSG layer and accelerating the reaction rate of the alkali solution with the side surface N⁺The etching rate of the heavily doped layer realizes the edge insulation of the battery; and washing the silicon wafer with the edge etched by water to remove the aqueous alkali on the surface, washing the silicon wafer by using an HF solution with the mass percentage concentration of 5-10% for 200-500 s to remove the BSG layer on the front side and the PSG layer on the back side of the silicon wafer, and drying after washing.

(4) Depositing Al on the front surface of the silicon wafer₂O₃And (5) passivating the film.

Depositing a layer of Al with the thickness of about 4nm on the boron diffusion layer on the front surface of the silicon wafer by adopting an atomic layer deposition method₂O₃And (5) passivating the film.

(5) Al on front side of silicon wafer by novel laser process₂O₃And carrying out local windowing treatment on the passivation film.

Selecting laser light source with wavelength of 532nm and power of 10W as Al on the front surface of the silicon wafer₂O₃The passivation film is subjected to local windowing treatment, wherein the graph of the local windowing is kept consistent with the electrode graph of the front side of the battery, the width size of the laser windowing is controlled to be consistent with the size of the printed front side electrode, and the depth of the laser windowing is controlled to be consistent with the size of the Al₂O₃The thickness of the passivation film is kept consistent.

In this embodiment, the fact that the pattern of the local window is identical to the electrode pattern on the front surface of the battery means that the patterns are completely identical or close to each other, and the depth of the local window is equal to that of Al₂O₃The thickness of the passivation film is kept consistent, which means that the depths of the passivation film and the passivation film are completely consistent or close to each other.

In this embodiment, the selection of the laser wavelength and the power is crucial to the laser windowing process, so as to ensure that the boron diffusion layer of the silicon wafer substrate is not affected or is affected very little in the windowing process.

(6) And silicon nitride films with the thickness of 70-80 nm are respectively deposited on the front surface and the back surface of the silicon wafer.

And respectively depositing silicon nitride films on the front side and the back side of the silicon wafer by adopting a PECVD method.

(7) And respectively printing a positive electrode and a back electrode on the front side and the back side of the silicon wafer, and sintering to obtain the N-type solar cell.

Printing Ag-Al paste on the front side of a silicon wafer by adopting screen printing, printing Ag paste on the back side of the silicon wafer, drying at 200-360 ℃ for 10-40 s, and then, putting into a sintering furnace for co-sintering, wherein the sintering peak temperature is 830 +/-3 ℃, and the sintering peak time is 1-4 s.

Example 2

Same as example 1, except that Al in the step (4)₂O₃The thickness of the passivation film is 5nm, a laser light source with the wavelength of 532nm and the power of 12w is selected for applying to Al on the front surface of the silicon wafer₂O₃And carrying out local windowing treatment on the passivation film.

Example 3

Same as example 1, except that Al in the step (4)₂O₃The thickness of the passivation film is 6nm, and a laser light source with the wavelength of 532nm and the power of 20w is selected to emit Al on the front surface of the silicon wafer₂O₃And carrying out local windowing treatment on the passivation film.

Example 4

Same as example 1, except that Al in the step (4)₂O₃The thickness of the passivation film is 4 nm; and etching Al by using corrosive slurry containing hydrofluoric acid in the step (5)₂O₃Passivation film of Al₂O₃The passivation film is screen-printed with corrosive slurry containing hydrofluoric acid, wherein the pattern of the screen printing screen is consistent with the electrode pattern on the front surface of the battery, and the etching depth of the corrosive slurry is the same as that of Al₂O₃The thickness of the passive film is kept consistent, and the passive film can be selectively matched with Al on the front surface of the silicon wafer through corrosive slurry₂O₃The passive film reacts to etch Al₂O₃And (5) removing the corrosive slurry by washing with water after the etching is finished under the action of the passivation film.

Example 5

The same as example 4, except that A in the step (4)l₂O₃The thickness of the passivation film was 6 nm.

Example 6

Same as example 4, except that Al in the step (4)₂O₃The thickness of the passivation film was 8 nm.

Comparative example 1

Method for manufacturing a solar cell using conventional N-type solar cell, in which Al is contained₂O₃The thickness of the passivation film is 4nm, not to Al₂O₃And carrying out local windowing treatment on the passivation film, wherein the sintering peak temperature is 830 +/-1 ℃, and the sintering peak time is 1-4 s.

Comparative example 2

Method for manufacturing a solar cell using conventional N-type solar cell, in which Al is contained₂O₃The thickness of the passivation film is 5nm, not to Al₂O₃And local windowing is carried out on the passivation film, the sintering peak temperature is 835 +/-1 ℃, and the sintering peak time is 1-4 s.

Comparative example 3

Method for manufacturing a solar cell using conventional N-type solar cell, in which Al is contained₂O₃The thickness of the passivation film is 6nm, not to Al₂O₃And local windowing is carried out on the passivation film, the sintering peak temperature is 840 +/-1 ℃, and the sintering peak time is 1-4 s.

The N-type solar cells manufactured in examples 1 to 3 and comparative examples 1 to 3 were tested for conversion efficiency and various electrical properties, and the relevant data are shown in table 1.

TABLE 1

As can be seen from Table 1, the manufacturing method of the present invention is directed to Al of different thicknesses₂O₃The window of the sintering peak temperature of the passivation film is wide, the conversion efficiency of the manufactured N-type solar cell is improved by about 0.05% on average, good electrical property data are obtained, the sintering peak temperature does not need to be adjusted manually and frequently, the downtime of the production process is reduced, and the production efficiency is improved.