CN113035996B - A high-efficiency battery based on high-concentration boron-containing nano-silicon paste and its manufacturing method - Google Patents

Abstract

The invention discloses a method for manufacturing a high-efficiency battery based on nano silicon slurry containing high-concentration boron, which comprises the following steps: s1, taking a silicon wafer, cleaning and texturing, setting an SE (selective emitter) area on the front surface of the silicon wafer, and printing phosphorus-containing nano silicon slurry in the SE area; s2 in POCl ₃ Performing phosphorus diffusion in the atmosphere to form a phosphorus-doped region in the SE region, thereby obtaining phosphorus-silicon glass; s3, removing the phosphorosilicate glass, carrying out back etching, depositing an antireflection film on the front side of the silicon wafer, and depositing a passivation film on the back side of the silicon wafer; s4, printing high-concentration boron nano silicon slurry on the passivation film on the back of the silicon wafer, and scanning by using laser to realize localized boron doping; s5, printing aluminum paste on the back of the silicon wafer, and printing silver paste on the SE structure on the front of the silicon wafer; and S6, sintering to form the battery. The invention also discloses a high-efficiency battery manufactured by the method. According to the invention, the sintering temperature is reduced by forming the SE structure and carrying out local localized boron doping, so that the improvement of the battery efficiency is effectively realized.

Description

A high-efficiency battery based on high-concentration boron-containing nano-silicon paste and its manufacturing method

technical field

The invention belongs to the technical field of solar cells, and in particular relates to a high-efficiency cell based on high-concentration boron-containing nano-silicon paste and a manufacturing method.

Background technique

Crystalline silicon solar cells are currently the mainstream in the photovoltaic market due to their high conversion efficiency and long service life. At present, commercial mass-produced crystalline silicon solar cells are mainly p-type cells. Compared with p-type conventional batteries, p-type PERC (Passivated Emitter and Rear Contact, passivated emitter back field point contact) batteries have the following advantages: (1) Internal back reflection is enhanced to reduce long-wave optical loss. (2) High-quality backside passivation greatly improves the open-circuit voltage (Voc) and short-circuit current (Isc) of PERC cells, resulting in higher conversion efficiency, and the highest conversion efficiency can approach or exceed 22%. Moreover, since the manufacturing process of PERC batteries (as shown in a in Figure 3) is highly compatible with the manufacturing process of P-type conventional batteries, the cost and efficiency of introducing PERC battery technology from the manufacturing process of P-type conventional batteries is low and efficient. The annual production capacity of PERC batteries will completely replace the existing P-type conventional batteries.

However, to achieve an average PERC battery mass production efficiency of over 22% with the traditional PERC process and technical reserves, it is necessary to superimpose a variety of advanced technologies, which not only increases the cost and difficulty of battery manufacturing, or requires substantial additions and changes to existing These solutions cannot meet the industry's application requirements beyond PERC batteries.

At present, a method to improve the performance of PERC cells is to print boron-doped silicon nanoparticle paste on the passivation film on the back of the PERC cells to upgrade the PERC structure to a similar PERL (Passivated Emitter Rear Localized, Passivated Emitter Rear Localized, Passivated Emitter Rear Localized). domain diffusion) structure, its main steps include: printing boron-containing nano-silicon paste on the passivation film on the back of the battery (the mainstream is the laminated structure of Al ₂ O 3 and SiN _x ) according to the designed pattern; using a suitable laser (public The data shows that it is 532nm, pulse type but not limited to this type) to scan the pattern of the borosilicate paste coating film after pre-drying, and use the instantaneous high temperature thermal effect generated by the laser to open the passivation film under the coating film ( The back electrode and the contact channel of the substrate silicon wafer), and at the same time, the boron contained in the slurry is doped into the predetermined area on the back of the silicon wafer (that is, the laser simultaneously completes the two functions of opening the passivation film and local boron doping) ; Finally, the aluminum paste is printed on the back side, and then sintered together with the silver paste on the front of the battery to form an improved PERC (similar to PERL) high-efficiency battery with a partially heavily boron-doped region. This kind of BSF (Back Surface Filed, back magnetic field) formed by local high-concentration laser boron doping instead of local aluminum paste thermal diffusion can significantly increase Voc (open circuit voltage) and FF (fill factor), thereby improving the conversion efficiency of the battery. However, this method has at least the following deficiencies, which lead to unstable battery efficiency improvement and low cost performance for mass production: (1) According to the traditional PERC battery manufacturing process, after laser local boron doping, it is necessary to print aluminum on the back of the battery The silver paste on the front side is then sintered at the same time to form the front and back electrodes with good contact with the silicon chip. Among them, the conventional silver paste generally requires a sintering temperature above 850°C in order to achieve good contact with the silicon chip, and the aluminum-silicon alloy The formation temperature is only 577°C, and the diffusion temperature of boron must be at least 1000°C. Considering the production cost and production capacity, the mass production can only choose high-temperature sintering with the front silver paste (that is, the sintering temperature is about 850). Such a high temperature The sintering process will cause an excessive reaction between the aluminum and silicon in the aluminum paste on the back, causing the aluminum that enters the silicon wafer from under the electrode to greatly exceed the B-BSF boron back field formed by laser doping (laser boron-doped The depth usually can only reach about 5um, and aluminum can penetrate more than 10um into the silicon wafer under high temperature conditions), thus destroying or offsetting the efficiency improvement effect that laser boron doping should have. (2) The boron content in boron nano-silicon slurry is limited by the synthesis method of silicon nanoparticles, and the boron-silicon molar ratio is ≤0.02. Under high temperature conditions, it is difficult to ensure the laser boron doping effect under the condition of interference caused by excessive reaction between aluminum and silicon. Some efficiency improvement effect.

In addition, there is also a method to improve the performance of PERC batteries, that is, SE-PERC technology (where SE is SelectiveEmitter, selective emitter), as shown in b in Figure 3, using POCl ₃ (phosphorus oxychloride) on the front of PERC batteries The PSG (phosphosilicate glass) formed after phosphorus diffusion is supplemented with laser irradiation under appropriate conditions to form a patterned phosphorus re-doped region (SE). Compared with standard PERC, this method can stably increase the cell efficiency by more than 0.15% on average. The SE structure can greatly reduce the impedance between the silver electrode and the silicon chip, making it possible for the silver paste on the front of the battery and the silicon chip to achieve good contact under low-temperature sintering conditions. Moreover, only from the perspective of achieving good contact between the front silver electrode and the silicon chip, the SE structure with a higher phosphorus doping concentration is more conducive to achieving good contact between the front silver paste and the silicon chip at a lower temperature. . However, in SE-PERC technology, the phosphorus diffusion concentration achieved by PSG formed after POCl ₃ diffusion is limited, it is difficult to greatly reduce the sintering temperature, and it is impossible to effectively prevent the excessive reaction between aluminum and silicon from forming B-BSF. Thus, the efficiency of the battery can be effectively improved; however, if the concentration of phosphorus is too high, the incident light of the window part outside the SE structure that is irradiated by sunlight will be lost, so that the effect of improving the conversion efficiency of the battery is not obvious. In addition, in order to achieve a higher concentration of phosphorus doped SE structure, one method is to use higher density laser conditions to obtain higher phosphorus concentration, but this will cause greater damage to the silicon wafer (due to POCl ₃ diffusion formed PSG has almost no absorption for the laser wavelength used), the gain outweighs the loss, and it cannot effectively improve the battery efficiency.

Contents of the invention

The problem to be solved by the present invention is to provide a high-efficiency battery based on high-concentration boron-containing nano-silicon paste and a manufacturing method for the above deficiencies in the prior art. By forming an SE (Selective Emitter, selective emitter) structure and performing local Localized boron doping reduces the sintering temperature, thereby effectively improving battery efficiency.

According to one aspect of the present invention, disclose a kind of preparation method based on the high-efficiency battery containing high-concentration boron nano-silicon slurry, its technical scheme is as follows:

A method for manufacturing a high-efficiency battery based on high-concentration boron-containing nano-silicon paste, comprising:

S1, taking the silicon wafer, cleaning the texture, setting the SE area on the front side of the silicon wafer, and printing phosphorus-containing nano-silicon paste on the SE area;

S2, phosphorus diffusion is carried out in POCl3 atmosphere, forming a phosphorus re-doped region in the SE region;

S3, removing the phosphosilicate glass formed on the surface of the silicon wafer during the phosphorus diffusion process, performing back etching, depositing an anti-reflection film on the front of the silicon wafer, and depositing a passivation film on the back of the silicon wafer;

S4, printing high-concentration boron nano-silicon paste on the passivation film on the back of the silicon wafer, and then scanning with laser to achieve localized boron doping;

S5, printing aluminum paste on the back of the silicon wafer, and printing silver paste on the SE structure on the front of the silicon wafer;

S6, performing sintering to form a battery.

Preferably, in step S4, the high-concentration boron nano-silicon slurry refers to a molar ratio of boron to silicon of 0.2-2.5.

Preferably, in step S4, the printing area of the high-concentration boron nano-silicon paste is larger than the set area of localized boron doping.

Preferably, in step S4, the wavelength of the laser is 532nm-1040nm.

Preferably, in step S4, the thickness of the high-concentration boron nano-silicon paste printed on the passivation film on the back of the silicon wafer is 1.5-2.5 μm after the dry film.

Preferably, the sintering temperature is 570-780°C.

Preferably, step S1 also includes drying the phosphorus-containing nano-silicon slurry, the average particle diameter of silicon nanoparticles in the phosphorus-containing nano-silicon slurry is not more than 50nm, and the phosphorus content is not less than 5x10^19atoms/cm3; The drying temperature is 180-250° C., and the drying time is 8-15 minutes.

Compared with the prior art, the method for manufacturing high-efficiency batteries based on high-concentration boron nano-silicon paste provided by the present disclosure has the following beneficial effects:

(1) At this stage, only aluminum paste can be used to form the back electrode in mass production. For batteries without a front SE structure, the high-temperature sintering conditions of front-side silver must be used. Under this high-temperature condition, the excessive reaction between aluminum and silicon must be It will weaken or offset the efficiency improvement effect that local boron doping should have.

The B/Al-BSF (boron-aluminum mixed back field) formed by local boron doping and aluminum paste sintering is used on the back to replace the Al-BSF ( Aluminum back field), the prepared battery structure is similar to PERL (Passivated Emitter Rear Localized, Passivated Emitter Rear Localized) battery, which can improve the conversion efficiency of the battery. Compared with the traditional SE-PERC battery, the absolute value of the efficiency can be increased by 0.4 %above.

(2) Compared with the gas diffusion of simple POCl ₃ in the traditional method, the present invention uses the pre-set SE structure area on the front side of the silicon wafer, and then prints in the SE area to achieve local high-concentration phosphorus diffusion more easily and efficiently. The required silicon nanoparticle slurry containing a quantitative phosphorus concentration is then subjected to conventional phosphorus thermal diffusion in a POCl ₃ atmosphere to form the desired SE structure with a higher concentration of phosphorus. The SE structure can greatly reduce the surface resistance Rs between the front silver and the silicon wafer (the surface resistance Rs can be controlled at 50-90ohm/sq), and the higher concentration of phosphorus-doped SE structure can reduce the sintering temperature, thereby maximizing the protection The formed boron back field is not eroded by the aluminum paste, thereby effectively improving battery efficiency. At the same time, lowering the sintering temperature can reduce energy consumption and increase production capacity.

(3) Compared with the traditional method of using laser PSG to form the SE structure, the present invention adopts a thermal diffusion process, which avoids possible damage to the silicon wafer at the stage of laser doping to form the SE structure, and is conducive to improving battery efficiency and long-term stability improvement, and the present invention requires less equipment, does not need to add lasers with mass production capacity requirements, and has strong compatibility with existing PERC technology, but uses a phosphorus-containing silicon paste on the basis of standard PERC technology. The addition of a printing process with an alignment function is beneficial to realize the upgrade from the standard PERC production line to the production line required by the technology of the present invention, and can reduce costs.

According to another aspect of the present invention, a high-efficiency battery manufactured by the above-mentioned method is disclosed, and its technical scheme is as follows:

A high-efficiency battery made by the method described above, comprising: silver electrodes, anti-reflection film, silicon wafer, aluminum paste layer and passivation film,

A heavily doped phosphorus area and a lightly doped area are provided on the front side of the silicon wafer, the antireflection film is arranged on the outer layer of the lightly doped area, the heavily doped phosphorus area passes through the antireflection film and contacts the silicon wafer, and the silver electrode is provided on phosphorus heavily doped regions;

The passivation film is arranged on the back side of the silicon wafer, and a boron heavily doped region is arranged on the passivation film, and the boron heavily doped region passes through the passivation film and contacts the silicon wafer, and the aluminum paste layer is provided on the passivation film.

Preferably, the silicon wafer is a P-type single crystal silicon wafer.

Preferably, the Rs (ie surface resistance) of the phosphorous heavily doped region is 55-60 ohm/sq, and the Rs of the boron heavily doped region is 12±2 ohm/sq.

In the high-efficiency battery of the present disclosure, due to the SE structure with high phosphorus concentration on the front side, a good contact can be formed between the silver electrode and the silicon wafer under low-temperature sintering conditions, while under low-temperature sintering conditions, the excessive reaction between the back aluminum and silicon will be suppressed. Inhibiting and protecting the B-BSF (boron back field) effect formed by the previous localized laser boron doping, so that the photoelectric conversion efficiency (absolute value) of the cell can be increased by more than 0.4%.

Description of drawings

Fig. 1 is the process flow chart of the manufacturing method based on the high-efficiency battery containing high-concentration boron nano-silicon slurry in the embodiment of the present disclosure;

2 is a schematic structural view of a high-efficiency battery (i.e. SE-PERL battery) based on a high-concentration boron-containing nano-silicon paste in an embodiment of the present disclosure;

Fig. 3 is a comparison diagram of a manufacturing method of a high-efficiency battery based on a high-concentration boron-containing nano-silicon paste in an embodiment of the present disclosure and a process flow of the prior art;

FIG. 4 is a comparison diagram of the effect of the high-efficiency battery based on the high-concentration boron-containing nano-silicon paste in the embodiment of the present disclosure and the battery in the prior art.

In the figure: 1-silver electrode; 2-anti-reflection film; 3-lightly doped area; 4-phosphorus heavily doped area; 5-silicon wafer; 6-boron heavily doped area; 7-aluminum paste layer; 8-passivation film ;

a is standard PERC; b is SE-PERC; c is SE-PERL.

Detailed ways

The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Apparently, the described embodiments are part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without making creative efforts fall within the protection scope of the present invention.

Due to the limited phosphorus diffusion concentration and high sintering temperature in the prior art (especially PERC technology), PSG formed by POCl ₃ diffusion causes a series of defects to cause low battery conversion efficiency. Therefore, in order to solve the above-mentioned problems existing in the prior art, the present invention discloses a method for making a high-efficiency battery based on high-concentration boron-containing nano-silicon paste, including:

S1, taking the silicon wafer, cleaning the texture, setting the SE area on the front side of the silicon wafer, and printing phosphorus-containing nano-silicon paste on the SE area;

S2, perform phosphorus diffusion in POCl3 atmosphere, form phosphosilicate glass (PSG) on the surface of the silicon wafer, and form a phosphorus re-doped region in the SE region;

S3, removing the phosphosilicate glass formed on the surface of the silicon wafer during the phosphorus diffusion process, performing back etching, depositing an anti-reflection film on the front of the silicon wafer, and depositing a passivation film on the back of the silicon wafer;

S4, printing high-concentration boron nano-silicon paste on the passivation film on the back of the silicon wafer, and then scanning with laser to achieve localized boron doping;

S5, printing aluminum paste on the back of the silicon wafer, and printing silver paste on the SE structure on the front of the silicon wafer;

S6, performing sintering to form a battery.

Correspondingly, the present disclosure also provides a high-efficiency battery prepared by the above method, including: a silver electrode, an antireflection film, a silicon wafer, an aluminum paste layer, a passivation film,

A heavily doped phosphorus area and a lightly doped area are provided on the front side of the silicon wafer, the antireflection film is arranged outside the lightly doped area, the heavily phosphorus doped area passes through the antireflection film and contacts the silicon wafer, and the silver electrode is arranged on the On the heavily phosphorus-doped region;

The passivation film is arranged on the back side of the silicon wafer, and a boron heavily doped region is arranged on the passivation film, and the boron heavily doped region passes through the passivation film and contacts the silicon wafer, and the aluminum paste layer is provided on the passivation film.

Example 1

As shown in Figure 1, this embodiment discloses a method for making a high-efficiency battery based on a high-concentration boron-containing nano-silicon paste, including:

Step S1, taking the silicon wafer, cleaning the texture, setting the SE area on the front side of the silicon wafer, and printing phosphorus-containing nano-silicon paste on the SE area.

In this embodiment, the silicon wafer is a P-type single crystal silicon wafer. Of course, other types of silicon wafers may also be used, which are not further limited in this embodiment.

In this embodiment, step S1 further includes drying the printed phosphorus-containing nano-silicon paste. Wherein, the average particle size of the silicon nanoparticles in the phosphorous-containing nano-silicon paste is no more than 50nm, and the phosphorus content is no less than 5x10^ ¹⁹ atoms/cm ³ . The drying temperature is preferably 180-250°C, and the drying time is preferably 8-15 minutes. The thickness of the phosphorus-containing film layer formed after drying is preferably controlled at about 1.8 μm, and the line width is preferably controlled at about 148 μm.

It should be noted that, the printing in this embodiment preferably adopts conventional screen printing technology, which will not be described in detail below.

In step S2, phosphorus is diffused in POCl ₃ atmosphere to form phosphosilicate glass (PSG for short, that is, a silicon dioxide layer containing phosphorus atoms) on the surface of the silicon wafer, and form a phosphorus heavily doped region (ie n++) in the SE region.

In this embodiment, phosphorus diffusion adopts conventional phosphorus thermal diffusion process conditions to form a low-damage phosphorus re-doped region (n++) in the region printed with phosphorus-containing nano-silicon paste, that is, to form an SE structure. The lightly doped region (n+) between the electrode and the electrode), this SE structure helps to ensure good contact between the silver electrode on the front of the battery and the silicon substrate on the substrate even under low-temperature sintering conditions.

In this embodiment, the Rs (ie surface resistance) of the phosphorous heavily doped region is preferably controlled at 55-60 ohm/sq.

Step S3, removing the phosphosilicate glass, performing back etching, depositing an anti-reflection film on the front side of the silicon wafer, and depositing a passivation film on the back side of the silicon wafer.

In this embodiment, the phosphorus-silicate glass is removed and the backside is etched according to the method in the normal PERC process, which will not be repeated here. Both the anti-reflection film and the passivation film are preferably deposited from Al ₂ O ₃ or SiN _x materials.

Step S4, printing a high-concentration boron nano-silicon paste on the passivation film on the back of the silicon wafer, and then scanning with a laser to achieve localized boron doping to form a boron heavily doped region (p++).

Considering the effect of local boron doping on battery efficiency in the method of the embodiment of the present disclosure, and the total amount and surface of boron entering the silicon wafer through the opening of the passivation film under the printed high-concentration boron nano-silicon paste pattern concentrations are closely related. The boron-silicon molar ratio in the high-concentration boron nano-silicon slurry (organic solvent dispersion with a solid content of 5-10% including silicon-boron composite nanoparticles, hereinafter referred to as boron-containing silicon slurry) in this embodiment should be ≥0.2 , preferably 0.2-2.5. Due to the thickness of the boron-containing silicon paste layer after drying under certain conditions (the preferred drying temperature is 200°C and the drying time is 10min), the boron-containing silicon paste layer directly affects the total amount of boron that enters the silicon wafer through the opening of the passivation film. , in order to avoid laser damage to the passivation film and silicon wafer other than the opening of the passivation film, the wavelength of the laser should meet the requirements of opening and doping of the passivation film, and also satisfy the above-mentioned boron-containing silicon paste. It has absorption, that is: the irradiation energy of the laser should not only ensure the absorption through the boron-containing silicon paste layer, but also easily open the passivation film, and realize the amount of boron that can effectively improve the battery efficiency (practice proves that When the boron doping amount is more than 10^ ²¹ atoms/ ^cm3, the battery efficiency can be effectively improved, and the battery efficiency improvement effect can reach more than 0.4%) doped into the silicon wafer. In this embodiment, the wavelength of the preferred laser is 532nm-1040nm, so as to avoid the laser energy density reaching the surface of the passivation film being too low, resulting in failure to achieve a sufficient amount of boron doping and avoiding possible damage to the surrounding area caused by excessive laser energy. Low battery efficiency caused by passivation film or silicon wafer damage. Theoretically, the higher the boron content in the boron-containing silicon paste, the smaller the film thickness after drying, the more likely it is to achieve the required boron doping amount under the condition of smaller laser energy density, but in practice it is found that using It is difficult to uniformly control the thickness of the dried boron paste below 1 μm by screen printing technology. Therefore, in this embodiment, the dry film thickness of the printed boron-containing silicon paste is preferably 1.5-2.5 μm. In addition, a thinner dry film thickness is also conducive to meeting the mass production conditions.

Moreover, considering the need to avoid damage caused by direct laser irradiation on the silicon wafer and the accuracy of laser alignment, the printed pattern of the high-concentration boron nano-silicon paste is larger than the predetermined contact area between the back aluminum and the silicon wafer, that is, high The printing area of boron-containing nano-silicon paste should be larger than the set area of localized boron doping. For example, a good contact between the back aluminum and the silicon wafer requires a line width of 40um, and the printing line width of boron-containing silicon paste should be above 80um.

Step S5, printing aluminum paste on the back of the silicon wafer, and printing silver paste on the SE structure on the front of the silicon wafer.

In this embodiment, printing aluminum paste on the back of the silicon wafer refers to printing a low-temperature sinterable aluminum paste (such as special aluminum paste for PERC batteries) on the entire (single-sided battery) or part (two-sided battery) printing area that can cover the boron-containing silicon paste. A), the silver paste printed on the front side can use the special silver paste B for PERC batteries (the silver electrode is obtained after sintering).

Step S6, sintering to form a battery.

Specifically, under the premise of ensuring a good contact between the front silver electrode and the silicon wafer, the front silver and the back aluminum are co-sintered at the lowest possible temperature, and the front silver electrode and the silicon chip are formed by one-time sintering. The good contact between the wafers, the aluminum paste layer on the back and the silicon wafer finally forms a high-efficiency cell with a SE-PERL structure, as shown in Figure 2. In this embodiment, the sintering temperature is 570-780° C., which is lower than the sintering temperature (about 850° C.) of the conventional RERC process, that is, low-temperature sintering is realized.

This embodiment also discloses a high-efficiency battery based on high-concentration boron nano-silicon paste prepared by the above method, as shown in Figure 2, including a silver electrode 1, an anti-reflection film 2, a silicon wafer 5, an aluminum paste layer 7 and a passivation battery. Chemical film8. in:

Silicon chip 5, preferably adopting P-type monocrystalline silicon silicon chip as substrate;

The front side of the silicon wafer 5 is provided with a phosphorus heavily doped region 4 (i.e. SE structure) and a lightly doped region 3, and an antireflection film 2 is arranged outside the lightly doped region 3, and the phosphorus heavily doped region 4 passes through the antireflection film 2 and silicon The sheets form a good contact, and a silver electrode 1 (obtained after sintering of silver paste) is provided in the phosphorous heavily doped region 4;

A passivation film 8 is provided on the back side of the silicon wafer 5, and a boron heavily doped region 6 is provided on the passivation film 8, and the boron heavily doped region 6 passes through the passivation film 8 to form good contact with the silicon wafer 5, and the boron heavily doped The Rs of the region 6 is 12±2ohm/sq, and the passivation film 8 is provided with an aluminum paste layer 7 .

For the high-efficiency battery prepared by the method of the embodiment of the present disclosure, due to the SE structure with high phosphorus concentration on the front side, a good contact can be formed between the silver electrode and the silicon chip under low-temperature sintering conditions, while under the low-temperature sintering condition, the back aluminum and silicon The excessive reaction will be suppressed, protecting the B-BSF (boron back field) effect formed by the previous localized laser boron doping, thereby improving the battery efficiency.

According to the electrical performance evaluation results of the trial battery, the selection and sintering conditions of low-temperature sintered aluminum paste and low-temperature sintered silver paste are optimized, and finally the maximum effect of local boron doping is achieved, which is more than 0.4% compared with SE-PERC battery The photoelectric conversion efficiency of the cell (also referred to herein as cell efficiency, abbreviated as Eff) is improved.

Example 2

As shown in c in Figure 3, this embodiment discloses a method for manufacturing a high-efficiency battery based on a high-concentration boron nano-silicon paste, which specifically includes the following steps:

Take a p-type monocrystalline silicon wafer with a size of 156㎜*156㎜ and a thickness of 180μm. After cleaning and texturing, select and set the SE area on the front side of the silicon wafer, and print the average particle size of silicon nanoparticles on the SE area. Phosphorus-containing nano-silicon paste not exceeding 50nm and phosphorus content not less than 5x10^ ¹⁹ atoms/cm ³ , dried at 200°C for 10 minutes, wherein the amount of phosphorus-containing nano-silicon paste printed should ensure that the dry film after drying is completed The thickness is 1.8 μm and the line width is 148 μm.

Then put it into a diffusion furnace to expand phosphorus under POCl ₃ atmosphere, form phosphosilicate glass PSG on the surface of the silicon wafer, and form a low-damage phosphorus re-doped area (n++) in the area printed with phosphorus-containing nano-silicon paste, that is, form SE structure, wherein the Rs of the phosphorous heavily doped region is controlled at 55-60ohm/sq.

Then, remove the PSG, perform back etching, deposit an anti-reflection film (such as aluminum oxide, silicon nitride, etc.) on the front of the silicon wafer, and deposit a passivation film (such as aluminum oxide, silicon nitride, etc.) on the back of the silicon wafer.

Then, on the passivation film on the back, printing borosilicate (B/Si) molar ratio is 2.2 containing high-concentration boron nano-silicon paste (wherein, the solid content of silicon-boron composite nano-particles is 8%, the average particle diameter of nano-particles About 20nm, TEM pictures show that the vast majority of boron is covered by silicon). Dry at 200°C for 10 minutes. The amount of nano-silicon paste containing high-concentration boron should be printed to ensure that the average thickness of the dry film after drying is 1.6 μm, and the average line width is 94 μm; the pulse waveform has a flat top wave. Features, spot size of 40μm*40μm, laser output power of 40W aimed at the pattern of the printing area containing high-concentration boron nano-silicon paste and scanning, the average line width of the laser irradiation pattern is about 42um, and the local boron-doped area Rs is controlled at 12±2ohm/sq.

Afterwards, low-temperature sinterable aluminum paste A is printed on the back surface, and low-temperature sinterable silver paste B is printed on the front side where the SE structure is aligned.

Finally, co-sintering is carried out at 720°C to obtain a high-efficiency battery with a SE-PERL structure.

After testing, the average photoelectric conversion efficiency of 50 solar cells prepared according to the above method was 22.05%. The specific test results are shown in FIG. 4 .

Example 3

This example discloses a method for manufacturing a high-efficiency battery based on high-concentration boron-containing nano-silicon paste. Compared with Example 2, the main difference is that the SE-PERC improved method developed by Dill Laser Company is used to form the SE structure. The specific steps as follows:

A p-type monocrystalline silicon wafer with a size of 156mm*156mm and a thickness of 180μm was used. After cleaning and texturing, it was directly placed in a diffusion furnace to perform phosphorus expansion under the same conditions as in Example 1 under a _POCl3 atmosphere to form PSG;

Then, the PSG formed by thermal diffusion of phosphorus is irradiated with a pulsed laser with a flat-top wave characteristic at an output power of 20 W to form an SE structure equivalent to that of Example 1, wherein the line width of the laser-processed area is about 120 μm, and the laser-doped area Rs is about 70- 90ohm/sq;

Then, after removing PSG and etching on the back, an anti-reflection film is deposited on the front, and a passivation film is deposited on the back;

Then, on the passivation film on the back side, print the same high-concentration boron nano-silicon paste (that is, the B/Si molar ratio is 2.2, etc.) About 1.7 μm, the average line width is 96 μm, and then adopt the laser alignment irradiation under the same conditions as in Example 1, the average line width of the laser irradiation pattern is about 44 μm, and the local boron-doped region Rs is controlled at 12 ± 2ohm/sq;

After that, PERC special aluminum paste C is printed on the back side, and the low-temperature sinterable silver paste D slightly smaller than the SE structure pattern is printed on the front side in alignment with the SE structure area;

Finally, co-sintering is carried out at 780°C to obtain high-efficiency cells with SE-PERL mechanism.

After testing, the average photoelectric conversion efficiency of 50 solar cells produced by the above method is 21.88%. The specific test results are shown in FIG. 4 .

Comparative example 1

The battery manufactured by DR Laser’s SE-PERC method is used as Comparative Example 1, and its manufacturing steps are as follows:

The SE structure is prepared by the same method as in Example 3;

The boron-containing silicon paste is not printed on the passivation film on the back (different from Examples 2 and 3), and the pulse pattern of the laser for opening the passivation film is still flat-topped. The spot size is also 40 μm*40 μm, and the output The power is 25W, and after laser scanning, a grooved area with an average line width of about 42 μm is formed on the passivation film;

On the basis of the above, the standard aluminum paste for PERC is printed on the back side, and the silver paste slightly smaller than the SE structure pattern is printed on the front side to align with the SE structure area;

Co-sinter the back aluminum and the front silver at 840°C to finally complete the fabrication of the SE-PERC battery.

After testing, the average efficiency of 50 solar cells produced by the above method is 21.65%. The specific test results are shown in FIG. 4 .

It can be seen from FIG. 4 that the open circuit voltage (Voc), short circuit current (Isc), fill factor (FF), and battery efficiency (Eff) of the battery made by the embodiment of the present disclosure are better than those of the battery made by the method of the comparative example. Therefore, the present disclosure The method in the embodiment can effectively improve the battery efficiency, and the battery efficiency of the battery having the SE structure formed by the method in Example 2 of the present disclosure is more obvious.

It can be understood that, the above embodiments are only exemplary embodiments adopted for illustrating the principle of the present invention, but the present invention is not limited thereto. Those skilled in the art can make various modifications and improvements without departing from the spirit and essence of the embodiments of the present invention, and these modifications and improvements are also regarded as the protection scope of the present invention.

Claims (8)

1. A method for making a high-efficiency battery based on high-concentration boron nano-silicon paste, comprising: S1, taking the silicon wafer, cleaning the texture, setting the SE area on the front side of the silicon wafer, and printing phosphorus-containing nano-silicon paste on the SE area; S2, carry out phosphorus diffusion in POCl ₃ atmosphere, and form a phosphorus re-doped region in the SE region, that is, form an SE structure; S3, removing the phosphosilicate glass formed on the surface of the silicon wafer during the phosphorus diffusion process, performing back etching, depositing an anti-reflection film on the front of the silicon wafer, and depositing a passivation film on the back of the silicon wafer; S4, printing high-concentration boron nano-silicon paste on the passivation film on the back of the silicon wafer, and then scanning with laser to achieve localized boron doping; S5, printing aluminum paste on the back of the silicon wafer, and printing silver paste on the SE structure on the front of the silicon wafer; S6, performing sintering to form a battery; The average particle size of silicon nanoparticles in the phosphorus-containing nano-silicon slurry is not more than 50nm, the phosphorus content is not less than 5x10^ ¹⁹ atoms/cm ³ , and the Rs of the phosphorus re-doped area is controlled at 55-60ohm/sq; The high-concentration boron nano-silicon slurry means that the molar ratio of boron to silicon is 0.2-2.5; The sintering temperature is 570-720°C. 2. The manufacturing method of high-efficiency batteries based on high-concentration boron nano-silicon paste according to claim 1, characterized in that, in step S4, the printing area of the high-concentration boron nano-silicon paste is larger than that of localized boron-doped Set the area. 3. The method for manufacturing high-efficiency batteries based on high-concentration boron-containing nano-silicon paste according to claim 1, characterized in that, in step S4, the wavelength of the laser is 532nm-1040nm. 4. The manufacturing method of high-efficiency batteries based on high-concentration boron nano-silicon paste according to claim 1, characterized in that, in step S4, the high-concentration boron nano-silicon is printed on the passivation film on the back side of the silicon wafer The thickness of the slurry is 1.5-2.5 μm after the dry film. 5. The manufacturing method of high-efficiency batteries based on high-concentration boron-containing nano-silicon paste according to claim 1, characterized in that, in step S1, also includes drying phosphorus-containing nano-silicon paste, The drying temperature is 180-250° C., and the drying time is 8-15 minutes. 6. A high-efficiency battery made by the method according to any one of claims 1-5, comprising silver electrode (1), anti-reflection film (2), silicon wafer (5), aluminum paste layer (7) and passivation Chemical film (8), is characterized in that, The front side of the silicon wafer is provided with a phosphorus heavily doped area (4) and a lightly doped area (3), the antireflection film is arranged outside the lightly doped area, and the phosphorus heavily doped area passes through the antireflection film and the silicon wafer contact, the silver electrode is provided on the phosphorous heavily doped region; The passivation film is arranged on the back side of the silicon wafer, and a boron heavily doped region (6) is arranged on the passivation film, and the boron heavily doped region passes through the passivation film and contacts the silicon wafer , the aluminum paste layer is arranged on the passivation film. 7. The high-efficiency battery based on high-concentration boron-containing nano-silicon paste according to claim 6, wherein the silicon wafer is a P-type monocrystalline silicon wafer. 8. the high-efficiency battery based on containing high-concentration boron nano-silicon paste according to claim 7, characterized in that, the Rs of the phosphorus re-doped region (4) is 55-60ohm/sq, and the boron re-doped region ( 6) The Rs is 12±2ohm/sq.

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