Solar cell and preparation method and application thereof

Abstract

The invention relates to a solar cell and a preparation method and application thereof. The solar cell comprises an N-type silicon substrate, a P-type doped silicon layer and a PN junction located between the N-type silicon substrate and the P-type doped silicon layer. In the PN junction, the doping concentration distribution gradient of the P-type doping element in the direction from the P-type doping silicon layer to the N-type silicon substrate is smaller than or equal to 1.5 * 10 < 18 > cm <-3 > / mu m. The solar cell provided by the invention has good UV attenuation resistance, and the UV attenuation phenomenon in the outdoor long-time use process can be reduced.

Description

Technical Field

[0001] The present application relates to the field of photovoltaic technology, and particularly to a solar cell, a preparation method thereof, and an application thereof. Background Art

[0002] The principle of solar cell power generation is mainly the photoelectric effect of semiconductors. A silicon solar cell refers to a solar cell with silicon as the base material. When sunlight shines on the silicon solar cell, the photon energy is transferred to silicon atoms, causing the electrons in the silicon atoms to transition into free electrons, thereby generating electron-hole pairs. Under the action of the internal electric field of the cell, electrons and holes move towards different electrodes respectively, forming an electric current, and realizing the conversion from solar energy to electrical energy. Silicon solar cells have the characteristics of high conversion efficiency, environmental friendliness, and strong adaptability, and are widely used in a variety of different scenarios. However, traditional solar cells have poor anti-UV attenuation ability, and there is an obvious UV attenuation phenomenon during long-term outdoor use. Summary of the Invention

[0003] Based on this, it is necessary to provide a solar cell, a preparation method thereof, and an application thereof. The solar cell of the present application has good anti-UV attenuation ability and can reduce the UV attenuation phenomenon during long-term outdoor use.

[0004] In a first aspect, the present application provides a solar cell, including an N-type silicon substrate, a P-type doped silicon layer, and a PN junction located between the N-type silicon substrate and the P-type doped silicon layer; in the PN junction, the doping concentration distribution gradient of the P-type doping element in the direction from the P-type doped silicon layer to the N-type silicon substrate is less than or equal to 1.5×10 18 cm -3 / μm.

[0005] In some embodiments, the junction depth of the PN junction is 1.2 μm to 1.5 μm.

[0006] In some embodiments, the solar cell includes at least one of a PERC solar cell, a TOPCon solar cell, and an HJT solar cell.

[0007] In some embodiments, the N-type silicon substrate has a first surface and a second surface arranged oppositely. On the first surface, the P-type doped silicon layer, a first passivation layer, and a first electrode are sequentially stacked, and the first electrode passes through the first passivation layer and contacts the P-type doped silicon layer; on the second surface, a tunneling oxide layer, an N-type doped silicon layer, a second passivation layer, and a second electrode are sequentially stacked, and the second electrode passes through the second passivation layer and contacts the N-type doped silicon layer.

[0008] Second aspect, the present application provides a method for manufacturing a solar cell, including the following steps:

[0009] Providing an N-type silicon substrate;

[0010] Preparing a P-type doped silicon layer on the surface of the N-type silicon substrate to form a PN junction between the N-type silicon substrate and the P-type doped silicon layer; in the PN junction, the doping concentration distribution gradient of the P-type doping element in the direction from the P-type doped silicon layer to the N-type silicon substrate is less than or equal to 1.5×10 18 cm -3 / μm.

[0011] In some embodiments, preparing the P-type doped silicon layer on the surface of the N-type silicon substrate includes the following steps:

[0012] Performing a first deposition using a first process gas including a P-type doping source to form a pre-doped layer on the surface of the N-type silicon substrate, where the doping concentration of the P-type doping element in the pre-doped layer is greater than or equal to 1×10 20 cm -3 ;

[0013] Performing a second deposition using a second process gas including the P-type doping source, where the flow rate of the P-type doping source in the second process gas is less than the flow rate of the P-type doping source in the first process gas;

[0014] Performing high-temperature junction pushing to form the PN junction.

[0015] In some embodiments, the flow rate of the P-type doping source in the first deposition is 500 sccm to 1000 sccm; the flow rate of the P-type doping source in the second deposition is 200 sccm to 500 sccm.

[0016] In some embodiments, the high-temperature junction pushing includes multiple junction pushing processes with gradually increasing temperatures performed in sequence.

[0017] In some embodiments, the high-temperature junction pushing includes the following steps:

[0018] A first junction pushing process, where the temperature of the first junction pushing process is 850°C to 900°C and the time is 20 min to 30 min;

[0019] A second junction pushing process, where the temperature of the second junction pushing process is 900°C to 950°C and the time is 40 min to 60 min;

[0020] A third junction pushing process, where the temperature of the third junction pushing process is 1000°C to 1050°C and the time is 10 min to 15 min.

[0021] In a third aspect, the present application provides a photovoltaic module, including the solar cell described in any one of the above, or a solar cell prepared by the preparation method of the solar cell described in any one of the above.

[0022] In the above solar cell, in the PN junction, the doping concentration distribution gradient of the P-type doping element in the direction from the P-type doped silicon layer to the N-type silicon substrate is less than or equal to 1.5×10 18 cm -3 / μm. The smaller doping concentration distribution gradient in the PN junction enables the concentration distribution of high-energy carriers formed in the PN junction to be relatively flat under the irradiation of ultraviolet light, thereby reducing the migration kinetic energy of high-energy carriers and minimizing the bombardment effect generated at the PN junction interface by high-energy carriers. Furthermore, it can reduce the damage to the junction region caused by high-energy carriers and the resulting lattice defects. The solar cell of the present application has good anti-UV attenuation ability and can reduce the UV attenuation phenomenon during long-term outdoor use. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 is a schematic structural diagram of a solar cell provided by an embodiment of the present application;

[0024] Figure 2 is a comparative schematic diagram of the boron doping concentration distribution curves in the PN junctions of the solar cells in Examples 1 to 6 and Comparative Example 1;

[0025] Figure 3 is a comparative schematic diagram of the electroluminescence test appearances of the solar cell in Example 1 before and after the UV test; wherein, Figure 3 a in is the appearance schematic diagram before the UV test, Figure 3 b in is the appearance schematic diagram after the UV test;

[0026] Figure 4 is a comparative schematic diagram of the electroluminescence test appearances of the solar cell in Example 2 before and after the UV test; wherein, Figure 4 a in is the appearance schematic diagram before the UV test, Figure 4 b in is the appearance schematic diagram after the UV test;

[0027] Figure 5 is a comparative schematic diagram of the electroluminescence test appearances of the solar cell in Example 3 before and after the UV test; wherein, Figure 5 a in is the appearance schematic diagram before the UV test, Figure 5 b in is the appearance schematic diagram after the UV test;

[0028] Figure 6 is a comparative schematic diagram of the electroluminescence test appearances of the solar cell in Example 4 before and after the UV test; wherein, Figure 6 a in is the appearance schematic diagram before the UV test,Figure 6 In figure b is the schematic diagram of the appearance after UV test;

[0029] Figure 7 It is the schematic diagram of the comparison of the electroluminescence test appearance before and after the UV test of the solar cell in Example 5; among which, Figure 7 In figure a is the schematic diagram of the appearance before UV test, Figure 7 In figure b is the schematic diagram of the appearance after UV test;

[0030] Figure 8 It is the schematic diagram of the comparison of the electroluminescence test appearance before and after the UV test of the solar cell in Example 6; among which, Figure 8 In figure a is the schematic diagram of the appearance before UV test, Figure 8 In figure b is the schematic diagram of the appearance after UV test;

[0031] Figure 9 It is the schematic diagram of the comparison of the electroluminescence test appearance before and after the UV test of the solar cell in Comparative Example 1; among which, Figure 9 In figure a is the schematic diagram of the appearance before UV test, Figure 9 In figure b is the schematic diagram of the appearance after UV test.

[0032] Description of the reference numerals

[0033] 1 - N-type silicon substrate; 2 - P-type doped silicon layer; 3 - First passivation layer; 4 - First electrode; 5 - Tunneling oxide layer; 6 - N-type doped silicon layer; 7 - Second passivation layer; 8 - Second electrode. Detailed implementation manners

[0034] To make the above objects, features and advantages of the present application more obvious and understandable, the following will give a detailed description of the specific implementation manners of the present application. Many specific details are set forth in the following description in order to fully understand the present application. However, the present application can be implemented in many other ways different from those described herein, and those skilled in the art can make similar improvements without departing from the connotation of the present application. Therefore, the present application is not limited by the specific embodiments disclosed below.

[0035] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the technical field to which this application belongs. The terms used in the specification of this application herein are only for the purpose of describing specific embodiments, and are not intended to limit this application. The term "and / or" used herein includes any and all combinations of one or more of the related listed items.

[0036] In the description of the present application, it should be understood that the orientation or positional relationship indicated by the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus should not be construed as a limitation to the present application.

[0037] In addition, the terms "first" and "second" are only used for descriptive purposes and should not be construed as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include at least one of such features. In the description of the present application, the meaning of "a plurality" is at least two, such as two, three, etc., unless otherwise specifically and clearly defined.

[0038] In the present application, unless otherwise clearly specified and limited, the terms "mounted", "connected", "connected to", "fixed", etc. should be understood in a broad sense. For example, it may be a fixed connection, a detachable connection, or integrated; it may be a mechanical connection or an electrical connection; it may be directly connected or indirectly connected through an intermediate medium, and it may be the communication inside two elements or the interaction relationship between two elements, unless otherwise clearly limited. For those of ordinary skill in the art, the specific meanings of the above terms in the present application can be understood according to specific circumstances.

[0039] The applicant has found that one of the main reasons for the UV attenuation phenomenon of solar cells during long-term outdoor use is the bombardment effect of high-energy carriers excited by ultraviolet high-energy photons on the PN junction interface in the short-circuit state, resulting in an increase in the density of recombination centers and damage to the junction region. However, in traditional solar cells, the doping concentration distribution gradient of the P-type doping element in the PN junction is relatively large, and there will be a strong electric field in the PN junction. In the short-circuit working state, the strong electric field in the PN junction is likely to intensify the transport of high-energy carriers, making the high-energy carriers have greater kinetic energy, thereby colliding with the lattice and causing damage to the junction region. Therefore, the traditional solar cells have relatively weak anti-UV attenuation ability.

[0040] Based on this, an embodiment of the present application provides a solar cell, including an N-type silicon substrate, a P-type doped silicon layer, and a PN junction located between the N-type silicon substrate and the P-type doped silicon layer; in the PN junction, the doping concentration distribution gradient of the P-type doping element in the direction from the P-type doped silicon layer to the N-type silicon substrate is less than or equal to 1.5×10 18 cm-3 / μm.

[0041] It can be understood that the doping concentration distribution gradient of the P-type doping element refers to the absolute value of the average change rate of the doping concentration of the P-type doping element in the PN junction with the junction depth. In the above solar cell, in the PN junction, the doping concentration distribution gradient of the P-type doping element is less than or equal to 1.5×10 18 cm -3 / μm. A smaller doping concentration distribution gradient in the PN junction can make the concentration distribution of high-energy carriers formed in the PN junction relatively flat under ultraviolet light irradiation, thereby reducing the migration kinetic energy of high-energy carriers, reducing the bombardment effect generated by high-energy carriers at the PN junction interface, and further reducing the damage of high-energy carriers to the junction region and the resulting lattice defects. The solar cell of the present application has good anti-UV attenuation ability and can reduce the UV attenuation phenomenon during long-term outdoor use.

[0042] In some of these embodiments, in the PN junction, the doping concentration distribution gradient of the P-type doping element is 1×10 17 cm -3 / μm~1.5×10 18 cm -3 / μm.

[0043] Optionally, in the PN junction, the doping concentration distribution gradient of the P-type doping element is 1×10 17 cm -3 / μm, 2×10 17 cm -3 / μm, 3×10 17 cm -3 / μm, 5×10 17 cm -3 / μm, 6×10 17 cm -3 / μm, 8×10 17 cm -3 / μm, 1×10 18 cm -3 / μm, 1.2×10 18 cm -3 / μm or 1.5×10 18 cm -3 / μm, or, in the PN junction, the doping concentration distribution gradient of the P-type doping element can also be within the range between any two of the above doping concentration distribution gradients.

[0044] In some of these embodiments, the junction depth of the PN junction is 1.2μm~1.5μm.

[0045] In the above PN junction, within the range of the doping concentration distribution gradient of the P-type doping element, in combination with a relatively long junction depth of 1.2 μm to 1.5 μm, the migration kinetic energy of high-energy carriers can be further reduced, and the bombardment effect generated at the PN junction interface by high-energy carriers can be reduced. Optionally, the junction depth of the PN junction is 1.2 μm, 1.22 μm, 1.25 μm, 1.28 μm, 1.3 μm, 1.32 μm, 1.35 μm, 1.38 μm, 1.4 μm, 1.42 μm, 1.45 μm, 1.48 μm or 1.5 μm, or the junction depth of the PN junction can also be within the range between any two of the above junction depths.

[0046] In some embodiments, the solar cell includes at least one of a PERC solar cell, a TOPCon solar cell, and an HJT solar cell.

[0047] Refer to Figure 1 As shown, in some embodiments, the N-type silicon substrate 1 has a first surface and a second surface that are oppositely arranged. A P-type doped silicon layer 2, a first passivation layer 3, and a first electrode 4 are sequentially stacked on the first surface. The first electrode 4 passes through the first passivation layer 3 and contacts the P-type doped silicon layer 2; a tunneling oxide layer 5, an N-type doped silicon layer 6, a second passivation layer 7, and a second electrode 8 are sequentially stacked on the second surface. The second electrode 8 passes through the second passivation layer 7 and contacts the N-type doped silicon layer 6.

[0048] Another embodiment of the present application provides a method for manufacturing a solar cell, including the following steps:

[0049] Provide an N-type silicon substrate;

[0050] Prepare a P-type doped silicon layer on the surface of the N-type silicon substrate to form a PN junction located between the N-type silicon substrate and the P-type doped silicon layer; in the PN junction, the doping concentration distribution gradient of the P-type doping element in the direction from the P-type doped silicon layer to the N-type silicon substrate is less than or equal to 1.5×10 18 cm -3 / μm.

[0051] In some embodiments, preparing a P-type doped silicon layer on the surface of the N-type silicon substrate includes the following steps:

[0052] Perform a first deposition using a first process gas including a P-type doping source to form a pre-doped layer on the surface of the N-type silicon substrate. The doping concentration of the P-type doping element in the pre-doped layer is greater than or equal to 1×10 20 cm -3 ;

[0053] Perform a second deposition using a second process gas including a P-type doping source. The flow rate of the P-type doping source in the second process gas is less than the flow rate of the P-type doping source in the first process gas;

[0054] High-temperature annealing is performed to form a PN junction.

[0055] In the method for preparing the above P-type doped silicon layer, a pre-doped layer with a relatively high doping concentration is first formed by a P-type doping source with a relatively high flow rate, and then the flow rate of the P-type doping source is reduced. While adjusting the concentration distribution of the P-type doping element, the total doping concentration can also be increased compared to the traditional process.

[0056] In some of these embodiments, the doping concentration of the P-type doping element in the pre-doped layer is 1×10 20 cm -3 ~1×10 21 m -3 .

[0057] Optionally, the doping concentration of the P-type doping element in the pre-doped layer is 1×10 20 cm -3 , 2×10 20 cm -3 , 3×10 20 cm -3 , 4×10 20 cm -3 , 5×10 20 cm -3 , 6×10 20 cm -3 , 7×10 20 cm -3 , 8×10 20 cm -3 , 9×10 20 cm -3 , or 1×10 21 cm -3 , or the doping concentration of the P-type doping element in the pre-doped layer can also be within the range between any two of the above doping concentrations.

[0058] In some of these embodiments, the flow rate of the P-type doping source in the first deposition is 500 sccm to 1000 sccm; the flow rate of the P-type doping source in the second deposition is 200 sccm to 500 sccm.

[0059] Optionally, the flow rate of the P-type doping source in the first deposition is 500 sccm, 550 sccm, 600 sccm, 650 sccm, 700 sccm, 750 sccm, 800 sccm, 850 sccm, 900 sccm, 950 sccm or 1000 sccm, or the flow rate of the P-type doping source in the first deposition can also be within the range between any two of the above flow rates.

[0060] Optionally, the flow rate of the P-type doping source in the second deposition is 200 sccm, 250 sccm, 300 sccm, 350 sccm, 400 sccm, 450 sccm or 500 sccm. Alternatively, the flow rate of the P-type doping source in the second deposition can also be within the range between any two of the above flow rates.

[0061] In some embodiments, the P-type doping source includes BCl3.

[0062] In some embodiments, the first process gas further includes oxygen.

[0063] In some embodiments, the flow rate of oxygen in the first deposition is 300 sccm to 500 sccm.

[0064] Optionally, the flow rate of oxygen in the first deposition is 300 sccm, 320 sccm, 350 sccm, 380 sccm, 400 sccm, 420 sccm, 450 sccm, 480 sccm or 500 sccm. Alternatively, the flow rate of oxygen in the first deposition can also be within the range between any two of the above flow rates.

[0065] In some embodiments, the second process gas further includes oxygen.

[0066] In some embodiments, the flow rate of oxygen in the second deposition is 300 sccm to 500 sccm.

[0067] Optionally, the flow rate of oxygen in the second deposition is 300 sccm, 320 sccm, 350 sccm, 380 sccm, 400 sccm, 420 sccm, 450 sccm, 480 sccm or 500 sccm. Alternatively, the flow rate of oxygen in the second deposition can also be within the range between any two of the above flow rates.

[0068] In some embodiments, the high-temperature annealing includes multiple annealing processes with gradually increasing temperatures performed in sequence.

[0069] Through the high-temperature annealing with multiple annealing processes having gradually increasing temperatures, a PN junction with a relatively deep junction depth and a gentle doping concentration distribution of P-type doping elements can be formed.

[0070] In some embodiments, the high-temperature annealing includes the following steps:

[0071] The first annealing process, the temperature of the first annealing process is 850 °C to 900 °C, and the time is 20 min to 30 min;

[0072] The second annealing process, the temperature of the second annealing process is 900 °C to 950 °C, and the time is 40 min to 60 min;

[0073] The third push - knot treatment, the temperature of the third push - knot treatment is 1000°C to 1050°C, and the time is 10 min to 15 min.

[0074] Within the parameter ranges of each step of the above - mentioned high - temperature push - knot, by gradually increasing the temperature and advancing for a relatively long time, it is convenient to form a PN - junction with a relatively deep junction depth and a gentle doping concentration distribution of P - type doping elements.

[0075] Optionally, the temperature of the first push - knot treatment is 850°C, 860°C, 870°C, 880°C, 890°C or 900°C, or the temperature of the first push - knot treatment can also be within the range between any two of the above temperatures.

[0076] Optionally, the time of the first push - knot treatment is 20 min, 22 min, 24 min, 26 min, 28 min or 30 min, or the time of the first push - knot treatment can also be within the range between any two of the above times.

[0077] Optionally, the temperature of the second push - knot treatment is 900°C, 910°C, 920°C, 930°C, 940°C or 950°C, or the temperature of the second push - knot treatment can also be within the range between any two of the above temperatures.

[0078] Optionally, the time of the second push - knot treatment is 40 min, 42 min, 44 min, 46 min, 48 min, 50 min, 52 min, 54 min, 56 min, 58 min or 60 min, or the time of the second push - knot treatment can also be within the range between any two of the above times.

[0079] Optionally, the temperature of the third push - knot treatment is 1000°C, 1010°C, 1020°C, 1030°C, 1040°C or 1050°C, or the temperature of the third push - knot treatment can also be within the range between any two of the above temperatures.

[0080] Optionally, the time of the third push - knot treatment is 10 min, 11 min, 12 min, 13 min, 14 min or 15 min, or the time of the third push - knot treatment can also be within the range between any two of the above times.

[0081] Another embodiment of the present application provides a photovoltaic module, including the solar cell of any one of the above, or the solar cell prepared by the preparation method of the solar cell of any one of the above.

[0082] The following are specific examples

[0083] Example 1

[0084] Preparation of the solar cell:

[0085] (1) Provide an N-type silicon substrate with a pyramidal suede on the front;

[0086] (2) Boron diffusion: Perform the first deposition using BCl3 and oxygen to form a pre-doped layer. Among them, the flow rate of BCl3 is 500 sccm, the flow rate of oxygen is 400 sccm, the time is 800 s, and the temperature is 790 °C; reduce the flow rate of BCl3, the flow rate of BCl3 is 200 sccm, the flow rate of oxygen is 400 sccm, the time is 160 s, and the temperature is 830 °C, and perform the second deposition;

[0087] (3) High-temperature drive-in: Perform the first drive-in treatment at 850 °C for 1200 s, the second drive-in treatment at 900 °C for 2400 s, and the third drive-in treatment at 1000 °C for 600 s;

[0088] (4) Backside etching: Clean the plating layer around the N-type silicon substrate and polish the backside;

[0089] (5) Backside deposition: Sequentially deposit a tunneling oxide layer and a phosphorus-doped polysilicon layer on the backside of the N-type silicon substrate;

[0090] (6) Prepare a passivation layer: Sequentially deposit an alumina layer + a silicon nitride layer on the front as the first passivation layer, and sequentially deposit an alumina layer + a silicon nitride layer on the back as the second passivation layer;

[0091] (7) Metallization: Print pastes on the first passivation layer and the second passivation layer respectively and sinter them at high temperature to form an alloy contact and prepare a finished battery.

[0092] Example 2

[0093] Preparation of solar cell:

[0094] The preparation method of the solar cell in Example 2 is substantially the same as that in Example 1, and the only difference is that:

[0095] (2) Boron diffusion: The flow rate of BCl3 in the first deposition is 600 sccm; the flow rate of BCl3 in the second deposition is 300 sccm;

[0096] (3) High-temperature drive-in: Perform the first drive-in treatment at 860 °C for 1320 s, the second drive-in treatment at 910 °C for 2640 s, and the third drive-in treatment at 1010 °C for 660 s.

[0097] Example 3

[0098] Preparation of solar cell:

[0099] The preparation method of the solar cell in Example 3 is substantially the same as that in Example 1, and the only difference is that:

[0100] (2)Boron diffusion: The flow rate of BCl3 in the first deposition is 700 sccm; the flow rate of BCl3 in the second deposition is 400 sccm;

[0101] (3)High-temperature pushing and annealing: The first pushing and annealing treatment is carried out at 870 °C for 1440 s, the second pushing and annealing treatment is carried out at 920 °C for 2880 s, and the third pushing and annealing treatment is carried out at 1020 °C for 720 s.

[0102] Example 4

[0103] Preparation of solar cell:

[0104] The preparation method of the solar cell in Example 4 is substantially the same as that in Example 1, and the only difference is that:

[0105] (2)Boron diffusion: The flow rate of BCl3 in the first deposition is 800 sccm; the flow rate of BCl3 in the second deposition is 500 sccm;

[0106] (3)High-temperature pushing and annealing: The first pushing and annealing treatment is carried out at 880 °C for 1560 s, the second pushing and annealing treatment is carried out at 930 °C for 3120 s, and the third pushing and annealing treatment is carried out at 1030 °C for 780 s.

[0107] Example 5

[0108] Preparation of solar cell:

[0109] The preparation method of the solar cell in Example 5 is substantially the same as that in Example 1, and the only difference is that:

[0110] (2)Boron diffusion: The flow rate of BCl3 in the first deposition is 900 sccm; the flow rate of BCl3 in the second deposition is 500 sccm;

[0111] (3)High-temperature pushing and annealing: The first pushing and annealing treatment is carried out at 890 °C for 1680 s, the second pushing and annealing treatment is carried out at 940 °C for 3360 s, and the third pushing and annealing treatment is carried out at 1040 °C for 840 s.

[0112] Example 6

[0113] Preparation of solar cell:

[0114] The preparation method of the solar cell in Example 6 is substantially the same as that in Example 1, and the only difference is that:

[0115] (2)Boron diffusion: The flow rate of BCl3 in the first deposition is 1000 sccm; the flow rate of BCl3 in the second deposition is 500 sccm;

[0116] (3)High-temperature drive-in: The first drive-in treatment was carried out at 900 °C for 1800 s, the second drive-in treatment was carried out at 950 °C for 3600 s, and the third drive-in treatment was carried out at 1050 °C for 900 s.

[0117] Comparative Example 1

[0118] Preparation of solar cells:

[0119] The preparation method of the solar cell in Comparative Example 1 was substantially the same as that in Example 1, and the only difference was that:

[0120] (2)Boron diffusion: Deposition was carried out using BCl3 and oxygen to form a P-type doped silicon layer. Among them, the flow rate of BCl3 was 1400 sccm, the flow rate of oxygen was 400 sccm, the time was 1200 s, and the temperature was 900 °C;

[0121] (3)High-temperature drive-in: High-temperature drive-in was carried out at 888 °C for 300 s.

[0122] The solar cells prepared in Examples 1 to 6 and Comparative Example 1 were subjected to UV tests. The test method was as follows: Using light intensity of 180 W / m 2 ~200 W / m 2 , the wavelength was 280 nm to 400 nm, among which the ultraviolet light with UVB (280 nm to 320 nm) accounting for 3% to 10% was used to irradiate the solar cell at a temperature of 60 °C ± 5 °C, with a cumulative irradiation of 120 kWh / m, and the electrical performance tests before and after the UV test were carried out to calculate the attenuation value of UV120. At the same time, the electroluminescence tests before and after the UV test were also carried out on the solar cells prepared in Examples 1 to 6 and Comparative Example 1.

[0123] Referring to Figure 2 as shown, Figure 2 It is a comparative schematic diagram of the boron doping concentration distribution curves in the PN junctions of the solar cells in Examples 1 to 6 and Comparative Example 1. It can be seen that for the solar cells prepared in Examples 1 to 6, the doping concentration distribution gradient of the P-type doping element in the PN junction is less than that in Comparative Example 1 and less than or equal to 1.5×10 18 cm -3 / μm. The doping concentration distribution gradients of the P-type doping element in the PN junctions of the solar cells in Examples 1 to 6 and Comparative Example 1, and the attenuation of the electrical performance tests before and after the UV test are shown in the following table:

[0124]

[0125] As can be seen from the above table, in Comparative Example 1, after the UV test, the efficiency attenuation of the solar cell with a traditional PN junction prepared by the traditional preparation method reached 8.54%. In Examples 1 to 6, among the prepared solar cells, the doping concentration distribution gradient of the P-type doping element in the PN junction was less than 1.5×10 18 cm -3 / μm. After the UV test, the efficiency attenuations were 2.45% to 4.66% respectively, all much less than that of the solar cell in Comparative Example 1. At the same time, as shown in Figures 3 to 9 , it can be seen that the electroluminescence test result of the solar cell in Comparative Example 1 was significantly blackened after the UV test. Among the electroluminescence test results of the solar cells in each example after the UV test, the blackening phenomenon was better than that in Comparative Example 1. At the same time, by comparing the test results of each example, it can also be seen that the flatter the PN junction curve, that is, the smaller the doping concentration distribution gradient of the P-type doping element in the PN junction, the stronger the ability of the solar cell to resist IV attenuation.

[0126] The technical features of the above-described embodiments can be combined arbitrarily. For the sake of brevity of description, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered as the scope described in this specification.

[0127] The above-described embodiments merely represent several implementation manners of the present application. The description is relatively specific and detailed, but it should not be construed as a limitation on the scope of the invention patent. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present application, several modifications and improvements can be made, and these all belong to the protection scope of the present application. Therefore, the protection scope of the patent of the present application shall be subject to the appended claims, and the specification and drawings can be used to explain the content of the claims.

Claims

1. A solar cell, characterized in that, It includes an N-type silicon substrate, a P-type doped silicon layer, and a PN junction located between the N-type silicon substrate and the P-type doped silicon layer; in the PN junction, the doping concentration distribution gradient of the P-type doping element in the direction from the P-type doped silicon layer to the N-type silicon substrate is less than or equal to 1.5×10 18 cm -3 / μm.

2. The solar cell according to claim 1, wherein The junction depth of the PN junction is 1.2 μm to 1.5 μm.

3. The solar cell according to claim 1, wherein The solar cell includes at least one of a PERC solar cell, a TOPCon solar cell, and an HJT solar cell.

4. The solar cell according to claim 1, characterized in that, The N-type silicon substrate has a first surface and a second surface disposed opposite to each other. A P-type doped silicon layer, a first passivation layer, and a first electrode are sequentially stacked on the first surface, and the first electrode passes through the first passivation layer and contacts the P-type doped silicon layer; A tunneling oxide layer, an N-type doped silicon layer, a second passivation layer, and a second electrode are sequentially stacked on the second surface, and the second electrode passes through the second passivation layer and contacts the N-type doped silicon layer.

5. A method for preparing a solar cell, characterized in that, It includes the following steps: Provide an N-type silicon substrate; A P-type doped silicon layer is prepared on the surface of the N-type silicon substrate to form a PN junction located between the N-type silicon substrate and the P-type doped silicon layer; in the PN junction, the doping concentration distribution gradient of the P-type doping element in the direction from the P-type doped silicon layer to the N-type silicon substrate is less than or equal to 1.5×10 18 cm -3 / μm.

6. The method for preparing a solar cell according to claim 5, wherein, Preparing a P-type doped silicon layer on the surface of the N-type silicon substrate includes the following steps: Perform a first deposition using a first process gas including a P-type doping source to form a pre-doped layer on the surface of the N-type silicon substrate, where the doping concentration of the P-type doping element in the pre-doped layer is greater than or equal to 1×10 20 cm -3 ; Perform a second deposition using a second process gas including the P-type doping source, and the flow rate of the P-type doping source in the second process gas is less than the flow rate of the P-type doping source in the first process gas; High-temperature diffusion to form the PN junction.

7. The manufacturing method of the solar cell according to claim 6, characterized in that, The flow rate of the P-type doping source in the first deposition is 500 sccm to 1000 sccm; the flow rate of the P-type doping source in the second deposition is 200 sccm to 500 sccm.

8. The method for preparing a solar cell according to claim 6, wherein The high-temperature diffusion includes multiple diffusion treatments with gradually increasing temperatures performed in sequence.

9. The manufacturing method of the solar cell according to claim 8, characterized in that, The high-temperature diffusion includes the following steps: A first diffusion treatment, the temperature of the first diffusion treatment is 850 °C to 900 °C, and the time is 20 min to 30 min; A second diffusion treatment, the temperature of the second diffusion treatment is 900 °C to 950 °C, and the time is 40 min to 60 min; A third diffusion treatment, the temperature of the third diffusion treatment is 1000 °C to 1050 °C, and the time is 10 min to 15 min.

10. A photovoltaic module, characterized in that, It includes the solar cell according to any one of claims 1 to 4, or the solar cell prepared by the preparation method of the solar cell according to any one of claims 5 to 9.

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