Photovoltaic cell and method for producing a photovoltaic cell, photovoltaic module

Abstract

The application relates to a photovoltaic cell and a preparation method thereof, and a photovoltaic module. The photovoltaic cell comprises a silicon substrate, a doped silicon layer and a metal electrode. The silicon substrate comprises a first surface and a second surface arranged oppositely. The first surface comprises a first region and a second region, and the second surface comprises a third region and a fourth region. The doped silicon layer is arranged on at least one of the first surface and the second surface. The doping concentration of the doped silicon layer in the first region is higher than that of the doped silicon layer in the second region, and / or the doping concentration of the doped silicon layer in the third region is greater than that of the doped silicon layer in the fourth region. A plurality of holes are arranged on the surface of the doped silicon layer away from the silicon substrate, and the holes are located in the first region and / or the third region. The metal electrode is electrically connected with the doped silicon layer, and the metal electrode fills the holes. The photovoltaic cell can effectively improve the re-doping effect of the grid line contact position.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of photovoltaic, in particular to a photovoltaic cell, a preparation method thereof and a photovoltaic module. BACKGROUND

[0002] Silicon-based photovoltaic cell is a kind of photovoltaic cell widely used at present. In the silicon-based photovoltaic cell, P-type silicon and N-type silicon are formed by doping, and a PN junction is formed at the junction of the two, generating a built-in electric field. Photogenerated carriers move to the N region and the P region under the action of the built-in electric field, thereby realizing the separation of the carriers. When the external circuit is closed, the separated electrons and holes flow in the circuit to form a current, thereby realizing the conversion of solar energy into electrical energy.

[0003] In order to improve the conversion efficiency of the silicon-based photovoltaic cell, selective re-doping can be performed in the doped silicon layer after diffusion doping to form a re-doped region at the contact area between the metal electrode and the doped silicon layer. However, due to the small diffusion coefficient of the doping element in silicon, the effect of re-doping is not obvious in the preparation method of the conventional photovoltaic cell, and the improvement of the conversion efficiency of the silicon-based photovoltaic cell is limited. SUMMARY

[0004] Therefore, it is necessary to provide a photovoltaic cell, a preparation method thereof and a photovoltaic module. The photovoltaic cell of the present application can effectively improve the re-doping effect at the grid line contact position, improve the contact area and contact effect of the region with high doping concentration between the metal electrode and the doped silicon layer, and further improve the conversion efficiency of the photovoltaic cell.

[0005] In a first aspect, the present application provides a photovoltaic cell, comprising a silicon substrate, a doped silicon layer and a metal electrode, wherein the silicon substrate comprises a first surface and a second surface arranged oppositely; the first surface comprises a first region and a second region, and the second surface comprises a third region and a fourth region; the doped silicon layer is arranged on at least one of the first surface and the second surface; the doping concentration of the doped silicon layer located in the first region is higher than the doping concentration of the doped silicon layer located in the second region, and / or the doping concentration of the doped silicon layer located in the third region is greater than the doping concentration of the doped silicon layer located in the fourth region; a plurality of holes are arranged on the surface of the doped silicon layer away from the silicon substrate, and the holes are located in the first region and / or the third region; the metal electrode is electrically connected with the doped silicon layer, and the metal electrode fills the holes.

[0006] In some embodiments, the diameter of the holes is 50 nm to 250 nm.

[0007] In some embodiments, the depth of the holes is 20 nm to 500 nm.

[0008] In some embodiments, the plurality of holes are arranged in an array.

[0009] In some embodiments, the holes are arranged at a density of 16 holes per μm 2 400 holes per μm 2 .

[0010] In some embodiments, the doped silicon layer comprises a first doped silicon layer on the first surface and a second doped silicon layer on the second surface, the first doped silicon layer and the second doped silicon layer being oppositely doped;

[0011] The first doped silicon layer in the first region has a doping concentration of 3 x 1019cm-3 18 cm-3 -3 3 x 1019cm-3 19 cm-3 -3 The first doped silicon layer in the second region has a doping concentration of 1 x 1019cm-3 18 cm-3 -3 3 x 1019cm-3 18 cm-3 -3 ;

[0012] The second doped silicon layer in the third region has a doping concentration of 3 x 1019cm-3 20 cm-3 -3 3 x 1019cm-3 21 cm-3 -3 The second doped silicon layer in the fourth region has a doping concentration of 1 x 1019cm-3 20 cm-3 -3 3 x 1019cm-3 20 cm-3 -3 .

[0013] In some embodiments, the first doped silicon layer has a thickness of 0.1 μm to 2 μm.

[0014] In some embodiments, the second doped silicon layer has a thickness of 30 nm to 200 nm.

[0015] In some embodiments, the first surface has sequentially stacked thereon the first doped silicon layer, a first anti-reflective layer, and a first metal electrode; the first doped silicon layer has a plurality of first holes on a surface thereof distal to the silicon substrate; and the first metal electrode is electrically connected through the first anti-reflective layer and the first doped silicon layer and fills the first holes.

[0016] The second surface is sequentially stacked with a tunneling oxide layer, the second doped silicon layer, a second anti-reflection layer, and a second metal electrode; the second doped silicon layer is provided with a plurality of second holes on a surface away from the silicon substrate; and the second metal electrode is electrically connected through the second anti-reflection layer and the second doped silicon layer and fills each of the second holes.

[0017] In some embodiments, the depth of the first holes accounts for 25% to 80% of the thickness of the first doped silicon layer.

[0018] In some embodiments, the depth of the second holes accounts for 30% to 75% of the thickness of the second doped silicon layer.

[0019] In a second aspect, the present application provides a method for preparing a photovoltaic cell, comprising the following steps:

[0020] providing a silicon substrate comprising a first surface and a second surface arranged oppositely; the first surface comprises a first region and a second region, and the second surface comprises a third region and a fourth region;

[0021] forming a plurality of holes on at least one of the first surface and the second surface;

[0022] diffusion doping on the surface after forming the holes to form a doped silicon layer, the doping concentration of the doped silicon layer in the first region is higher than that of the doped silicon layer in the second region, and / or the doping concentration of the doped silicon layer in the third region is higher than that of the doped silicon layer in the fourth region; the holes are located in the first region and / or the third region;

[0023] forming a metal electrode on a surface of the doped silicon layer away from the silicon substrate, the metal electrode being electrically connected to the doped silicon layer and filling each of the holes.

[0024] In some embodiments, forming a plurality of holes on at least one of the first surface and the second surface comprises the following steps:

[0025] forming a plurality of first holes on the first surface by first laser drilling.

[0026] In some embodiments, the first laser drilling uses a Bessel beam; the energy of a single laser pulse is 0.02 μJ to 1.5 μJ; and the diameter of the light spot is 50 nm to 300 nm.

[0027] In some embodiments, the first laser drilling has a pulse frequency of 1 KHz to 1000 KHz, a pulse width of 10 fs to 1000 fs, and a wavelength of 200 nm to 400 nm.

[0028] In some embodiments, forming a plurality of holes on at least one of the first surface and the second surface comprises the following steps:

[0029] forming an intrinsic silicon layer on the second surface;

[0030] forming a plurality of second holes on a surface of the intrinsic silicon layer away from the silicon substrate by second laser drilling.

[0031] In some embodiments, the second laser drilling uses a Bessel beam, a single laser pulse has an energy of 0.01 μJ to 0.5 μJ, and a spot has a diameter of 50 nm to 300 nm.

[0032] In some embodiments, the second laser drilling has a pulse frequency of 1 KHz to 300 KHz, a wavelength of 250 nm to 350 nm, and a pulse width of 50 fs to 500 fs.

[0033] In some embodiments, the method further comprises, before forming a metal electrode on a surface of the doped silicon layer away from the silicon substrate, the following steps:

[0034] forming an anti-reflection layer on a surface of the doped silicon layer away from the silicon substrate.

[0035] In a third aspect, the present application provides a photovoltaic module, comprising:

[0036] a cover plate;

[0037] at least one cell string, the cell string comprising the photovoltaic cell of any one of the above or the photovoltaic cell prepared by the method of any one of the above; and

[0038] an encapsulation layer, the encapsulation layer being between the cover plate and the cell string, the cover plate being connected to the cell string through the encapsulation layer.

[0039] In the photovoltaic cell, the region with a high doping concentration of the doped silicon layer is provided with a plurality of holes, the metal electrode is electrically connected to the doped silicon layer and fills the holes, which can effectively improve the re-doping effect of the grid line contact position, increase the contact area and contact effect of the metal electrode and the region with a high doping concentration of the doped silicon layer, and further improve the conversion efficiency of the photovoltaic cell. BRIEF DESCRIPTION OF DRAWINGS

[0040] Figure 1 Structure diagram of a photovoltaic cell according to an embodiment of the present application;

[0041] Figure 2 Structure diagram of a hole distribution according to an embodiment of the present application;

[0042] Figure 3 Structure diagram of forming a first hole on a first surface of a silicon substrate;

[0043] Figure 4 Structure diagram of forming a first hole on a first surface of a silicon substrate; Figure 3 Structure diagram of preparing a first doped silicon layer based on the same;

[0044] Figure 5 Structure diagram of preparing a tunneling oxide layer and an intrinsic silicon layer based on the same; Figure 4 Structure diagram of preparing a tunneling oxide layer and an intrinsic silicon layer based on the same;

[0045] Figure 6 Structure diagram of forming a second hole based on the same; Figure 5

[0046] Structure diagram of forming a second hole based on the same; Figure 7 Figure 6 Structure diagram of preparing a second doped silicon layer based on the same.

[0047] 10 - silicon substrate; 11 - first hole; 12 - first region; 13 - second region; 20 - first doped silicon layer; 30 - passivation layer; 40 - first anti-reflection layer; 50 - first metal electrode; 60 - tunneling oxide layer; 70' - intrinsic silicon layer; 70 - second doped silicon layer; 71 - second hole; 80 - second anti-reflection layer; 90 - second metal electrode. DETAILED DESCRIPTION

[0048] In order to make the above objectives, features and advantages of the present application more clear and comprehensible, the specific embodiments of the present application are described in detail below. In the following description, a lot of specific details are set forth in order to fully understand the present application. However, the present application can be implemented in many different ways other than those described herein, and those skilled in the art can make similar improvements without departing from the spirit of the present application, and therefore the present application is not limited to the specific embodiments disclosed below.

[0049] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used in the description of the application herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed items.

[0050] ​In the description of the present application, it needs to be understood that the orientation or positional relationship indicated by the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like is based on the orientation or positional relationship shown in the drawings, and is only for the purpose of facilitating the description of the present application and simplifying the description, and does not indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation of the present application.

[0051] In addition, the terms "first", "second" are only for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the technical features indicated. Therefore, the features defined with "first", "second" can explicitly or implicitly include at least one of the features. In the description of the present application, the meaning of "a plurality of" is at least two, such as two, three, etc., unless otherwise explicitly specified and limited.

[0052] In the present application, unless otherwise explicitly specified and limited, the terms "mounting", "connection", "connection", "fixing" and the like should be understood in a broad sense, for example, it can be fixedly connected, or it can be detachably connected, or it can be integrated; it can be mechanically connected, or it can be electrically connected; it can be directly connected, or it can be indirectly connected through an intermediate medium; it can be the internal communication of two elements or the interaction relationship between two elements, unless otherwise explicitly limited. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0053] Reference Figure 1 As shown in the drawings, an embodiment of the present application provides a photovoltaic cell, comprising a silicon substrate 10, a doped silicon layer and a metal electrode, the silicon substrate 10 comprises a first surface and a second surface arranged oppositely; the first surface comprises a first region 12 and a second region 13, and the second surface comprises a third region and a fourth region; the doped silicon layer is arranged on at least one of the first surface and the second surface; the doping concentration of the doped silicon layer located in the first region 12 is higher than the doping concentration of the doped silicon layer located in the second region 13, and / or the doping concentration of the doped silicon layer located in the third region is greater than the doping concentration of the doped silicon layer located in the fourth region; the doped silicon layer is provided with a plurality of holes on the surface away from the silicon substrate 10, and the holes are located in the first region 12 and / or the third region; the metal electrode is electrically connected with the doped silicon layer, and the metal electrode fills the holes.

[0054] In the photovoltaic cell, the region with high doping concentration of the doped silicon layer is provided with a plurality of holes, the metal electrode is electrically connected with the doped silicon layer and the metal electrode fills the holes, which can effectively improve the heavy doping effect of the grid line contact position, improve the contact area and contact effect of the metal electrode and the region with high doping concentration of the doped silicon layer, and further improve the conversion efficiency of the photovoltaic cell. It can be understood that in order to realize local heavy doping in the prior art, the doping temperature or laser heavy doping method can be used. However, the above method for realizing heavy doping is easy to cause damage to the original film layer. In the photovoltaic cell of the present application, the holes are prepared, and in the process of diffusion doping, the doping source will enter the holes, which can realize heavy doping of the film layer near the holes without changing the original doping process. At the same time, in the subsequent preparation process of the metal electrode, the electrode paste can also enter the holes to realize electrical contact with the heavily doped silicon material near the holes, improve the contact area and contact effect of the metal electrode and the region with high doping concentration of the doped silicon layer, and further improve the conversion efficiency of the photovoltaic cell.

[0055] It can be understood that in the process of diffusion doping, the doping source will enter the holes to form enrichment in the holes, and a region with high doping concentration can be formed in the doped silicon layer at the hole wall and the hole bottom, thereby facilitating the metal electrode and the doped silicon layer with high doping concentration to have a larger contact area.

[0056] In some embodiments, the diameter of the hole is 50-250 nm.

[0057] In some embodiments, the depth of the hole is 20-500 nm.

[0058] It can be understood that the diameter of the hole is the average value of any number of holes selected during sampling, and the depth of the hole is the average value of any number of holes selected during sampling. The diameter and depth of the hole can be measured by scanning electron microscope measurement method or optical profiler measurement method. The diameter and depth of the hole can be adjusted for different materials and thicknesses of the film layer. The lower limit of the diameter of the hole is mainly limited by the technology of laser drilling. When the diameter of the hole is too large or the depth of the hole is too small, the degree of increasing the contact area and contact effect of the metal electrode and the region with high doping concentration in the doped silicon layer is limited. The depth of the hole is mainly limited by the thickness of the film layer. Alternatively, the diameter of the hole is 50 nm, 80 nm, 100 nm, 120 nm, 150 nm, 180 nm, 200 nm, 220 nm or 250 nm, or the diameter of the hole can also be within the range between any two diameters. Alternatively, the depth of the hole is 20 nm, 50 nm, 80 nm, 100 nm, 150 nm, 200 nm, 250 nm, 300 nm, 350 nm, 400 nm, 450 nm, 500 nm or 500 nm, or the depth of the hole can also be within the range between any two depths.

[0059] In some embodiments, the plurality of holes are arranged in an array.

[0060] The plurality of holes are arranged in an array, the distribution of the doping source is more uniform during the diffusion doping process, and a more uniform heavy doping effect can be achieved for the area where the gate line is prepared, thereby improving the contact area and contact effect of the metal electrode and the region with high doping concentration in the doped silicon layer.

[0061] In some embodiments, the distribution density of the holes is 16 / μm 2 400 / μm 2 .

[0062] For example, referring to Figure 2 , a morphology of an array of holes that can be implemented is shown in Figure 2 . When the diameter of the hole is 50 nm and the holes are arranged in an array, the maximum distribution density of the holes is 20x20 per square micrometer, i.e. 400 / μm 2 . When the diameter of a single hole is 250 nm and the holes are arranged in an array, the maximum distribution density of the holes is 4x4 per square micrometer, i.e. 16 / μm 2 . Within the range of the distribution density of the holes described above, the effect of improving the contact area and contact effect of the metal electrode and the region with high doping concentration in the doped silicon layer is good. Alternatively, the distribution density of the holes is 16 / μm 2 , 25 / μm 2 , 36 / μm 264 / μm 2 100 / μm 2 225 / μm 2 324 / μm 2 or 400 / μm 2 Alternatively, the distribution density of the holes can also be within a range between any two of the above distribution densities.

[0063] In some embodiments, the doped silicon layer includes a first doped silicon layer 20 on the first surface and a second doped silicon layer 70 on the second surface, the first doped silicon layer 20 and the second doped silicon layer 70 being oppositely doped. The first doped silicon layer 20 on the first region 12 has a doping concentration of 3x10 18 cm -3 ~3x10 19 cm -3 The first doped silicon layer 20 on the second region 13 has a doping concentration of 1x10 18 cm -3 ~3x10 18 cm -3 The second doped silicon layer 70 on the third region has a doping concentration of 3x10 20 cm -3 ~3x10 21 cm -3 The second doped silicon layer 70 on the fourth region has a doping concentration of 1x10 20 cm -3 ~3x10 20 cm -3 .

[0064] In some embodiments, the first doped silicon layer 20 is P-type doped.

[0065] In some embodiments, the second doped silicon layer 70 is N-type doped.

[0066] It can be understood that in a TOPCon cell, an N-type silicon wafer is usually used as the silicon substrate 10, and the doping elements include at least one of P, As, Sb and Bi. The first doped silicon layer 20 is formed by directly performing P-type doping on the front surface of the silicon substrate 10, and the second doped silicon layer 70 is formed by performing N-type doping after preparing the intrinsic silicon layer 70' on the back surface of the silicon substrate 10. The doping concentration of the first doped silicon layer 20 is usually less than that of the second doped silicon layer 70.

[0067] Optionally, the first doped silicon layer 20 on the first region 12 has a doping concentration of 3x10 18 cm -3 , 4x10 18 cm -3, 5 x 10 18 cm -3 , 6 x 10 18 cm -3 , 7 x 10 18 cm -3 , 8 x 10 18 cm -3 , 9 x 10 18 cm -3 , 1 x 10 19 cm -3 , 2 x 10 19 cm -3 , or 3 x 10 19 cm -3 , or the doping concentration of the first doped silicon layer 20 located in the first region 12 can also be within a range between any two of the above doping concentrations.

[0068] Optionally, the doping concentration of the first doped silicon layer 20 located in the second region 13 is 1 x 10 18 cm -3 , 1.2 x 10 18 cm -3 , 1.5 x 10 18 cm -3 , 1.8 x 10 18 cm -3 , 2 x 10 18 cm -3 , 2.2 x 10 18 cm -3 , 2.5 x 10 18 cm -3 , 2.8 x 10 18 cm -3 , or 3 x 10 18 cm -3 , or the doping concentration of the first doped silicon layer 20 located in the second region 13 can also be within a range between any two of the above doping concentrations.

[0069] Optionally, the doping concentration of the second doped silicon layer 70 located in the third region is 3 x 10 20 cm -3 , 4 x 10 20 cm -3 , 5 x 10 20 cm -3 , 6 x 10 20 cm -3 , 7 x 10 20 cm -3 , 8 x 10 20 cm -3 , 9 x 10 20 cm -31 x 10 21 cm -3 2 x 10 21 cm -3 3 x 10 21 cm -3 Alternatively, the doping concentration of the second doped silicon layer 70 located in the third region can also be within a range between any two of the above-mentioned doping concentrations.

[0070] Optionally, the doping concentration of the second doped silicon layer 70 located in the fourth region is 1 x 10 20 cm -3 1.2 x 10 20 cm -3 1.5 x 10 20 cm -3 1.8 x 10 20 cm -3 2 x 10 20 cm -3 2.2 x 10 20 cm -3 2.5 x 10 20 cm -3 2.8 x 10 20 cm -3 3 x 10 20 cm -3 Alternatively, the doping concentration of the second doped silicon layer 70 located in the fourth region can also be within a range between any two of the above-mentioned doping concentrations.

[0071] In some embodiments, the thickness of the first doped silicon layer 20 is 0.1 μm to 2 μm.

[0072] Optionally, the thickness of the first doped silicon layer 20 is 0.1 μm, 0.2 μm, 0.3 μm, 0.4 μm, 0.5 μm, 0.6 μm, 0.7 μm, 0.8 μm, 0.9 μm, 1 μm, 1.2 μm, 1.4 μm, 1.6 μm, 1.8 μm or 2 μm, or the thickness of the first doped silicon layer 20 can also be within a range between any two of the above-mentioned thicknesses.

[0073] In some embodiments, the thickness of the second doped silicon layer 70 is 30 nm to 200 nm.

[0074] Optionally, the thickness of the second doped silicon layer 70 is 30 nm, 40 nm, 50 nm, 60 nm, 70 nm, 80 nm, 90 nm, 100 nm, 120 nm, 140 nm, 160 nm, 180 nm or 200 nm, or the thickness of the second doped silicon layer 70 can also be within a range between any two of the above-mentioned thicknesses.

[0075] In some embodiments, the first surface is sequentially stacked with the first doped silicon layer 20, the first anti-reflection layer 40, and the first metal electrode 50. The first doped silicon layer 20 is provided with the first holes 11 away from the surface of the silicon substrate 10. The first metal electrode 50 is electrically connected through the first anti-reflection layer 40 and the first doped silicon layer 20, and fills each of the first holes 11. The second surface is sequentially stacked with the tunneling oxide layer 60, the second doped silicon layer 70, the second anti-reflection layer 80, and the second metal electrode 90. The second doped silicon layer 70 is provided with the second holes 71 away from the surface of the silicon substrate 10. The second metal electrode 90 is electrically connected through the second anti-reflection layer 80 and the second doped silicon layer 70, and fills each of the second holes 71.

[0076] Referring again to Figure 1 As shown in FIG. 1, the battery structure of the present application can form holes on the front and back surfaces of the battery at the same time, and can improve the contact area and contact effect of the regions with higher doping concentration in the metal electrode and the doped silicon layer on the front and back surfaces of the battery.

[0077] In some embodiments, the photovoltaic cell further comprises a passivation layer 30 between the first doped silicon layer 20 and the first anti-reflection layer 40.

[0078] In some embodiments, the material of the passivation layer 30 comprises at least one of SiO x , SiO x , HfO2, ZrO2, and AlO x .

[0079] In some embodiments, the material of the first anti-reflection layer 40 comprises at least one of TiN, SiO x , MgF2, and SiN x .

[0080] In some embodiments, the material of the second anti-reflection layer 80 comprises at least one of TiN, SiO x , MgF2, and SiN x .

[0081] In some embodiments, the material of the tunneling oxide layer 60 comprises SiO x .

[0082] In some embodiments, the depth of the first holes 11 accounts for 25% to 80% of the thickness of the first doped silicon layer 20.

[0083] In the range of the proportion of the depth of the first hole 11 to the thickness of the first doped silicon layer 20, the effect of local heavy doping is better, the effect of improving the contact between the grid line and the heavy doping area is better, and the higher conversion efficiency of the photovoltaic cell is facilitated. At the same time, it can also avoid the piercing of the metal paste caused by the too large proportion of the depth of the first hole 11 to the thickness of the first doped silicon layer 20. Optionally, the proportion of the depth of the first hole 11 to the thickness of the first doped silicon layer 20 is 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75% or 80%, or the proportion of the depth of the first hole 11 to the thickness of the first doped silicon layer 20 can also be in the range between any two of the above proportions.

[0084] In some embodiments, the proportion of the depth of the second hole 71 to the thickness of the second doped silicon layer 70 is 30% to 75%.

[0085] In the range of the proportion of the depth of the second hole 71 to the thickness of the second doped silicon layer 70, the effect of local heavy doping is better, the effect of improving the contact between the grid line and the heavy doping area is better, and the higher conversion efficiency of the photovoltaic cell is facilitated. At the same time, it can also avoid the piercing of the metal paste caused by the too large proportion of the depth of the second hole 71 to the thickness of the second doped silicon layer 70. Optionally, the proportion of the depth of the second hole 71 to the thickness of the second doped silicon layer 70 is 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70% or 75%, or the proportion of the depth of the second hole 71 to the thickness of the second doped silicon layer 70 can also be in the range between any two of the above proportions.

[0086] Another embodiment of the present application provides a method for preparing a photovoltaic cell, comprising the following steps:

[0087] Providing a silicon substrate 10, the silicon substrate 10 comprising a first surface and a second surface arranged oppositely; the first surface comprising a first region 12 and a second region 13, and the second surface comprising a third region and a fourth region;

[0088] Forming a plurality of holes on at least one of the first surface and the second surface;

[0089] Performing diffusion doping on the surface after forming the holes to form a doped silicon layer, the doping concentration of the doped silicon layer located in the first region 12 is higher than the doping concentration of the doped silicon layer located in the second region 13, and / or the doping concentration of the doped silicon layer located in the third region is greater than the doping concentration of the doped silicon layer located in the fourth region; the holes are located in the first region 12 and / or the third region;

[0090] A metal electrode is prepared on the surface of the doped silicon layer away from the silicon substrate 10, and the metal electrode is electrically connected to the doped silicon layer and fills the holes.

[0091] After the holes are formed, diffusion doping is performed on the surface of the silicon substrate 10, and in the process of diffusion doping, the doping source enters the holes and forms enrichment in the holes, so that the film layer near the holes can be re-doped without changing the original doping process. When the metal electrode is prepared on the surface of the doped silicon layer away from the silicon substrate 10, the electrode paste will enter the holes, and through sintering, the metal-semiconductor contact can be formed with the sidewall of the hole and the re-doped area at the bottom of the hole, thereby improving the contact area and contact effect between the metal electrode and the area with high doping concentration in the doped silicon layer, and improving the conversion efficiency of the photovoltaic cell.

[0092] It should be noted that when the electrode paste is used to prepare the metal electrode through sintering treatment, at least the width of the metal electrode should cover the width of the area where the holes are opened. Since the electrode paste has a certain fluidity, the width of the prepared metal electrode can also be greater than the width of the area where the holes are opened.

[0093] In some embodiments, forming a plurality of holes on at least one of the first surface and the second surface comprises the following steps:

[0094] A plurality of first holes 11 are formed on the first surface by first laser drilling.

[0095] In some embodiments, the first surface is a textured surface.

[0096] It can be understood that the first surface can be subjected to a texturing process to form a pyramid textured surface, then a plurality of first holes 11 are formed on the first surface by first laser drilling, and then diffusion doping is performed. Generally, the height and width of the pyramid are in the range of 1 µm to 10 µm, and the size of the holes of the present application is much smaller than the size of the pyramid. That is, when the textured surface is drilled by laser, it can be understood that the drilling is performed on the sidewall of the pyramid along the thickness direction of the silicon substrate.

[0097] In some embodiments, the first laser drilling uses a Bessel beam for first laser drilling.

[0098] In some embodiments, the energy of a single laser pulse of the first laser drilling is 0.02 µJ to 1.5 µJ.

[0099] In some embodiments, the frequency of the pulse of the first laser drilling is 1 KHz to 1000 KHz.

[0100] In some embodiments, the pulse width of the laser of the first laser drilling is 10 fs to 1000 fs.

[0101] In some embodiments, the wavelength of the laser of the first laser drilling is 200 nm to 400 nm.

[0102] In some embodiments, the diameter of the spot of the first laser drilling is 50 nm to 300 nm.

[0103] In some embodiments, forming the plurality of holes on at least one of the first surface and the second surface comprises the following steps:

[0104] An intrinsic silicon layer 70' is prepared on the second surface of the silicon substrate 10;

[0105] A plurality of second holes 71 are formed by second laser drilling on the surface of the intrinsic silicon layer 70' away from the silicon substrate 10.

[0106] In some embodiments, the second laser drilling uses a Bessel beam for the second laser drilling.

[0107] In some embodiments, the energy of a single laser pulse of the second laser drilling is 0.01 μJ to 0.5 μJ.

[0108] In some embodiments, the frequency of the pulse of the second laser drilling is 1 KHz to 300 KHz.

[0109] In some embodiments, the pulse width of the laser of the second laser drilling is 50 fs to 500 fs.

[0110] In some embodiments, the wavelength of the laser of the second laser drilling is 250 nm to 350 nm.

[0111] In some embodiments, the diameter of the spot of the second laser drilling is 50 nm to 300 nm.

[0112] It can be understood that for the TOPCon cell, the holes prepared on the front surface of the silicon substrate 10 are directly laser drilled on the silicon substrate 10, and the holes prepared on the back surface of the silicon substrate 10 are first prepared on the intrinsic silicon layer 70', and then laser drilled on the surface of the intrinsic silicon layer 70', therefore, the process parameters of the first laser drilling and the second laser drilling can be different. The truncated Bessel beam is an approximately non-diffracting beam, and the light intensity remains basically unchanged within a long distance. By shaping the incident laser into a Bessel beam through elements such as a cone lens and a spatial light modulator, a small focal spot and a long focal depth of the focused light field can be obtained, and laser drilling with a controllable depth-diameter ratio can be realized.

[0113] Optionally, the energy of the single laser pulse of the first laser drilling is 0.02 μJ, 0.05 μJ, 0.1 μJ, 0.2 μJ, 0.5 μJ, 0.8 μJ, 1 μJ, 1.2 μJ, or 1.5 μJ, or the energy of the single laser pulse of the first laser drilling can also be within a range between any two of the above.

[0114] Optionally, the frequency of the pulse of the first laser drilling is 1 KHz, 2 KHz, 5 KHz, 10 KHz, 20 KHz, 50 KHz, 100 KHz, 200 KHz, 500 KHz, 800 KHz, or 1000 KHz, or the frequency of the pulse of the first laser drilling can also be within a range between any two of the above.

[0115] Optionally, the pulse width of the laser of the first laser drilling is 10 fs, 20 fs, 50 fs, 100 fs, 200 fs, 500 fs, 800 fs, or 1000 fs, or the pulse width of the laser of the first laser drilling can also be within a range between any two of the above.

[0116] Optionally, the wavelength of the laser of the first laser drilling is 200 nm, 220 nm, 240 nm, 260 nm, 280 nm, 300 nm, 320 nm, 340 nm, 360 nm, 370 nm, or 400 nm, or the wavelength of the laser of the first laser drilling can also be within a range between any two of the above.

[0117] Optionally, the diameter of the spot of the first laser drilling is 50 nm, 80 nm, 100 nm, 120 nm, 150 nm, 180 nm, 200 nm, 220 nm, 250 nm, 280 nm, or 300 nm, or the diameter of the spot of the first laser drilling can also be within a range between any two of the above.

[0118] Optionally, the energy of the single laser pulse of the second laser drilling is 0.01 μJ, 0.02 μJ, 0.05 μJ, 0.08 μJ, 0.1 μJ, 0.2 μJ, 0.3 μJ, 0.4 μJ, or 0.5 μJ, or the energy of the single laser pulse of the second laser drilling can also be within a range between any two of the above.

[0119] Optionally, the frequency of the pulse of the second laser drilling is 1 KHz, 2 KHz, 5 KHz, 10 KHz, 20 KHz, 50 KHz, 100 KHz, 150 KHz, 200 KHz, 250 KHz, or 300 KHz, or the frequency of the pulse of the second laser drilling can also be within a range between any two of the above.

[0120] Optionally, the pulse width of the laser for the second laser aperture is 50fs, 100fs, 150fs, 200fs, 250fs, 300fs, 350fs, 400fs, 450fs, or 500fs, or the pulse width of the laser for the second laser aperture can be within the range of any two of the above pulse widths.

[0121] Optionally, the wavelength of the laser used for the second laser aperture is 250nm, 260nm, 270nm, 280nm, 290nm, 300nm, 310nm, 320nm, 330nm, 340nm, or 350nm, or the wavelength of the laser used for the second laser aperture can be within the range of any two of the above wavelengths.

[0122] Optionally, the diameter of the laser spot of the second laser aperture is 50nm, 80nm, 100nm, 150nm, 200nm, 250nm or 300nm, or the diameter of the laser spot of the second laser aperture can be within the range of any two of the above diameters.

[0123] In some embodiments, the following steps are further included before fabricating the metal electrode on the surface of the doped silicon layer away from the silicon substrate 10:

[0124] An antireflection layer is prepared on the surface of the doped silicon layer away from the silicon substrate 10.

[0125] In some embodiments, the method for preparing a photovoltaic cell includes the following steps:

[0126] S10: A first hole 11 is formed on the first surface of the silicon substrate 10.

[0127] Reference Figure 3 As shown, Figure 3 This is a schematic diagram of the structure in which a first hole 11 is formed on the first surface of a silicon substrate 10.

[0128] S20: Perform first diffusion doping on the first surface of the silicon substrate 10 to prepare a first doped silicon layer 20.

[0129] Reference Figure 4 As shown, Figure 4 In order to be in Figure 3 A schematic diagram of the structure of the first doped silicon layer 20 prepared on the basis of the above.

[0130] S30: A tunneling oxide layer 60 and an intrinsic silicon layer 70' are sequentially formed on the second surface of the silicon substrate 10.

[0131] Reference Figure 5 As shown, Figure 5 In order to be in Figure 4 A schematic diagram of the structure of the tunneling oxide layer 60 and the intrinsic silicon layer 70' prepared on the basis.

[0132] S40: Forming a second hole 71 on the surface of the intrinsic silicon layer 70' away from the silicon substrate 10.

[0133] Referring to Figure 6 illustrated, Figure 6 is a structural schematic diagram of forming the second hole 71 on the basis of Figure 5 .

[0134] S50: Second doping is performed on the intrinsic silicon layer 70' to form a second doped silicon material layer.

[0135] Referring to Figure 7 illustrated, Figure 7 is a structural schematic diagram of preparing the second doped silicon layer 70 on the basis of Figure 6 .

[0136] S60: A passivation layer 30 and a first anti-reflection layer 40 are sequentially prepared on the surface of the first doped silicon layer 20.

[0137] S70: A first metal electrode 50 is prepared on the surface of the first anti-reflection layer 40, the first metal electrode 50 contacts the first anti-reflection layer 40 and the first doped silicon layer 20 through the first anti-reflection layer 40 and the first doped silicon layer 20, and fills each first hole 11.

[0138] S80: A second anti-reflection layer 80 is prepared on the surface of the second anti-reflection layer 80.

[0139] S90: A second metal electrode 90 is prepared on the surface of the second anti-reflection layer 80, the second metal electrode 90 contacts the second anti-reflection layer 80 and the second doped silicon layer 70 through the second anti-reflection layer 80 and the second doped silicon layer 70, and fills each second hole 71.

[0140] Referring to Figure 1 illustrated, Figure 1 is a structural schematic diagram of the photovoltaic cell after the first metal electrode 50 and the second metal electrode 90 are prepared.

[0141] Another embodiment of the present application provides a photovoltaic module, comprising:

[0142] a cover plate;

[0143] at least one cell string, the cell string comprising the photovoltaic cell of any one of the above or the photovoltaic cell prepared by the preparation method of any one of the above; and

[0144] an encapsulation layer, the encapsulation layer being located between the cover plate and the cell string, and the cover plate being connected with the cell string through the encapsulation layer.

[0145] Any combination of the technical features in the above-described embodiments can be made, and for the sake of brevity, not all possible combinations are described, however, it is to be understood that the application encompasses all such possible combinations.

[0146] The above-described embodiments only express several implementation manners of the application, and the description is relatively specific and detailed, but it should not be understood as a limitation on the patent scope of the application. It should be pointed out that, for ordinary skilled persons in the art, several modifications and improvements can be made without departing from the concept of the application, and these all belong to the protection scope of the application. Therefore, the patent protection scope of the application should be subject to the appended claims, and the description and drawings can be used to explain the content of the claims.

Claims

1. A photovoltaic cell, characterized in that, The device includes a silicon substrate, a doped silicon layer, and a metal electrode. The silicon substrate includes a first surface and a second surface disposed opposite to each other. The first surface includes a first region and a second region, and the second surface includes a third region and a fourth region. The doped silicon layer is disposed on at least one of the first surface and the second surface. The doping concentration of the doped silicon layer located in the first region is higher than that of the doped silicon layer located in the second region, and / or, the doping concentration of the doped silicon layer located in the third region is greater than that of the doped silicon layer located in the fourth region. A plurality of holes are disposed on the surface of the doped silicon layer away from the silicon substrate, and the holes are located in the first region and / or the third region. The metal electrode is electrically connected to the doped silicon layer and fills the holes.

2. The photovoltaic cell according to claim 1, characterized in that, The diameter of the hole is 50nm~250nm; and / or, The depth of the hole is 20nm~500nm; and / or, The distribution density of the pores is 16 per μm. 2 ~400 particles / μm 2 .

3. The photovoltaic cell according to claim 1, characterized in that, The multiple holes are arranged in an array.

4. The photovoltaic cell according to any one of claims 1 to 3, characterized in that, The doped silicon layer includes a first doped silicon layer located on the first surface and a second doped silicon layer located on the second surface, wherein the doping types of the first doped silicon layer and the second doped silicon layer are opposite. The doping concentration of the first doped silicon layer located in the first region is 3 × 10⁻⁶. 18 cm -3 ~3×10 19 cm -3 The doping concentration of the first doped silicon layer located in the second region is 1×10⁻⁶. 18 cm -3 ~3×10 18 cm -3 ; The doping concentration of the second doped silicon layer located in the third region is 3 × 10⁻⁶. 20 cm -3 ~3×10 21 cm -3 The doping concentration of the second doped silicon layer located in the fourth region is 1×10⁻⁶. 20 cm -3 ~3×10 20 cm -3 .

5. The photovoltaic cell according to claim 4, characterized in that, The thickness of the first doped silicon layer is 0.1 μm to 2 μm; and / or, The thickness of the second doped silicon layer is 30nm~200nm.

6. The photovoltaic cell according to claim 4, characterized in that, A first doped silicon layer, a first antireflection layer, and a first metal electrode are sequentially stacked on the first surface; a plurality of first holes are provided on the surface of the first doped silicon layer away from the silicon substrate; the first metal electrode passes through the first antireflection layer and the first doped silicon layer and is electrically connected to fill each of the first holes; A tunneling oxide layer, a second doped silicon layer, a second antireflection layer, and a second metal electrode are sequentially stacked on the second surface; a plurality of second holes are provided on the surface of the second doped silicon layer away from the silicon substrate; the second metal electrode passes through the second antireflection layer and the second doped silicon layer and is electrically connected to fill each of the second holes.

7. The photovoltaic cell according to claim 6, characterized in that, The depth of the first hole accounts for 25% to 80% of the thickness of the first doped silicon layer; and / or, The depth of the second hole accounts for 30% to 75% of the thickness of the second doped silicon layer.

8. A method for preparing a photovoltaic cell, characterized in that, Includes the following steps: A silicon substrate is provided, the silicon substrate including a first surface and a second surface disposed opposite to each other; the first surface includes a first region and a second region, and the second surface includes a third region and a fourth region; A plurality of holes are formed on at least one of the first surface and the second surface; Diffusion doping is performed on the surface after the formation of the hole to form a doped silicon layer. The doping concentration of the doped silicon layer in the first region is higher than that in the second region, and / or the doping concentration of the doped silicon layer in the third region is higher than that in the fourth region; the hole is located in the first region and / or the third region. A metal electrode is formed on the surface of the doped silicon layer away from the silicon substrate. The metal electrode is electrically connected to the doped silicon layer and fills each of the pores.

9. The method for preparing a photovoltaic cell according to claim 8, characterized in that, Forming a plurality of holes on at least one of the first surface and the second surface includes the following steps: Multiple first holes are formed on the first surface by a first laser aperture.

10. The method for preparing a photovoltaic cell according to claim 9, characterized in that, In the first laser aperture: a Bessel beam is used to perform the first laser aperture; the energy of a single laser pulse is 0.02μJ~1.5μJ; and the diameter of the laser spot is 50nm~300nm.

11. The method for preparing a photovoltaic cell according to claim 9, characterized in that, In the first laser aperture: the pulse frequency is 1KHz~1000KHz; the laser pulse width is 10fs~1000fs; and the laser wavelength is 200nm~400nm.

12. The method for preparing a photovoltaic cell according to claim 8, characterized in that, Forming a plurality of holes on at least one of the first surface and the second surface includes the following steps: An intrinsic silicon layer is prepared on the second surface; Multiple second holes are formed on the surface of the intrinsic silicon layer away from the silicon substrate by a second laser aperture.

13. The method for preparing a photovoltaic cell according to claim 12, characterized in that, In the second laser aperture: a Bessel beam is used for the second laser aperture; the energy of a single laser pulse is 0.01μJ~0.5μJ; and the diameter of the spot is 50nm~300nm.

14. The method for preparing a photovoltaic cell according to claim 12, characterized in that, In the second laser aperture: the laser pulse width is 50fs~500fs; the laser wavelength is 250nm~350nm; and the pulse frequency is 1KHz~300KHz.

15. A photovoltaic module, characterized in that, include: Cover plate; At least one battery string, the battery string comprising a photovoltaic cell according to any one of claims 1 to 7, or a photovoltaic cell prepared by the method of preparing a photovoltaic cell according to any one of claims 8 to 14; as well as An encapsulation layer is located between the cover plate and the battery string, and the cover plate is connected to the battery string through the encapsulation layer.

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