Solar cell and method for preparing the same

Abstract

The present invention relates to a solar cell and a method for preparing the same. The above preparation method includes the steps of: disposing grid line paste on a battery body; applying a bias voltage between the battery body and the grid line paste; performing a laser-assisted sintering process on the grid line paste. In the laser-assisted sintering treatment, the laser energy density on the grid line region is less than the laser energy density on both sides of the grid line region. The laser energy density on both sides of the region is relatively high to form a sufficiently large current, and the generated heat can melt the metal and the inorganic material, enabling the two to diffuse into each other to form an alloy and form a good ohmic contact. The energy density of the grid line region is relatively low or even zero, reducing the melting or vaporization phenomenon of the grid line during the sintering process, and reducing the situation where the aspect ratio and surface morphology of the grid line affect the battery efficiency. The preparation method of the above solar cell has a large laser process window.

Description

Technical Field

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

[0002] After printing grid line paste on a solar cell, it needs to be sintered to form metallized grid lines. Laser-assisted sintering essentially separates the two key steps of surface film erosion and contact formation during the high-temperature sintering process by utilizing the highly concentrated and controllable characteristics of the laser energy density, so as to achieve the effect of precise regulation of the sintering process. The principle of laser-assisted sintering is to irradiate the grid line paste with a laser, and the current generated by it conducts along the path with low contact resistance under the action of an external bias voltage. In a short time, a high-intensity current will generate huge heat, melting metals and inorganic materials such as silicon nitride and silicon oxide, causing the two to diffuse into each other to form an alloy, thereby reducing the contact resistance and increasing the fill factor. The duration of the sintering process matches the carrier lifetime, and it stops rapidly within milliseconds after the laser passes, so that the heat fails to damage the surface film layer in other areas, thereby improving the battery efficiency.

[0003] When the laser energy density is relatively high, the laser will melt or even vaporize the surface of the grid line when irradiating on the grid line, thus changing the aspect ratio and surface morphology of the grid line and affecting the battery efficiency. Therefore, generally a lower laser energy density is adopted to reduce the melting or vaporization of the grid line. However, since laser-assisted sintering requires a certain laser energy density to generate a large enough current, if the laser energy density is insufficient, the generated current is not enough to melt the metal and inorganic materials, and a good ohmic contact cannot be formed, which will also affect the battery efficiency. Therefore, although adopting a lower laser energy density reduces the thermal effect of laser radiation on the grid line, when the laser energy density is too low, it will also affect the battery efficiency, and the process window of laser-assisted sintering is small. Summary of the Invention

[0004] Based on this, it is necessary to provide a solar cell and a preparation method thereof to solve the problem that both too high and too low laser energy density will affect the battery efficiency and the process window is small.

[0005] One object of the present invention is to provide a preparation method of a solar cell, and the solution is as follows:

[0006] A preparation method of a solar cell includes the following steps:

[0007] Set grid line paste on the battery body;

[0008] Apply a bias voltage between the battery body and the grid line paste;

[0009] The grid line paste is subjected to laser-assisted sintering treatment. In the laser-assisted sintering treatment, the laser energy density on the grid line region is less than the laser energy density on the two side regions of the grid line region, and the grid line paste is located on the grid line region.

[0010] In one embodiment, a first laser beam is irradiated on the grid line paste to sinter the grid line paste; the light spot of the first laser beam includes an intermediate region and a first side region and a second side region respectively located on both sides of the intermediate region, and the energy densities of the first side region and the second side region are both higher than the energy density of the intermediate region. The intermediate region is irradiated on the grid line paste, and the first side region and the second side region are respectively irradiated on both sides of the grid line paste.

[0011] In one embodiment, a second laser beam and a third laser beam are respectively irradiated on both sides of the grid line paste to sinter the grid line paste, and the light spots of the second laser beam and the third laser beam are arranged at intervals.

[0012] In one embodiment, the width of the intermediate region is greater than or equal to the width of the grid line paste.

[0013] In one embodiment, the ratio of the width of the intermediate region to the width of the grid line paste is (1.2 - 2):1.

[0014] In one embodiment, the width of the intermediate region is 20 μm - 60 μm.

[0015] In one embodiment, the widths of the first side region and the second side region are independently 50 μm - 150 μm. In one embodiment, the energy density of the intermediate region is 0.02 J / cm 2 ~0.1 J / cm 2 。

[0016] In one embodiment, the energy densities of the first side region and the second side region are independently 0.2 J / cm 2 ~1 J / cm 2 。

[0017] In one embodiment, the first laser beam is obtained by transforming a Gaussian laser through a diffractive optical element.

[0018] In one embodiment, the Gaussian laser is a circular laser.

[0019] In one embodiment, the energy densities of the second laser beam and the third laser beam are independently 0.2 J / cm 2 ~1 J / cm 2。

[0020] In one embodiment, the spacing distance between the spot of the second laser beam and the spot of the third laser beam is 10 μm to 50 μm greater than the width of the grid line paste.

[0021] Another object of the present invention is to provide a solar cell, which is prepared by the preparation method described in any one of the above embodiments.

[0022] Compared with the traditional scheme, the preparation method of the above solar cell has the following beneficial effects:

[0023] The preparation method of the above solar cell performs a laser-assisted sintering process on the grid line paste provided on the battery body. In the laser-assisted sintering process, the laser energy density on the grid line area is less than the laser energy density on both sides of the grid line area. The laser energy density on both sides is relatively high to form a sufficiently large current, and the generated heat can melt the metal and inorganic materials, enabling the two to diffuse into each other to form an alloy and form a good ohmic contact. The energy density of the grid line area is relatively low, even zero, reducing the melting or gasification of the grid line during the sintering process, and reducing the situation where the aspect ratio and surface morphology of the grid line change and affect the battery efficiency. The laser process window of the preparation method of the above solar cell is relatively large.

[0024] The above solar cell avoids damage to the grid line caused by high-energy density laser irradiation, and the grid line and the battery body can form a good ohmic contact, and a high fill factor and conversion efficiency can be obtained. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 is a schematic flow chart of the preparation method of the solar cell according to an embodiment of the present invention;

[0026] Figure 2 is a schematic diagram of setting grid line paste on the battery body and irradiating with a first laser beam;

[0027] Figure 3 is a diagram showing the positional relationship between the spot of the first laser beam and the grid line paste, and the grid line paste is shown as a dotted line in the figure;

[0028] Figure 4 is a schematic diagram of the method for generating the first laser beam;

[0029] Figure 5 is a schematic flow chart of the preparation method of the solar cell according to another embodiment of the present invention;

[0030] Figure 6 is a schematic diagram of setting grid line paste on the battery body and irradiating with a second laser beam and a third laser beam;

[0031] Figure 7 It is a diagram showing the positional relationship between the spot of the second laser beam and the spot of the third laser beam and the grid line paste, and the grid line paste is shown as a dotted line in the figure.

[0032] Description of the reference numerals:

[0033] 10. Solar cell; 100. Cell body; 110. Substrate; 120. Tunneling layer; 130. Doped polysilicon layer; 140. First functional layer; 150. Emitter; 160. Second functional layer; 20. Grid line paste; 30. First laser beam; 31. Intermediate region; 32. First side region; 33. Second side region; 40. Second laser beam; 50. Third laser beam; 60. Laser source; 70. Diffractive optical element; 80. Lens. Detailed implementation manners

[0034] For the convenience of understanding the present invention, the present invention will be described more comprehensively below with reference to the relevant drawings. Preferred embodiments of the present invention are shown in the drawings. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. The purpose of providing these embodiments is to make the understanding of the disclosure content of the present invention more thorough and comprehensive.

[0035] It should be noted that when an element is referred to as being "disposed on" another element, it can be directly on the other element or there may also be an intermediate element. When an element is considered to be "connected" to another element, it can be directly connected to the other element or there may be an intermediate element at the same time. The terms "vertical", "horizontal", "left", "right" and similar expressions used herein are only for the purpose of illustration and do not represent the only implementation manner.

[0036] In the description of the present invention, it should be understood that the terms "first" and "second" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly specifying the quantity or order of the indicated technical features.

[0037] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the technical field to which the present invention belongs. The terms used in the description of the present invention herein are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The term "and / or" used herein includes any and all combinations of one or more of the related listed items.

[0038] The present invention provides a method for preparing a solar cell, comprising the following steps:

[0039] Dispose grid line paste on the cell body;

[0040] Apply a bias voltage between the battery body and the grid line paste;

[0041] Perform laser-assisted sintering on the grid line paste. In the laser-assisted sintering process, the laser energy density on the grid line region is less than that on the two side regions of the grid line region, and the grid line paste is located on the grid line region.

[0042] The above method for preparing a solar cell performs a laser-assisted sintering process on the grid line paste provided on the battery body. In the laser-assisted sintering process, the laser energy density on the grid line region is less than that on the two side regions of the grid line region. The laser energy density of the two side regions is relatively high to form a large enough current, and the generated heat can melt the metal and inorganic materials, enabling the two to diffuse into each other to form an alloy and form a good ohmic contact. The energy density of the grid line region is relatively low, even zero, reducing the melting or vaporization of the grid lines during the sintering process, and reducing the situation where the aspect ratio and surface morphology of the grid lines change and affect the battery efficiency. The above method for preparing a solar cell has a large laser process window.

[0043] As Figure 1 shown, the method 100 for preparing a solar cell according to an embodiment of the present invention includes the following steps:

[0044] Step S110, set the grid line paste on the battery body.

[0045] As Figure 2 shown, the solar cell 10 is a TOPCon cell (tunnel layer passivated contact cell). For a TOPCon cell, since burn-through pastes are used on both the front and back sides, the efficiency improvement potential of laser-assisted sintering is higher than that of a PERC cell (emitter and back passivated cell).

[0046] More specifically, the battery body 100 of the solar cell 10 includes a substrate 110, a tunnel layer 120, a doped polysilicon layer 130, a first functional layer 140, an emitter 150, and a second functional layer 160.

[0047] The tunnel layer 120 is provided on the first side of the substrate 110. The doped polysilicon layer 130 is provided on the tunnel layer 120, and the first functional layer 140 is provided on the doped polysilicon layer 130. The emitter 150 is provided on the second side of the substrate 110. The second functional layer 160 is provided on the emitter 150. The first functional layer 140 and the second functional layer 160 can be, but are not limited to, a passivation layer, an antireflection layer, etc. The material of the passivation layer can be, but is not limited to, one or more of alumina film layers. The material of the antireflection layer can be, but is not limited to, one or more of silicon nitride film layers. The grid line paste 20 is provided on the first functional layer 140 and the second functional layer 160.

[0048] Optionally, the solar cell 10 is not limited to a TOPCon cell, and can also be, for example, a BC cell or the like.

[0049] In one example, the grid line paste 20 is disposed on the cell body through a coating process. The coating method can be, but is not limited to, one or more of screen printing, pad printing, spin coating, slot coating, spraying, and laser transfer printing.

[0050] In one example, the grid line paste 20 is a silver powder paste.

[0051] In one example, the width W of the grid line paste 20 4 is 10 μm to 30 μm. Further, it is 15 μm to 30 μm. In one example, the width W of the grid line paste 20 4 is 20 μm to 30 μm. In some specific examples, the width W of the grid line paste 20 4 includes, but is not limited to, 20 μm, 22 μm, 24 μm, 26 μm, 28 μm, 30 μm, etc.

[0052] In the present invention, "width" refers to the dimension in a direction perpendicular to the extension direction of the grid line paste.

[0053] Step S120, apply a bias voltage between the cell body and the grid line paste 20.

[0054] In one example, the specific steps of applying the bias voltage include:

[0055] An external power supply applies a bias voltage to the cell body through the bottom conductive platform and the top conductive probe row. The magnitude of the bias voltage is 5V to 20V.

[0056] Step S130, as Figure 2 and Figure 3 shown, use the first laser beam 30 to irradiate the grid line paste 20 to sinter the grid line paste 20. The spot of the first laser beam 30 includes an intermediate region 31 and a first side region 32 and a second side region 33 respectively located on both sides of the intermediate region 31. The energy density of the first side region 32 and the second side region 33 is higher than the energy density of the intermediate region 31. The intermediate region 31 irradiates the grid line paste 20, and the first side region 32 and the second side region 33 respectively irradiate both sides of the grid line paste 20.

[0057] The formation of the above-mentioned first laser beam 30 can be achieved through optical path design or by using optical devices to make the laser radiation energy distributed in regions.

[0058] As Figure 4As shown, in one example, the first laser beam 30 is generated by a laser source 60 to produce a Gaussian laser, and then the Gaussian laser is transformed through a diffractive optical element (DOE) 70. After passing through the diffractive optical element 70, the Gaussian laser can form a spot energy distribution with lower energy in the middle and higher energy on both sides. In one example, the above Gaussian laser is a Gaussian circular laser. The Gaussian circular laser can form a rectangular spot with a lower-middle and higher-side energy distribution after passing through the diffractive optical element.

[0059] As Figure 4 shown, in one example, the spot of the first laser beam 30 is a rectangular spot. The middle region 31, the first side region 32, and the second side region 33 are three juxtaposed rectangular regions. The first laser beam 30 can be obtained by transforming a Gaussian circular laser through the diffractive optical element 70.

[0060] In other examples, the spot of the first laser beam 30 is not limited to being a rectangular spot. For example, it can also be a circular spot, an elliptical spot, etc., as long as it has the energy distribution characteristics of low energy density in the middle region 31 and high energy density in the first side region 32 and the second side region 33.

[0061] Furthermore, after passing through the diffractive optical element 70, the Gaussian laser can adjust the spot size through a lens 80. The lens 80 is, for example, a concave lens, a convex lens, etc.

[0062] Preferably, the width W of the middle region 31 1 is not less than the width W of the grid line paste 20 4 , so as to align the middle region 31 on the grid line paste 20. In one example, the width W of the middle region 31 1 is the same as the width W of the grid line paste 20 4 . Furthermore, the width W of the middle region 31 1 and the width W of the grid line paste 20 4 are both any value between 20 μm and 30 μm.

[0063] In one example, the width W of the middle region 31 1 is greater than the width W of the grid line paste 20 4 , so as to better cover the irradiation on the grid line paste 20 by the middle region 31.

[0064] In one example, the ratio of the width W of the middle region 31 1 to the width W of the grid line paste 20 4 is (1.2 - 2)∶1. Furthermore, the width W of the middle region 31 1 and the width W of the grid line paste 20 4The ratio is (1.5 - 2)∶1. In some specific examples, the width W of the middle region 31 1 and the width W of the grid line paste 20 4 include but are not limited to ratios such as 1.2∶1, 1.5∶1, 1.8∶1, 2∶1, etc.

[0065] In one example, the width W1 of the middle region 31 is 10 μm to 50 μm greater than the width W of the grid line paste 20. Further, the width W of the middle region 31 4 is 10 μm to 30 μm greater than the width W of the grid line paste 20. In some specific examples, the width W of the middle region 31 1 is greater than the width W of the grid line paste 20 4 by including but not limited to 10 μm, 20 μm, 30 μm, 40 μm, 50 μm, etc. 1 In one example, the width W1 of the middle region 31 is 20 μm to 60 μm. Further, the width W1 of the middle region 31 is 20 μm to 50 μm. In some specific examples, the width W of the middle region 31 4 includes but is not limited to 20 μm, 30 μm, 40 μm, 50 μm, 60 μm, etc.

[0066] It can be understood that in other examples, the width W of the middle region 31 1 can also be less than the width W of the grid line paste 20

[0067] 1 4 , and in this way, the thermal influence of laser radiation on the grid lines can also be reduced to a certain extent.

[0068]

[0069] In one example, the energy density of the middle region 31 is below 0.1 J / cm 2 In one example, the energy density of the middle region 31 is 0.05 J / cm 2 to 0.1 J / cm 2 In one example, the energy density of the middle region 31 is 0.05 J / cm 2 to 0.08 J / cm 2 When the energy density of the middle region 31 is within the above range, the thermal influence of laser radiation on the grid lines can be effectively reduced.

[0069] In one example, the first side region 32 and / or the second side region 33 are irradiated outside the grid line paste 20, that is, there is a gap between the first side region 32 and / or the second side region 33 and the grid line paste 20. The width of the gap is the width W by which the middle region 31 extends beyond the grid line paste 20 on one side 4。The energy densities of the first side region 32 and the second side region 33 are relatively high to generate a sufficiently large current, generate a sufficiently large amount of heat, melt the metal and silicon materials, enable the two to diffuse into each other, form a silicon-containing alloy, thereby reducing the contact resistance and increasing the fill factor. At the same time, the first side region 32 and / or the second side region 33 are irradiated outside the gate line paste 20 to reduce the melting or vaporization of the gate lines.

[0070] In one example, the width W of the first side region 32 2 and the width W of the second side region 33 3 are independently 50 μm to 150 μm. Further, the width W of the first side region 32 2 and the width W of the second side region 33 3 are independently 50 μm to 100 μm. The width W of the first side region 32 2 and the width W of the second side region 33 3 can be the same or different.

[0071] In one example, the energy density of the first side region 32 and the energy density of the second side region 33 are independently 0.2 J / cm 2 ~1 J / cm 2 . Further, the energy density of the first side region 32 and the energy density of the second side region 33 are independently 0.2 J / cm 2 ~0.8 J / cm 2 . The energy density of the first side region 32 and the energy density of the second side region 33 can be the same or different.

[0072] In one example, the wavelength of the first laser beam 30 is 532 nm to 1064 nm.

[0073] Optionally, the first laser beam 30 can be a pulsed laser or a continuous laser. When the first laser beam 30 is a pulsed laser, the pulse width can be, but is not limited to, 30 ns to 100 μs.

[0074] The preparation method 100 of the above-mentioned solar cell performs a laser-assisted sintering process on the grid line paste 20 disposed on the battery body, and performs sintering by applying a bias voltage and irradiating with a first laser beam 30. The light spot of the first laser beam 30 includes an intermediate region 31 and a first side region 32 and a second side region 33 respectively located on both sides of the intermediate region 31. Among them, the energy density of the first side region 32 and the second side region 33 is relatively high to form a sufficiently large current, and the generated heat can melt the metal and the inorganic material, so that the two diffuse into each other to form an alloy and form a good ohmic contact. The intermediate region 31 irradiates on the grid line paste 20, and the energy density of the intermediate region 31 is relatively low, reducing the melting or vaporization phenomenon of the grid line during the sintering process, and reducing the situation that the aspect ratio and surface topography of the grid line change and affect the battery efficiency. The preparation method 100 of the above-mentioned solar cell has a large laser process window.

[0075] As Figure 5 shown, the preparation method 200 of the solar cell according to another embodiment of the present invention includes the following steps:

[0076] Step S210, disposing a grid line paste on the battery body.

[0077] As Figure 6 shown, the solar cell 10 is a TOPCon cell. Optionally, the solar cell 10 is not limited to being a TOPCon cell, and may also be, for example, a BC type cell or the like.

[0078] In one example, the grid line paste 20 is disposed on the battery body by coating. The coating method may be, but is not limited to, one or more of screen printing, pad printing, spin coating, slot coating, spraying, and laser transfer printing.

[0079] In one example, the grid line paste 20 is a silver powder paste.

[0080] In one example, the grid line paste 20 is disposed on the battery body in a linear shape.

[0081] In one example, the width W of the grid line paste 20 4 is 10 μm to 30 μm. Further, it is 15 μm to 30 μm. In one example, the width W of the grid line paste 20 4 is 20 μm to 30 μm. In some specific examples, the width W of the grid line paste 20 4 includes, but is not limited to, 20 μm, 22 μm, 24 μm, 26 μm, 28 μm, 30 μm, etc.

[0082] Step S220, applying a bias voltage between the battery body and the grid line paste 20.

[0083] In one example, the specific steps of applying a bias voltage include:

[0084] An external power supply applies a bias voltage to the battery body through the bottom conductive platform and the top conductive probe row. The magnitude of the bias voltage is 5V to 20V.

[0085] Step S230, as Figure 6 and Figure 7 shown, the second laser beam 40 and the third laser beam 50 are respectively irradiated on both sides of the grid line paste 20 to sinter the grid line paste 20, and the spots of the second laser beam 40 and the spots of the third laser beam 50 are arranged at intervals.

[0086] In Figure 7 the specific example shown, the spots of the second laser beam 40 and the spots of the third laser beam 50 are rectangular spots. In other examples, the spots of the second laser beam 40 and the spots of the third laser beam 50 are not limited to rectangular spots, and can also be circular spots, elliptical spots, etc. As long as there is an interval between the spots of the second laser beam 40 and the spots of the third laser beam 50 during the irradiation, the grid line paste 20 is located within this interval.

[0087] Preferably, the interval distance W 5 between the spots of the second laser beam 40 and the spots of the third laser beam 50 is not less than the width W 4 of the grid line paste 20. In one example, the above interval distance W 5 is the same as the width W 4 of the grid line paste 20. Further, both the above interval distance W 5 and the width W 4 of the grid line paste 20 are any value between 20μm and 30μm.

[0088] In one example, the above interval distance W 5 is greater than the width W 4 of the grid line paste 20 to better prevent the second laser beam 40 and the third laser beam 50 from irradiating onto the grid line paste 20.

[0089] In one example, the above interval distance W 5 is 10μm to 50μm larger than the width W 4 of the grid line paste 20. Further, the above interval distance W 5 is 10μm to 30μm larger than the width W 4 of the grid line paste 20. In some specific examples, the above interval distance W5 is 10μm, 20μm, 30μm, 40μm, 50μm, etc. larger than the width W 4 of the grid line paste 20, including but not limited to these values.

[0090] In one example, the above-mentioned spacing distance W 5 is 10 μm to 50 μm. Further, the above-mentioned spacing distance W 5 is 20 μm to 50 μm. In some specific examples, the above-mentioned spacing distance W 5 includes but is not limited to 10 μm, 20 μm, 30 μm, 40 μm, 50 μm, etc.

[0091] In one example, the width W of the spot of the second laser beam 40 6 and the width W of the spot of the third laser beam 50 7 are independently 50 μm to 150 μm. Further, the width W of the spot of the second laser beam 40 6 and the width W of the spot of the third laser beam 50 7 are independently 50 μm to 100 μm. The width W of the spot of the second laser beam 40 6 and the width W of the spot of the third laser beam 50 7 can be the same or different.

[0092] In one example, the energy density of the second laser beam 40 and the energy density of the third laser beam 50 are independently 0.2 J / cm 2 to 1 J / cm 2 . Further, the energy density of the second laser beam 40 and the energy density of the third laser beam 50 are independently 0.2 J / cm 2 to 0.8 J / cm 2 . The energy density of the third laser beam 50 and the energy density of the third laser beam 50 can be the same or different.

[0093] In one example, the wavelengths of the second laser beam 40 and the third laser beam 50 are independently 532 nm to 1064 nm.

[0094] Optionally, the first laser beam 30 and the third laser beam 50 can be pulsed lasers or continuous lasers. When the first laser beam 30 and the third laser beam 50 are pulsed lasers, the pulse width can be but is not limited to 30 ns to 100 ns.

[0095] The preparation method 200 of the above-mentioned solar cell performs a laser-assisted sintering process on the grid line paste 20 disposed on the battery body. By applying a bias voltage and irradiating both sides of the grid line paste 20 with a second laser beam 40 and a third laser beam 50 respectively, sintering is carried out. The spots of the second laser beam 40 and the third laser beam 50 are spaced apart, reducing the melting or vaporization phenomenon of the grid lines during the sintering process, and reducing the situation where the aspect ratio and surface morphology of the grid lines change and affect the battery efficiency. In this way, the second laser beam 40 and the third laser beam 50 can adopt a relatively high energy density to form a sufficiently large current, and the generated heat can melt the metal and inorganic materials, enabling the two to diffuse into each other to form an alloy and form a good ohmic contact. The preparation method 200 of the above-mentioned solar cell has a relatively large laser process window.

[0096] Furthermore, the present invention also provides a solar cell, which is prepared by the above-mentioned preparation method.

[0097] The above-mentioned solar cell avoids the damage to the grid lines caused by high-energy density laser irradiation, and the grid lines and the battery body can form a good ohmic contact, and a relatively high fill factor and conversion efficiency can be obtained.

[0098] The following will be further described in conjunction with specific examples and comparative examples, but the present invention is not limited to the following specific examples.

[0099] Example 1

[0100] The preparation method of the solar cell provided in this example includes the following steps:

[0101] Step 1, as Figure 2 and Figure 3 shown, a grid line paste is disposed on a TOPCon battery body (TOPCon battery). The width W of the grid line paste 20 4 is 20 μm.

[0102] Step 2, a bias voltage is applied between the battery body and the grid line paste.

[0103] Step 3, a first laser beam 30 is irradiated on the grid line paste 20 to sinter the grid line paste 20. The spot of the first laser beam 30 includes a middle region 31, a first side region 32 and a second side region 33 which are three juxtaposed rectangular regions.

[0104] The first laser beam 30 generates a circular Gaussian laser by a laser source 60, and then the circular Gaussian laser is transformed by a diffractive optical element (DOE) to form a spot energy distribution with lower energy in the middle and higher energy on both sides.

[0105] The width W of the middle region 31 1 is 40 μm, and the energy density is 0.075 J / cm2 The width W of the first side region 32 2 and the width W of the second side region 33 3 are both 100 μm, and the energy density is both 0.6 J / cm 2 .

[0106] The grid lines on both the front and back sides of the solar cell are formed by the above method.

[0107] Example 2

[0108] The preparation method of the solar cell provided in this example includes the following steps:

[0109] Steps 1 to 2 are the same as steps 1 to 2 in Example 1.

[0110] Step 3: Use the second laser beam 40 and the third laser beam 50 to irradiate both sides of the grid line paste 20 respectively to sinter the grid line paste 20. The light spots of the second laser beam 40 and the third laser beam 50 are both rectangular light spots and are arranged at intervals.

[0111] The interval distance W between the light spots of the second laser beam 40 and the third laser beam 50 5 is 40 μm. The width W of the light spot of the second laser beam 40 6 and the width W of the light spot of the third laser beam 50 7 are both 100 μm, and the energy density is both 0.6 J / cm 2 .

[0112] The grid lines on both the front and back sides of the solar cell are formed by the above method.

[0113] Comparative Example 1

[0114] The preparation method of the solar cell in this comparative example includes the following steps:

[0115] Steps 1 to 2 are the same as steps 1 to 2 in Example 1.

[0116] Step 3: Use a laser beam to irradiate the grid line paste 20 to sinter the grid line paste 20. The laser beam used in this comparative example is different from the first laser beam 30 in that the light spot has a uniform energy density, and the energy density is 0.075 J / cm 2 .

[0117] The grid lines on both the front and back sides of the solar cell are formed by the above method.

[0118] Comparative Example 2

[0119] The preparation method of the solar cell in this comparative example includes the following steps:

[0120] Steps 1 to 2 are the same as steps 1 to 2 in Example 1.

[0121] Step 3: irradiate the grid line paste 20 with a laser beam to sinter the grid line paste 20. The laser beam used in this comparative example is different from the first laser beam 30 in that the light spot has a uniform energy density, and the energy density is 0.6 J / cm 2 .

[0122] The grid lines on both the front and back sides of the solar cell are formed by the above method.

[0123] Use an IV test instrument to perform performance tests on the solar cells prepared in the above Examples 1-2 and Comparative Examples 1-2, including open circuit voltage, short circuit current, fill factor, and conversion efficiency. The test conditions of the IV test instrument are STC: AM1.5 spectrum, 1000 W / m 2 , 25 degrees Celsius, and the light intensity uniformity distribution of 3 A. The test results are shown in Table 1.

[0124] Table 1 Performance test results of the solar cells prepared in Examples 1-2 and Comparative Examples 1-2

[0125]

[0126] As can be seen from the results in Table 1, Examples 1-2 adopt the improved laser irradiation method of the present invention, and compared with Comparative Examples 1-2, the performance of the solar cells such as fill factor and conversion efficiency has been improved. The laser energy density used in Comparative Example 1 is relatively low, resulting in insufficient current and unable to form a good ohmic contact. While the laser energy density used in Comparative Example 2 is relatively high, when irradiated on the grid line paste, it causes certain damage to it, both of which result in a low fill factor and conversion efficiency.

[0127] The technical features of the above 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 recorded in this specification.

[0128] The above embodiments only represent several implementation manners of the present invention, and their descriptions are relatively specific and detailed, but they should not be construed as limiting 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 invention, several deformations and improvements can still be made, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the present invention patent should be subject to the appended claims.

Claims

1. A method for preparing a solar cell, characterized in that: The following steps are involved: Disposing a grid line slurry on a grid line region of a battery body; Applying a bias voltage between the battery body and the grid line paste; The gate line slurry is subjected to a laser assisted sintering process, in which the laser energy density on the gate line region is less than the laser energy density on both sides of the gate line region, and the gate line slurry is located on the gate line region.

2. The preparation method according to claim 1, characterized in that The laser assisted sintering process comprises: A first laser beam is used to irradiate the grid line paste to sinter the grid line paste; the light spot of the first laser beam includes a middle area and a first side area and a second side area respectively located on both sides of the middle area, the energy density of the first side area and the second side area are both higher than the energy density of the middle area, the middle area is irradiated on the grid line paste, and the first side area and the second side area are respectively irradiated on both sides of the grid line paste; or The second laser beam and the third laser beam are used to irradiate the two sides of the grid line paste respectively to sinter the grid line paste, and the light spot of the second laser beam and the light spot of the third laser beam are arranged at intervals.

3. The preparation method according to claim 2, characterized in that: The preparation method meets at least one of the following characteristics (1) to (2): (1) The width of the middle region is greater than or equal to the width of the gate line paste; (2) The ratio of the width of the middle region to the width of the gate line paste is (1.2-2):

1.

4. The preparation method according to claim 2 or 3, characterized in that: The preparation method meets at least one of the following characteristics (1) to (2): (1) The width of the middle region is 30 μm to 50 μm; (2) The width of the first side region and the width of the second side region are each independently 50 μm to 150 μm.

5. The preparation method according to claim 2 or 3, characterized in that: The preparation method meets at least one of the following characteristics (1) to (2): (1) The energy density of the middle region is 0.02 J / cm 2 ~0.1J / cm 2 ; (2) The energy density of the first side region and the energy density of the second side region are independently 0.2 J / cm 2 ~1J / cm 2 .

6. The preparation method according to claim 2 or 3, characterized in that: The first laser beam is obtained by transforming Gaussian laser through a diffraction optical element.

7. The preparation method according to claim 6, characterized in that: The Gaussian laser is a circular laser.

8. The preparation method according to claim 2, characterized in that: The energy density of the second laser beam and the energy density of the third laser beam are independently 0.2 J / cm 2 ~1J / cm 2 .

9. The preparation method according to claim 2 or 8, characterized in that: The spacing distance between the light spot of the second laser beam and the light spot of the third laser beam is 10 μm to 50 μm greater than the width of the gate line paste.

10. A solar cell, characterized in that: It is prepared by the preparation method according to any one of claims 1 to 9.

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