Method for manufacturing a solar cell

Abstract

A manufacturing method according to an embodiment of the present invention may include the following steps: providing a solar cell including a semiconductor substrate and a semiconductor layer, the absorption coefficient of the semiconductor layer being higher than that of the semiconductor substrate and formed on at least one side of the semiconductor substrate such that the semiconductor layer faces the laser orientation; emitting a laser beam onto the semiconductor layer to form a groove in the solar cell; and dividing the solar cell into a plurality of sheets along the groove.

Description

Technical Field

[0001] The present disclosure relates to a method for manufacturing a solar cell, which reduces thermal damage when the solar cell is divided into a plurality of parts. Background Art

[0002] In recent years, there has been an increasing interest in alternative energy sources to replace conventional energy sources such as oil and coal, which are expected to be depleted. Therefore, solar cells for generating electric power from solar energy have received attention.

[0003] A typical solar cell is made of semiconductor portions of different conductive types (e.g., p-type and n-type) forming a p-n junction and electrodes connected to the semiconductor portions of different conductive types. With this configuration, a plurality of solar cells are combined to form a solar cell module, thereby generating and obtaining electric power.

[0004] As a way to improve the power generation efficiency of solar cells, a method for manufacturing a solar cell module has been proposed by dividing a finished solar cell equipped with all necessary components into a plurality of parts and interconnecting them.

[0005] When a solar cell is divided into a plurality of parts, since the solar cell is a semiconductor, a semiconductor scribing process is employed. The scribing process refers to a process of forming grooves in the surface of a wafer by a diamond cutter, a laser, etc. to cut the wafer into individual chips.

[0006] One of the well-known scribing processes involves forming grooves by irradiating one surface of a solar cell with a laser along a scribing line, and physically dividing the solar cell into a plurality of parts along the grooves.

[0007] However, when irradiated with a laser, due to the high energy of the laser, the solar cell is thermally damaged, which results in a reduction in the efficiency of the solar cell. Summary of the Invention

[0008] Technical Problem

[0009] The present disclosure has been made in view of the above circumstances, and one aspect of the present disclosure is thermal damage that occurs when a solar cell is irradiated with a laser.

[0010] Technical Solution

[0011] In a solar cell, a semiconductor substrate and a semiconductor layer having an absorption coefficient higher than that of the semiconductor substrate are arranged such that the semiconductor layer formed on at least one side of the semiconductor substrate faces the laser; grooves are formed in the solar cell by directing the laser to the semiconductor layer; and the solar cell is divided into a plurality of parts along the grooves.

[0012] The groove can be formed to penetrate through the semiconductor layer and even extend to a part of the semiconductor substrate, and the depth of the groove can be 30% to 70% of the thickness of the semiconductor substrate.

[0013] The groove can be formed along the center line of the solar cell to divide the solar cell into two parts, or multiple grooves can be formed in the solar cell to divide the solar cell into three or more parts.

[0014] When the laser has a wavelength of 1024 nm, the semiconductor layer can be 600 nm thick or thicker, and when the laser has a wavelength of 532 nm, the semiconductor layer can be 180 nm thick or thicker.

[0015] The semiconductor layer can be polycrystalline silicon, and the semiconductor substrate can be single-crystalline silicon.

[0016] The semiconductor layer can be formed on the back surface of the semiconductor substrate.

[0017] The semiconductor layer can include a first conductive region and a second conductive region. The first conductive region contains a first conductive dopant with a polarity opposite to that of the semiconductor substrate, the second conductive region contains a second conductive dopant with the same polarity as the semiconductor substrate, and the groove can be formed in the second conductive region.

[0018] The semiconductor layer can include a first conductive dopant with a polarity opposite to that of the semiconductor substrate, and a control passivation layer can be formed between the semiconductor layer and the semiconductor substrate.

[0019] Advantageous Effects

[0020] According to an exemplary embodiment of the present disclosure, since the semiconductor layer serves as a layer for absorbing part of the energy of the laser irradiating the solar cell, thermal damage to the semiconductor substrate can be reduced.

[0021] The semiconductor layer can be configured as a semiconductor layer having a higher absorption coefficient than the semiconductor substrate, and in particular, in the present disclosure, one of the existing components, that is, the semiconductor layer configured as a polycrystalline silicon layer, can be used without adding a new layer to the solar cell. Description of the Drawings

[0022] Figure 1 is a view schematically showing the process of forming grooves in a solar cell to divide the solar cell into multiple parts according to an exemplary embodiment of the present disclosure.

[0023] Figure 2 is a flowchart showing a manufacturing method according to an exemplary embodiment of the present disclosure.

[0024] Figure 3 is a graph showing how the absorption coefficient varies according to the crystallinity of different types of silicon.

[0025] Figure 4 is a graph showing test results of the cutting depth of a groove based on the presence or absence of a semiconductor layer made of polysilicon.

[0026] Figure 5 is a graph showing the reduction of the power output of a solar cell with respect to the stored pulsed energy.

[0027] Figure 6 is a graph showing how the absorption depth varies according to the crystallinity of different types of silicon.

[0028] Figure 7 and Figure 8 is a view of a laser for forming a groove in a solar cell.

[0029] Figure 9 is a view showing the structure of a solar cell according to an exemplary embodiment applicable to the present invention.

[0030] Figure 10 is a view showing Figure 9 a cross-section of the solar cell shown.

[0031] Figure 11 shows another embodiment of a solar cell to which the manufacturing method of the present disclosure can be applied. Detailed Description

[0032] Now, various embodiments of the present disclosure will be described in detail, examples of which are shown in the drawings. However, the present invention can be implemented in many alternative forms and should not be construed as limited to the embodiments set forth herein.

[0033] In the drawings, for clarity and simplicity of description, illustrations of components unrelated to the embodiments of the present disclosure are omitted. Throughout the disclosure, the same reference numerals denote the same or very similar elements. In the drawings, for clarity of description, the thickness, width, etc. of the elements are enlarged or reduced and should not be construed as limited to those shown in the drawings.

[0034] It should also be understood that throughout the specification, when an element is referred to as "comprising" another element, the term "comprising" specifies the presence of the other element, but does not exclude the presence of other additional elements, unless the context clearly indicates otherwise. Further, it should be understood that when an element such as a layer, region, or plate is referred to as being "on" another element, one element can be directly on the other element and there can also be one or more intermediate elements. In contrast, when an element such as a layer, region, or plate is referred to as being "directly on" another element, there are no one or more intermediate elements.

[0035] In addition, if the thickness, width, or length of a certain component is the same as that of another component, it means that the two components have the same thickness, width, or length within the tolerance of the process error.

[0036] Therefore, if the process error tolerance is 10%, it means that their thicknesses are considered the same within the 10% process error tolerance. The following description will be given based on the assumption that the process error tolerance is 10%.

[0037] In addition, one side and the other side of the semiconductor substrate refer to the opposite sides of the plane of the semiconductor substrate. Thus, for example, if one side of the semiconductor substrate is the front side of the semiconductor substrate on which light falls, the other side of the semiconductor substrate refers to the back side of the semiconductor substrate. Conversely, if one side of the semiconductor substrate is the back side of the semiconductor substrate, the other side of the semiconductor substrate may refer to the front side of the semiconductor substrate.

[0038] For ease of explanation, the following description will be based on the assumption that one side of the semiconductor substrate is the front side of the semiconductor substrate and the other side of the semiconductor substrate is the back side of the semiconductor substrate.

[0039] Figure 1 is a view schematically showing a process of forming grooves in a solar cell to divide the solar cell into multiple parts according to an exemplary embodiment of the present disclosure. Figure 2 is a flowchart showing a manufacturing method according to an exemplary embodiment of the present disclosure.

[0040] As used herein, the term "solar cell" refers to a finished product, such as solar cells 100 and 1000 to be described later, which includes a plurality of components for generating electricity on a semiconductor substrate, such as a semiconductor substrate, a control passivation layer, first and second conductive regions containing impurities, an intrinsic semiconductor portion, an insulating layer, a back passivation layer, and first and second electrodes. The term "groove" refers to a groove formed by irradiating a solar cell with a laser to divide the solar cell into multiple parts.

[0041] Reference Figure 1 and Figure 2 , a solar cell 100 according to an exemplary embodiment of the present disclosure may include a semiconductor substrate 10 and a semiconductor layer 20 formed on at least one side of the semiconductor substrate 10.

[0042] The semiconductor substrate 10 may be made of at least one of single-crystalline silicon and polycrystalline silicon doped with a first or second conductive dopant. In one example, the semiconductor substrate 10 may be manufactured by doping a single-crystalline silicon wafer with a low concentration of a first or second conductive dopant.

[0043] Here, the first conductive dopant can be a p-type or n-type dopant, and the second conductive dopant can be the other type of dopant. Specifically, if the first conductive dopant is p-type and is one of trivalent atoms such as boron (B), aluminum (Al), gallium (Ga), and indium (In), then the second conductive dopant can be n-type and is one of pentavalent atoms such as phosphorus (P), arsenic (As), bismuth (Bi), and antimony (Sb). Thus, in one example, the first or second conductive dopant can be boron (B), and the other can be phosphorus (P).

[0044] The semiconductor substrate 10 can have a thickness that occupies 90% of the entire thickness of the solar cell, and in a preferred embodiment, the thickness of the semiconductor substrate 10 can be approximately 160 μm. Here, within a process error range of ±10%, the thicknesses are considered to be substantially the same.

[0045] In addition, the semiconductor layer 20 can be formed over the entire side surface of the semiconductor substrate 10 and can be made of a semiconductor material having an absorption coefficient higher than that of the semiconductor substrate 10. In one example, if the semiconductor substrate 10 is single-crystalline silicon, then the semiconductor layer 20 can be polycrystalline silicon having an absorption coefficient higher than that of single-crystalline silicon.

[0046] The semiconductor layer 20 can be used as a functional layer that, when the semiconductor substrate 10 is irradiated with a laser, prevents thermal damage to the semiconductor substrate 10 caused by the high energy of the laser by partially absorbing the laser. The thickness of the semiconductor layer 20 can be set in consideration of the absorption depth so as to be used as an effective absorption layer, which will be described in detail later.

[0047] In addition, the semiconductor layer 20 can have a predetermined thickness so as to be used as one layer constituting the solar cell. In an example, the semiconductor layer 20 can be configured as a layer forming a conductive region, and in this case, the semiconductor layer 20 can have a thickness of 250 to 300 μm. Once the semiconductor layer 20 is configured as one layer constituting the solar cell, when the solar cell is divided, it can be used as an absorption layer, thereby preventing deterioration of the solar cell and contributing to an improvement in productivity because it is not necessary to add new components to the solar cell.

[0048] Meanwhile, although Figure 1 it is shown that the semiconductor layer 20 is directly formed on one surface of the semiconductor substrate 10, the present disclosure is not limited thereto, and another layer can be interposed between the two layers. Here, the term "directly" means that one surface of the semiconductor layer 20 is formed on one surface of the semiconductor substrate 10 without an intermediate layer between the semiconductor layer 20 and the semiconductor substrate 10.

[0049] Figure 1(A) shows a semiconductor substrate 10 irradiated with a laser 30. According to the manufacturing method of the present invention, it is desirable that the laser 30 first irradiates the semiconductor layer 20 and then irradiates the semiconductor substrate 10, rather than directly irradiating the semiconductor substrate 10 according to time. In one example, the semiconductor layer 20 can be arranged to face the laser 30 (S10), and the laser 30 can be guided towards the semiconductor substrate 10 standing vertically from the semiconductor layer 20 (S20).

[0050] Various types of lasers commonly available on the market can be used as the laser 30. In one instance, depending on the wavelength of the laser, the laser 30 can be a 532 nm laser or a 1024 nm laser, and in some lasers, the thickness of the semiconductor layer 20 can be adjusted.

[0051] Figure 1 (B) shows a groove 40 formed by the irradiation of the laser 30. When the semiconductor substrate 10 is irradiated with a laser, laser ablation occurs as the locally irradiated area is heated by the laser, thereby forming the groove 40. However, in an exemplary embodiment of the present disclosure, the laser 30 irradiates the semiconductor substrate 10 after passing through the semiconductor layer 20 having an absorption coefficient higher than that of the semiconductor substrate 10, and part of the laser is thus absorbed by the semiconductor layer 20, thereby reducing the thermal damage to the semiconductor substrate 10. Its effects will be described in detail below with reference to other drawings.

[0052] After the groove 40 is formed on one surface of the solar cell 100, the solar cell 100 can be divided into multiple parts by applying a physical impact to the solar cell 100 (S30).

[0053] Preferably, the depth dt of the groove 40 formed in the solar cell 100 is 30% to 70% of the thickness ds of the solar cell 100. Here, the thickness ds of the solar cell 100 can be substantially equal to the thickness of the semiconductor substrate because the thickness of the layer covering the semiconductor substrate is very small compared to the thickness of the semiconductor substrate. If the depth dt of the groove 40 is less than 30% of the thickness ds, the solar cell may not split along the groove 40 but break when the solar cell is divided into multiple parts along the groove 40. If the depth dt of the groove 40 is greater than 70% of the thickness ds, this may cause serious thermal damage to the solar cell 100 during the formation of the groove 40, which may lead to a sharp drop in the efficiency of the solar cell.

[0054] Figure 3 is a graph showing how the absorption coefficient varies according to the crystallinity of different types of silicon. In Figure 3 , silicon shows the relationship between the light absorption coefficient of single-crystalline silicon and the wavelength, and polycrystalline silicon shows the relationship between the light absorption coefficient of polycrystalline silicon and the wavelength.

[0055] This curve shows that there is no difference in the absorption coefficient between single-crystalline silicon and polycrystalline silicon at wavelengths of about 400 nm or shorter. Thus, it can be seen that when using a laser with a wavelength of 400 nm or shorter, the semiconductor layer 20 cannot function as an absorption layer, making it difficult to reduce thermal damage to the semiconductor substrate 10.

[0056] In addition, this figure clearly shows that at wavelengths of 400 nm or longer, as the wavelength increases, the absorption coefficient of polycrystalline silicon becomes higher than that of single-crystalline silicon. Thus, if a laser with a wavelength of 400 nm or longer is used, polycrystalline silicon absorbs the laser better than single-crystalline silicon, and as a result, thermal damage to the semiconductor substrate 10 can be reduced.

[0057] Meanwhile, Figure 4 is a curve showing the test results of the cutting depth of the groove based on the presence or absence of a semiconductor layer made of polycrystalline silicon. Here, the pulse energy stored on the x-axis represents the total energy of the laser irradiated onto the solar cell.

[0058] From Figure 4 the curve, it can be seen that the cutting depth increases linearly with the increase in the stored pulse energy. Moreover, it can be seen that when the laser is irradiated onto a solar cell with a semiconductor layer, compared with when the laser is irradiated onto a solar cell without a semiconductor layer, with the same stored pulse energy, the groove is formed deeper.

[0059] These test results show that when forming a groove in a solar cell with a semiconductor layer, if the solar cell with a semiconductor layer is used with a semiconductor layer that is the same as the solar cell without a semiconductor layer, the depth of the groove can be the same as the depth of the groove in the solar cell without a semiconductor layer. As a result, this can lead to less thermal damage to the solar cell with a semiconductor layer.

[0060] This can be Figure 5 clearly seen. Figure 5 is a curve showing that the power output of the solar cell decreases with respect to the stored pulse energy.

[0061] As shown in the figure, it can be seen that the power output of the solar cell decreases linearly with the increase in the stored pulse energy. When applied to Figure 3 , these results show that the solar cell with a semiconductor layer has less thermal damage than the solar cell without a semiconductor layer.

[0062] Table 1 below shows the requirements for the laser used in the above tests of Figure 4 and Figure 5 , and the laser is scanned 10 times.

[0063] [Table 1]

[0064]

[0065] Figure 6 It is a graph showing how the absorption depth varies according to the crystallinity of different types of silicon. The absorption depth is defined as "1 / absorption coefficient", which refers to the transmission depth from the incident surface, at which depth about 36% of the energy of the irradiated light can be absorbed. It can be seen from the graph that the absorption coefficient increases linearly with the increase of wavelength, and single-crystalline silicon has a better absorption coefficient than polycrystalline silicon at the same wavelength.

[0066] Meanwhile, Figure 3 it shows that at wavelengths of 400 nm or longer, the absorption coefficient of polycrystalline silicon is higher than that of single-crystalline silicon. In view of this, in an exemplary embodiment of the present disclosure, a laser with a wavelength of 400 nm or longer is preferably used; more preferably, a laser with a wavelength of 532 nm (hereinafter referred to as 532 laser) and a laser with a wavelength of 1024 nm (hereinafter referred to as 1024 laser) can be used.

[0067] However, as Figure 6 shown, if the thickness of the semiconductor layer 20 is 180 nm, then polycrystalline silicon absorbs 36% of the light with a wavelength of 532 nm. Therefore, in a solar cell having the Figure 1 shown structure, if the semiconductor layer 20 has a thickness of 180 nm or greater, the semiconductor layer 20 absorbs about 36% of the laser, and projects the remaining part onto the semiconductor substrate 10, thereby reducing the thermal damage to the semiconductor substrate 10.

[0068] In contrast, when the 532 laser is directly irradiated on single-crystalline silicon, the same effect is obtained only when the thickness of the semiconductor layer 20 is at least 1280 nm.

[0069] That is to say, in an exemplary embodiment of the present invention, by forming the semiconductor layer 20 on the semiconductor substrate 10, the thermal damage caused by the laser can be effectively reduced.

[0070] When using the 1024 laser, if the polycrystalline silicon is 600 nm thick, it absorbs 36% of the light. Therefore, in a solar cell having the Figure 1 shown structure, the semiconductor layer 20 needs to be 600 nm thick or thicker in order to effectively reduce the thermal damage to the semiconductor substrate 10.

[0071] Figure 7 It is a view of the laser for forming a groove in the solar cell.

[0072] Lasers can be classified as continuous lasers or pulsed lasers. Continuous lasers oscillate without interruption on the time axis. When forming grooves using a continuous laser, the solar cell is heated without an idle period (cooling period), and thermal damage accumulates on the solar cell along the time axis, which is undesirable.

[0073] In contrast, pulsed lasers irradiate laser light intermittently in synchronization with the oscillation frequency of the pulses. Therefore, the solar cell can alternate between heating periods and cooling periods, thus effectively reducing thermal damage compared to continuous lasers.

[0074] In a pulsed laser, one emission from the laser is referred to as a light spot 60, and the laser is projected during the scanning time. Here, the scanning time represents the period during which the laser is projected along the scribing line 50.

[0075] When forming grooves, it is better to form grooves by multiple scans than by a single scan in order to reduce thermal damage to the solar cell.

[0076] The number of scans can be adjusted by the pulse energy. The pulse energy is the amount of energy of one emission from the laser. The total stored pulse energy used to form the groove can be obtained by multiplying the pulse energy uj by the total number of irradiations, and the depth of the groove and the maximum power Pmax of the laser are determined by the total stored pulse energy.

[0077] The laser scans the solar cell along the scanning line (or scribing line) 50. A groove line can be formed on the surface of the solar cell by about 10 scans, and the number of scans can be adjusted by parameters such as the scanning speed and the pulse energy.

[0078] Figure 7 It is shown that the scanning line 50 is formed along the center line of the solar cell 100 to divide the solar cell 100 into two parts. Here, the expression "divide the solar cell into two parts" means dividing the solar cell into two pieces such that the widths (based on the vertical length of the drawing) of the two pieces are equal.

[0079] In an exemplary embodiment of the present disclosure, as Figure 8 shown, the solar cell 100 can be divided into n parts. Here, for example, n is an integer, and Figure 8 n in Figure 8, the first scan line 501 may be located at the upper part of the solar cell, and the second scan line 502 may be located at the lower part of the solar cell, such that the solar cell 100 is divided into three parts. Here, after the solar cell is divided, a first width d1 between the edge of the solar cell and the first scan line 501, a second width d2 between the first scan line 501 and the second scan line 502, and a third width d3 between the second scan line 502 and the other edge of the solar cell may be equal.

[0080] As described above, a laser is irradiated along the first scan line 501 and the second scan line 502. As a result, two groove lines are formed on the surface of the solar cell, and by applying a physical impact to the solar cell, the solar cell can be divided into first to third solar cell chips 100n. Hereinafter, a solar cell to which the above manufacturing method of the present invention can be applied will be described. Figure 9 is a view showing the structure of a solar cell according to an exemplary embodiment to which the present invention is applicable. Figure 10 is a view showing a cross section of the solar cell.

[0081] Referring to these drawings, examples of the solar cell may include a semiconductor substrate 110, control passivation layers 132 and 160, a first conductive region 170, a second conductive region 120, an intrinsic semiconductor portion 190, an insulating layer 130, a back passivation layer 180, a plurality of first electrodes 140, and a plurality of second electrodes 150.

[0082] The semiconductor substrate 110 may be made of at least one of monocrystalline silicon and polycrystalline silicon doped with a first or second conductive dopant. In one example, the semiconductor substrate 110 may be manufactured by doping a monocrystalline silicon wafer with a low concentration of a first or second conductive dopant.

[0083] Here, the first conductive dopant may be a p-type or n-type dopant, and the second conductive dopant may be the other dopant.

[0084] Specifically, if the first conductive dopant is p-type, which is one of trivalent atoms such as boron (B), aluminum (Al), gallium (Ga), and indium (In), then the second conductive dopant may be n-type, which is one of pentavalent atoms such as phosphorus (P), arsenic (As), bismuth (Bi), and antimony (Sb).

[0085] Therefore, in one example, the first or second conductive dopant may be boron (B), and the other may be phosphorus (P).

[0086] The control passivation layers 132 and 160 may be provided to be in direct contact with the entire back surface of the semiconductor substrate 110, and may include a dielectric material.

[0087] The control passivation layers 132 and 160 can allow carriers generated in the semiconductor substrate 110 to pass through and can perform a passivation function on the back surface of the semiconductor substrate 110. To this end, the control passivation layers 132 and 160 can be formed to have a thickness of 0.5 nm to 2 nm.

[0088] The control passivation layers 132 and 160 can be made of a dielectric material such as SiCx or SiOx.

[0089] The first conductive region 170 can be formed on the front or back surface of the semiconductor substrate 110 and can include the same conductive region as the semiconductor substrate 110.

[0090] In one example, the first conductive region 170 can refer to a region doped with the same dopant as the conductive dopant of the semiconductor substrate 110 at a concentration lower than the dopant concentration of the semiconductor substrate 110.

[0091] In one example, the first conductive region 170 can include a front electric field portion 171 and a back electric field portion 172.

[0092] The front electric field portion 171 can be formed on the entire front surface of the semiconductor substrate 110 and can be doped with the same conductive dopant as the semiconductor substrate 110 at a high concentration.

[0093] In one instance, the front electric field portion 171 can be formed by thermally diffusing a conductive dopant into the front surface of the semiconductor substrate 110. Thus, the front electric field portion 171 can be made of the same silicon material as the semiconductor substrate 110.

[0094] In one example, if the semiconductor substrate 110 is made of single-crystalline silicon, the front electric field portion 171 can also be made of single-crystalline silicon.

[0095] The back electric field portion 172 can longitudinally extend parallel to the second conductive region 120 on the back surface of the semiconductor substrate 110 and can be made of highly doped polysilicon doped with the same conductive dopant as the semiconductor substrate 110. In this way, the back electric field portion 172 can perform its function.

[0096] In one example, the back electric field portion 172 can be formed to be in direct contact with the back surfaces of the control passivation layers 132 and 160 and can be spaced apart from the second conductive region 120.

[0097] The second conductive region 120 can extend in the longitudinal direction parallel to the back electric field portion 172 on the back surface of the semiconductor substrate 110, can be doped with a conductive dopant opposite to that of the semiconductor substrate 110, and can form a p-n junction with the semiconductor substrate 110, with the control passivation layer 132 therebetween. In this way, the second conductive region 120 can be used as an emitter portion.

[0098] The intrinsic semiconductor portion 190 may be formed in the space between the back electric field portion 172 of the first conductive region 170 and the second conductive region 120 in the region above the back surface of the control passivation layer 132. Different from the first conductive region 170 and the second conductive region 120, the intrinsic semiconductor portion 190 may be made of an intrinsic polysilicon layer that is not doped with the first conductive dopant or the second conductive dopant.

[0099] In this way, the back electric field portion 172 of the first conductive region 170, the second conductive region 120, and the intrinsic semiconductor portion 190 located above the control passivation layer 132 may be made of a silicon material having a different crystallinity from the silicon material of the semiconductor substrate 110, and as described above, they may be formed as a semiconductor layer that serves as an absorption layer in the laser process. In this case, one of the existing components may act as the absorption layer without configuring an additional layer in the solar cell. Therefore, thermal damage to the solar cell can be easily reduced without increasing the manufacturing cost and the number of manufacturing processes.

[0100] In an example, if the semiconductor substrate 110 is made of, for example, single-crystalline silicon, the semiconductor layer (i.e., the back electric field portion 172 of the first conductive region 170, the second conductive region 120, and the intrinsic semiconductor portion 190) may be made of a material having an absorption coefficient higher than that of the semiconductor substrate 110 (e.g., polysilicon or a hybrid material of polysilicon and amorphous silicon). If the back electric field portion 172 of the first conductive region 170 and the second conductive region 120 are made of polysilicon, then as described above, their thicknesses may be determined according to the wavelength of the laser used. If the laser has a wavelength of 532 nm, the semiconductor layer may have a thickness of preferably 180 nm or more. If the laser has a wavelength of 1024 nm, the semiconductor layer may have a thickness of preferably 600 nm or more.

[0101] The insulating layer 130 may be located on at least one side or the other side of the semiconductor substrate 110. In one example, as Figure 1 shown, the insulating layer 130 may be located on one side of the semiconductor substrate 110, i.e., the front surface. However, this is not necessarily limited to Figure 1 , and in some cases, if the solar cell is a bifacial solar cell in which light falls on not only one side but also the other side of the semiconductor substrate 110, the insulating layer 130 may be located on the other side of the semiconductor substrate 110, i.e., the back surface.

[0102] Furthermore, in the case where a conductive region such as the front electric field portion 171 is formed on the semiconductor substrate 110, as Figure 1 shown, the insulating layer 130 may be located on the front electric field portion 171. However, in the case where the front electric field portion 171 is not formed, as compared with Figure 1In contrast, the insulating layer 130 may be configured to be in direct contact with the front surface of the semiconductor substrate 110.

[0103] Here, one side of the semiconductor substrate 110 may be the front surface of a solar cell on which light directly falls from the semiconductor substrate 110, and the other side of the semiconductor substrate 110 may be the back surface of the solar cell that is disposed opposite to the side on which light is reflected and falls.

[0104] The insulating layer 130 may minimize the reflectance of light falling on the semiconductor substrate 110 from the outside, block UV rays from the outside, prevent etching of the insulating layer 130 caused by acetic acid generated due to moisture penetration into a sealing material (e.g., EVA, one of the components of a solar cell module), prevent loss of carriers generated in the substrate due to UV rays, and increase the open-circuit voltage V OC and short-circuit current of the solar cell module, thereby increasing the overall efficiency of the solar cell module.

[0105] A plurality of first electrodes 140 may be connected to the second conductive region 120 and extend in the longitudinal direction. The first electrodes 140 may collect carriers that have migrated to the second conductive region 120.

[0106] A plurality of second electrodes 150 may be connected to the back electric field portion 172 of the first conductive region 170 and extend parallel to the first electrodes 140 in the longitudinal direction. The second electrodes 150 may collect carriers that have migrated to the first conductive region 170.

[0107] Except for the regions where the first and second electrodes 140 and 150 are formed, a rear passivation layer 180 may be formed on the back surface of the back electric field portion 172 of the first conductive region 170, the back surface of the second conductive region 120, and the back surface of the intrinsic semiconductor portion 190.

[0108] The back passivation layer 180 removes defects caused by dangling bonds formed on the back surfaces of the polysilicon layers formed in the second conductive region 120, the first conductive region 170, and the intrinsic semiconductor portion 190, thereby preventing carriers generated in the semiconductor substrate 110 from being annihilated by recombination through the dangling bonds.

[0109] The solar cell applied to the solar cell module according to the present disclosure is not necessarily limited to Figure 1 , and except that the first electrode 140 and the second electrode 150 in the solar cell are formed on the back surface of the semiconductor substrate 110, the components may be changed.

[0110] For example, the front electric field portion 171 of the first conductive region 170 may be omitted. In this case, the insulating layer 130 may be configured to be in direct contact with the front surface of the semiconductor substrate 110.

[0111] Meanwhile, it is desirable that in a solar cell constructed as such, the laser irradiates the opposite side (e.g., the back surface) of the light-receiving surface. When the laser irradiates the semiconductor substrate 110, as the surface of the semiconductor substrate 110 melted by the laser cools, a groove 40 is formed. At this time, due to the high heat of the laser, the area around the groove 40 also receives heat energy, thereby breaking the stable bond between the crystals, which leads to an increase in the number of recombination points. For this reason, it is desirable that when irradiating the solar cell with a laser, the laser does not irradiate the light-receiving surface of the semiconductor surface 110, but irradiates the opposite side.

[0112] The back surface of the solar cell is configured to include a first conductive region 170 and a second conductive region 120, and the first conductive region 170 forms a p-n junction with the semiconductor substrate 110. Therefore, it is desirable that the laser does not irradiate the region where the p-n junction is formed. As is well known, a solar cell generates electricity through the p-n junction between the semiconductor substrate and the emitter. In addition, the p-n junction region is damaged by the laser irradiation of the region forming the emitter, which inevitably leads to a reduction in the power generation efficiency of the solar cell.

[0113] In view of this, in the present disclosure, it is preferred that the laser does not irradiate the region forming the emitter. In an example, if the first conductive region 170 forms the emitter and the second conductive region 120 forms the back electric field portion, the laser can be irradiated onto the back surface, i.e., the opposite side of the light-receiving surface, or onto the region forming the second conductive region 120 to avoid the region forming the emitter. In this case, the laser can be irradiated along the length direction of the electrode 140. When the laser irradiates the second conductive region 120, the length direction of the electrode 140 corresponds to the scanning direction of the laser. Therefore, the laser is configured not to cross the metal electrode, which provides the advantage of forming a groove in the solar cell without electrode interference.

[0114] Figure 11 Another embodiment of a solar cell to which the manufacturing method of the present disclosure can be applied is shown. Although the foregoing solar cell is a back-contact solar cell in which light enters through the back surface of the solar cell, the solar cell according to this exemplary embodiment can be configured as a bifacial light-receiving solar cell capable of receiving light entering through both the front surface and the back surface.

[0115] The solar cell 1000 may include a semiconductor substrate 1200, conductive regions 2000 and 3000 formed in or on the semiconductor substrate 1200, and electrodes 4200 and 4400 connected to the conductive regions 2000 and 3000.

[0116] In one example, the conductive regions 2000 and 3000 may include a first conductive region 2000 and a second conductive region 3000 having different conductive types. The electrodes 4200 and 4400 may include a first electrode 4200 connected to the first conductive region 2000 and a second electrode 4400 connected to the second conductive region 3000.

[0117] The semiconductor substrate 1200 may include a first or second conductive dopant having a relatively low doping concentration, which may be a crystalline substrate, such as a single crystal or polycrystalline silicon substrate. In this case, at least one of the front surface and the back surface of the semiconductor substrate 1200 may have a texture structure or an antireflection structure having pyramidal ridges to minimize reflection. The drawings show a double-sided light-receiving solar cell in which ridges are formed on both the front and back surfaces.

[0118] The conductive regions 2000 and 3000 may include a first conductive region 2000 of a first conductive type located on one side (e.g., the front or back surface) of the semiconductor substrate 1200 and a second conductive region 3000 of a second conductive type located on the other side (e.g., the other side) of the semiconductor substrate 1200. The conductive regions 2000 and 3000 may be of a different conductive type from the semiconductor substrate 1200 or may have a higher doping concentration than the semiconductor substrate 1200.

[0119] In a preferred embodiment, the first conductive region 2000 serving as an emitter may be configured as a doped region corresponding to a part of the semiconductor substrate 1200, and thus improve the characteristics of the junction with the semiconductor substrate 1200.

[0120] In addition, the second conductive region 3000, which is desired to be a back electric field portion, is configured as a semiconductor layer formed on the semiconductor substrate 1200 separately from the semiconductor substrate 1200. As described above, the semiconductor layer 3000 may be made of a material having an absorption coefficient higher than that of the semiconductor substrate 1200 so as to serve as an absorber of the projected laser. For example, if the semiconductor substrate 1200 is made of single crystal silicon, the second conductive region 3000 may be made of polycrystalline silicon.

[0121] Regarding the thickness of the second conductive region 3000, if the projected laser is a 532 laser, the semiconductor layer 3000 may have a thickness of 180 nm or more, and if the projected laser is a 1024 laser, the semiconductor layer 3000 may have a thickness of 600 nm or more.

[0122] The first passivation layer 22 and / or the antireflection layer 24 as the first insulating film may be located on (e.g., in contact with) the front surface of the semiconductor substrate 12 (more precisely, the first conductive region 20 formed on the front surface of the semiconductor substrate 12). The second passivation layer 32 as the second insulating film may be located on (e.g., in contact with) the back surface of the semiconductor substrate 12 (more precisely, the second conductive region 30 formed on the back surface of the semiconductor substrate 12). The antireflection layer 24 and the second passivation layer 32 may be made of various insulating materials. In one example, the first passivation layer 22, the antireflection layer 24, or the second passivation layer 32 may have a multilayer film structure composed of a single film or two or more films selected from a silicon nitride film, a hydrogenated silicon nitride film, a silicon oxide film, a silicon oxynitride film, an aluminum oxide film, a silicon carbide film, MgF2, Zn2O, TiO2, and CeO2. However, the present disclosure is not limited to the above.

[0123] In addition, a control passivation layer 3100 may be formed between the semiconductor substrate 1200 and the semiconductor layer 3000 to provide a tunneling effect. The control passivation layer 3100 may allow carriers generated in the semiconductor substrate 1200 to pass through and may perform a passivation function on the back surface of the semiconductor substrate 1200. To this end, the control passivation layer 3100 may have a thickness of 0.5 nm to 2 nm.

[0124] The control passivation layer 300 may be made of a dielectric material such as SiCx or SiOx.

[0125] The first electrode 42 is electrically connected to the first conductive region 20 through an opening formed through the first insulating film, and the second electrode 44 is electrically connected to the second conductive region 30 through an opening formed through the second insulating film. The first electrode 42 and the second electrode 44 may be made of various conductive materials (e.g., metals) and may have various shapes.

[0126] Although the exemplary embodiments of the present disclosure have been described in detail, the scope of the present disclosure is not limited thereto, and various modifications and improvements made by those skilled in the art by using the basic concepts of the present disclosure defined in the claims also fall within the scope of the present disclosure.

Claims

1. A method for manufacturing a solar cell, the method comprising the following steps: In the solar cell, a semiconductor substrate and a semiconductor layer having an absorption coefficient higher than that of the semiconductor substrate are arranged such that the semiconductor layer formed on at least one side of the semiconductor substrate faces the laser; Forming a groove in the solar cell by directing the laser onto the semiconductor layer; And Dividing the solar cell into multiple parts along the groove; The groove is formed through the semiconductor layer and even into a part of the semiconductor substrate, and the depth of the groove is 30% to 70% of the thickness of the semiconductor substrate; The semiconductor layer is polysilicon, and the semiconductor substrate is monocrystalline silicon; When the laser has a wavelength of 1024 nm, the semiconductor layer is 600 nm or thicker; Alternatively, when the laser has a wavelength of 532 nm, the semiconductor layer is 180 nm or thicker; The semiconductor layer is formed on the back surface of the semiconductor substrate, and the semiconductor layer includes a first conductive region and a second conductive region. The first conductive region contains a first conductive dopant having a polarity opposite to that of the semiconductor substrate, and the second conductive region contains a second conductive dopant having the same polarity as the semiconductor substrate; The groove is formed in the second conductive region.

2. The method according to claim 1, wherein The groove is formed along the center line of the solar cell so as to divide the solar cell into two parts.

3. The method according to claim 1, wherein Forming multiple grooves in the solar cell to divide the solar cell into three or more parts.

4. The method according to claim 1, wherein, Forming a control passivation layer between the semiconductor layer and the semiconductor substrate.

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