Solar cell and laser etching method

Abstract

The present disclosure relates to a solar cell and a laser etching method. The solar cell includes a silicon substrate, a P-type region, an N-type region and an isolation groove. The silicon substrate has a front side and a back side arranged opposite to each other. The P-type region, the N-type region and the isolation groove are all arranged on the back side of the silicon substrate. The width of the isolation groove in a first direction gradually decreases in a direction away from the silicon substrate. The isolation groove of the solar cell is arranged in an inverted trapezoidal structure, which can improve the photoelectric conversion efficiency of the solar cell and improve the performance of the entire solar cell.

Description

Technical Field

[0001] The present disclosure relates to the technical field of solar cell manufacturing, and in particular to a solar cell and a laser etching method. Background Art

[0002] The isolation grooves of the solar cells in the related art affect the propagation of light, and the light is easily transmitted through the isolation grooves, causing unnecessary light loss, affecting the photoelectric conversion efficiency of the solar cell, and further affecting the performance of the entire solar cell.

[0003] At the same time, during the isolation trench manufacturing process, after the laser is used to open the groove on the doping layer, a small amount of radiation energy remains on the groove wall. During the etching process, side erosion areas are easily generated on the groove wall. As a result, during the subsequent phosphorus diffusion operation, phosphorus diffusion will also form in the side erosion areas, affecting the performance of the manufactured solar cells and even causing short circuit problems. Summary of the invention

[0004] The purpose of the present disclosure is to provide a solar cell and a laser etching method to solve the above-mentioned problems in the related art.

[0005] In order to achieve the above object, one aspect of the present disclosure provides a solar cell, the solar cell comprising a silicon substrate, a P-type region, an N-type region and an isolation groove, the silicon substrate having a front side and a back side arranged opposite to each other, the P-type region, the N-type region and the isolation groove are all arranged on the back side of the silicon substrate; Wherein, the P-type region includes a first dielectric layer and a P-type doped layer, the first dielectric layer covers the back side of the silicon substrate, and the P-type doped layer covers the first dielectric layer; The N-type region comprises a second dielectric layer and an N-type doped layer, wherein the second dielectric layer covers the back side of the silicon substrate, and the N-type doped layer covers the second dielectric layer; Wherein, the width dimension of the isolation groove in the first direction gradually decreases along the direction away from the silicon substrate; Wherein, the first direction is set to be a direction parallel to the silicon substrate.

[0006] Optionally, the first dielectric layer and the second dielectric layer are both configured as silicon oxide layers; or, The first dielectric layer and the second dielectric layer are both configured as intrinsic amorphous silicon layers; or, One of the first dielectric layer and the second dielectric layer is configured as a silicon oxide layer, and the other is configured as an intrinsic amorphous silicon layer.

[0007] Optionally, the P-type doped layer and the N-type doped layer are both configured as doped polysilicon layers; or, The P-type doped layer and the N-type doped layer are both configured as doped amorphous silicon layers; or, One of the P-type doping layer and the N-type doping layer is configured as a doped polysilicon layer, and the other is configured as a doped amorphous silicon layer.

[0008] A second aspect of the present disclosure also provides a laser etching method for preparing the above-mentioned solar cell, comprising the following steps: Performing laser processing twice on the surface of the solar cell, the areas processed by the lasers twice partially overlap, and the areas of the areas processed by the lasers twice decrease in sequence to form a grooved area; The grooved region is etched to form the isolation groove.

[0009] Optionally, the surface of the solar cell is laser processed twice, the areas processed by the lasers twice partially overlap, and the areas of the areas processed by the lasers twice decrease in sequence, including: Performing a first laser irradiation process on the surface of the solar cell to form a first laser processing area on the surface of the solar cell, specifically, forming a first laser spot with a first laser power, irradiating the first laser spot on the surface of the solar cell, and moving the first laser spot once along a first path to peel off a portion of the surface of the solar cell; performing a second laser irradiation process on the first laser processing area, wherein the area of ​​the second laser irradiation process is smaller than the area of ​​the first laser processing area, Specifically, the first laser processing area is irradiated with laser at least once to form a groove in the first laser processing area, and the groove is formed until the depth of the groove reaches a preset depth, thereby completing the grooving.

[0010] Optionally, irradiating the first laser processing area with laser light at least once to form a groove in the first laser processing area until the depth of the groove reaches a preset depth to complete the grooving includes: forming a second laser spot with a second laser power, and irradiating the second laser spot on the first laser processing area; The second laser spot moves once along the second path, peeling off part of the surface of the first laser processing area and forming a groove. If the depth of the groove is less than the preset depth, the operation is repeated until the depth of the groove reaches the preset depth to complete the grooving; otherwise, the grooving is completed directly.

[0011] Optionally, the first laser power and the second laser power are both set to 1%-99% of a preset power, and the sum of the first laser power and the second laser power is equal to the preset power.

[0012] Optionally, an irradiation area of ​​the first laser spot is larger than an irradiation area of ​​the second laser spot, and an overlap rate between the irradiation area of ​​the first laser spot and the irradiation area of ​​the second laser spot is 10%-99%.

[0013] Optionally, the width of the first laser spot and the width of the second laser spot are both set to 20 μm-150 μm, and the preset depth is 50 nm-200 nm.

[0014] Optionally, etching the grooved area includes: The exposed doped layer is first etched with an alkaline solution, and after the exposed doped layer is completely etched, a portion of the dielectric layer is exposed; Etching the exposed dielectric layer with an alkaline solution, and after the exposed dielectric layer is completely etched, a portion of the silicon substrate is exposed; Etching the exposed portion of the silicon substrate with an alkaline solution; The etching rates of the doped layer and the dielectric layer are both lower than the etching rate of the silicon substrate, the etching rates of the doped layer and the dielectric layer are both 1 μm / 100 s, and the etching rate of the silicon substrate is 2 μm / 100 s.

[0015] The above technical solution adopts the structure of the inverted trapezoidal isolation groove. On the one hand, when the light reaches the side of the inverted trapezoidal isolation groove, due to its tilt angle and special geometric shape, the light will be refracted and scattered multiple times, rather than simply transmitted to the outside of the solar cell. These refracted and scattered light have more opportunities to be absorbed by the material inside the solar cell. On the other hand, due to the inverted trapezoidal isolation groove morphology design, the opening of the isolation groove is smaller, the light capture effect is better, and the photons transmitted from the front of the solar cell are reduced, thereby reducing the reflection and transmission loss of light, so that more photons can participate in the photoelectric conversion process, thereby improving the photoelectric conversion efficiency of the solar cell and improving the performance of the entire solar cell.

[0016] Other features and advantages of the present disclosure will be described in detail in the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The accompanying drawings are used to provide a further understanding of the present disclosure and constitute a part of the specification. Together with the following specific embodiments, they are used to explain the present disclosure but do not constitute a limitation of the present disclosure. In the accompanying drawings: Figure 1 is a schematic flow chart of a laser etching method in one embodiment of the present disclosure; Figure 2 is a schematic diagram of the process of the first laser processing in one embodiment of the present disclosure; Figure 3is a schematic diagram of the process of the second laser processing in one embodiment of the present disclosure; Figure 4 is a structural schematic diagram of an initial state of a laser etching method in one embodiment of the present disclosure; Figure 5 is a schematic structural diagram of the first laser processing of the laser etching method in one embodiment of the present disclosure; Figure 6 is a structural schematic diagram of the second laser processing of the laser etching method in one embodiment of the present disclosure; Figure 7 is a schematic structural diagram of an etching process of a laser etching method in one embodiment of the present disclosure; Figure 8 Schematic diagram of the structure of a solar cell in one embodiment of the present disclosure.

[0018] Description of Reference Numerals 1. Silicon substrate, 2. Dielectric layer, 3. Doping layer, 4. Mask layer.

[0019] 100. P-type region, 101. N-type region, 102. first dielectric layer, 103. second dielectric layer, 104. P-type doped layer, 105. N-type doped layer, 106. isolation trench, 107. aluminum oxide layer, 108. silicon nitride layer. DETAILED DESCRIPTION

[0020] The specific implementation of the present disclosure is described in detail below in conjunction with the accompanying drawings. It should be understood that the specific implementation described herein is only used to illustrate and explain the present disclosure, and is not used to limit the present disclosure.

[0021] In the present disclosure, unless otherwise stated, directional words such as "upper, lower, left, right" are usually defined by the direction of the drawing, and "inner" and "outer" refer to the inside and outside of the relevant parts. In addition, the terms "first", "second", etc. are only used to distinguish descriptions and cannot be understood as indicating or implying relative importance.

[0022] In the description of the present disclosure, it is also necessary to explain that, unless otherwise clearly specified and limited, the terms "disposed" and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection, it can be a direct connection, it can be indirectly connected through an intermediate medium, and it can be the internal communication of two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present disclosure can be understood according to specific circumstances.

[0023] TBC solar cells are cells formed by combining IBC cells and TOPCon. They are based on N-type silicon wafers and use SiO XA doping layer is used as a passivation film, and the positive and negative electrodes of the battery are printed on the back area of ​​the battery cell. The Gap area (isolation groove) on the back of the battery and the front of the battery are both velvet structures, in which the Gap area is formed by laser etching.

[0024] The isolation grooves of the solar cells in the related art affect the propagation of light, and the light is easily transmitted through the isolation grooves, causing unnecessary light loss, affecting the photoelectric conversion efficiency of the solar cell, and further affecting the performance of the entire solar cell.

[0025] For this reason, Figure 8 As shown, a first aspect of the present disclosure provides a solar cell.

[0026] The solar cell includes a silicon substrate 1 , a P-type region 100 , an N-type region 101 and an isolation groove 106 . The silicon substrate 1 has a front side and a back side that are oppositely arranged. The P-type region 100 , the N-type region 101 and the isolation groove 106 are all arranged on the back side of the silicon substrate 1 .

[0027] The isolation trench 106 is between the P-type region 100 and the N-type region 101 , and the P-type region 100 and the N-type region 101 are separated by the isolation trench 106 .

[0028] The P-type region 100 includes a first dielectric layer 102 and a P-type doping layer 104, wherein the first dielectric layer 102 covers the back side of the silicon substrate 1, and the P-type doping layer 104 covers the first dielectric layer 102. The N-type region 101 includes a second dielectric layer 103 and an N-type doping layer 105, wherein the second dielectric layer 103 covers the back side of the silicon substrate 1, and the N-type doping layer 105 covers the second dielectric layer 103.

[0029] Thus, the first dielectric layer 102 and the P-type doped layer 104 are sequentially stacked on the back side of the silicon substrate 1 , and the second dielectric layer 103 and the N-type doped layer 105 are sequentially stacked on the back side of the silicon substrate 1 .

[0030] The width of the isolation groove 106 in the first direction gradually decreases in the direction away from the silicon substrate 1. The first direction is set to be a direction parallel to the silicon substrate 1. The cross-sectional shape of the isolation groove 106 can be an inverted trapezoid, that is, the cross-sectional width of the isolation groove 106 becomes smaller and smaller in the direction away from the silicon substrate 1.

[0031] Among them, in the design of solar cells, the structure and performance of the isolation groove 106 play a vital role in the photoelectric conversion efficiency of the solar cell. In this embodiment, through a specific structural setting, that is, using an inverted trapezoidal isolation groove 106, it is possible to affect the propagation and utilization of light and the behavior of carriers in many aspects, thereby significantly affecting the energy conversion efficiency of the solar cell.

[0032] Specifically, from the perspective of light propagation, when light hits a solar cell, part of the light will be transmitted from the front to the back, while another part of the light may enter the interior of the solar cell from the back. In a traditional planar structure or an inappropriate isolation groove 106 design, when light propagates inside the solar cell, especially when it reaches the isolation groove 106 area, due to the existence of the interface, a relatively strong reflection phenomenon often occurs. This reflection will cause the light that could have been absorbed and utilized by the solar cell to return to the outside of the solar cell, thereby causing light loss, which directly reduces the light energy that the solar cell can capture and utilize.

[0033] In the above technical solution, the situation is different when the structure of the inverted trapezoidal isolation groove 106 is adopted. On the one hand, when the light reaches the side of the inverted trapezoidal isolation groove 106, due to its tilt angle and special geometric shape, the light will be refracted and scattered multiple times, rather than simply transmitted to the outside of the solar cell. These refracted and scattered light rays have more opportunities to be absorbed by the materials inside the solar cell. On the other hand, due to the morphological design of the inverted trapezoidal isolation groove 106, the opening of the isolation groove 106 is smaller, and the light capture effect is better, reducing the photons transmitted from the front of the solar cell, thereby reducing the reflection and transmission losses of light, so that more photons can participate in the photoelectric conversion process, thereby improving the photoelectric conversion efficiency of the solar cell and improving the performance of the entire solar cell.

[0034] On the other hand, due to its own physical and chemical properties, the area of ​​the isolation groove 106 usually has a poor passivation effect, resulting in a more serious carrier recombination on the corresponding surface of the silicon substrate 1. In the area where the isolation groove 106 is not set, the surface will be passivated. For example, for the Topcon structure (passivation structure) battery, since the area of ​​the isolation groove 106 does not have the chemical passivation of the tunneling layer and the field passivation of the doped poly (polycrystalline silicon) and the selective transmission of carriers, the surface defects and impurities are not captured and recombinated. The life and activity of the carriers are maintained, so that they can participate more effectively in the current transmission process, thereby improving the key performance parameters of the battery such as the open circuit voltage, short circuit current and fill factor. However, in the area of ​​the isolation groove 106, due to the poor passivation effect, the carriers in the area of ​​the isolation groove 106 are easily affected by factors such as surface defects and impurities, resulting in a serious recombination phenomenon. When the carrier recombination increases, the minority carrier lifetime will be significantly reduced. The reduction in the minority carrier lifetime means that the minority carriers have been recombined before participating in the conduction process and cannot effectively contribute to the generation and transmission of current. At the same time, the surface recombination rate of poorly passivated cells is accelerated, which will lead to a decrease in the open circuit voltage of the solar cell. The open circuit voltage is an important indicator for measuring the internal electric field strength and carrier separation ability of solar cells. Its reduction directly reflects the loss of carriers inside the solar cell. In addition, the short-circuit current will also decrease because the number of carriers involved in conduction decreases and the current transmission capacity decreases. The fill factor, as a parameter to measure the ratio of the battery output power to the ideal power, will also decrease due to the decrease in open circuit voltage and short circuit current, ultimately leading to a decrease in the photoelectric conversion efficiency of the solar cell. Therefore, it is necessary to minimize the width of the isolation groove.

[0035] In the above technical solution, the design of the inverted trapezoidal isolation trench 106 can further reduce the width of the isolation trench 106, thereby reducing the negative impact of the isolation trench 106 on key performance parameters of the solar cell, such as open circuit voltage, short circuit current and fill factor.

[0036] Optionally, an aluminum oxide layer 107 may be further covered on the P-type doping layer 104 and the N-type doping layer 105 , and the aluminum oxide layer 107 is covered with a silicon nitride layer 108 .

[0037] Optionally, in an embodiment of the present disclosure, the first dielectric layer 102 and the second dielectric layer 103 are both configured as silicon oxide layers. In other words, the first dielectric layer 102 and the second dielectric layer 103 are the same.

[0038] Optionally, the P-type doping layer 104 and the N-type doping layer 105 are both configured as doped polysilicon layers. In other words, the P-type region 100 and the N-type region 101 both form a TOPCON structure (passivation structure).

[0039] Optionally, in another embodiment of the present disclosure, the first dielectric layer 102 and the second dielectric layer 103 are both configured as intrinsic amorphous silicon layers. In other words, the first dielectric layer 102 and the second dielectric layer 103 are the same.

[0040] Optionally, the P-type doping layer 104 and the N-type doping layer 105 are both configured as doped amorphous silicon layers. In other words, the P-type region 100 and the N-type region 101 both form a HJT structure (heterojunction structure).

[0041] Optionally, in another embodiment of the present disclosure, one of the first dielectric layer 102 and the second dielectric layer 103 is configured as a silicon oxide layer, and the other is configured as an intrinsic amorphous silicon layer. In other words, the first dielectric layer 102 and the second dielectric layer 103 are different.

[0042] Optionally, one of the P-type doped layer 104 and the N-type doped layer 105 is configured as a doped polysilicon layer, and the other is configured as a doped amorphous silicon layer. That is, one of the P-type region 100 and the N-type region 101 may form a TOPCON structure, and the other may form a HJT structure.

[0043] Optionally, in an embodiment of the present disclosure, the first dielectric layer 102 or the second dielectric layer 103 is configured as a silicon oxide layer, and the thicknesses of the first dielectric layer 102 and the second dielectric layer 103 may be configured to be different.

[0044] It should be noted that when the thickness of the first dielectric layer 102 and the second dielectric layer 103 are set differently, the carrier transmission mechanism is different. When the thickness of the first dielectric layer 102 and the second dielectric layer 103 is less than 2nm, the first dielectric layer 102 and the second dielectric layer 103 are tunneling layers, and the carriers are mainly transported by tunneling. When the thickness of the first dielectric layer 102 and the second dielectric layer 103 is less than or greater than 2nm, the carriers are transported through the holes on the first dielectric layer 102 and the second dielectric layer 103.

[0045] In the manufacturing process of solar cells, after laser grooves are used to open grooves on the doped layer, a small amount of radiation energy remains on the groove wall. During the wet etching process, the groove wall is prone to side etching, resulting in side etching areas on the groove wall. Therefore, during the subsequent phosphorus diffusion operation, phosphorus diffusion will also form in the side etching area, affecting the performance of the manufactured solar cell and even causing short circuit problems.

[0046] For this reason, Figure 1-Figure 7 As shown, one aspect of the present disclosure provides a laser etching method, comprising the following steps: S101, performing laser processing twice on the surface of the solar cell, wherein the areas processed by the two laser processes partially overlap, and the areas of the areas processed by the two laser processes decrease in sequence, thereby forming a grooved area.

[0047] S102 , etching the grooved area to form an isolation groove 106 .

[0048] The two laser processed areas partially overlap means that the two laser processed areas are the same area, which is processed twice, and the area of ​​the area processed by the first laser is large, and the area of ​​the area processed by the second laser is small. The isolation groove 106 is opened by laser etching.

[0049] In the above technical solution, by overlapping the areas processed by the two laser processes and reducing the area of ​​the processed area, the side wall of the notch of the grooved area formed after the two laser processes can form a step-like structure, that is, a sunken platform structure, through which the grooved area and the ungrooved area can be separated, producing a buffering effect, so that a small amount of radiation energy generated by the laser processing remains at the position of the sunken platform and does not affect the ungrooved area. In addition, the operation of the two laser processes can reduce the power of a single laser process, so that the residual radiation energy can also be significantly weakened. Therefore, during the etching process, the side erosion phenomenon of the groove wall can be greatly improved, the side erosion area can be avoided, the performance of the manufactured solar cell can be guaranteed, and the risk of short circuit can be reduced.

[0050] Optionally, in one embodiment of the present disclosure, the surface of the solar cell is laser processed twice, the areas processed by the two lasers partially overlap, and the areas of the areas processed by the two lasers decrease in sequence, including: The surface of the solar cell is subjected to a first laser irradiation process, and a first laser processing area is formed on the surface of the solar cell.

[0051] The first laser irradiation process can partially remove the position where the groove is needed on the surface of the solar cell, so as to form a first laser processing area. It is understandable that the first laser processing area can be a shallow groove.

[0052] A second laser irradiation process is performed on the first laser processing area, and the area of ​​the second laser irradiation process is smaller than the area of ​​the first laser processing area.

[0053] The second laser irradiation process is a second laser process based on the first laser processing area, that is, based on the shallow groove formed by the first laser irradiation process, further grooves are opened to deepen the depth of the grooves.

[0054] The area of ​​the second laser irradiation processing area is smaller than the area of ​​the first laser processing area, which means that on the basis of the first laser processing area, the second laser irradiation processing is laser processed on the surface of part of the first laser processing area. As a result, the first laser processing area is close to the area that does not need laser processing, and can be processed without the second laser irradiation, so that the area does not receive the radiation energy of the second laser irradiation, and at the same time, a spacing effect can be generated to form a transition effect, which can avoid the side erosion of the groove.

[0055] Optionally, in one embodiment of the present disclosure, performing a first laser irradiation process on the surface of the solar cell includes: S201 , forming a first laser spot with a first laser power, and irradiating the first laser spot onto a surface of a solar cell.

[0056] S202 , the first laser spot moves once along the first path to peel off a portion of the surface of the solar cell.

[0057] Among them, after the first laser spot is irradiated on the surface of the solar cell, as the first laser spot moves, the surface of the solar cell at different positions can be peeled off and removed to form a first laser processing area with a shallow groove structure. In some examples, the first path can move from left to right, and one movement can be one movement from left to right. The position and shape of the grooves on the surface of the solar cell can be controlled according to the drawings, and the corresponding openings for the first laser spot to pass through are set on the drawings. Of course, the first path can also move from right to left.

[0058] Optionally, in one embodiment of the present disclosure, performing a second laser irradiation process on the first laser processing area includes: The laser is irradiated on the first laser processing area at least once to form a groove in the first laser processing area, and the groove is completed until the depth of the groove reaches a preset depth.

[0059] In the second laser irradiation process, laser irradiation is performed in the first laser processing area, and grooves are further formed in the first laser processing area to form a groove. Specifically, the number of laser irradiations can be determined according to the depth of the groove. If the depth of the groove reaches a preset depth after one laser irradiation, the laser irradiation can be stopped. If the depth of the groove does not reach the preset depth after one laser irradiation, the laser can be irradiated again to see if the depth of the groove reaches the preset depth. The process is repeated until the depth of the groove reaches the preset depth, the groove is formed, and the laser irradiation is stopped.

[0060] Optionally, in one embodiment of the present disclosure, irradiating the first laser processing area with laser light at least once to form a groove in the first laser processing area, and until the depth of the groove reaches a preset depth, the grooving is completed, including: S301, forming a second laser spot with a second laser power, and irradiating the second laser spot on the first laser processing area; S302, the second laser spot moves once along the second path, peeling off part of the surface of the first laser processing area and forming a groove. If the depth of the groove is less than the preset depth, the operation is repeated until the depth of the groove reaches the preset depth to complete the grooving; otherwise, the grooving is completed directly.

[0061] Among them, after the second laser spot is irradiated on the surface of the first laser processing area, as the second laser spot moves, the surface of the first laser processing area at different positions can be peeled off and removed, and further grooves can be formed on the basis of the shallow groove structure formed in the first laser processing area to form grooves. In some examples, the second path can move from left to right, and one movement can be from left to right. In other examples, the second path can also move from right to left. The position and shape of the grooves on the surface of the first laser processing area can be controlled according to the drawings, and a corresponding opening for the second laser spot to pass through is set on the drawings.

[0062] It is understandable that when the depth of the groove is less than the preset depth, the second laser spot is moved once more along the second path, and the surface of the first laser processing area is repeatedly irradiated with the laser to achieve the groove opening effect until the depth of the groove reaches the preset depth. The specific number of times the second laser spot is moved can be set according to the actual situation. Of course, if the second laser spot moves once along the second path, the depth of the formed groove reaches the preset depth, and the groove opening is directly completed.

[0063] Optionally, in one embodiment of the present disclosure, the first laser power and the second laser power are both set to 1%-99% of the preset power, and the sum of the first laser power and the second laser power is equal to the preset power. By setting in this way, the single laser power can be reduced, the residual single radiation energy can be reduced, and the efficiency of the slotting can be guaranteed.

[0064] It can be understood that the first laser power and the second laser power are both less than the preset power, so that the depth of the groove opened by a single laser processing is less than the preset depth. Two laser processing operations need to be superimposed to reach the preset depth and complete the grooving. The positions of the residual radiation energy of the two laser processing are different, and the residual radiation energy is small, which can avoid side erosion, thereby ensuring the performance of the manufactured solar cell.

[0065] Optionally, in one embodiment of the present disclosure, the irradiation area of ​​the first laser spot is larger than the irradiation area of ​​the second laser spot, and the overlap rate between the irradiation area of ​​the first laser spot and the second laser spot is 10%-99%. By setting in this way, it can be ensured that after the second laser spot is irradiated on the first laser processing area, a step structure can be formed on the first laser processing area, thereby generating a spacing effect and reducing the side erosion phenomenon. It should be noted that the overlap rate between the irradiation area of ​​the first laser spot and the irradiation area of ​​the second laser spot can be set according to actual needs and can be controlled by drawings. The width between the first laser spot and the second laser spot can be specified on the drawings. The smaller the width, the higher the overlap rate, and the larger the width, the lower the overlap rate.

[0066] Optionally, in one embodiment of the present disclosure, the width of the first laser spot and the width of the second laser spot are both set to 20μm-150μm. By setting in this way, the width of the first laser spot and the width of the second laser spot can be adjusted according to different slot widths, which can improve the slot accuracy. It should be noted that the width of the slot formed after two laser processing is 5μm smaller than the preset slot width. The preset slot width can be between 100μm-500μm.

[0067] Optionally, the preset depth is 50nm-200nm. It should be noted that the preset depth can be set according to actual needs, and there is no excessive restriction here. The preset depth only needs to be greater than the depth of the BSG (back surface field structure).

[0068] Optionally, in one embodiment of the present disclosure, the solar cell includes a silicon substrate 1, a dielectric layer 2, a doping layer 3 and a mask layer 4, the dielectric layer 2 covers the back side of the silicon substrate 1, the doping layer 3 covers the dielectric layer 2, the mask layer 4 covers the doping layer 3, and laser processing is used to peel off a portion of the mask layer 4 to expose a portion of the doping layer 3.

[0069] It can be understood that the two laser processes are both for stripping off the mask layer 4 so that the doping layer 3 can be exposed and removed by etching.

[0070] Optionally, etching the grooved area includes: The exposed doped layer 3 is first etched with an alkaline solution, and after the exposed doped layer 3 is completely etched, a portion of the dielectric layer 2 is exposed.

[0071] The exposed dielectric layer 2 is etched with an alkaline solution. After the exposed dielectric layer 2 is completely etched, a portion of the silicon substrate 1 is exposed.

[0072] The exposed portion of the silicon substrate 1 is etched using an alkaline solution.

[0073] The etching rates of the doped layer 3 and the dielectric layer 2 are both lower than the etching rate of the silicon substrate 1 , the etching rates of the doped layer 3 and the dielectric layer 2 are both 1 μm / 100 s, and the etching rate of the silicon substrate 1 is 2 μm / 100 s.

[0074] By reducing the etching rate of the doping layer 3 and the etching rate of the dielectric layer 2, it is possible to control the etching of the doping layer 3 and the dielectric layer 2, thereby controlling the depth of the side etching, thereby greatly reducing the degree of the side etching and avoiding the formation of the side etching area.

[0075] The depth of the doping layer 3 and the dielectric layer 2 is 0.5 μm. The doping layer 3 and the dielectric layer 2 exposed by the grooves are completely removed by wet etching, and the etching depth of the silicon substrate 1 is 2 μm-10 μm.

[0076] It can be understood that after etching, the doping layer 3 and the dielectric layer 2 in the groove are removed, and part of the silicon substrate 1 is removed.

[0077] Optionally, in one embodiment of the present disclosure, the cross-sectional shape of the isolation groove 106 formed by the laser etching method may be an inverted trapezoid. The etching rate may be controlled so that the etching degree of the groove wall near the bottom of the groove is small, so that the cross-sectional shape of the groove after etching may be an inverted trapezoid. Of course, in other examples, the inverted trapezoidal isolation groove 106 may also be formed by other methods.

[0078] The preferred embodiments of the present disclosure are described in detail above in conjunction with the accompanying drawings; however, the present disclosure is not limited to the specific details in the above embodiments. Within the technical concept of the present disclosure, a variety of simple modifications can be made to the technical solution of the present disclosure, and these simple modifications all fall within the protection scope of the present disclosure.

[0079] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present disclosure will not further describe various possible combinations.

[0080] In addition, various embodiments of the present disclosure may be arbitrarily combined, and as long as they do not violate the concept of the present disclosure, they should also be regarded as the contents disclosed by the present disclosure.

Claims

1. A solar cell, characterized in that: The solar cell comprises a silicon substrate, a P-type region, an N-type region and an isolation groove, wherein the silicon substrate has a front side and a back side arranged opposite to each other, and the P-type region, the N-type region and the isolation groove are all arranged on the back side of the silicon substrate; Wherein, the P-type region includes a first dielectric layer and a P-type doped layer, the first dielectric layer covers the back side of the silicon substrate, and the P-type doped layer covers the first dielectric layer; The N-type region comprises a second dielectric layer and an N-type doped layer, wherein the second dielectric layer covers the back side of the silicon substrate, and the N-type doped layer covers the second dielectric layer; Wherein, the width dimension of the isolation groove in the first direction gradually decreases along the direction away from the silicon substrate; Wherein, the first direction is set to be a direction parallel to the silicon substrate.

2. The solar cell according to claim 1, characterized in that The first dielectric layer and the second dielectric layer are both configured as silicon oxide layers; or, The first dielectric layer and the second dielectric layer are both configured as intrinsic amorphous silicon layers; or, One of the first dielectric layer and the second dielectric layer is configured as a silicon oxide layer, and the other is configured as an intrinsic amorphous silicon layer.

3. The solar cell according to claim 1, characterized in that The P-type doped layer and the N-type doped layer are both configured as doped polysilicon layers; or, The P-type doped layer and the N-type doped layer are both configured as doped amorphous silicon layers; or, One of the P-type doping layer and the N-type doping layer is configured as a doped polysilicon layer, and the other is configured as a doped amorphous silicon layer.

4. A laser etching method for preparing a solar cell as claimed in any one of claims 1 to 3, characterized in that: The following steps are involved: Performing laser processing twice on the surface of the solar cell, the areas processed by the lasers twice partially overlap, and the areas of the areas processed by the lasers twice decrease in sequence to form a grooved area; The grooved region is etched to form the isolation groove.

5. The laser etching method according to claim 4, characterized in that: The laser processing is performed twice on the surface of the solar cell, the areas processed by the laser processing twice partially overlap, and the areas of the areas processed by the laser processing twice decrease in sequence, including: Performing a first laser irradiation process on the surface of the solar cell to form a first laser processing area on the surface of the solar cell, specifically, forming a first laser spot with a first laser power, irradiating the first laser spot on the surface of the solar cell, and moving the first laser spot once along a first path to peel off a portion of the surface of the solar cell; performing a second laser irradiation process on the first laser processing area, wherein the area of ​​the second laser irradiation process is smaller than the area of ​​the first laser processing area, Specifically, the first laser processing area is irradiated with laser at least once to form a groove in the first laser processing area, and the groove is formed until the depth of the groove reaches a preset depth, thereby completing the grooving.

6. The laser etching method according to claim 5, characterized in that: The step of irradiating the first laser processing area with laser light at least once to form a groove in the first laser processing area until the depth of the groove reaches a preset depth to complete the grooving includes: forming a second laser spot with a second laser power, and irradiating the second laser spot on the first laser processing area; The second laser spot moves once along the second path, peeling off part of the surface of the first laser processing area and forming a groove. If the depth of the groove is less than the preset depth, the operation is repeated until the depth of the groove reaches the preset depth to complete the grooving; otherwise, the grooving is completed directly.

7. The laser etching method according to claim 6, characterized in that: The first laser power and the second laser power are both set to 1%-99% of a preset power, and the sum of the first laser power and the second laser power is equal to the preset power.

8. The laser etching method according to claim 6, characterized in that: An irradiation area of ​​the first laser spot is larger than an irradiation area of ​​the second laser spot, and an overlap rate between the irradiation area of ​​the first laser spot and the irradiation area of ​​the second laser spot is 10%-99%.

9. The laser etching method according to claim 6, characterized in that: The width of the first laser spot and the width of the second laser spot are both set to 20 μm-150 μm, and the preset depth is 50 nm-200 nm.

10. The laser etching method according to any one of claims 4 to 9, characterized in that: Etching the grooved area includes: The exposed doped layer is first etched with an alkaline solution, and after the exposed doped layer is completely etched, a portion of the dielectric layer is exposed; Etching the exposed dielectric layer with an alkaline solution, and after the exposed dielectric layer is completely etched, a portion of the silicon substrate is exposed; Etching the exposed portion of the silicon substrate with an alkaline solution; The etching rates of the doped layer and the dielectric layer are both lower than the etching rate of the silicon substrate, the etching rates of the doped layer and the dielectric layer are both 1 μm / 100 s, and the etching rate of the silicon substrate is 2 μm / 100 s.

Images