Photovoltaic cell etching equipment, photovoltaic cell and preparation method

Abstract

The invention provides photovoltaic cell etching equipment, a photovoltaic cell and a preparation method, relates to the technical field of photovoltaics, and aims to solve the technical problem that the thickness of the photovoltaic cell is not uniform after the photovoltaic cell is prepared. The photovoltaic cell etching equipment comprises a barrel, a rotational flow device and a bearing structure, and the barrel is used for containing etching liquid; the bearing structure is used for horizontally placing the photovoltaic cell in the etching liquid, and the center of the photovoltaic cell is located on the central axis of the rotational flow device; the central axis of the rotational flow device coincides with the central axis of the barrel, and the rotational flow device is used for enabling the etching liquid to form annular water flow so that the photovoltaic cell can form a structure with the thick middle and the thin edge. The photovoltaic cell prepared by the etching equipment can make up for the characteristic that the middle is thin and the edge is thick in the preparation of the functional layer in the subsequent process, and finally a photovoltaic cell finished product with uniform thickness is formed.

Description

Technical Field

[0001] This invention relates to the field of photovoltaic technology, and in particular to a photovoltaic cell etching apparatus, a photovoltaic cell, and a method for its fabrication. Background Technology

[0002] The statements in this section are merely background information related to the present invention and do not necessarily constitute prior art.

[0003] Photovoltaic cells require multiple tubular high-temperature diffusion devices to deposit functional films on the substrate during fabrication. These include methods such as Low Pressure Chemical Vapor Deposition (LPCVD), Plasma Enhanced Chemical Vapor Deposition (PECVD), and atomic layer deposition (ALD). Due to variations in the flow state of the process gas stream within the tubular diffusion equipment, photovoltaic cells placed within often exhibit a thickness distribution at the edges and a thinner center after deposition (diffusion).

[0004] In subsequent manufacturing processes, uneven thickness of photovoltaic cells makes them more prone to warping during sintering and light injection. This increases the breakage rate of photovoltaic cells and causes uneven welding tension during the subsequent welding of photovoltaic modules, which can lead to desoldering of photovoltaic cells and affect the yield of photovoltaic modules. Summary of the Invention

[0005] The purpose of this invention is to provide a photovoltaic cell etching device, a photovoltaic cell, and a preparation method to solve the technical problem of uneven thickness after photovoltaic cell preparation.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] In a first aspect, the present invention provides a photovoltaic cell etching apparatus, comprising a cylindrical body, a swirling device, and a supporting structure, wherein the cylindrical body is used to contain an etching solution;

[0008] The supporting structure is used to place the photovoltaic cell flat in the etching solution, and the center of the photovoltaic cell is located on the central axis of the swirling device;

[0009] The central axis of the swirling device coincides with the central axis of the cylinder. The swirling device is used to form an annular water flow of the etching liquid so that the photovoltaic cell forms a structure that is thick in the middle and thin at the edges.

[0010] According to at least one embodiment of the present invention, the swirling device includes a plurality of rotating blades, the width of which increases along a direction away from the center of rotation; and / or,

[0011] The rotating blade is formed by twisting a trapezoidal strip.

[0012] According to at least one embodiment of the present invention, the swirling device is located above or below the supporting structure.

[0013] According to at least one embodiment of the present invention, the distance between the supporting structure and the swirling device, and the distance between the supporting structure and the liquid surface, are both greater than or equal to 30 cm.

[0014] According to at least one embodiment of the present invention, the cross-sectional shape of the cylinder is circular, and the ratio of the rotation diameter of the swirling device to the diameter of the cylinder is (5-8):10.

[0015] According to at least one embodiment of the present invention, the etching apparatus further includes a heating device, the heating device being circumferentially disposed on the cylinder wall along the cylinder body; and / or,

[0016] The temperature of the heating device can be continuously adjusted.

[0017] According to at least one embodiment of the present invention, the rotational speed of the cyclone device ranges from 30 rpm to 120 rpm; and / or,

[0018] The rotational speed of the cyclone device can be continuously adjusted; and / or,

[0019] Along the radial direction of the cylinder, the temperature difference between the center temperature and the edge temperature of the etching solution ranges from 10℃ to 40℃; and / or,

[0020] The center temperature of the etching solution ranges from 40℃ to 80℃.

[0021] According to at least one embodiment of the present invention, the etching solution includes a polishing solution; and / or,

[0022] The etching solution includes one of an alkaline solution or an acidic solution; and / or

[0023] The height difference between the middle and edge parts of the photovoltaic cell ranges from 100nm to 1000nm.

[0024] In a second aspect, exemplary embodiments of the present invention also provide a method for fabricating a photovoltaic cell, wherein the photovoltaic cell is etched using the etching equipment described in the first aspect; the method further includes:

[0025] A functional layer is deposited on the photovoltaic cell using a tubular diffusion device. The functional layer has a structure that is thin in the middle and thick at the edges, so that the photovoltaic cell forms a structure with uniform thickness.

[0026] According to at least one embodiment of the present invention, the tubular diffusion device includes one of PECVD, LPCVD, or ALD; and / or,

[0027] The functional layer includes at least one of an N-type doped polysilicon layer, a P-type doped polysilicon layer, a tunneling oxide layer, a passivation antireflection layer, or an emitter layer; and / or,

[0028] The photovoltaic cells include TOPCon cells or back-contact cells.

[0029] Thirdly, an exemplary embodiment of the present invention also provides a photovoltaic cell, wherein the thickness of the center of the silicon substrate is greater than the thickness of the edge.

[0030] According to at least one embodiment of the present invention, the thickness of the silicon substrate gradually decreases from the center of the silicon substrate toward the edge of the silicon substrate.

[0031] In one or more technical solutions provided in the exemplary embodiments of the present invention, at least one of the following beneficial effects can be achieved.

[0032] An exemplary embodiment of the photovoltaic cell etching apparatus of the present invention includes a cylindrical body, a swirling device, and a supporting structure disposed within the cylindrical body. The cylindrical body contains an etching solution for etching photovoltaic cells, such as an alkaline solution used in polishing processes. The supporting structure places one or more photovoltaic cells below the surface of the etching solution, with the photovoltaic cells placed horizontally and their centers located on the central axis of the swirling device. The swirling device is also placed below the liquid surface, with its central axis coinciding with the central axis of the cylindrical body. When the swirling device generates a circular water flow within the cylindrical body, the flow velocity of the etching solution in the center of the photovoltaic cells is less than that at the edges of the cells, meaning there is a gradient in the water flow velocity in the radial direction of the cylindrical body. This means that under the influence of centrifugal force, the etching solution further away from the vortex center rotates faster, has a faster reaction rate, and removes more of the photovoltaic cell, resulting in a thinner edge thickness; while the etching solution closer to the vortex center rotates slower, has a slower reaction rate, and removes less of the photovoltaic cell, resulting in a thicker center thickness. Thus, a photovoltaic cell with thin edges and a thick center is formed in this etching apparatus.

[0033] Compared to conventional chemical etching (polishing) equipment in existing technologies, which produces photovoltaic cells with uniform thickness, subsequent tubular diffusion equipment such as PECVD, LPCVD, and ALD inevitably deposits functional layers that are thicker at the edges and thinner in the middle, resulting in uneven thickness of the final photovoltaic cell. The photovoltaic cell with thin edges and thick middle formed by the etching equipment in the exemplary embodiment of this invention can achieve uniform thickness of the final photovoltaic cell after the deposition of functional layers with thick edges and thin middle in subsequent tubular equipment. This avoids cell warping, thereby reducing the breakage rate of photovoltaic cells and reducing the risk of desoldering caused by uneven welding tension due to warping during subsequent photovoltaic module manufacturing, thus improving the yield of photovoltaic modules. Attached Figure Description

[0034] The accompanying drawings illustrate exemplary embodiments of the invention and, together with the description thereof, serve to explain the principles of the invention. These drawings are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification.

[0035] Figure 1 This is a cross-sectional structural schematic diagram of an etching apparatus according to an embodiment of the present invention;

[0036] Figure 2 This is a top view of an etching apparatus according to an embodiment of the present invention.

[0037] Figure 3 This is a schematic diagram of the substrate of a photovoltaic cell according to an embodiment of the present invention;

[0038] Figure 4 This is a schematic diagram of a photovoltaic cell (finished product) according to an embodiment of the present invention.

[0039] Figure label:

[0040] 10. Swirl device; 11. Rotating blades;

[0041] 20. Cylinder body;

[0042] 30. Substrate; 31. Passivation and antireflection layer; 32. Composite structure layer;

[0043] 40. Etching solution;

[0044] 50. Heating device. Detailed Implementation

[0045] To make the technical problems to be solved, the technical solutions, and the beneficial effects of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the present invention and are not intended to limit the present invention.

[0046] The fabrication of photovoltaic cells requires the deposition of functional layers through multiple tubular diffusion devices. Due to the uneven airflow distribution within these devices, photovoltaic cells often exhibit a thin center and thick edges after fabrication. In subsequent processes, such as electrode metallization, this uneven thickness can lead to severe edge warping, resulting in reduced yield.

[0047] To address the aforementioned problems, the etching apparatus provided in the exemplary embodiment of this invention utilizes the radially gradient velocity of the etching solution flowing through the photovoltaic cell to control different reaction rates in the radial portion of the photovoltaic cell, thereby enabling the photovoltaic cell to be manufactured with a structure that is thicker at the center and thinner at the edges. This structure can compensate for the uneven thickness of the functional layer caused by subsequent tubular diffusion processes, thus resulting in a photovoltaic cell with uniform thickness.

[0048] It should be noted that the etching equipment provided in the exemplary embodiments of the present invention can be used in multiple process steps depending on the actual photovoltaic cell manufacturing process. It is applicable not only to the fabrication of TOPCon cells and BC cells, but also to the fabrication of other types of photovoltaic cells.

[0049] Figure 1 This is a cross-sectional structural schematic diagram of an etching apparatus according to an embodiment of the present invention; Figure 2 This is a top view schematic diagram of an etching apparatus according to an embodiment of the present invention. Figure 1 and Figure 2 As shown, the photovoltaic cell etching apparatus provided by the exemplary embodiment of the present invention includes a cylindrical body 20, a swirling device 10, and a supporting structure. The cylindrical body 20 is used to contain an etching solution 40. The supporting structure is used to place the photovoltaic cell flat in the etching solution 40, and the center of the photovoltaic cell is located on the central axis of the swirling device 10. The central axis of the swirling device 10 coincides with the central axis of the cylindrical body 20. The swirling device 10 is used to form an annular water flow of the etching solution 40 so that the photovoltaic cell forms a structure that is thick in the middle and thin at the edges.

[0050] In practical applications, the etching equipment places the photovoltaic cells in a chemical etching solution 40 and performs controlled etching to remove damaged layers or other functional layers. The cylinder 20 has sufficient depth to hold a sufficient amount of etching solution 40. The swirling device 10 and the photovoltaic cells in the supporting structure are immersed in the etching solution 40. Specifically, the photovoltaic cells are in a roughly horizontal state, and the plane of rotation of the swirling device 10 is also immersed in the etching solution 40 in a roughly horizontal state. The central axis of the swirling device 10 coincides with the central axis of the cylinder 20, that is, the centers of the photovoltaic cells, the swirling device 10, and the cylinder 20 are roughly on a vertical line.

[0051] When the vortex device 10 rotates, the etching solution 40 generates a rotating water flow. Due to the centrifugal force, the flow rate of the water changes radially on the photovoltaic cell. The etching solution 40 further away from the center of the vortex rotates faster and reacts faster, resulting in more of the photovoltaic cell being etched away and a thinner edge. Conversely, the etching solution 40 closer to the center of the vortex rotates slower and reacts slower, resulting in less of the photovoltaic cell being etched away and a thicker center. This process forms a photovoltaic cell with thin edges and a thick center in the etching equipment.

[0052] The following text uses the silicon substrate of photovoltaic cells as an example for introduction.

[0053] When the silicon substrate 30 is immersed in the etching solution 40, the rotating water flow generated by the swirling device 10 produces a radially gradient water flow velocity on both surfaces of the silicon substrate 30, thus forming parabolic surfaces. During the subsequent deposition of functional layers on one or both surfaces using a tubular diffusion device, the functional layers inevitably form a film that is thicker at the edges and thinner in the middle. Based on this, after forming the functional layer on the silicon substrate 30 with thin edges and thicker in the middle, the silicon substrate 30 can offset the thickness differences caused by subsequent processes, forming a photovoltaic cell with uniform thickness. In subsequent processes, such as the metallization of printed electrodes, this avoids severe warping of the photovoltaic cell, thereby reducing the breakage rate of the photovoltaic cell and lowering the risk of desoldering due to uneven welding tension caused by warping during subsequent photovoltaic module manufacturing, thus improving the yield of the photovoltaic module.

[0054] The principle behind the etching equipment described above for forming photovoltaic cells that are thin at the edges and thick in the middle is as follows:

[0055] Let the side length of the photovoltaic cell be d. We will take points at 1 / 2d and 1 / 4d distances from the center of the photovoltaic cell as examples.

[0056] When the swirling device 10 drives the etching fluid 40 to rotate, they have the same angular velocity ω. At this time, the linear velocities of the points at 1 / 2d and 1 / 4d are 1 / 2ωd and 1 / 4ωd, respectively. The amount of etching fluid 40 flowing through the corresponding points is 1 / 2ωdρΔt and 1 / 4ωdρΔt, where Δt is a time element. That is, the farther the point is from the center of the photovoltaic cell, the more etching fluid 40 flows through per unit time.

[0057] Since the etching reaction rate is proportional to the amount of etching solution 40, the reaction rate exhibits an arc-shaped gradient distribution. After etching, the surface of the photovoltaic substrate 30 is arc-shaped. The closer to the center of the photovoltaic substrate 30, the slower the reaction rate, the less silicon substrate 30 is removed, and the thicker the photovoltaic substrate 30. Conversely, the farther away from the center of the photovoltaic substrate 30, the faster the reaction rate, the more silicon substrate 30 is removed, and the thinner the photovoltaic substrate 30. Based on this, a structure like... Figure 3 The substrate 30 of the photovoltaic cell shown, wherein, Figure 3 This is a schematic diagram of the substrate of a photovoltaic cell according to an embodiment of the present invention.

[0058] For example, the chemical etching solution 40 can be either an alkaline solution or an acidic solution. When the chemical etching solution 40 is an alkaline solution, the alkaline solution can be potassium hydroxide, sodium hydroxide, etc., and the mass concentration of the alkaline solution is in the range of 1% to 10%, for example, the mass concentration can be 2%, 4%, 5%, 6%, 7%, 9%, etc.

[0059] For example, in the case where the chemical etching solution 40 is an alkaline solution, it can be called polishing, which is used to chemically etch the substrate 30 or functional layer of the photovoltaic cell to remove unnecessary parts.

[0060] like Figure 2 As shown, the swirl device 10 provided in the exemplary embodiment of the present invention can be a turbine-like or steam turbine-like structure. The swirl device 10 includes a plurality of rotating blades 11, and the width of the rotating blades 11 increases along the direction away from the center of rotation.

[0061] In some embodiments, the rotating blade 11 is narrower near the center of rotation and wider near the edge. The rotating blade 11 is formed by twisting a trapezoidal strip along its centerline (an isosceles trapezoidal strip), which can ensure that the laminar flow at the edge of the rotating blade 11 can be smoothly separated, thereby forming a large amount of high-velocity turbulence.

[0062] For example, the rotating blade 11 can be made of a titanium alloy or a polymer material such as polytetrafluoroethylene that is resistant to corrosion by etching solution 40.

[0063] In some embodiments, the swirl device 10 is located below the supporting structure, such as... Figure 1 As shown. For example, the vortex device 10 is located at the bottom of the cylinder, and its rotating shaft can pass through the bottom of the cylinder and be connected to a servo motor located outside the cylinder body 20. At this time, the supporting structure is located directly above the vortex device 10, that is, the battery cell is located directly above the vortex device 10. It can be understood that the supporting structure can be suspended in the etching solution 40 by a suspension device such as a robotic arm or hook located on the cylinder cover or above the cylinder body 20.

[0064] In other embodiments, the swirling device 10 is located above the supporting structure, that is, the swirling device 10 is suspended in the etching liquid 40 near the liquid surface. For example, the swirling device 10 is suspended in the etching liquid 40 by means of a suspension device such as a mechanical arm or hook, similar to the suspension of a ceiling fan. The supporting structure can be suspended in a deeper part of the etching liquid 40 or set on the bottom wall of the cylinder 20 so that the battery cells are located in the rotating water flow generated by the swirling device 10. It is understood that the span of the bracket used to suspend the supporting structure can be larger than that of the bracket used to suspend the swirling device 10, and the two do not interfere with each other.

[0065] In both of the above-mentioned relative positional relationships between the swirling device 10 and the supporting structure, the swirling device 10 can generate annular water flow with gradient velocity on both surfaces of the solar cell. The water vortex driven by the swirling device 10 when it rotates can completely cover the substrate 30 of the photovoltaic cell.

[0066] For example, the distance between the supporting structure and the swirling device 10, and the distance between the supporting structure and the liquid surface are both greater than or equal to 30 cm.

[0067] In practical applications, the supporting structure is a frame structure with multiple slots arranged vertically. Each slot is used to place (support) one solar cell, meaning that multiple photovoltaic cells are arranged along the depth direction of the etching solution 40. A radially gradient flow of water can also be formed between two adjacent photovoltaic cells, meaning that both surfaces of each photovoltaic cell can be etched. This arrangement allows for the simultaneous etching of multiple photovoltaic cells, improving production efficiency.

[0068] For example, the distance between each photovoltaic cell and the swirling device 10, and between each photovoltaic cell and the liquid surface, is greater than or equal to 30cm, for example, it can be 30cm, 40cm, 50cm, 60cm, 70cm, 80cm, 90cm or within any two of the above values.

[0069] Within the aforementioned spacing range, the swirling device 10 can generate a stable gradient swirling velocity on the surface of the solar cell, thereby enabling precise control of the etching amount at various locations on the photovoltaic cell.

[0070] In some embodiments, the cross-sectional shape of the cylindrical body 20 provided in the exemplary embodiment of the present invention can be one of a rectangle, an ellipse, or a circle.

[0071] When the cross-sectional shape of the cylinder 20 is circular, the ratio of the rotation diameter of the swirling device 10 to the diameter of the cylinder 20 is (5-8):10, for example, it can be 5.5:10, 6:10, 6.5:10, 7:10, 7.5:10, etc.

[0072] When the rotation diameter of the swirling device 10 is large, for example, more than 0.8 times the diameter of the cylinder 20, the turbulence generated by the tips of its rotating blades 11 collides with the inner wall of the cylinder 20, resulting in reflected waves. This makes it difficult to control the water flow velocity at the blade tips, thus affecting the formation of the parabolic surface of the silicon substrate 30. Conversely, when the rotation diameter of the swirling device 10 is small, for example, less than 0.5 times the diameter of the cylinder 20, space is wasted significantly. Therefore, when the ratio of the rotation diameter of the swirling device 10 to the diameter of the cylinder 20 is (5-8):10, the flow velocity uncertainty caused by the inner wall of the cylinder 20 can be minimized while making full use of the internal space of the cylinder 20.

[0073] For example, the diameter of the cylinder 20 is 5 to 10 times the side length of the photovoltaic cell, such as 5 times, 5.5 times, 6 times, 6.5 times, 7 times, 7.5 times, 8 times, 8.5 times, 9 times, 9.5 times, 10 times, or within any two of the above values.

[0074] like Figure 2 As shown, the etching apparatus provided in the exemplary embodiment of the present invention further includes a heating device 50, which is arranged circumferentially around the cylinder wall of the cylinder 20.

[0075] For example, the heating device 50 can be an annular thermocouple wire, electric heating coil / heating ring, etc., embedded in the interlayer or groove of the cylinder 20 to uniformly wrap the cylinder 20, so that the heating device 50 maintains a continuous and stable heat flux through the inner wall surface of the cylinder 20 at the same operating temperature. For example, a silicon nitride thermometer is used for measurement, and the temperature of the inner wall surface of the cylinder 20 is controlled within ±2℃ by a PID control system.

[0076] When the heating device 50 heats the cylinder wall of the cylinder 20, the temperature of the etching solution 40 gradually decreases from the inner wall towards the center. For example, along the radial direction of the cylinder 20, the temperature difference between the center temperature and the edge temperature of the etching solution 40 ranges from 10℃ to 40℃, such as 10℃, 15℃, 20℃, 25℃, 30℃, 35℃, 40℃, or any two of the above values.

[0077] For example, the center temperature of the etching solution 40 is in the range of 40°C to 80°C, such as 40°C, 45°C, 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, 80°C or any two of the above values.

[0078] The temperature of the etching solution 40 decreases closer to the vortex center, resulting in a slower reaction (etching) rate; conversely, the temperature increases further away from the vortex center, leading to a faster reaction (etching) rate. Thus, through the coordinated operation of the vortex device 10 and the heating device 50, a gradient change in the radial reaction (etching) rate of the photovoltaic cell can be achieved. The reaction rate is proportional to the amount of etching solution 40 and the reaction temperature, resulting in less silicon substrate 30 being etched away near the center of the photovoltaic cell and more silicon substrate 30 being etched away closer to the edge. The reaction rate exhibits a parabolic gradient distribution along the radial direction of the photovoltaic cell, and the surface of the etched photovoltaic substrate 30 is arc-shaped.

[0079] In some embodiments, the temperature of the heating device 50 can be continuously adjusted. The rotation speed of the swirling device 10 can also be continuously adjusted, thereby allowing the temperature and rotation speed to be adjusted to the appropriate level according to the required thickness of the photovoltaic cell substrate 30.

[0080] For example, the rotational speed of the cyclone device 10 is in the range of 30 rpm to 120 rpm, such as 30 rpm, 35 rpm, 40 rpm, 45 rpm, 50 rpm, 55 rpm, 60 rpm, 65 rpm, 70 rpm, 75 rpm, 80 rpm, 85 rpm, 90 rpm, 95 rpm, 100 rpm, 105 rpm, 110 rpm, 115 rpm, 120 rpm, or any two of the above values.

[0081] For example, the etching time of the alkaline solution ranges from 100s to 350s, such as 100s, 120s, 140s, 160s, 180s, 200s, 220s, 240s, 260s, 280s, 300s, 320s, 340s, or any two of the above values.

[0082] For example, the weight reduction of the photovoltaic cell before and after etching is controlled within 0.05g to 1g, such as 0.05g, 0.1g, 0.15g, 0.2g, 0.25g, 0.3g, 0.35g, 0.4g, 0.45g, 0.5g, 0.55g, 0.6g, 0.65g, 0.7g, 0.75g, 0.8g, 0.85g, 0.9g, 0.95g, 1g, or within any two of the above values.

[0083] Considering that after the photovoltaic cell is etched in the etching equipment, a functional layer with a thin center and thick edges is subsequently formed in the tubular diffusion equipment, such as PECVD, LPCVD or ALD, ultimately forming a photovoltaic cell with uniform thickness, the height difference between the middle part and the edge part of the etched photovoltaic cell ranges from 100nm to 1000nm. For example, it can be 100nm, 150nm, 200nm, 250nm, 300nm, 350nm, 400nm, 450nm, 500nm, 550nm, 600nm, 650nm, 700nm, 750nm, 800nm, 850nm, 900nm, 950nm, 1000nm or any two of the above values.

[0084] As can be seen from the above, the etching apparatus provided in the exemplary embodiment of the present invention, through continuous adjustment of the temperature of the heating device 50 and continuous adjustment of the speed of the swirling device 10, can achieve a parabolic gradient change in the radial reaction (etching) rate of the photovoltaic cell during the etching process, thereby forming a gradient change in the radial thickness of the photovoltaic cell, resulting in a structure that is thick in the middle and thin at the edges. This compensates for the formation of a functional layer that is thin in the middle and thick at the edges in the subsequent tubular diffusion equipment, thereby forming a photovoltaic cell product with uniform thickness.

[0085] An exemplary embodiment of the present invention also provides a method for fabricating a photovoltaic cell, wherein the photovoltaic cell is etched using the etching equipment of any of the above embodiments; wherein the fabrication method further includes:

[0086] A functional layer is deposited on a photovoltaic cell using a tubular diffusion apparatus. The functional layer has a structure that is thin in the middle and thick at the edges to ensure a uniform thickness structure in the photovoltaic cell. In the tubular diffusion apparatus, the flow pattern of the process gas varies; the gas flow rate is high near the edge of the photovoltaic cell and low near the center. Therefore, the functional layer deposited on the substrate 30 exhibits a structure that is thick at the edges and thin at the center.

[0087] In practical applications, based on the process of depositing functional layers in photovoltaic cells, the unavoidable height difference (thin in the middle and thick at the edges) between the middle and edge parts of each functional layer in the radial direction is calculated.

[0088] The required height difference (thicker in the middle and thinner at the edges) of the substrate 30 of the photovoltaic cell is calculated based on the thickness difference of the aforementioned functional layers.

[0089] By controlling the rotation speed of the vortex device 10 in the etching equipment in conjunction with the temperature of the heating device 50 and the etching time, a substrate 30 with the required height difference is formed, such as... Figure 3 As shown.

[0090] Then, corresponding functional layers are deposited on one and / or both surfaces of the substrate 30. Exemplarily, the functional layer may be at least one of an N-type doped polysilicon layer, a P-type doped polysilicon layer, a tunneling oxide layer, a passivation antireflection layer 31, or an emitter layer.

[0091] The photovoltaic cell preparation method of the exemplary embodiment of the present invention is applicable to the preparation of various types of photovoltaic cells, including TOPCon cells or back contact cells.

[0092] An exemplary embodiment of the present invention also provides a photovoltaic cell, which includes a silicon substrate. As described above, during the fabrication process of the photovoltaic cell, the etching equipment provided in the embodiments of the present invention is used to etch the silicon substrate, such that the thickness at the center of the silicon substrate is greater than the thickness at the edge.

[0093] Since the thickness at the center of the silicon substrate is greater than that at the edge, it can compensate for the thickness difference caused by the deposition of functional film layers in the tubular diffusion equipment, resulting in a more uniform thickness in the final photovoltaic cell product.

[0094] like Figure 3 As shown, the thickness of the silicon substrate gradually decreases from the center of the silicon substrate to the edge of the silicon substrate.

[0095] For example, one surface (front or back) of a silicon substrate may be an outwardly convex curved surface, or both surfaces of a silicon substrate may be outwardly convex curved surfaces.

[0096] The following two specific embodiments further illustrate the above-mentioned photovoltaic cell fabrication method, taking an N-type silicon wafer as an example, with substrate 30 as an example.

[0097] Example 1 (TOPCon Battery)

[0098] (1) The silicon substrate 30 is polished in an etching equipment using an alkaline solution to remove the damaged layer and impurities on the substrate 30, thereby obtaining a clean silicon substrate 30.

[0099] (2) Boron diffusion is performed on the front side (light-receiving surface) of substrate 30 using LPCVD to form a P-type emitter layer;

[0100] (3) Using the HF single-sided etching process, the back side (backlight side) of the substrate 30 is removed. The borosilicate glass layer generated in step (2) is polished (etched) in the etching equipment to expose the substrate 30.

[0101] (4) A tunnel oxide layer and an N-type doped polysilicon layer are sequentially deposited on the back side of the substrate 30 using PECVD. The tunnel oxide layer and the N-type doped polysilicon layer are referred to as the composite structure layer 32, and the positions of the composite structure layer 32 are as follows: Figure 4 As shown, where, Figure 4This is a schematic diagram of a photovoltaic cell (finished product) according to an embodiment of the present invention;

[0102] (5) Remove the borosilicate glass layer that was coated in step (4) on the front side and the phosphosilicate glass layer formed on the back side;

[0103] (6) Passivation and antireflection layers 31 were deposited on the bottom and back surfaces respectively using PECVD to form a passivation and antireflection layer 31, as shown in the figure. Figure 4 The photovoltaic cell shown has a uniform radial thickness.

[0104] In the above preparation method, polishing (etching process) is used in steps (1) and (3); tubular diffusion equipment is used to deposit the corresponding functional layers in steps (2), (4) and (6); the height difference between the middle and the edge of the photovoltaic cell formed by steps (1) and (3) is compensated by the height difference between the middle and the edge of the functional layer formed by steps (2), (4) and (6), thereby forming a photovoltaic cell with uniform radial thickness.

[0105] Example 2 (Back Contact Battery)

[0106] (1) The silicon substrate 30 is polished in an etching equipment using an alkaline solution to remove the damaged layer and impurities on the substrate 30, thereby obtaining a clean silicon substrate 30.

[0107] (2) A composite structure layer 32 is deposited on the back side of the substrate 30 using LPCVD (a tunnel oxide layer and a P-type doped polysilicon layer are deposited along the direction away from the substrate 30).

[0108] (3) The composite structure layer 32 on the N region is removed by laser film opening, single-sided etching and alkaline polishing processes.

[0109] (4) A tunnel oxide layer and an N-type doped polysilicon layer are sequentially deposited on the back side using PECVD;

[0110] (5) Use laser film opening, single-sided etching and alkaline polishing processes to remove the tunnel oxide layer and N-type doped polysilicon layer formed in step (4) on the P region.

[0111] (6) Use HF solution to remove the borosilicate glass layer that was coated on the front side of the substrate 30 in steps (2) and (4), and use alkaline solution to texturize the front side.

[0112] (7) Passivation and antireflection layers 31 were deposited on the bottom and back sides using PECVD.

[0113] In the above preparation method, polishing (etching process) is used in steps (1), (3) and (5); tubular diffusion equipment is used to deposit the corresponding functional layers in steps (2), (4) and (7); the height difference between the middle and the edge of the photovoltaic cell formed by steps (1), (3) and (5) is compensated by the height difference between the middle and the edge of the functional layer formed by steps (2), (4) and (7), so as to form a photovoltaic cell with uniform radial thickness.

[0114] The advantages of the above-mentioned photovoltaic cell preparation method over existing technologies are the same as those of the above-mentioned photovoltaic cell etching equipment, and will not be repeated here.

[0115] Those skilled in the art should understand that the above embodiments are merely for illustrating the present invention and are not intended to limit the scope of the invention. Those skilled in the art can make other changes or modifications based on the above disclosure, and these changes or modifications still fall within the scope of the present invention.

Claims

1. A photovoltaic cell etching apparatus, characterized in that, It includes a cylindrical body, a swirling device, and a supporting structure, wherein the cylindrical body is used to contain the etching solution; The supporting structure is used to place the photovoltaic cell flat in the etching solution, and the center of the photovoltaic cell is located on the central axis of the swirling device; The central axis of the swirling device coincides with the central axis of the cylinder. The swirling device is used to form an annular water flow of the etching liquid so that the photovoltaic cell forms a structure that is thick in the middle and thin at the edges.

2. The etching apparatus according to claim 1, characterized in that, The swirling device includes multiple rotating blades, the width of which increases along a direction away from the center of rotation; and / or, The rotating blade is formed by twisting a trapezoidal strip.

3. The etching apparatus according to claim 1, characterized in that, The swirling device is located above or below the supporting structure.

4. The etching apparatus according to claim 3, characterized in that, The distance between the supporting structure and the swirling device, and the distance between the supporting structure and the liquid surface, are both greater than or equal to 30 cm.

5. The etching apparatus according to any one of claims 1-4, characterized in that, The cross-sectional shape of the cylinder is circular, and the ratio of the rotation diameter of the swirling device to the diameter of the cylinder is (5-8):

10.

6. The etching apparatus according to claim 5, characterized in that, The etching apparatus further includes a heating device, which is circumferentially arranged around the cylinder wall; and / or... The temperature of the heating device can be continuously adjusted.

7. The etching apparatus according to claim 6, characterized in that, The rotational speed of the cyclone device is in the range of 30 rpm to 120 rpm; and / or, The rotational speed of the cyclone device can be continuously adjusted; and / or, Along the radial direction of the cylinder, the temperature difference between the center temperature and the edge temperature of the etching solution ranges from 10℃ to 40℃; and / or, The center temperature of the etching solution ranges from 40℃ to 80℃.

8. The etching apparatus according to claim 5, characterized in that, The etching solution includes a polishing solution; and / or, The etching solution includes one of an alkaline solution or an acidic solution; and / or The height difference between the middle and edge parts of the photovoltaic cell ranges from 100nm to 1000nm.

9. A method for preparing a photovoltaic cell, characterized in that, The photovoltaic cell is etched using the etching apparatus according to any one of claims 1-8; the method includes: A functional layer is deposited on the photovoltaic cell using a tubular diffusion device. The functional layer has a structure that is thin in the middle and thick at the edges, so that the photovoltaic cell forms a structure with uniform thickness.

10. A photovoltaic cell, comprising a silicon substrate, characterized in that, The thickness at the center of the silicon substrate is greater than the thickness at the edge; Preferably, the thickness of the silicon substrate gradually decreases from the center of the silicon substrate towards the edge of the silicon substrate.

Images