Rounded reagent and photovoltaic cell and method of making same

Abstract

The present disclosure relates to the technical field of solar cell, and particularly relates to a rounded reagent and a photovoltaic cell and a preparation method thereof. A textured pyramid structure is arranged on a poly removal area of the photovoltaic cell, and the top angle of the top of the pyramid and the bottom angle of the bottom of the pyramid are both rounded. The photovoltaic cell has excellent passivation performance and a double-sided rate simultaneously.

Description

Technical Field

[0001] This disclosure relates to the field of solar cell technology, and more specifically, to rounded corner reagents, photovoltaic cells, and methods for their preparation. Background Technology

[0002] The key to TOPCon cells lies in the stacked layer of tunneling silicon oxide and polysilicon on the back side. This stack provides chemical passivation through the tunneling silicon oxide layer and field passivation through the polysilicon layer. Combining these two passivation structures, the on-state voltage of TOPCon cells has now exceeded 740mV. Furthermore, due to the high phosphorus source concentration in the back poly layer, excellent ohmic contact can be achieved at the wire mesh end. However, when considering current improvement, as mentioned above, the high doping in the poly layer leads to enhanced Auger recombination, and the two are negatively correlated. Therefore, reducing parasitic absorption is a suitable method to increase short-current efficiency. Against this backdrop, poly thinning and polyfin technology have emerged. Polyfin technology retains the poly layer only in the back grid contact area, completely removing the poly layer in the non-grid area, increasing both current and bifaciality by up to 5%. However, it is still far from achieving the target bifaciality of 90% or 95%.

[0003] In view of this, this disclosure is hereby made. Summary of the Invention

[0004] The purpose of this disclosure is to provide a rounded corner reagent and a photovoltaic cell, as well as a method for preparing the same. The photovoltaic cell provided by this disclosure exhibits both excellent passivation properties and bifaciality.

[0005] This disclosure is implemented as follows: In a first aspect, this disclosure provides a photovoltaic cell, wherein a textured pyramid structure is provided on the poly-removed region of the photovoltaic cell, and the apex corner of the pyramid structure and the base corner of the pyramid structure are both rounded.

[0006] In an optional implementation, the radius of the apex corner is 60-100 degrees.

[0007] In an optional implementation, the radius of the bottom corner is 40-70 degrees.

[0008] In an optional embodiment, the height of the velvet pyramid structure is 0.7-0.8 μm.

[0009] In an optional embodiment, the photovoltaic cell also meets at least one of the following requirements: (1) A passivation layer is also provided on the velvet pyramid structure; (2) The photovoltaic cell further includes a poly finger region, and the ratio of the width of the poly finger region to the width of the poly removal region is (2:7)-(6:3). (3) The width of the poly removal region is 300-700μm.

[0010] Secondly, this disclosure provides a method for preparing a photovoltaic cell according to the foregoing embodiments, comprising: texturing the poly removal region of the photovoltaic cell; and then performing rounding treatment.

[0011] In an optional embodiment, the composition of the texturing agent used in texturing, by mass percentage, includes: 1.74-2.81% alkali, 1.16-1.69% texturing additives, and the remainder being water.

[0012] In an optional embodiment, the rounding agent used for the rounding treatment comprises DC1 and DC2, wherein, by mass percentage, DC1 comprises 65-75% HNO3, 0.15-0.25% HF, and the remainder is water; DC2 comprises 0.6-0.9% HF, 70-90 ppm O3, and the remainder is water.

[0013] In an optional implementation, the conditions for rounding the corners include: the rounding time is 8-12 minutes.

[0014] Thirdly, this disclosure provides a rounding reagent comprising DC1 and DC2, wherein, by mass percentage, DC1 comprises 65-75% HNO3, 0.15-0.25% HF, and the remainder is water; DC2 comprises 0.6-0.9% HF, 70-90 ppm O3, and the remainder is water.

[0015] This disclosure offers the following advantages: By setting a textured pyramid structure on the poly removal region, it enhances light trapping and improves the bifaciality of the photovoltaic cell. Simultaneously, rounding the apex and base corners of the textured pyramid structure reduces sharpness, providing a window for the uniform growth of the subsequent passivation film, thus ensuring the passivation effect and ultimately improving the efficiency of the photovoltaic cell. Attached Figure Description

[0016] To more clearly illustrate the technical solutions of this disclosure, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this disclosure and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1This is a schematic diagram of the structure of the TOPCon battery provided in an embodiment of this disclosure; Figure 2 A schematic flowchart illustrating the method for preparing a photovoltaic cell according to an embodiment of this disclosure; Figure 3 A schematic diagram of rounded corner treatment provided in an embodiment of this disclosure; Figure 4 The pyramid topography diagrams of S6 provided for comparative examples 2 and 3 of this disclosure. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of this disclosure clearer, the technical solutions in this disclosure will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0019] Firstly, this disclosure provides a photovoltaic cell, which can be a TOPCon cell or other photovoltaic cells containing a poly removal region. This disclosure uses a TOPCon cell as an example. The poly removal region of this photovoltaic cell has a textured pyramid structure, which can improve light trapping and increase the cell's bifaciality. However, setting the textured pyramid structure on the poly removal region significantly affects the on-state voltage and passivation effect of the TOPCon cell, thereby affecting its efficiency.

[0020] To overcome the defects caused by setting a textured pyramid structure on the poly removal area, this disclosure sets the top corner of the textured pyramid structure and the bottom corner of the pyramid structure as rounded corners. The rounded corners can reduce the sharpness of the area, provide a window for the uniform growth of the subsequent passivation layer, thereby reducing the on-voltage of the TOPCon cell and improving the passivation effect.

[0021] In some embodiments of this disclosure, the radius of the apex corner radius is 60-100 degrees. For example, it can be any value between 60 and 100 degrees, such as 60, 70, 80, 90, or 100 degrees. The radius of the bottom corner radius is 40-70 degrees. For example, it can be any value between 40 and 70 degrees, such as 40, 50, 60, or 70 degrees. Using the aforementioned radius of the corner not only reduces the dislocation density but also provides a uniform growth substrate for subsequent AlOx and SiNx passivation coatings. While enhancing light trapping through pyramidal textured surfaces, it also provides a uniform substrate morphology for the growth of the AlOx+SiNx passivation coating.

[0022] It should be noted that rounded corners refer to the fact that the original pyramid velvet surface has two sharp edges forming a sharp angle, and the embodiments of this disclosure process the sharp angle with an arc.

[0023] The radius of a rounded corner refers to the radius of the arc corresponding to the arc length of the sharp corner of a pyramid.

[0024] In some embodiments of this disclosure, the height of the velvet pyramid structure is 0.7-0.8 μm. For example, it can be any value between 0.7-0.8 μm, such as 0.7 μm, 0.71 μm, 0.72 μm, 0.73 μm, 0.74 μm, 0.75 μm, 0.76 μm, 0.77 μm, 0.78 μm, 0.79 μm, or 0.8 μm. Using the above-mentioned height in the velvet pyramid structure can further enhance the light-trapping effect and improve the dihedrality.

[0025] In some embodiments of this disclosure, the velvety pyramid structure is further provided with a passivation layer; the material forming the passivation layer can be an existing material, such as alumina and silicon nitride, and the structure of the passivation layer is also an existing structure, such as including a tunneling layer and a polycrystalline silicon layer.

[0026] In some embodiments of this disclosure, the width of the poly removal region is 300-700μm, for example, any value between 300μm and 700μm, such as 300μm, 400μm, 500μm, 600μm, 700μm, etc.

[0027] In some embodiments of this disclosure, the photovoltaic cell further includes a polyfin region, the ratio of the width of the polyfin region to the width of the polyremoved region being (2:7) to (6:3); for example, any value between (2:7) and (6:3) such as 2:7, 3:6, 4:5, 5:4, 6:3, etc.

[0028] It should be noted that the remaining structure of the TOPCon battery disclosed herein is the same as that of existing TOPCon batteries. Specifically, the structure of the TOPCon battery provided in this disclosure can be found in [link to relevant documentation]. Figure 1 , Figure 1 In the diagram, 1 represents the silicon wafer; 2 represents the aluminum oxide layer; 3 represents the silicon nitride layer; 4 represents the tunneling oxide layer; 5 represents the N-type poly layer; and 6 represents the metal front and back electrodes. The TOPCon cell structure diagram does not show the boron-deposited layer formed on the front side, but it is a boron source deposition layer in the textured surface of the cell's front side. Furthermore, while the poly removal area in the TOPCon cell structure diagram is not marked as a pyramid structure, the poly removal area on the back side of the cell has a pyramid textured surface.

[0029] Secondly, this disclosure also provides a method for preparing a photovoltaic cell, the flowchart of which can be found here. Figure 2The overall process includes steps such as texturing the front side, boron diffusion and post-oxidation, polishing, LPCVD / PECVD growth of TOPCon passivation structures, coating, and screen printing. The specific operations of these steps are not discussed in detail in this disclosure, but the specific conditions for these steps are provided. Specifically: S1, flocking; The texturing reagent comprises, by mass percentage, 0.9-4% alkali, 0.09-1.2% texturing additive, and the balance being water. Specifically, the alkali includes, but is not limited to, hydroxides such as sodium hydroxide and potassium hydroxide, and the amount of alkali used is any value between 0.9% and 4%, such as 0.9%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, and 4%. The texturing additive is purchased from Topband, Xiaochen, and Shichuang. The amount of texturing additive used is any value between 0.09% and 0.12%, such as 0.09%, 0.1%, 0.11%, and 0.12%. The reaction time is 300-470 seconds, and the reaction temperature is 60-80℃.

[0030] S2, Boron expansion; The deposition temperature was 810-870℃, the deposition time was 400-600s, the boron source flow rate was 100-300sccm, the oxygen flow rate was 500-1000sccm, the nitrogen flow rate was 2400sccm-3500sccm, the advance temperature was 910-940℃, the time was 800-1000s, the oxidation temperature was 1035-1050℃, the time was 3900-4500s, the textured region concentration was 1E18-6E18, and the doping depth was 0.7-1.1um.

[0031] S3, Polishing; The polishing reagent comprises the following components by mass percentage: 1.05-1.35% alkali, 0.35-0.55% polishing additive, and the balance being water. Specifically, the alkali includes, but is not limited to, hydroxides such as sodium hydroxide and potassium hydroxide, and the amount of alkali used is any value between 1.05% and 1.35%, such as 1.05%, 1.10%, 1.15%, 1.20%, 1.25%, 1.30%, and 1.35%. The polishing additive is purchased from Topband, Xiaochen, and Shichuang. The amount of polishing reagent used is any value between 0.35% and 0.55%, such as 0.35%, 0.4%, 0.45%, 0.5%, and 0.55%. The reaction time is 250-350 seconds, and the reaction temperature is 75-83℃.

[0032] S4, TOPCon passivation structure; This includes, but is not limited to, LPCVD in-situ and PECVD in-situ growth. This disclosure utilizes LPCVD for in-situ growth. Specifically, the tunneling oxide layer growth is performed at a deposition temperature of 600-620℃ and a reaction time of 400-600 s; the intrinsic amorphous silicon layer is grown at 590-620℃ with a reaction time of 1500-2300 s; phosphorus doping is performed at a deposition temperature of 800-830℃ with a time of 900-1100 s; the boron source flow rate is 1400-1800 sccm; the oxidation flow rate is 500-1000 sccm; the advance temperature is 900-940℃ with a time of 1000-1400 s; the oxidation temperature is 860-900℃ with a time of 1300-1600 s; and the surface concentration is 2E20-4E20.

[0033] S5, laser-based graphics; Based on the number of subgrid elements in the screen, different widths of poly blanks (i.e., non-poly removal areas) can be achieved in the subgrids. The width of the poly blanks is 200-600um. Different spot overlap rates are designed during the laser patterning process to ensure that the interface between the poly and the laser has a conical structure, thereby changing the carrier transport and increasing the carrier lifetime.

[0034] S6, wet etching; Texturing is performed on the poly removal area. The texturing reagent, by mass percentage, comprises: 1.74-2.81% alkali, 1.16-1.69% texturing additive, and the balance being water. Specifically, the alkali includes, but is not limited to, hydroxides such as sodium hydroxide and potassium hydroxide, and the amount of alkali used is any value between 1.74% and 2.81%, such as 1.74%, 1.75%, 1.8%, 1.9%, 2.0%, 2.1%, 2.2%, 2.3%, 2.4%, 2.5%, 2.6%, 2.7%, and 2.81%. The texturing additive is purchased from Topband, Xiaochen, and Shichuang. The amount of texturing additive used is 1.16%, 1.2%, 1.3%, 1.5%, 1.6%, and 1.69%, etc., ranging from 1.16% to 1.69%. The reaction time is 200-300 s, and the reaction temperature is 60-75℃.

[0035] The pyramidal structure formed by the pile forming process is rounded at the corners. See the diagram for a schematic of the rounded corner process. Figure 3 Rounded corners refer to rounding the sharp top and bottom corners of the velvet pyramid structure.

[0036] The components used in the rounded corner treatment include DC1, which, by mass percentage, comprises 65-75% HNO3, 0.15-0.25% HF, and the remainder is water; the DC1 treatment time is 8-12 minutes.

[0037] Specifically, the HNO3 content in DC1 is any value between 65% and 75%, such as 65%, 66%, 67%, 68%, 69%, 70%, 71%, 72%, 73%, 74%, and 75%. The HF content is any value between 0.15% and 0.25%, such as 0.15%, 0.16%, 0.17%, 0.18%, 0.19%, 0.20%, 0.21%, 0.22%, 0.23%, 0.24%, and 0.25%, with the remainder being water.

[0038] DC1 solution undergoes the following reaction:

[0039] The reaction principle is as follows: at the depth of the pyramid, the solubility of HF is low, and the reaction products are difficult to diffuse, causing "traffic jams" in the deep valleys. This "blockage" makes the etching rate at the bottom of the valley faster than that at the peak, and eventually the bottom of the valley is worn down.

[0040] The components used in the rounding treatment also include DC2; DC2 consists of 0.6-0.9% HF, 70-90 ppm O3, and the remainder is water; DC2 is used for 8-12 minutes.

[0041] Specifically, the HF content in DC2 is any value between 0.6% and 0.9%, such as 0.6%, 0.65%, 0.7%, 0.75%, 0.8%, 0.85%, 0.9%; and the O3 dosage is any value between 70% and 90% ppm, such as 70 ppm, 75 ppm, 80 ppm, 85 ppm, 90 ppm.

[0042] The DC2 solution undergoes the following reaction:

[0043] The reaction principle is as follows: O3 first reacts with Si to grow SiO2, but the content of O3 in the solution is extremely low, and it is easier to accumulate at the peak. The O3 at the peak is rapidly consumed, which drives HF to concentrate on etching the peak, while at the valley, O3 is difficult to reach, and the etching is slow.

[0044] In summary, this disclosure achieves a pyramidal morphology with uniform size and rounded apex and base corners through the combined action of DC1 and DC2 solutions. The arc formed by the pyramid's apex along its side edges (i.e., the arc of the apex corner) is 60°-100°, and the arc formed by the pyramid's base along its side edges (i.e., the arc of the base corner) is 40°-70°. In this structure, the rounded arcs formed by the pyramid's apex and base not only reduce dislocation density but also provide a uniform growth substrate for subsequent AlOx and SiNx coatings. While enhancing light trapping through the pyramidal textured surface, it also provides a uniform substrate morphology for the growth of AlOx+SiNx.

[0045] S7, passivation layer coating; A 3-8nm aluminum oxide layer and a 60-140nm silicon nitride layer are formed on the front and back of the battery.

[0046] S8, screen printing; Electrodes are fabricated on the front and back of the battery using silver paste.

[0047] The features and performance of this disclosure will be further described in detail below with reference to embodiments.

[0048] Example 1 This embodiment provides a method for preparing a photovoltaic cell, including: S1. Texturing the raw silicon wafer (purchased from Zhonghuan). The texturing reagent consists of the following components: 0.9% NaOH, 0.09% texturing additive (purchased from Shichuang TS57V10), and 99.01% H2O; the reaction time is 300s, and the reaction temperature is 60℃.

[0049] S2. Boron diffusion is performed on the silicon wafer after step S1. The deposition temperature is 810℃, the deposition time is 400s, the boron source flow rate is 100sccm, the oxygen flow rate is 500sccm, the nitrogen flow rate is 2400sccm, the push temperature is 910℃, the time is 800s, the oxidation temperature is 1035℃, the time is 3900s, the textured region concentration is 1E18, and the doping depth is 0.7um.

[0050] S3. Polish the silicon wafer after step S2. The polishing reagent consists of the following components: 1.05% NaOH, 0.35% polishing additive (purchased from Xiaochen AT20-1), and 98.6% water; the reaction time is 250s and the reaction temperature is 75℃.

[0051] S4. After step S3, perform TOPCon passivation structure growth on the silicon wafer. LPCVD is used for in-situ growth. The tunnel oxide layer is grown at a deposition temperature of 600℃ for 400s, and the intrinsic amorphous silicon layer is grown at 590℃ for 1500s. For phosphorus doping, the deposition temperature is 800℃ for 900s, the boron source flow rate is 1400 sccm, the oxidation flow rate is 500 sccm, the drive temperature is 900℃ for 1000s, the oxidation temperature is 860℃ for 1300s, and the surface concentration is 2E20.

[0052] S5. After completing step S4, perform laser patterning on the silicon wafer. Leave a 200µm margin for the secondary gate poly.

[0053] S6. After step S5, perform wet etching on the silicon wafer. The texturing reagent composition is as follows: 1.74% NaOH, 1.16% texturing additive, H2O 97.1%; reaction time is 200s, reaction temperature is 60℃. DC1 consists of 65% HNO3, 0.15% HF, and the balance is water, 8mins. DC2 consists of 75ppm O3, 0.6% HF, and the balance is water, 8mins.

[0054] S7. After completing step S6, passivation layer coating is applied to the silicon wafer, forming 3nm aluminum oxide and 60nm silicon nitride layers on the front and back of the battery.

[0055] S8. After completing S7, screen print the silicon wafer. Then, use silver paste to fabricate electrodes on the front and back of the battery.

[0056] Example 2 This embodiment provides a method for preparing a photovoltaic cell, including: S1. Texturing the raw silicon wafer. The texturing reagent consists of the following components: 4% NaOH, 1.2% texturing additive, and 94.8% H2O; the reaction time is 470s, and the reaction temperature is 80℃.

[0057] S2. Boron diffusion is performed on the silicon wafer after step S1. The deposition temperature is 870℃, the deposition time is 600s, the boron source flow rate is 300sccm, the oxygen flow rate is 1000sccm, the nitrogen flow rate is 3500sccm, the push temperature is 940℃, the time is 1000s, the oxidation temperature is 1050℃, the time is 4500s, the textured region concentration is 6E18, and the doping depth is 1.1um.

[0058] S3. Polish the silicon wafer after step S2. The polishing reagent consists of the following components: 1.35% NaOH, 0.55% polishing additive, and 98.1% water; the reaction time is 350 seconds, and the reaction temperature is 83°C.

[0059] S4. After step S3, perform TOPCon passivation structure growth on the silicon wafer. LPCVD is used for in-situ growth. The tunnel oxide layer is grown at a deposition temperature of 620℃ for 600s, and the intrinsic amorphous silicon layer is grown at 620℃ for 2300s. For phosphorus doping, the deposition temperature is 830℃ for 1100s, the boron source flow rate is 1800 sccm, the oxidation flow rate is 1000 sccm, the drive temperature is 940℃ for 1400s, and the oxidation temperature is 900℃ for 1600s. The surface concentration is 4E20.

[0060] S5. After step S4, perform laser patterning on the silicon wafer. The poly width for the secondary gate is 600µm. S6. After step S5, perform wet etching on the silicon wafer. The texturing reagent composition is as follows: 2.81% NaOH, 1.69% texturing additive, 95.5% water; reaction time is 300s, reaction temperature is 75℃. DC1 consists of 75% HNO3, 0.25% HF, and the balance is water, 12mins; DC2 consists of 90ppmO3, 0.9% HF, and the balance is water; 12mins.

[0061] S7. After completing step S6, passivation layer coating is applied to the silicon wafer, forming an 8nm aluminum oxide layer and a 140nm silicon nitride layer on the front and back of the battery.

[0062] S8. After completing S7, screen print the silicon wafer. Then, use silver paste to fabricate electrodes on the front and back of the battery.

[0063] Example 3 This embodiment provides a method for preparing a photovoltaic cell, including: S1. Texturing the raw silicon wafer. The texturing reagent consists of the following components: 2.5% NaOH, 1.0% texturing additive, and 96.5% H2O; the reaction time is 380s, and the reaction temperature is 70℃.

[0064] S2. Boron diffusion is performed on the silicon wafer after step S1. The deposition temperature is 840℃, the deposition time is 500s, the boron source flow rate is 200sccm, the oxygen flow rate is 700sccm, the nitrogen flow rate is 2900sccm, the push temperature is 930℃, the time is 900s, the oxidation temperature is 1045℃, the time is 4200s, the textured region concentration is 4E18, and the doping depth is 1.0um.

[0065] S3. Polish the silicon wafer after step S2. The polishing reagent consists of the following components: 1.20% NaOH, 0.45% polishing additive, and 98.35% water; the reaction time is 300 seconds, and the reaction temperature is 79°C.

[0066] S4. After step S3, perform TOPCon passivation structure growth on the silicon wafer. LPCVD is used for in-situ growth. The tunnel oxide layer is grown at a deposition temperature of 610℃ for 500s, and the intrinsic amorphous silicon layer is grown at 605℃ for 1900s. For phosphorus doping, the deposition temperature is 815℃ for 1000s, the boron source flow rate is 1600 sccm, the oxidation flow rate is 800 sccm, the drive temperature is 920℃ for 1200s, the oxidation temperature is 880℃ for 1450s, and the surface concentration is 3E20.

[0067] S5. After completing step S4, perform laser patterning on the silicon wafer. The poly width of the secondary gate is 400um.

[0068] S6. After step S5, perform wet etching on the silicon wafer. The texturing reagent composition is as follows: 2.45% NaOH, 1.36% texturing additive, 96.19% water; reaction time is 250s, reaction temperature is 68℃. DC1 consists of 68% HNO3, 0.2% HF, and the balance is water, 10mins; DC2 consists of 80ppm O3, 0.8% HF, and the balance is water; 10mins.

[0069] S7. After completing step S6, passivation layer coating is applied to the silicon wafer, forming a 6nm aluminum oxide layer and a 100nm silicon nitride layer on the front and back of the battery.

[0070] S8. After completing S7, screen print the silicon wafer. Then, use silver paste to fabricate electrodes on the front and back of the battery.

[0071] Example 4 This embodiment provides a method for preparing a photovoltaic cell, including: S1. Texturing the raw silicon wafer. The texturing reagent consists of the following components: 2.5% NaOH, 1.0% texturing additive, and 96.5% H2O; the reaction time is 380s, and the reaction temperature is 70℃.

[0072] S2. Boron diffusion is performed on the silicon wafer after step S1. The deposition temperature is 840℃, the deposition time is 500s, the boron source flow rate is 200sccm, the oxygen flow rate is 700sccm, the nitrogen flow rate is 2900sccm, the push temperature is 930℃, the time is 900s, the oxidation temperature is 1045℃, the time is 4200s, the textured region concentration is 4E18, and the doping depth is 1.0um.

[0073] S3. Polish the silicon wafer after step S2. The polishing reagent consists of the following components: 1.20% NaOH, 0.45% polishing additive, and 98.35% water; the reaction time is 300 seconds, and the reaction temperature is 79°C.

[0074] S4. After step S3, perform TOPCon passivation structure growth on the silicon wafer. LPCVD is used for in-situ growth. The tunnel oxide layer is grown at a deposition temperature of 610℃ for 500s, and the intrinsic amorphous silicon layer is grown at 605℃ for 1900s. For phosphorus doping, the deposition temperature is 815℃ for 1000s, the boron source flow rate is 1600 sccm, the oxidation flow rate is 800 sccm, the drive temperature is 920℃ for 1200s, the oxidation temperature is 880℃ for 1450s, and the surface concentration is 3E20.

[0075] S5. After completing step S4, perform laser patterning on the silicon wafer. The poly width of the secondary gate is 400um.

[0076] S6. After step S5, perform wet etching on the silicon wafer. The texturing reagent composition is as follows: 1.74% NaOH, 1.16% texturing additive, H2O 97.1%; reaction time is 200s, reaction temperature is 60℃. DC1 consists of 65% HNO3, 0.15% HF, and the balance is water, 8mins. DC2 consists of 75ppm O3, 0.6% HF, and the balance is water, 8mins.

[0077] S7. After completing step S6, passivation layer coating is applied to the silicon wafer, forming a 6nm aluminum oxide layer and a 100nm silicon nitride layer on the front and back of the battery.

[0078] S8. After completing S7, screen print the silicon wafer. Then, use silver paste to fabricate electrodes on the front and back of the battery.

[0079] Example 5 This embodiment provides a method for preparing a photovoltaic cell, including: S1. Texturing the raw silicon wafer. The texturing reagent consists of the following components: 2.5% NaOH, 1.0% texturing additive, and 96.5% H2O; the reaction time is 380s, and the reaction temperature is 70℃.

[0080] S2. Boron diffusion is performed on the silicon wafer after step S1. The deposition temperature is 840℃, the deposition time is 500s, the boron source flow rate is 200sccm, the oxygen flow rate is 700sccm, the nitrogen flow rate is 2900sccm, the push temperature is 930℃, the time is 900s, the oxidation temperature is 1045℃, the time is 4200s, the textured region concentration is 4E18, and the doping depth is 1.0um.

[0081] S3. Polish the silicon wafer after step S2. The polishing reagent consists of the following components: 1.20% NaOH, 0.45% polishing additive, and 98.35% water; the reaction time is 300 seconds, and the reaction temperature is 79°C.

[0082] S4. After step S3, perform TOPCon passivation structure growth on the silicon wafer. LPCVD is used for in-situ growth. The tunnel oxide layer is grown at a deposition temperature of 610℃ for 500s, and the intrinsic amorphous silicon layer is grown at 605℃ for 1900s. For phosphorus doping, the deposition temperature is 815℃ for 1000s, the boron source flow rate is 1600 sccm, the oxidation flow rate is 800 sccm, the drive temperature is 920℃ for 1200s, the oxidation temperature is 880℃ for 1450s, and the surface concentration is 3E20.

[0083] S5. After completing step S4, perform laser patterning on the silicon wafer. The poly width of the secondary gate is 400um.

[0084] S6. After step S5, perform wet etching on the silicon wafer. The texturing reagent composition is as follows: 2.81% NaOH, 1.69% texturing additive, 95.5% water; reaction time is 300s, reaction temperature is 75℃. DC1 consists of 75% HNO3, 0.25% HF, and the balance is water, 12mins; DC2 consists of 90ppmO3, 0.9% HF, and the balance is water; 12mins.

[0085] S7. After completing step S6, passivation layer coating is applied to the silicon wafer, forming a 6nm aluminum oxide layer and a 100nm silicon nitride layer on the front and back of the battery.

[0086] S8. After completing S7, screen print the silicon wafer. Then, use silver paste to fabricate electrodes on the front and back of the battery.

[0087] Comparative Example 1 This comparative example provides a method for preparing a photovoltaic cell, including: S1. Texturing the raw silicon wafer. The texturing reagent consists of the following components: 2.5% NaOH, 1.0% texturing additive, and 96.5% H2O; the reaction time is 380s, and the reaction temperature is 70℃.

[0088] S2. Boron diffusion is performed on the silicon wafer after step S1. The deposition temperature is 840℃, the deposition time is 500s, the boron source flow rate is 200sccm, the oxygen flow rate is 700sccm, the nitrogen flow rate is 2900sccm, the push temperature is 930℃, the time is 900s, the oxidation temperature is 1045℃, the time is 4200s, the textured region concentration is 4E18, and the doping depth is 1.0um.

[0089] S3. Polish the silicon wafer after step S2. The polishing reagent consists of the following components: 1.20% NaOH, 0.45% polishing additive, and 98.35% water; the reaction time is 300 seconds, and the reaction temperature is 79°C.

[0090] S4. After step S3, perform TOPCon passivation structure growth on the silicon wafer. LPCVD is used for in-situ growth. The tunnel oxide layer is grown at a deposition temperature of 610℃ for 500s, and the intrinsic amorphous silicon layer is grown at 605℃ for 1900s. For phosphorus doping, the deposition temperature is 815℃ for 1000s, the boron source flow rate is 1600 sccm, the oxidation flow rate is 800 sccm, the drive temperature is 920℃ for 1200s, the oxidation temperature is 880℃ for 1450s, and the surface concentration is 3E20.

[0091] S5. After completing step S4, perform laser patterning on the silicon wafer. The poly width of the secondary gate is 400um.

[0092] S6. After step S5, perform wet etching on the silicon wafer. The texturing reagent consists of the following components: 2.45% NaOH, 1.36% texturing additive, and 96.19% water; the reaction time is 250 seconds, and the reaction temperature is 68°C.

[0093] S7. After completing step S6, passivation layer coating is applied to the silicon wafer, forming a 6nm aluminum oxide layer and a 100nm silicon nitride layer on the front and back of the battery.

[0094] S8. After completing S7, screen print the silicon wafer. Then, use silver paste to fabricate electrodes on the front and back of the battery.

[0095] Comparative Example 2 This comparative example provides a method for preparing a photovoltaic cell, including: S1. Texturing the raw silicon wafer. The texturing reagent consists of the following components: 2.5% NaOH, 1.0% texturing additive, and 96.5% H2O; the reaction time is 380s, and the reaction temperature is 70℃.

[0096] S2. Boron diffusion is performed on the silicon wafer after step S1. The deposition temperature is 840℃, the deposition time is 500s, the boron source flow rate is 200sccm, the oxygen flow rate is 700sccm, the nitrogen flow rate is 2900sccm, the push temperature is 930℃, the time is 900s, the oxidation temperature is 1045℃, the time is 4200s, the textured region concentration is 4E18, and the doping depth is 1.0um.

[0097] S3. Polish the silicon wafer after step S2. The polishing reagent consists of the following components: 1.20% NaOH, 0.45% polishing additive, and 98.35% water; the reaction time is 300 seconds, and the reaction temperature is 79°C.

[0098] S4. After step S3, perform TOPCon passivation structure growth on the silicon wafer. LPCVD is used for in-situ growth. The tunnel oxide layer is grown at a deposition temperature of 610℃ for 500s, and the intrinsic amorphous silicon layer is grown at 605℃ for 1900s. For phosphorus doping, the deposition temperature is 815℃ for 1000s, the boron source flow rate is 1600 sccm, the oxidation flow rate is 800 sccm, the drive temperature is 920℃ for 1200s, the oxidation temperature is 880℃ for 1450s, and the surface concentration is 3E20.

[0099] S5. After completing step S4, perform laser patterning on the silicon wafer. The poly width of the secondary gate is 400um.

[0100] S6. After step S5, perform wet etching on the silicon wafer. The texturing reagent consists of: 2.45% NaOH, 1.36% texturing additive, and 96.19% water; the reaction time is 250s, and the reaction temperature is 68℃. DC1 consists of 68% HNO3, 0.2% HF, and the balance is water, for 10mins.

[0101] S7. After completing step S6, passivation layer coating is applied to the silicon wafer, forming a 6nm aluminum oxide layer and a 100nm silicon nitride layer on the front and back of the battery.

[0102] S8. After completing S7, screen print the silicon wafer. Then, use silver paste to fabricate electrodes on the front and back of the battery.

[0103] Comparative Example 3 This comparative example provides a method for preparing a photovoltaic cell, including: S1. Texturing the raw silicon wafer. The texturing reagent consists of the following components: 2.5% NaOH, 1.0% texturing additive, and 96.5% H2O; the reaction time is 380s, and the reaction temperature is 70℃.

[0104] S2. Boron diffusion is performed on the silicon wafer after step S1. The deposition temperature is 840℃, the deposition time is 500s, the boron source flow rate is 200sccm, the oxygen flow rate is 700sccm, the nitrogen flow rate is 2900sccm, the push temperature is 930℃, the time is 900s, the oxidation temperature is 1045℃, the time is 4200s, the textured region concentration is 4E18, and the doping depth is 1.0um.

[0105] S3. Polish the silicon wafer after step S2. The polishing reagent consists of the following components: 1.20% NaOH, 0.45% polishing additive, and 98.35% water; the reaction time is 300 seconds, and the reaction temperature is 79°C.

[0106] S4. After step S3, perform TOPCon passivation structure growth on the silicon wafer. LPCVD is used for in-situ growth. The tunnel oxide layer is grown at a deposition temperature of 610℃ for 500s, and the intrinsic amorphous silicon layer is grown at 605℃ for 1900s. For phosphorus doping, the deposition temperature is 815℃ for 1000s, the boron source flow rate is 1600 sccm, the oxidation flow rate is 800 sccm, the drive temperature is 920℃ for 1200s, the oxidation temperature is 880℃ for 1450s, and the surface concentration is 3E20.

[0107] S5. After completing step S4, perform laser patterning on the silicon wafer. The poly width of the secondary gate is 400um.

[0108] S6. After step S5, perform wet etching on the silicon wafer. The texturing reagent consists of: 2.45% NaOH, 1.36% texturing additive, and 96.19% water; the reaction time is 250s, and the reaction temperature is 68℃. DC2 consists of 80ppm O3, 0.8% HF, and the balance is water; 10mins.

[0109] S7. After completing step S6, passivation layer coating is applied to the silicon wafer, forming a 6nm aluminum oxide layer and a 100nm silicon nitride layer on the front and back of the battery.

[0110] S8. After completing S7, screen print the silicon wafer. Then, use silver paste to fabricate electrodes on the front and back of the battery.

[0111] Comparative Example 4 This comparative example provides a method for preparing a photovoltaic cell, including: S1. Texturing the raw silicon wafer. The texturing reagent consists of the following components: 2.5% NaOH, 1.0% texturing additive, and 96.5% H2O; the reaction time is 380s, and the reaction temperature is 70℃.

[0112] S2. Boron diffusion is performed on the silicon wafer after step S1. The deposition temperature is 840℃, the deposition time is 500s, the boron source flow rate is 200sccm, the oxygen flow rate is 700sccm, the nitrogen flow rate is 2900sccm, the push temperature is 930℃, the time is 900s, the oxidation temperature is 1045℃, the time is 4200s, the textured region concentration is 4E18, and the doping depth is 1.0um.

[0113] S3. Polish the silicon wafer after step S2. The polishing reagent consists of the following components: 1.20% NaOH, 0.45% polishing additive, and 98.35% water; the reaction time is 300 seconds, and the reaction temperature is 79°C.

[0114] S4. After step S3, perform TOPCon passivation structure growth on the silicon wafer. LPCVD is used for in-situ growth. The tunnel oxide layer is grown at a deposition temperature of 610℃ for 500s, and the intrinsic amorphous silicon layer is grown at 605℃ for 1900s. For phosphorus doping, the deposition temperature is 815℃ for 1000s, the boron source flow rate is 1600 sccm, the oxidation flow rate is 800 sccm, the drive temperature is 920℃ for 1200s, the oxidation temperature is 880℃ for 1450s, and the surface concentration is 3E20.

[0115] S5. After step S5, perform wet etching on the silicon wafer. The texturing reagent consists of the following components: 2.45% NaOH, 1.36% texturing additive, and 96.19% water; the reaction time is 250 seconds, and the reaction temperature is 68°C.

[0116] S6. After step S6 is completed, a passivation layer is deposited on the silicon wafer, forming a 6nm aluminum oxide layer and a 100nm silicon nitride layer on the front and back of the battery.

[0117] S7. After completing S7, screen print the silicon wafer. Then, use silver paste to fabricate electrodes on the front and back of the battery.

[0118] Comparative Example 5 This comparative example provides a method for preparing a photovoltaic cell, including: S1. Texturing the raw silicon wafer. The texturing reagent consists of the following components: 2.5% NaOH, 1.0% texturing additive, and 96.5% H2O; the reaction time is 380s, and the reaction temperature is 70℃.

[0119] S2. Boron diffusion is performed on the silicon wafer after step S1. The deposition temperature is 840℃, the deposition time is 500s, the boron source flow rate is 200sccm, the oxygen flow rate is 700sccm, the nitrogen flow rate is 2900sccm, the push temperature is 930℃, the time is 900s, the oxidation temperature is 1045℃, the time is 4200s, the textured region concentration is 4E18, and the doping depth is 1.0um.

[0120] S3. Polish the silicon wafer after step S2. The polishing reagent consists of the following components: 1.20% NaOH, 0.45% polishing additive, and 98.35% water; the reaction time is 300 seconds, and the reaction temperature is 79°C.

[0121] S4. After step S3, perform TOPCon passivation structure growth on the silicon wafer. LPCVD is used for in-situ growth. The tunnel oxide layer is grown at a deposition temperature of 610℃ for 500s, and the intrinsic amorphous silicon layer is grown at 605℃ for 1900s. For phosphorus doping, the deposition temperature is 815℃ for 1000s, the boron source flow rate is 1600 sccm, the oxidation flow rate is 800 sccm, the drive temperature is 920℃ for 1200s, the oxidation temperature is 880℃ for 1450s, and the surface concentration is 3E20.

[0122] S5. After completing step S4, perform laser patterning on the silicon wafer. The poly width of the secondary gate is 400um.

[0123] S6. After step S5, perform wet etching on the silicon wafer. The texturing reagent consists of the following components: 1.30% NaOH, 0.5% polishing additive, and 98.20% water; the reaction time is 270 seconds, and the reaction temperature is 68°C.

[0124] S7. After completing step S6, passivation layer coating is applied to the silicon wafer, forming a 6nm aluminum oxide layer and a 100nm silicon nitride layer on the front and back of the battery.

[0125] S8. After completing S7, screen print the silicon wafer. Then, use silver paste to fabricate electrodes on the front and back of the battery.

[0126] Test Example 1 The photovoltaic cells prepared in Examples 1-3 and Comparative Examples 1-4 were tested to detect the efficiency (Eta), short-circuit current (Isc), open-circuit voltage (Uoc), and fill factor (FF) of the photovoltaic cells, as shown in Table 1.

[0127] Table 1 Test results of photovoltaic cells

[0128] The pyramidal morphology of S6 was observed in Comparative Examples 2 and 3; the results are shown in [reference needed]. Figure 4 .

[0129] according to Figure 4 As shown in Table 1, the pyramid in Comparative Example 2 has no sharp points at the bottom, the pyramid in Comparative Example 3 has no sharp peaks at the top, and the pyramid in Example 3 has no sharp peaks at the top and bottom. The bifaciality of Comparative Examples 2 and 3 is lower than that of Example 3, indicating that setting a textured pyramid structure on the poly removal area, and having rounded corners at the top and bottom of the textured pyramid structure, can improve the bifaciality.

[0130] The above description is merely a preferred embodiment of this disclosure and is not intended to limit this disclosure. Various modifications and variations can be made to this disclosure by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this disclosure should be included within the scope of protection of this disclosure.

Claims

1. A photovoltaic cell, characterized in that, A textured pyramid structure is provided on the poly removal area of ​​the photovoltaic cell, and the top corner of the pyramid structure and the bottom corner of the pyramid structure are both rounded.

2. The photovoltaic cell according to claim 1, characterized in that, The radius of the apex is 60-100 degrees.

3. The photovoltaic cell according to claim 1, characterized in that, The radius of the bottom corner is 40-70 degrees.

4. The photovoltaic cell according to claim 1, characterized in that, The height of the velvet pyramid structure is 0.7-0.8 μm.

5. The photovoltaic cell according to claim 1, characterized in that, The photovoltaic cell also meets at least one of the following requirements: (1) A passivation layer is also provided on the velvet pyramid structure; (2) The photovoltaic cell further includes a poly finger region, and the ratio of the width of the poly finger region to the width of the poly removal region is (2:7)-(6:3). (3) The width of the poly removal region is 300-700μm.

6. A method for preparing a photovoltaic cell according to claim 1, characterized in that, include: Texturing is performed on the poly removal region of the photovoltaic cell; Then, round the corners.

7. The preparation method according to claim 6, characterized in that, By mass percentage, the composition of the flocking agent used in flocking includes: 1.74-2.81% alkali, 1.16-1.69% flocking additives, and the remainder is water.

8. The preparation method according to claim 6, characterized in that, The rounding reagent used for rounding treatment consists of two components: DC1 and DC2. By mass percentage, DC1 comprises 65-75% HNO3, 0.15-0.25% HF, and the remainder is water; DC2 comprises 0.6-0.9% HF, 70-90 ppm O3, and the remainder is water.

9. The preparation method according to claim 6, characterized in that, The conditions for rounding corners include: the rounding corner processing time is 8-12 minutes.

10. A rounded corner reagent, characterized in that, It includes DC1 and DC2, wherein, by mass percentage, DC1 includes 65-75% HNO3, 0.15-0.25% HF, and the remainder is water; DC2 includes 0.6-0.9% HF, 70-90 ppm O3, and the remainder is water.

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