A back-contact solar cell, a preparation method thereof, and a battery module

Abstract

The present invention belongs to the technical field of solar cells, and particularly relates to a back-contact solar cell, a preparation method thereof, and a battery module. In this back-contact solar cell, a carbon-doped silicon nitride layer is provided on the silicon nitride layer on the passivation layer. Since the carbon-doped silicon nitride film layer has strong acid resistance, it cannot be corroded by strong alkalis and is not easily corroded by strong acids in the texturing cleaning solution, reducing the corrosion rate of the film layer in HF acid. This is beneficial to the corrosion resistance of the subsequent film layers in the solution, maintaining the stability and consistency of the manufacturing process, and improving the production yield. At the same time, by setting the refractive indices of the silicon nitride layer and the carbon-doped silicon nitride layer included in the stacked antireflection layer to decrease sequentially from the inside to the outside, it is beneficial to maintaining the optical effect of the front antireflection layer of the battery and improving the optical performance.

Description

Technical Field

[0001] The present invention belongs to the technical field of solar cells, and particularly relates to a back-contact solar cell, a preparation method thereof, and a battery module. Background Art

[0002] When the existing back-contact solar cell is prepared, after a third semiconductor layer and an antireflection layer are formed on the front side of the silicon wafer, wet chemical cleaning is performed. In order to ensure good antireflection effect, the top layer of the existing antireflection layer generally adopts a nitrogen-rich silicon nitride film layer (nitrogen-rich means that the content of nitrogen is relatively high, and generally the refractive index of nitrogen-rich silicon nitride is below 1.98). However, the nitrogen-rich silicon nitride film layer generally has poor corrosion resistance to solutions. When the concentration of the solution fluctuates due to liquid replenishment or factors such as temperature, the film thickness of the antireflection layer will fluctuate greatly, and the antireflection effect will be greatly reduced, resulting in a decrease in the short-circuit current density of the battery and affecting the battery performance.

[0003] It should be noted that this part of the content of the present invention only provides the background technology related to the present invention, and does not necessarily constitute the prior art or the well-known technology. Summary of the Invention

[0004] The object of the present invention is to provide a back-contact solar cell, a preparation method thereof, and a battery module to solve the technical problem that the thickness of the antireflection layer on the front side of the solar cell is unstable, resulting in a decrease in the short-circuit current density.

[0005] To achieve the above object, in the first aspect, the present invention provides a back-contact solar cell, comprising:

[0006] A silicon wafer having a front side and a back side;

[0007] A first semiconductor layer disposed on the back side of the silicon wafer, the first semiconductor layer comprising a tunneling oxide layer and an N-type doped polysilicon layer formed in sequence on the back side of the silicon wafer; the first semiconductor layer is partitioned by a plurality of second semiconductor opening regions, and the second semiconductor opening regions and the surfaces of the first semiconductor layer around the second semiconductor opening regions are all covered with a second semiconductor layer; a first semiconductor opening region is provided between adjacent second semiconductor opening regions, and the first semiconductor opening region partitions the second semiconductor layer;

[0008] A passivation layer and a stacked antireflection layer, the passivation layer and the stacked antireflection layer are disposed on the front side of the silicon wafer in sequence; wherein, the stacked antireflection layer comprises a silicon nitride layer and a carbon-doped silicon nitride layer, and the silicon nitride layer is closer to the passivation layer than the carbon-doped silicon nitride layer; the total thickness of the stacked antireflection layer is 80-130 nm, wherein the thickness of the silicon nitride layer is 50-120 nm and the refractive index is 1.9-2.2; the thickness of the carbon-doped silicon nitride layer is 1-50 nm and the refractive index is 1.7-1.9.

[0009] Optionally, the carbon-doped silicon nitride layer is a carbon-doped silicon nitride film layer with the same concentration throughout the layer, and the carbon doping concentration is 1×10 18 ~9×10 19 cm -3 .

[0010] Optionally, the carbon doping concentration of the carbon-doped silicon nitride layer gradually increases from the side close to the silicon wafer to the side far from the silicon wafer, and the carbon doping concentration ranges from 1×10 18 ~9×10 19 cm -3 .

[0011] Optionally, the first semiconductor layer includes a tunneling silicon oxide layer and an N-type doped polysilicon layer. The thickness of the tunneling silicon oxide layer is 1 - 2 nm, and the thickness of the N-type doped polysilicon layer is 80 - 140 nm.

[0012] Optionally, the width of the first semiconductor opening region is 400 μm - 600 μm, and the width of the second semiconductor opening region is 200 μm - 300 μm.

[0013] Optionally, the back-contact solar cell further includes: an insulating groove; the insulating groove is located between adjacent first semiconductor opening regions and second semiconductor opening regions; a transparent conductive film layer covers both the first semiconductor opening region and the second semiconductor layer, and the insulating groove separates the transparent conductive film layer located in the first semiconductor opening region from the transparent conductive film layer located on the second semiconductor layer.

[0014] In a second aspect, the present invention further provides a method for manufacturing a back-contact solar cell for manufacturing the back-contact solar cell as described in the first aspect, including:

[0015] S1. Provide a double-sided polished silicon wafer;

[0016] S2. Form a first semiconductor layer and a mask layer on the back surface of the silicon wafer;

[0017] S3. Etch an opening on the back surface of the silicon wafer for the first time to form a second semiconductor opening region;

[0018] S4. Texturize and clean the front and back opening regions of the above silicon wafer;

[0019] S5. Form a passivation layer and a stacked antireflection layer on the front surface of the silicon wafer; the stacked antireflection layer includes a silicon nitride layer and a carbon-doped silicon nitride layer formed in sequence on the passivation layer;

[0020] When the stacked antireflection layer is deposited, the deposition temperature is 350 to 600 °C. When depositing the silicon nitride layer, the mass flow rate of silane is 800 to 2000 sccm, the mass flow rate of ammonia is 6000 to 15000 sccm, the deposition pressure is 1300 to 2500 mtorr, and the power is 5 kW to 20 kW; when depositing the carbon-doped silicon nitride layer, the mass flow rate of silane is 800 to 2000 sccm, the mass flow rate of ammonia is 6000 to 15000 sccm, the mass flow rate of methane is 500 to 2000 sccm, the deposition pressure is 1300 to 2500 mtorr, and the power is 5 kW to 20 kW;

[0021] S6. Remove the backside overplating and clean the second semiconductor opening area;

[0022] The removal of the backside overplating and the cleaning of the second semiconductor opening area are carried out using an HF acid solution. The mass percentage of HF acid in the HF acid solution is 1% to 10%, the mass percentage of deionized water is 90% to 99%, the treatment temperature is 20 °C to 30 °C, and the removal time is 30 to 500 s;

[0023] S7. Form a second semiconductor layer on the backside of the silicon wafer;

[0024] S8. Etch an opening on the backside of the silicon wafer for the second time to form a first semiconductor opening area;

[0025] S9. Deposit a transparent conductive film layer on the backside of the silicon wafer;

[0026] S10. Etch an opening on the backside of the silicon wafer for the third time to form an insulating groove;

[0027] S11. Form metal electrodes at the first semiconductor opening and the second semiconductor opening on the backside of the silicon wafer respectively.

[0028] Optionally, there is a certain positive correlation between the refractive index N of the silicon nitride layer and the carbon-doped silicon nitride layer in the stacked antireflection layer and its etching rate C1 (Å / S) in HF, specifically:

[0029] The relationship between the refractive index of the silicon nitride layer and the carbon-doped silicon nitride layer and the etching rate in 5% HF is:

[0030] N = 1.91 + 0.0319*C1 + 1.461*(C1~0.79125) 2 + 5.427*(C1~0.791) 3 .

[0031] Optionally, the cleaning time t ≤ D / (9C2), where t is in seconds, D is the total thickness of the stacked antireflection layer in angstroms, and C2 is the average etching rate of the stacked antireflection layer in 5% HF acid.

[0032] Optionally, in step S4, it includes:

[0033] The texturing solution is a mixed solution of potassium hydroxide or sodium hydroxide, a texturing additive and water, wherein the mass percentage of potassium hydroxide or sodium hydroxide is 1% - 5%, and the mass percentage of the texturing additive is 0.5% - 1%. The texturing time is 10 - 60 minutes, and the texturing temperature is 70°C - 85°C.

[0034] Optionally, in step S4, it further includes:

[0035] During the texturing cleaning process, the first mask layer on the back of the silicon wafer is also removed by the final cleaning solution. The solution used to remove the first mask layer is an HF acid solution. The mass percentage of HF acid in the HF acid solution is 0.5% - 5%, the mass percentage of hydrogen peroxide is 3% - 10%, and the mass percentage of deionized water is 95% - 99.5%. The treatment temperature is 20°C - 30°C, and the removal time is 60s - 500s.

[0036] In a third aspect, the present invention also provides a battery assembly, including: the back-contact solar cell as described in the first aspect.

[0037] The embodiments of the present invention at least have the following beneficial effects:

[0038] Through the above technical solutions of the present invention, by doping carbon into the silicon nitride layer, the carbon-doped silicon nitride film layer has strong acid resistance. In the texturing cleaning solution, it cannot be corroded by strong alkali and is not easily corroded by strong acid, reducing the corrosion rate of the film layer in HF acid. This is beneficial to the corrosion resistance of the subsequent film layer in the solution, maintaining the stability and consistency of the manufacturing process, and improving the production yield. At the same time, by setting that the refractive indices of the silicon nitride layer and the carbon-doped silicon nitride layer included in the stacked antireflection layer decrease from inside to outside, it is beneficial to maintaining the optical effect of the front antireflection layer of the battery and improving the optical performance. Description of the Drawings

[0039] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following will briefly introduce the drawings required to be used in the embodiments. It should be understood that the following drawings only show some embodiments of the present invention, and therefore should not be regarded as limiting the scope. For those of ordinary skill in the art, without creative efforts, other relevant drawings can also be obtained based on these drawings.

[0040] Figure 1 It is a schematic structural diagram of a back-contact solar cell provided by an embodiment of the present invention;

[0041] Figure 2A schematic diagram of the relationship between the refractive index of a film layer of a back-contact solar cell and the corrosion rate of the film layer in HF acid provided by an embodiment of the present invention;

[0042] Figure 3 A schematic flow chart of a method for preparing a back-contact solar cell provided in an embodiment of the present invention.

[0043] In the figure:

[0044] 1-silicon wafer; 2-tunneling silicon oxide layer; 3-type doped polysilicon layer; 4-passivation layer; 5-stacked anti-reflection layer; 51-silicon nitride layer; 52-carbon-doped silicon nitride layer; 6-intrinsic hydrogenated amorphous silicon layer; 7-P-type doped amorphous silicon layer or P-type microcrystalline silicon layer; 8-transparent conductive film layer; 9-metal electrode. DETAILED DESCRIPTION

[0045] In the present invention, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0046] In the present invention, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may mean that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. Moreover, a first feature being "above", "above" or "above" a second feature may mean that the first feature is directly above or obliquely above the second feature, or simply means that the first feature is higher in level than the second feature. A first feature being "below", "below" or "below" a second feature may mean that the first feature is directly below or obliquely below the second feature, or simply means that the first feature is lower in level than the second feature.

[0047] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article. Among them, the terms "optional" and "optional" all mean that they may be included or not included (or may be present or not).

[0048] like Figure 1 As shown, an embodiment of the present invention provides a back contact solar cell, comprising:

[0049] Silicon wafer 1 with a front side and a back side. The silicon wafer 1 serves as a base layer and is generally polished to improve the adhesion of subsequent film layers, thereby enhancing the film layer stability.

[0050] A first semiconductor layer is disposed on the back side of the silicon wafer 1. The first semiconductor layer includes a tunneling silicon oxide layer 2 and an N-type doped polysilicon layer 3 formed in sequence on the back side of the silicon wafer 1. The first semiconductor layer is partitioned by a plurality of second semiconductor opening regions W2. The second semiconductor opening regions W2 and the surface of the first semiconductor layer around the second semiconductor opening regions are all covered with a second semiconductor layer. A first semiconductor opening region W1 is provided between adjacent second semiconductor opening regions, and the first semiconductor opening region W1 partitions the second semiconductor layer. The semiconductor film layers of the first semiconductor region and the second semiconductor region finally form the P region and the N region of the solar cell.

[0051] A passivation layer 4 and a stacked antireflection layer 5 are disposed on the front side of the silicon wafer 1 in sequence. Among them, the stacked antireflection layer 5 includes a silicon nitride layer 51 and a carbon-doped silicon nitride layer 52. The silicon nitride layer 51 is closer to the passivation layer 4 than the carbon-doped silicon nitride layer 52, that is, the silicon nitride layer 51 is on the inner side and the carbon-doped silicon nitride layer 52 is on the outer side, so as to protect the inner silicon nitride layer 51. Among them, the total thickness of the stacked antireflection layer 5 is 80 - 130 nm, the thickness of the silicon nitride layer 51 is 50 - 120 nm, and the refractive index is 1.9 - 2.2; the thickness of the carbon-doped silicon nitride layer 52 is 1 - 50 nm, and the refractive index is 1.7 - 1.9.

[0052] As Figure 2 is a schematic diagram of the relationship between the refractive index of the carbon-doped silicon nitride layer 52 and its etching rate in HF acid. It can be seen from Figure 2 that there is a certain positive correlation between the refractive index of the film layer in the present invention and the etching rate of the film layer in HF, that is, the smaller the refractive index of the film layer, the slower its corresponding etching rate. Thus, reducing the refractive index of the film layer by carbon doping is beneficial to reducing the etching rate, thereby protecting the inner silicon nitride layer 51 and further improving the film layer stability of the silicon nitride layer 51.

[0053] It should be noted that the carbon-doped silicon nitride layer 52 is formed by doping carbon elements during the preparation of silicon nitride. The specific implementation form of carbon doping is, for example, adding methane to the reaction gas for preparing the silicon nitride layer 51.

[0054] In the back-contact solar cell of the present invention, by carbon-doping the silicon nitride layer 51, the carbon-doped silicon nitride film layer has strong acid resistance. In the texturing and cleaning solution, it can neither be corroded by strong alkali nor easily corroded by strong acid, thereby reducing the corrosion rate of the film layer in HF acid (hydrofluoric acid). This is beneficial to the corrosion resistance of the subsequent film layer in the solution, maintaining the stability and consistency of the process, and improving the production yield. At the same time, by arranging the silicon nitride layer 51 and the carbon-doped silicon nitride layer 52 included in the stacked anti-reflection layer 5, the refractive index decreases from the inside to the outside, which is beneficial to maintaining the optical effect of the anti-reflection layer on the front side of the battery and improving the optical performance.

[0055] Optionally, the carbon-doped silicon nitride layer 52 is a carbon-doped silicon nitride film layer with the same concentration throughout, that is, the doping concentration of each region of the carbon-doped silicon nitride layer 52 is the same, and the carbon doping concentration is 1×10 18 ~9×10 19 cm -3 .

[0056] Optionally, the carbon-doped silicon nitride layer 52 has a carbon-doping concentration that gradually increases from a side close to the silicon wafer 1 to a side away from the silicon wafer 1 , that is, the carbon-doping concentration is lower near the inner layer and higher near the outer layer.

[0057] Optionally, the carbon doping concentration ranges from low to high 1×10 18 ~9×10 19 cm -3 , that is, the carbon doping concentration varies within this range. Specifically, for every increase of 1 / 3-1 / 5 of the thickness, the doping concentration is 0.5-4 times the doping concentration of the previous layer. For example, the initial concentration is 1×10 18 cm -3 , the doping concentration of each 1 / 3 thickness is 2.5 times the doping concentration of the previous layer, so the concentration gradient is 1×10 18 cm -3 , 2.5×10 18 cm -3 , 6.25×10 18 cm -3 The increase in doping concentration gradient is beneficial to improving the corrosion resistance of the film while ensuring the optical effect.

[0058] Optionally, the thickness ratio of the silicon nitride layer 51 to the carbon-doped silicon nitride layer 52 is 1:(0.0083-1), and the etching rate of the carbon-doped silicon nitride layer 52 in a 5% HF solution is ≤0.05nm / s. By controlling the appropriate film thickness ratio and etching rate, it is beneficial to improve the stability and yield of the process while taking into account the optical effect.

[0059] Optionally, the first semiconductor layer includes a tunneling silicon oxide layer 2 and an N-type doped polysilicon layer 3. The thickness of the tunneling silicon oxide layer 2 is 1 to 2 nm, and the thickness of the N-type doped polysilicon layer 3 is 80 to 140 nm.

[0060] Optionally, the width of the first semiconductor opening region is 400 μm to 600 μm, and the width of the second semiconductor opening region is 200 μm to 300 μm.

[0061] Optionally, the back-contact solar cell further includes: an insulating groove; the insulating groove is located between the adjacent first semiconductor opening region and the second semiconductor opening region. A transparent conductive film layer 8 is covered on both the first semiconductor opening region and the second semiconductor layer, and the insulating groove separates the transparent conductive film layer 8 located in the first semiconductor opening region from the transparent conductive film layer 8 located on the second semiconductor layer.

[0062] In a second aspect, as Figure 3 shown, an embodiment of the present invention further provides a method for manufacturing a back-contact solar cell for manufacturing the back-contact solar cell as described in the foregoing embodiments. The manufacturing method includes:

[0063] S1. Provide a double-sided polished silicon wafer 1.

[0064] Specifically, the silicon wafer 1 has a front side and a back side, which are polished to achieve this. Among them, the front side refers to the light-receiving surface of the silicon wafer 1, and the back side is the opposite side of the light-receiving surface. In the embodiment of the present invention, usually, the side close to the silicon wafer 1 is the inner side, and the side far from the silicon wafer 1 is the outer side. Optionally, the silicon wafer 1 is an N-type single-crystal silicon wafer 1, for example: a Czochralski single-crystal silicon wafer 1 or a cast single-crystal silicon wafer 1.

[0065] S2. Form a first semiconductor layer and a mask layer on the back side of the silicon wafer 1.

[0066] Optionally, the first semiconductor layer includes a tunneling silicon oxide layer 2 and an N-type doped polysilicon layer 3. The thickness of the tunneling silicon oxide layer 2 is 1 - 2 nm, and the thickness of the N-type doped polysilicon layer 3 is 80 - 140 nm. Both the tunneling silicon oxide layer 2 and the N-type doped polysilicon layer 3 are sequentially deposited and annealed at high temperature using a tube-type polysilicon deposition furnace. The deposition temperature is 400 - 500 °C. When depositing the tunneling oxide layer, the mass flow rate of nitrous oxide is 8000 - 1200 sccm, the pressure is 100 - 200 Pa, the power of the power supply is 3 - 20 KW, and the time is 20 - 100 seconds; when depositing the N-type doped polysilicon layer 3, the mass flow rate of silane is 1000 - 3000 sccm, the mass flow rate of phosphine (2% PH3 and 98% H2) is 1000 - 2500 sccm, the mass flow rate of hydrogen is 7000 - 9000 sccm, the pressure is 100 - 300 Pa, the power of the power supply is 5 - 20 KW, and the time is 800 - 1300 seconds.

[0067] S3. Etch an opening on the back side of the silicon wafer 1 for the first time to form a second semiconductor opening area.

[0068] Optionally, the first etching of the opening can be carried out by laser or mask etching, as long as the second semiconductor opening area can be formed; among them, the laser can be ultraviolet or green laser, the pulse width is less than 10 ns, and the width of the formed second semiconductor opening area is 400 - 600 μm.

[0069] S4. Texturize and clean the front and back opening areas of the above-mentioned silicon wafer 1.

[0070] Specifically, the texturing solution is a mixed solution of potassium hydroxide or sodium hydroxide, a texturing additive, and water, where the mass percentage content of potassium hydroxide or sodium hydroxide is 1% - 5%, and the mass percentage content of the texturing additive is 0.5% - 1%. The texturing time is 10 - 60 minutes, and the texturing temperature is 70 °C - 85 °C.

[0071] S5. Form a passivation layer 4 and a stacked antireflection layer 5 on the front side of the silicon wafer 1; the stacked antireflection layer 5 includes a silicon nitride layer 51 and a carbon-doped silicon nitride layer 52 formed sequentially on the passivation layer 4.

[0072] When the stacked antireflection layer 5 is deposited, the deposition temperature is 350 - 600 °C. When depositing the silicon nitride layer 51, the mass flow rate of silane is 800 - 2000 sccm, the mass flow rate of ammonia is 6000 - 15000 sccm, the deposition pressure is 1300 - 2500 mtorr, and the power is 5 kw - 20 kw; when depositing the carbon-doped silicon nitride layer 52, the mass flow rate of silane is 800 - 2000 sccm, the mass flow rate of ammonia is 6000 - 15000 sccm, the mass flow rate of methane is 500 - 2000 sccm, the deposition pressure is 1300 - 2500 mtorr, and the power is 5 kw - 20 kw. That is, by adding methane, carbon doping of the silicon nitride film layer is achieved, thereby forming the carbon-doped silicon nitride layer 52.

[0073] Optionally, there is a certain positive correlation between the refractive index N of the silicon nitride layer 51 and the carbon-doped silicon nitride layer 52 in the stacked antireflection layer 5 and its etching rate C1 (Å / S) in HF, specifically:

[0074] The relationship between the refractive index of the silicon nitride layer 51 and the carbon-doped silicon nitride layer 52 and the etching rate in 5% HF is:

[0075] N = 1.91 + 0.0319*C1 + 1.461*(C1~0.79125) 2 + 5.427*(C1~0.791) 3 .

[0076] By regulating the relationship between the refractive index and the etching rate, it is beneficial to control a certain HF cleaning time during subsequent solution cleaning, improve the cleaning effect of the second semiconductor layer, and maintain a good antireflection effect on the front side.

[0077] S6. Remove the backside overplating and clean the second semiconductor opening area.

[0078] The removal of the backside overplating and the cleaning of the second semiconductor opening area are carried out using an HF acid solution. The mass percentage of HF acid in the HF acid solution is 1% - 10%, the mass percentage of deionized water is 90% - 99%, the treatment temperature is 20 °C - 30 °C, and the removal time is 30 - 500 s.

[0079] Optionally, the cleaning time t ≤ D / (9C2), where t is in units of S, D is the total thickness of the stacked antireflection layer 5 in units of Å, and C2 is the average etching rate of the stacked antireflection layer 5 in 5% HF acid.

[0080] In this embodiment, by controlling the cleaning time, the backside overplating can be effectively removed, and the thickness of the front antireflection layer can be effectively maintained, improving the antireflection effect on the front side.

[0081] S7. Form a second semiconductor layer on the back surface of the silicon wafer 1.

[0082] Optionally, the second semiconductor layer is formed by plate CVD. The thickness of the intrinsic hydrogenated amorphous silicon layer 6 is 4 - 8 nm, and the thickness of the P-type doped amorphous silicon layer or P-type microcrystalline silicon layer 7 is 6 - 12 nm. The deposition temperature of the second semiconductor layer is 150 - 250 °C.

[0083] S8. Etch an opening on the back surface of the silicon wafer 1 for the second time to form a first semiconductor opening region.

[0084] Optionally, the second etching of the opening is carried out by laser. The laser can be ultraviolet or green laser, and the pulse width is less than 10 ns. The width of the formed first semiconductor opening region is 200 - 300 μm.

[0085] S9. Deposit a transparent conductive film layer 8 on the back surface of the silicon wafer 1.

[0086] Optionally, physical vapor deposition technology (PVD) or reactive plasma deposition technology (RPD) is used to deposit a transparent conductive film on the back surface of the silicon wafer 1. The thickness of the transparent conductive film is 40 - 80 nm, and the material of the transparent conductive film can be indium oxide-based thin film doped with tin / tungsten / titanium / zinc or zinc oxide-based thin film doped with aluminum / boron.

[0087] S10. Etch an opening on the back surface of the silicon wafer 1 for the third time to form an insulating groove.

[0088] Optionally, a mask etching or laser method is used to etch an opening on the back surface of the silicon wafer 1 to form an insulating groove W3 between the first semiconductor and the second semiconductor. The width of the insulating groove W3 is 20 - 100 μm, and the resistance between the first semiconductor and the second semiconductor after etching is greater than 1 KΩ.

[0089] S11. Form metal electrodes 9 at the first semiconductor opening and the second semiconductor opening on the back surface of the silicon wafer 1 respectively.

[0090] Optionally, screen printing technology is used to form metal electrodes 9 on the surfaces of the first semiconductor opening region W1 and the second semiconductor opening region W2 on the back surface of the silicon wafer 1.

[0091] In a third aspect, an embodiment of the present invention further provides a battery module, including: a back contact solar cell as described in the foregoing embodiment.

[0092] The embodiments of the present invention are described in detail below. They are exemplary and are only used to explain the present invention and should not be construed as a limitation of the present invention.

[0093] Embodiment 1

[0094] As Figure 1 shown, a back contact solar cell includes:

[0095] A silicon wafer 1 having a front side and a back side. The silicon wafer 1 serves as a base layer and is generally polished to improve the adhesion of subsequent film layers, thereby enhancing the film layer stability.

[0096] A first semiconductor layer is disposed on the back side of the silicon wafer 1. The first semiconductor layer includes a tunneling silicon oxide layer 2 and an N-type doped polysilicon layer 3 formed in sequence on the back side of the silicon wafer 1. The first semiconductor layer is partitioned by a plurality of second semiconductor opening regions W2. The second semiconductor opening regions W2 and the surface of the first semiconductor layer around the second semiconductor opening regions are all covered with a second semiconductor layer. A first semiconductor opening region W1 is provided between adjacent second semiconductor opening regions, and the first semiconductor opening region W1 partitions the second semiconductor layer. The semiconductor film layers of the first semiconductor region and the second semiconductor region finally form the P region and the N region of the solar cell.

[0097] A passivation layer 4 and a stacked antireflection layer 5 are disposed on the front side of the silicon wafer 1 in sequence. Among them, the stacked antireflection layer 5 includes a silicon nitride layer 51 and a carbon-doped silicon nitride layer 52. The silicon nitride layer 51 is closer to the passivation layer 4 than the carbon-doped silicon nitride layer 52. The total thickness of the stacked antireflection layer 5 is 110 nm, where the thickness of the silicon nitride layer 51 is 80 nm and the refractive index is 2.1. The thickness of the carbon-doped silicon nitride layer 52 is 30 nm and the refractive index is 1.8.

[0098] The embodiment of the present invention also provides a preparation method for the above-mentioned back-contact solar cell. When forming the carbon-doped silicon nitride layer 52 of the stacked antireflection layer 5 on the front side of the silicon wafer 1, the mass flow rate of silane is 1200 sccm, the mass flow rate of ammonia is 10800 sccm, the mass flow rate of methane is 1200 sccm, the deposition pressure is 1700 mtorr, the power is 12 kw, and the carbon doping concentration is 8.5×10 18 cm -3 .

[0099] Example 2

[0100] Referring to the back-contact solar cell of Example 1, the difference is that the total thickness of the stacked antireflection layer 5 is 80 nm, and the thickness of the silicon nitride layer 51 is 50 nm.

[0101] Example 3

[0102] Referring to the back-contact solar cell of Example 1, the difference is that the thickness of the silicon nitride layer 51 is 60 nm, and the thickness of the carbon-doped silicon nitride layer 52 is 50 nm.

[0103] Example 4

[0104] Referring to the back-contact solar cell of Embodiment 1, the difference is that the refractive index of the silicon nitride layer 51 is 1.95.

[0105] Embodiment 5

[0106] Referring to the back-contact solar cell of Embodiment 1, the difference is that the refractive index of the carbon-doped silicon nitride is 1.9.

[0107] Embodiment 6

[0108] Referring to the back-contact solar cell of Embodiment 1, the difference is that the carbon doping content in the carbon-doped silicon nitride layer 52 is 1.2×10 18 cm -3 .

[0109] Embodiment 7

[0110] Referring to the back-contact solar cell of Embodiment 1, the difference is that when depositing the carbon-doped silicon nitride layer 52, the deposition pressure is 1400 mtorr and the power is 9.5 kw.

[0111] Embodiment 8

[0112] Referring to the back-contact solar cell of Embodiment 1, the difference is that when depositing the carbon-doped silicon nitride layer 52, the deposition pressure is 1800 mtorr and the power is 16.5 kw.

[0113] Comparative Example 1

[0114] Referring to the back-contact solar cell of Embodiment 1, the difference is that the carbon-doped silicon nitride layer 52 is not provided, that is, it is all silicon nitride layer 51.

[0115] Comparative Example 2

[0116] Referring to the back-contact solar cell of Embodiment 1, the difference is that the antireflection layer is only the carbon-doped silicon nitride layer 52, and the thickness of the carbon-doped silicon nitride layer 52 is 110 nm and the refractive index is 1.8.

[0117] Comparative Example 3

[0118] Referring to the back-contact solar cell of Embodiment 1, the difference is that, referring to the back-contact solar cell of Embodiment 1, the difference is that the total thickness of the stacked antireflection layer 5 is 150 nm and the thickness of the silicon nitride is 140 nm.

[0119] Comparative Example 4

[0120] Referring to the back-contact solar cell of Embodiment 1, the difference is that, referring to the back-contact solar cell of Embodiment 1, the difference is that the total thickness of the stacked antireflection layer 5 is 70 nm and the thickness of the silicon nitride is 20 nm.

[0121] Comparative Example 5

[0122] Referring to the back-contact solar cell of Example 1, the difference is that the carbon doping content in the carbon-doped silicon nitride layer 52 is 1.9×10 20 cm -3 .

[0123] Test Example

[0124] The performance of the back-contact solar cells obtained in the above examples and comparative examples (including: thickness uniformity of the antireflection layer after passing through the solution, current density, open-circuit voltage, and conversion efficiency) was tested. The specific test results are shown in Table 1 below. Among them, the thickness uniformity of the antireflection layer after passing through the solution = (maximum value - minimum value) / (maximum value + minimum value) of the film layer thickness.

[0125] Table 1 Comparison of battery performance of different examples and comparative examples

[0126]

[0127] It can be seen from the above results that compared with the comparative example, adopting the embodiment scheme of the present invention can take into account both the thickness uniformity of the film layer and the electrical performance of the battery, which is beneficial to the stability of the efficiency. Further, according to Example 1 and Examples 2 to 8, adopting the preferred stacked antireflection layer scheme of the present invention can ensure the thickness uniformity of the film layer and is more beneficial to improving the conversion efficiency of the battery.

[0128] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited thereto. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solutions of the present invention, including any other suitable combination of each technical feature. These simple modifications and combinations should also be regarded as the content disclosed by the present invention and fall within the protection scope of the present invention.

Claims

1. A back contact solar cell, characterized in that: include: A silicon wafer having a front side and a back side; A first semiconductor layer is arranged on the back side of the silicon wafer, the first semiconductor layer comprises a tunneling silicon oxide layer and an N-type doped polysilicon layer sequentially formed on the back side of the silicon wafer; the first semiconductor layer is separated by a plurality of second semiconductor opening regions, the second semiconductor opening regions and the surface of the first semiconductor layer around the second semiconductor opening regions are covered with the second semiconductor layer; a first semiconductor opening region is provided between adjacent second semiconductor opening regions, the first semiconductor opening region separates the second semiconductor layer; A passivation layer and a laminated anti-reflection layer, wherein the passivation layer and the laminated anti-reflection layer are sequentially arranged on the front side of the silicon wafer; wherein the laminated anti-reflection layer comprises a silicon nitride layer and a carbon-doped silicon nitride layer, wherein the silicon nitride layer is closer to the passivation layer than the carbon-doped silicon nitride layer; wherein the total thickness of the laminated anti-reflection layer is 80-130 nm, wherein the thickness of the silicon nitride layer is 50-120 nm, and the refractive index is 1.9-2.2; and the thickness of the carbon-doped silicon nitride layer is 1-50 nm, and the refractive index is 1.7-1.9; The carbon doping concentration of the carbon-doped silicon nitride layer gradually increases from the side close to the silicon wafer to the side away from the silicon wafer, and the carbon doping concentration ranges from low to high, and is 1×10 18 ~9×10 19 cm -3 .

2. The back contact solar cell according to claim 1, characterized in that: The first semiconductor layer includes a tunneling silicon oxide layer and an N-type doped polysilicon layer. The thickness of the tunneling silicon oxide layer is 1-2 nm, and the thickness of the N-type doped polysilicon layer is 80-140 nm.

3. The back contact solar cell according to claim 1, characterized in that: The width of the first semiconductor opening region is 400 μm to 600 μm, and the width of the second semiconductor opening region is 200 μm to 300 μm.

4. The back contact solar cell according to claim 1, characterized in that: Also includes: Insulation slot; The insulating groove is located between the adjacent first semiconductor opening region and the second semiconductor opening region; The first semiconductor opening region and the second semiconductor layer are both covered with a transparent conductive film layer, and the insulating groove separates the transparent conductive film layer located in the first semiconductor opening region from the transparent conductive film layer located on the second semiconductor layer.

5. A method for preparing a back-contact solar cell, for preparing the back-contact solar cell according to any one of claims 1 to 4, characterized in that: include: S1. Provide a double-sided polished silicon wafer; S2, forming a first semiconductor layer and a mask layer on the back side of the silicon wafer; S3, etching an opening on the back side of the silicon wafer for the first time to form a second semiconductor opening region; S4, texturing and cleaning the front and back opening areas of the silicon wafer; S5, forming a passivation layer and a laminated anti-reflection layer on the front side of the silicon wafer; the laminated anti-reflection layer comprises a silicon nitride layer and a carbon-doped silicon nitride layer sequentially formed on the passivation layer; The deposition temperature of the stacked anti-reflection layer is 350-600° C., wherein when depositing the silicon nitride layer, the mass flow rate of silane is 800-2000 sccm, the mass flow rate of ammonia is 6000-15000 sccm, the deposition pressure is 1300-2500 mtorr, and the power is 5 kW-20 kW; when depositing the carbon-doped silicon nitride layer, the mass flow rate of silane is 800-2000 sccm, the mass flow rate of ammonia is 6000-15000 sccm, the mass flow rate of methane is 500-2000 sccm, the deposition pressure is 1300-2500 mtorr, and the power is 5 kW-20 kW; S6, removing the back side coating and cleaning the second semiconductor opening area; The method of removing the back side coating and cleaning the second semiconductor opening area adopts HF acid solution, wherein the mass percentage of HF acid in the HF acid solution is 1% to 10%, the mass percentage of deionized water is 90% to 99%, the processing temperature is 20° C. to 30° C., and the removal time is 30 to 500 seconds; S7, forming a second semiconductor layer on the back side of the silicon wafer; S8, etching an opening on the back side of the silicon wafer for the second time to form a first semiconductor opening region; S9, depositing a transparent conductive film layer on the back side of the silicon wafer; S10, etching an opening on the back side of the silicon wafer for the third time to form an insulating groove; S11, forming metal electrodes at the first semiconductor opening and the second semiconductor opening on the back side of the silicon wafer respectively.

6. The method for preparing a back-contact solar cell according to claim 5, characterized in that: The refractive index N of the silicon nitride layer and the carbon-doped silicon nitride layer in the stacked anti-reflection layer has a certain positive correlation with the corrosion rate C1 (Å / S) thereof in HF, specifically: The etching rate relationship between the refractive index of the silicon nitride layer and the carbon-doped silicon nitride layer in 5% HF is: N = 1.91 + 0.0319*C1 + 1.461*(C1~0.79125) 2 + 5.427*(C1~0.791) 3 。 7. The method for preparing a back contact solar cell according to claim 5, characterized in that: The cleaning time t≤D / (9C2), t is in S, D is the total thickness of the laminated anti-reflection layer in Å, and C2 is the average corrosion rate of the laminated anti-reflection layer in 5% HF acid.

8. The method for preparing a back-contact solar cell according to claim 6, characterized in that: In step S4, it includes: The texturing liquid for texturing cleaning is a mixture of potassium hydroxide or sodium hydroxide, texturing additives and water, wherein the mass percentage of potassium hydroxide or sodium hydroxide is 1%~5%, the mass percentage of texturing additives is 0.5%~1%, the texturing time is 10~60 minutes, and the texturing temperature is 70℃~85℃.

9. The method for preparing a back-contact solar cell according to claim 6, characterized in that: In step S4, it also includes: During the texturing and cleaning process, the first mask layer on the back of the silicon wafer is also removed through the final cleaning solution. The solution used to remove the first mask layer is HF acid solution. The mass percentage of HF acid in the HF acid solution is 0.5%~5%, the mass percentage of hydrogen peroxide is 3%~10%, and the mass percentage of deionized water is 95%~99.5%. The processing temperature is 20℃~30℃, and the removal time is 60s~500s.

10. A battery assembly, characterized in that: include: A back-contact solar cell as claimed in any one of claims 1 to 4.

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