A passivated contact solar cell and methods of making, assemblies, and systems thereof

Abstract

The present application relates to the technical field of photovoltaic cells, and particularly relates to a passivated contact solar cell, a preparation method, an assembly and a system thereof. The passivated contact solar cell comprises a silicon substrate, a p+ emitter, a front passivation anti-reflection film and a front electrode arranged on the surface of the p+ emitter and extending to the outside of the front passivation anti-reflection film in sequence on the front side of the silicon substrate, a tunneling oxide layer, a doped polysilicon layer, a back passivation film and a back electrode arranged on the back side of the silicon substrate in sequence, the surface of the doped polysilicon layer is a secondary light trapping structure, and the back electrode is arranged on the surface of the secondary light trapping structure through the back passivation film. The thickness of the back passivation film is 40-110 nm. The passivated contact solar cell can reduce the light reflectivity of the back side of the cell, reduce the contact resistance, improve the fill factor, and basically will not increase the recombination, so as to effectively improve the cell efficiency.

Description

Technical Field

[0001] This invention relates to the field of photovoltaic cell technology, specifically to a passivated contact solar cell and its preparation method, components, and system. Background Technology

[0002] With the development of solar cell technology, the demand for cell efficiency is increasing. Currently, the main high-efficiency cells in mass production are HIT and TOPCon. However, due to the high equipment investment cost, HIT cells cannot be widely adopted unless the issue of domestic equipment production is resolved in the short term. TOPCon cells, on the other hand, have a much lower investment cost than HIT cells because their process steps and equipment are compatible with the current mainstream PERC cells. Furthermore, TOPCon cells have a theoretical maximum efficiency of 28.7%, which is closest to the theoretical maximum efficiency of crystalline silicon (29.43%), making them a likely next-generation market favorite.

[0003] TOPCon cells are mainly based on PERT cells, with an ultrathin tunneling oxide layer combined with a heavily doped polycrystalline silicon layer deposited on the back of the cell. The tunneling oxide layer can reduce interfacial recombination between the silicon substrate and polycrystalline silicon through chemical passivation. Majority carriers are transported through tunneling, while minority carriers are difficult to tunnel through the oxide layer into the silicon substrate to be recombinated due to the potential barrier and the field effect of polycrystalline silicon. Therefore, better surface passivation and contact performance can be obtained.

[0004] However, the passivation contact structure on the back of existing TOPCon cells consists of an ultrathin tunneling oxide layer and a doped polycrystalline silicon layer. Specifically, the back of a typical TOPCon cell undergoes acid or alkali etching or polishing, resulting in an etched or polished surface. Then, a tunneling oxide layer and a doped polycrystalline silicon layer are deposited, followed by the deposition of front and back passivation films, and finally, the front and back metal electrodes are printed. Because the back of this existing TOPCon cell has an etched or polished surface, its light reflectivity is high, leading to low light utilization on the back side. This, in turn, results in low bifaciality and low cell efficiency. Furthermore, the specific surface area of ​​the doped polycrystalline silicon layer in contact with the back metal electrodes is low, resulting in high contact resistance, further hindering cell efficiency improvement. Application number CN201810660527.5 discloses a method for preparing a high-efficiency light-trapping textured surface using reactive ion etching (RIE). This method involves RIE on a silicon substrate with a gold nanoparticle mask to create a highly efficient textured surface with a serrated structure on the silicon substrate surface. While this can reduce light reflectivity and improve the silicon substrate's absorption efficiency of sunlight and the battery's photoelectric conversion efficiency, this method requires the preparation of gold nanoparticles as a mask before RIE, and the removal of the gold nanoparticle mask after RIE. This process is complex and cumbersome. Furthermore, the highly efficient textured surface with a serrated structure directly contacts the silicon substrate surface, which significantly increases recombination, reduces open-circuit voltage, and consequently decreases battery efficiency. Summary of the Invention

[0005] One of the objectives of this invention is to overcome the shortcomings of the prior art and provide a passivated contact solar cell that can reduce the light reflectivity on the back of the cell, reduce the contact resistance, increase the fill factor, and basically not increase recombination, thus effectively improving the cell efficiency.

[0006] The second objective of this invention is to provide a method for preparing passivated contact solar cells. This method eliminates the need for masking and mask removal steps, simplifying the process and making preparation easier, thus making it suitable for large-scale production.

[0007] A third objective of this invention is to provide a solar cell module employing the passivated contact solar cell.

[0008] The fourth objective of this invention is to provide a solar cell system that uses the solar cell module.

[0009] Based on this, the present invention discloses a passivated contact solar cell, comprising a silicon substrate. The front side of the silicon substrate is sequentially provided with a p+ emitter, a front passivation antireflection film, and a front electrode disposed on the surface of the p+ emitter and extending beyond the front passivation antireflection film. The back side of the silicon substrate is sequentially provided with a tunneling oxide layer, a doped polycrystalline silicon layer, a back passivation film, and a back electrode. The surface of the doped polycrystalline silicon layer is a secondary light-trapping structure. The back electrode is disposed on the surface of the secondary light-trapping structure via the back passivation film. The thickness of the back passivation film is 40–110 nm.

[0010] Preferably, the front side of the silicon substrate is a light-trapping structure, and the back side of the silicon substrate is a planar structure or a light-trapping structure.

[0011] More preferably, the secondary light-trapping structure is a nanoscale porous structure with a pore size of 50–300 nm and a pore depth of 50–300 nm.

[0012] Preferably, the silicon substrate is an N-type silicon substrate.

[0013] Preferably, the p+ emitter is a boron-doped p+ emitter, and the doped polycrystalline silicon layer is a phosphorus-doped n+ polycrystalline silicon layer.

[0014] Preferably, the tunneling oxide layer is silicon oxide with a thickness of 1 to 2 nm.

[0015] Preferably, the front passivation antireflection film is an antireflection film with an aluminum oxide passivation layer; the back passivation film is a silicon nitride passivation film.

[0016] This invention also discloses a method for preparing a passivated contact solar cell, comprising the following steps:

[0017] Step S1: The p+ emitter is fabricated on the front side of the silicon substrate;

[0018] Step S2: Prepare the tunneling oxide layer on the back side of the silicon substrate;

[0019] Step S3: Prepare the doped polycrystalline silicon layer on the surface of the tunneling oxide layer;

[0020] Step S4: Perform reactive ion etching on the back side of the doped polysilicon layer to form the secondary light-trapping structure on the surface of the doped polysilicon layer, and then prepare the back passivation film on the surface of the secondary light-trapping structure.

[0021] Step S5: Prepare the front passivation antireflection film on the surface of the p+ emitter, and then perform metallization treatment to form the front electrode extending beyond the front passivation antireflection film on the surface of the p+ emitter, and form the back electrode extending beyond the back passivation film on the surface of the secondary light-trapping structure of the doped polysilicon layer.

[0022] Preferably, before step S1, the method further includes a step of pre-treating the silicon substrate to form the light-trapping structure on the front and back sides of the silicon substrate;

[0023] Before step S3, the method further includes etching or polishing the back side of the silicon substrate to form the planar structure on the back side of the silicon substrate.

[0024] Preferably, in step S4, the specific steps for forming the secondary light-trapping structure are as follows: placing the silicon substrate processed in step S3 into a chemical vapor deposition reaction chamber and evacuating it to 10... -4 When the pressure is below Pa, SF6 and O2 gases are introduced to generate plasma for selective reactive ion etching of the surface of the doped polycrystalline silicon layer to form the secondary light-trapping structure.

[0025] The present invention also discloses a solar cell module, comprising, from top to bottom, a front material layer, a front encapsulation layer, a solar cell, a back encapsulation layer, and a back material layer, wherein the solar cell is a passivated contact solar cell as described above in the present invention.

[0026] The present invention also discloses a solar cell system, comprising one or more solar cell modules, wherein the solar cell module is one of the solar cell modules described above.

[0027] Compared with the prior art, the present invention has at least the following beneficial effects:

[0028] This invention provides a secondary light-trapping structure on the surface of a doped polycrystalline silicon layer on the back side of a passivated contact solar cell, and places the back electrode on the surface of the secondary light-trapping structure via a back passivation film. This results in a novel TOPCon cell structure, which offers the following advantages:

[0029] (1) Compared to the etched or polished surface on the back of existing TOPCon cells, the secondary light-trapping structure set on the back surface of the doped polycrystalline silicon layer and the back passivation film has a lower light reflectivity, which can effectively reduce the light reflectivity on the back of the TOPCon cell, improve the bifaciality, and thus improve the overall power of the cell. Moreover, the back passivation film with a thickness of 40-110 nm and the secondary light-trapping structure can enable the back of the cell to absorb more sunlight, thus improving the bifaciality. (2) The surface area of ​​the secondary light-trapping structure in contact with the back electrode is increased, which can obtain a lower contact resistance, thereby improving the fill factor. At the same time, since the secondary light-trapping structure is on the back surface of the doped polycrystalline silicon layer and does not directly contact the silicon substrate, even if lattice defects are introduced to the surface of the doped polycrystalline silicon layer during the preparation of the secondary light-trapping structure, it will not have a negative impact on the doped polycrystalline silicon layer. Therefore, its impact on cell recombination is small and can be ignored. Therefore, this passivated contact solar cell can improve the fill factor and bifaciality without affecting the open circuit voltage, and thus effectively improve the cell efficiency.

[0030] Furthermore, since the secondary light-trapping structure is fabricated on the doped polycrystalline silicon layer on the back of the battery and does not directly contact the silicon substrate, even if lattice defects are introduced on the surface of the doped polycrystalline silicon layer during the fabrication of the secondary light-trapping structure, these lattice defects will not significantly affect battery recombination. Therefore, this invention eliminates the need for masking the doped polycrystalline silicon layer before fabricating the secondary light-trapping structure, and also eliminates the need for etching the mask and repairing lattice defects on the surface of the doped polycrystalline silicon layer after fabrication. This greatly simplifies the fabrication process, is simple in method, and has low cost, making it particularly suitable for large-scale production. Attached Figure Description

[0031] Figure 1 This is a schematic diagram of the structure after step 1 in the preparation method of a passivated contact solar cell in Example 1.

[0032] Figure 2 This is a schematic diagram of the structure after step 2 in the preparation method of a passivated contact solar cell in Example 1.

[0033] Figure 3 This is a schematic diagram of the structure after step 3 in the preparation method of a passivated contact solar cell in Example 1.

[0034] Figure 4 This is a schematic diagram of the structure after step 4 in the preparation method of a passivated contact solar cell in Example 1.

[0035] Figure 5 This is a schematic diagram of the structure after step 5 in the preparation method of a passivated contact solar cell in Example 1.

[0036] Figure 6 This is a schematic diagram of the structure after step 6 in the preparation method of a passivated contact solar cell in Example 1.

[0037] Figure 7 This is a schematic diagram of the structure after step 7 in the preparation method of a passivated contact solar cell in Example 1.

[0038] Figure 8 This is a schematic diagram of the structure after step 8 in the preparation method of a passivated contact solar cell in Example 1.

[0039] Figure 9 This is a schematic diagram of the structure after step 9 in the preparation method of a passivated contact solar cell in Example 1.

[0040] Figure 10 This is a schematic diagram of the structure after step 3 in the preparation method of a passivated contact solar cell in Example 2.

[0041] Figure 11 This is a schematic diagram of the structure after step 9 in the preparation method of a passivated contact solar cell in Example 2.

[0042] Explanation of reference numerals: 1. Silicon substrate; 2. p+ emitter; 3. BSG film; 4. Tunneling oxide layer; 5. Amorphous silicon layer; 6. Doped polycrystalline silicon layer; 7. PSG film; 8. Front passivation antireflection film; 9. Back passivation film; 10. Front electrode; 11. Back electrode. Detailed Implementation

[0043] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0044] Example 1

[0045] This embodiment describes a passivated contact solar cell; see [link to example]. Figure 9 The device includes a silicon substrate 1; wherein the front surface of the silicon substrate 1 is a pyramid-shaped light-trapping structure to reduce the light reflectivity of the front surface of the battery and ensure the light utilization rate of the front surface of the battery; wherein the pyramid-shaped light-trapping structure is a micron-scale structure; while the back surface of the silicon substrate 1 is a planar structure, rather than a light-trapping structure or a secondary light-trapping structure, to reduce battery recombination and ensure a higher open-circuit voltage and battery efficiency.

[0046] The silicon substrate 1 has a p+ emitter 2 and a front passivation antireflection film 8 stacked sequentially on its front side, with a front electrode 10 extending beyond the front passivation antireflection film 8 on the surface of the p+ emitter 2. The silicon substrate 1 has a tunneling oxide layer 4, a doped polysilicon layer 6, and a back passivation film 9 stacked sequentially on its back side. The back surface of the doped polysilicon layer 6 is a secondary light-trapping structure, and the back passivation film 9 stacked on the back side of the doped polysilicon layer 6 is also a secondary light-trapping structure. The back electrode 11 is located on the back surface of the secondary light-trapping structure and extends beyond the back passivation film 9. This secondary light-trapping structure is a nanoscale porous structure with a hole size of 50–300 nm (if the hole is cylindrical, the hole size is the diameter of the cylinder; of course, the hole can also be conical or other shapes) and a hole depth of 50–300 nm.

[0047] In this passivated contact solar cell, the secondary light-trapping structure on the back surface of the doped polycrystalline silicon layer 6 and the back passivation film 9 not only significantly reduces light reflectivity and improves the bifaciality and overall power of the cell, but also greatly increases the specific surface area of ​​the secondary light-trapping structure on the back surface of the doped polycrystalline silicon layer 6 in contact with the back electrode 11. This results in lower contact resistance than conventional passivated contact solar cells while simultaneously reducing contact resistance through passivation, significantly improving the fill factor. Furthermore, since the secondary light-trapping structure is located on the back surface of the doped polycrystalline silicon and does not directly contact the silicon substrate 1, even if lattice defects are introduced to the surface of the doped polycrystalline silicon layer 6 during the fabrication of the secondary light-trapping structure, these defects will not negatively impact the doped polycrystalline silicon layer 6, and their influence on cell recombination is minimal and negligible. Therefore, this passivated contact solar cell can improve the fill factor and bifaciality without affecting the open-circuit voltage, thereby effectively improving cell efficiency.

[0048] To ensure the passivation contact performance, cell efficiency, and quality of the passivated contact solar cell, the silicon substrate 1 is preferably an N-type silicon substrate, the p+ emitter 2 is preferably a boron-doped p+ emitter 2, and the doped polycrystalline silicon layer 6 is preferably a phosphorus-doped n+ polycrystalline silicon layer. Furthermore, to ensure the passivation contact performance of the passivated contact solar cell, the tunneling oxide layer 4 is preferably silicon oxide with a thickness of 1–2 nm. In addition, the front passivation antireflection film 8 of the passivated contact solar cell is preferably an antireflection film with an aluminum oxide passivation layer, and the back passivation film 9 is preferably a silicon nitride passivation film with a thickness of 40–110 nm to improve the antireflection performance of the back passivation film 9; so that the back of the cell can absorb more sunlight, and the front passivation antireflection film 8 and the back passivation film 9 provide good protection and passivation for the front and back of the cell, respectively.

[0049] This embodiment also provides a method for preparing a passivated contact solar cell, which can simply and efficiently prepare the passivated contact solar cell with the structure described above in this embodiment; the preparation steps are as follows:

[0050] Step 1: Select a suitable silicon substrate 1 and pretreat the silicon substrate 1 to form a pyramid-shaped light-trapping structure on the front and back surfaces of the silicon substrate 1. The pretreatment method can be alkaline treatment or acid treatment, but is not limited to these two methods.

[0051] In one example of this embodiment, additives may be added during the alkali treatment process to promote the pretreatment process. The structure of the silicon substrate 1 after the pretreatment in step 1 is as follows. Figure 1 As shown.

[0052] Step 2 involves performing boron doping on the front side of the pretreated silicon substrate 1 to prepare a boron-doped p+ emitter 2. The boron doping method can be diffusion, spin coating, screen printing, or inkjet printing.

[0053] In one example of this embodiment, the diffusion process is as follows: In an atmospheric pressure tube, boron tribromide is used as the boron source to diffuse onto the front side of the silicon substrate 1. The diffusion temperature is 700–1000 °C, the time is 40–100 min, and the sheet resistance is 60–100 Ω / sqr. After boron source diffusion, a boron-doped p+ emitter 2 can be formed on the front side of the silicon substrate 1, and a BSG film 3 with a thickness of 60–120 nm is formed on the surface of the boron-doped p+ emitter 2. Specifically, the diffusion process uses a back-to-back insertion method, i.e., the diffusion surface faces outward and the non-diffusion surface faces inward. After completing the boron doping treatment in step 2, its structure is as follows. Figure 2 As shown.

[0054] Step 3: Etch or polish the back surface of the boron-doped silicon substrate 1 to remove the p+ emitter 2 and BSG film 3 deposited around the back surface of the silicon substrate 1 in Step 2, so that a planar structure is formed on the back surface of the silicon substrate 1, as shown in the figure. Figure 3 As shown.

[0055] Step 4: Prepare a tunneling oxide layer 4 on the back side of the etched or polished silicon substrate 1.

[0056] In one example of this embodiment, when the material of the tunneling oxide layer 4 is silicon oxide, the preparation method of the tunneling oxide layer 4 is nitric acid oxidation, high-temperature thermal oxidation or ozone oxidation, but is not limited to the above preparation methods.

[0057] Specifically, the steps for preparing silicon oxide using the nitric acid oxidation method are as follows: The pretreated silicon substrate 1 is placed in a nitric acid solution with a mass fraction of 45–80% and reacted for 4–8 minutes at a reaction temperature of 90–100°C. After the reaction, the silicon substrate 1 is rapidly dried using a nitrogen gun, thus obtaining a silicon oxide layer with a thickness of 1–2 nm on the back side of the silicon substrate 1, the structure of which is as follows: Figure 4 As shown.

[0058] Step 5: An amorphous silicon layer 5 is prepared on the entire back side of the tunneling oxide layer 4. The preparation method is physical vapor deposition (PVD), low-pressure chemical vapor deposition (LPCVD), plasma chemical vapor deposition (PECVD), or atmospheric pressure chemical vapor deposition (APCVD). Correspondingly, the equipment used to deposit the amorphous silicon layer 5 is a PVD equipment, an LPCVD equipment, a PECVD equipment, or an APCVD equipment.

[0059] In one example of this embodiment, the preparation process using the LPCVD method is as follows: [The process is carried out under a vacuum below 7 × 10⁻⁶]. -3 Under conditions of Torr and temperature of 550–700℃, SiH4 is introduced, followed by a deposition reaction of 10–40 min. Then, a vacuum is drawn to ensure the hazardous SiH4 gas is completely removed. Nitrogen gas is then introduced to atmospheric pressure, and after cooling, the layer is removed, thus preparing an amorphous silicon layer 5 on the surface of the tunneling oxide layer 4. Its structure is as follows: Figure 5 As shown.

[0060] Step 6 involves doping the entire back side of the amorphous silicon layer 5, followed by a high-temperature process to change the amorphous structure of the amorphous silicon layer 5 into a polycrystalline structure. This allows for the formation of a small and uniformly sized doped polycrystalline silicon layer 6 on the surface of the tunneling oxide layer 4. The doping process can be performed using diffusion, spin coating, ion implantation, screen printing, or inkjet printing.

[0061] In one example of this embodiment, the diffusion method is as follows: Phosphorus pentoxide is used as the phosphorus source in an atmospheric pressure tube to diffuse the phosphorus source onto the entire back side of the amorphous silicon layer 5. The diffusion temperature is 700–900°C, the time is 30–90 min, and the sheet resistance is 100–300 Ω / sqr. After phosphorus source diffusion, a phosphorus-doped n+ polycrystalline silicon layer is formed on the surface of the tunneling oxide layer 4, and a PSG film 7 with a thickness of 50–120 nm is formed on the surface of this phosphorus-doped n+ polycrystalline silicon layer, with the structure shown below. Figure 6 As shown; specifically, the plates are inserted back-to-back during the diffusion process, with the diffusion surface facing outwards and the non-diffusion surface facing inwards.

[0062] Step 7: The silicon substrate 1 after phosphorus diffusion treatment is chemically cleaned to remove the BSG film 3 and PSG film 7. An acid solution is used for the chemical cleaning. After chemical cleaning, its structure is as follows: Figure 7 As shown.

[0063] Step 8: The back side of the chemically cleaned doped polycrystalline silicon layer 6 is sequentially subjected to reactive ion etching and passivation treatment.

[0064] The reactive ion etching process is as follows: the silicon substrate 1 after step 7 is placed in the PECVD equipment chamber, and a vacuum is drawn to 10. -4 When the pressure is below Pa, two process gases, SF6 and O2, are introduced. O2 acts as a diluent gas, facilitating SF6 glow discharge and plasma generation. Simultaneously, O2 better modulates the etching selectivity, enabling anisotropic etching of the back side of the doped polysilicon layer 6. Specifically, when SF6 is introduced into the reaction chamber, the chemical reaction during glow discharge is: SF6 → SF6. 5+ +F * +e - The generated F * When a free radical reaches the surface of the doped polycrystalline silicon layer 6, the chemical reaction that occurs is: Si + F * →SiF4, where SiF4 is a volatile gas that can be pumped away, while the generated SF6 5+ and e - It can achieve reactive ion etching of the surface of doped polycrystalline silicon layer 6. The preferred gas flow rate of SF6 is 20-30 cm³. 3 The preferred flow rate of O2 is 3–10 cm³ / s. 3 The preferred reaction pressure is 200–300 mtorr, the preferred radio frequency power is 100–200 W, and the preferred etching rate is 800–200 nm / s, to ensure that a layer such as [missing information] can be formed on the back surface of the doped polysilicon layer 6. Figure 8 The secondary light-trapping structure shown.

[0065] Following reactive ion etching, a back-side passivation film 9 was fabricated within the same cavity. The fabrication conditions were: pressure 1500–2000 mTorr, power 6600 W–8600 W, SiH4:NH3 = 1:6, deposition temperature 400–500 °C, and deposition time 10–20 min, resulting in a silicon nitride passivation film with a thickness of 40–110 nm. Its structure is as follows: Figure 8 As shown.

[0066] Step 9: After the processing in step 8, a front passivation antireflection film 8 is prepared on the surface of the p+ emitter 2. Preferably, an aluminum oxide passivation layer is prepared by atomic layer deposition (ALD), followed by an antireflection layer prepared by PECVD or APCVD, thus completing the preparation of the front passivation antireflection film 8. Then, a metallization process is performed to form a front electrode 10 on the surface of the p+ emitter 2 and a back electrode 11 on the surface of the secondary light-trapping structure of the doped polycrystalline silicon layer 6. This completes the preparation of the passivated contact solar cell of this embodiment, with the structure as shown below. Figure 9As shown. In summary, in this embodiment, after preparing the tunneling oxide layer 4 and the doped polycrystalline silicon layer 6, a secondary light-trapping structure is prepared on the surface of the doped polycrystalline silicon layer 6 using reactive ion etching. Then, a back passivation film 9 is prepared within the same cavity as the reactive ion etching process, so that the back passivation film 9 on the back side of the doped polycrystalline silicon layer 6 also serves as a secondary light-trapping structure. Next, a front passivation antireflection film 8 is prepared, followed by the preparation of the front electrode 10 and the back electrode 11, to obtain a passivated contact solar cell (i.e., a new type of TOPCon cell). The main advantages of this passivated contact solar cell are:

[0067] (1) Compared with the etched or polished surface on the back of the existing TOPCon cell, the secondary light-trapping structure prepared on the surface of the doped polycrystalline silicon layer 6 and the back passivation film 9 has a lower light reflectivity, which can effectively reduce the light reflectivity on the back of the TOPCon cell and improve the bifaciality, thereby improving the overall power of the cell; (2) After reactive ion etching, the doped polycrystalline silicon layer 6 on the back of the passivated contact solar cell forms a secondary light-trapping structure on its back surface. Compared with the existing etched or polished surface, when the back electrode 11 is prepared in this passivated contact solar cell, the secondary light-trapping structure has a larger specific surface area in contact with the back electrode 11, which can obtain a lower contact resistance, thereby improving the fill factor. At the same time, since the secondary light-trapping structure is on the back surface of the doped polycrystalline silicon and does not directly contact the silicon substrate 1, even if lattice defects are introduced to the surface of the doped polycrystalline silicon layer 6 during the preparation of the secondary light-trapping structure, it will not have a negative impact on the doped polycrystalline silicon layer 6. Therefore, its impact on cell recombination is small and can be basically ignored. Therefore, the passivated contact solar cell can improve the fill factor and bifaciality without affecting the open circuit voltage, thereby effectively improving the cell efficiency. (3) In addition, since the secondary light trapping structure is prepared on the doped polycrystalline silicon layer 6 on the back of the cell and does not directly contact the silicon substrate 1, even if lattice defects are introduced on the surface of the doped polycrystalline silicon layer 6 during the preparation of the secondary light trapping structure, such lattice defects of the doped polycrystalline silicon layer 6 will not affect the cell recombination. (It should be noted that if the secondary light trapping structure is prepared on the front or back of the silicon substrate 1 of the cell using the preparation method of this embodiment, or on the surface of the p+ emitter 2 on the front of the cell, in order to ensure the normal use of the silicon substrate 1 and the p+ emitter 2 during the photoelectric conversion of the cell, it is necessary to mask the surface of the silicon substrate 1 or the p+ emitter 2 before preparing the secondary light trapping structure.) Theoretically, after fabricating the secondary light-trapping structure, a mask needs to be etched, and lattice defects on the surface of the silicon substrate 1 or p+ emitter 2 caused by the fabrication of the secondary light-trapping structure need to be repaired, making the fabrication process cumbersome. If the masking, etching, and lattice defect repair processes are not performed on the surface of the silicon substrate 1 or p+ emitter 2 of the battery, the recombination of the battery will be greatly increased, which will reduce the battery efficiency. Therefore, the present invention eliminates the need for masking the doped polycrystalline silicon layer 6 before fabricating the secondary light-trapping structure, and also eliminates the need for etching and repairing the lattice defects on the surface of the doped polycrystalline silicon layer 6 after fabrication. This greatly simplifies the fabrication process, is simple in method, and has low cost, making it particularly suitable for large-scale production.

[0068] This embodiment also discloses a solar cell module, including a front material layer, a front encapsulation layer, a solar cell, a back encapsulation layer, and a back material layer arranged sequentially from top to bottom. The solar cell is a passivated contact solar cell as described above in this embodiment.

[0069] This embodiment also discloses a solar cell system, including one or more solar cell modules, wherein the solar cell module is one of the solar cell modules described above in this embodiment.

[0070] Example 2

[0071] The passivated contact solar cell and its preparation method, components, and system in this embodiment are basically the same as those in Embodiment 1, with the only difference being:

[0072] This embodiment describes a method for preparing a passivated contact solar cell:

[0073] In step 3, only the p+ emitter 2 and BSG film 3 deposited around the back of the silicon substrate 1 in step 2 are removed, while the light-trapping structure on the back of the silicon substrate 1 is retained, and its structure is as follows. Figure 10 As shown.

[0074] The battery structure of a passivated contact solar cell obtained by the above preparation method in this embodiment is as follows: Figure 11 As shown.

[0075] Although preferred embodiments of the present invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments as well as all changes and modifications falling within the scope of the present invention.

[0076] The technical solution provided by the present invention has been described in detail above. Specific examples have been used to illustrate the principle and implementation of the present invention. The description of the above embodiments is only for the purpose of helping to understand the method and core idea of ​​the present invention. At the same time, for those skilled in the art, there will be changes in the specific implementation and application scope based on the idea of ​​the present invention. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A method for fabricating a passivated contact solar cell, the passivated contact solar cell comprising a silicon substrate, wherein a p+ emitter, a front passivation antireflection film, and a front electrode disposed on the surface of the p+ emitter and extending beyond the front passivation antireflection film are sequentially disposed on the front side of the silicon substrate, and a tunneling oxide layer, a doped polycrystalline silicon layer, a back passivation film, and a back electrode are sequentially disposed on the back side of the silicon substrate, characterized in that: The surface of the doped polycrystalline silicon layer is a secondary light-trapping structure, and the back electrode is disposed on the surface of the secondary light-trapping structure via a back passivation film; the thickness of the back passivation film is 40–110 nm. The method for preparing the passivated contact solar cell includes the following steps: Step S1: The p+ emitter is fabricated on the front side of the silicon substrate; Step S2: Prepare the tunneling oxide layer on the back side of the silicon substrate; Step S3: Prepare the doped polycrystalline silicon layer on the surface of the tunneling oxide layer; Step S4: Perform reactive ion etching on the back side of the doped polysilicon layer to form the secondary light-trapping structure on the surface of the doped polysilicon layer, and then prepare the back passivation film on the surface of the secondary light-trapping structure. Step S5: Prepare the front passivation antireflection film on the surface of the p+ emitter, and then perform metallization treatment to form the front electrode extending beyond the front passivation antireflection film on the surface of the p+ emitter, and form the back electrode extending beyond the back passivation film on the surface of the secondary light-trapping structure of the doped polysilicon layer.

2. The method for preparing a passivated contact solar cell according to claim 1, characterized in that, The front side of the silicon substrate has a light-trapping structure, and the back side of the silicon substrate has a planar structure or a light-trapping structure.

3. A method for preparing a passivated contact solar cell according to claim 1 or 2, characterized in that, The secondary light-trapping structure is a nanoscale porous structure with a pore size of 50–300 nm and a pore depth of 50–300 nm.

4. The method for preparing a passivated contact solar cell according to claim 1, characterized in that, The silicon substrate is an N-type silicon substrate.

5. The method for preparing a passivated contact solar cell according to claim 1, characterized in that, The p+ emitter is a boron-doped p+ emitter, and the doped polycrystalline silicon layer is a phosphorus-doped n+ polycrystalline silicon layer.

6. A method for preparing a passivated contact solar cell according to claim 1 or 5, characterized in that, The tunneling oxide layer is silicon oxide with a thickness of 1 to 2 nm.

7. The method for preparing a passivated contact solar cell according to claim 1, characterized in that, The front passivation antireflection film is an antireflection film with an aluminum oxide passivation layer; the back passivation film is a silicon nitride passivation film.

8. The method for preparing a passivated contact solar cell according to claim 2, characterized in that, Before step S1, the method further includes a step of pre-processing the silicon substrate to form the light-trapping structure on the front and back sides of the silicon substrate; Before step S3, the method further includes etching or polishing the back side of the silicon substrate to form the planar structure on the back side of the silicon substrate.

9. A method for preparing a passivated contact solar cell according to claim 1 or 8, characterized in that, In step S4, the specific steps for forming the secondary light-trapping structure are as follows: the silicon substrate processed in step S3 is placed in a chemical vapor deposition reaction chamber, and a vacuum is drawn to 10... -4 When the pressure is below Pa, SF6 and O2 gases are introduced to generate plasma for selective reactive ion etching of the surface of the doped polycrystalline silicon layer to form the secondary light-trapping structure.

10. A solar cell module, comprising, from top to bottom, a front material layer, a front encapsulation layer, a solar cell, a back encapsulation layer, and a back material layer, characterized in that: The solar cell is prepared by the method for preparing a passivated contact solar cell according to any one of claims 1-7.

11. A solar cell system comprising one or more solar cell modules, characterized in that: The solar cell module is the solar cell module according to claim 10.

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