Photovoltaic cell and preparation method thereof
By using pyramidal structures with different crystal structures at their apex and laser processing to form heavily doped regions in photovoltaic cells, the problem of metal electrodes damaging the passivation layer was solved, resulting in improved open-circuit voltage and electrical performance.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-11-14
- Publication Date
- 2026-03-13
AI Technical Summary
In existing passivated contact battery (TOPCon) technology, the passivation layer is damaged during the high-temperature ablation process of the metal electrode, which leads to increased metal contact recombination and makes it difficult to improve the open circuit voltage.
The pyramidal structure apex is made of silicon-containing materials with different crystal structures. The apex is combined with laser processing to form a heavily doped region. The metal contact points are reduced and metal contact recombination is reduced through weak burn-through process and laser-enhanced contact optimization technology.
It effectively reduces metal-to-metal contact recombination, increases the open-circuit voltage of photovoltaic cells, and improves electrical performance.
Smart Images
Figure CN121665773A_ABST
Abstract
Description
[0001] This application is a divisional application. The original application has the application number 202411629203.7 and the original application date is November 14, 2024. The entire contents of the original application are incorporated herein by reference. Technical Field
[0002] This invention relates to the field of photovoltaic technology, and in particular to photovoltaic cells and their preparation methods. Background Technology
[0003] Currently, mainstream passivated contact battery (TOPCon) technology and products feature a boron-diffused emitter on the front side of the battery, with a metal electrode penetrating the passivation layer on the emitter surface to form contact. During high-temperature ablation, the metal slurry melts and destroys the surface passivation layer, increasing surface carrier recombination. The numerous metal contact points also contribute to increased metal contact recombination, making it difficult to further improve the battery's open-circuit voltage. Summary of the Invention
[0004] This application proposes a photovoltaic cell and its preparation method, aiming to improve the metal contact recombination of the photovoltaic cell, thereby increasing the open-circuit voltage of the photovoltaic cell.
[0005] In a first aspect, embodiments of this application provide a photovoltaic cell, including a monocrystalline silicon substrate having a first surface and a second surface disposed opposite to each other, and a first doped semiconductor layer, a first passivation layer and a first electrode sequentially disposed on the first surface along a direction away from the monocrystalline silicon substrate; The first surface is formed with a textured surface, which has a plurality of first pyramid structures. Each first pyramid structure includes a body and a apex, wherein the apex is a silicon-containing material with a different crystal structure than the single-crystal silicon substrate. The portion of the first electrode corresponding to the first pyramid structure forms an electrical contact with the first doped semiconductor layer.
[0006] In some embodiments, along the length of the first electrode, the side of the first electrode facing the single-crystal silicon substrate has a plurality of spaced metal contact regions, and the electrode forms an electrical contact with the doped semiconductor layer through the metal contact regions.
[0007] In some embodiments, the first doped semiconductor layer includes a heavily doped region, the first electrode forms an electrical contact with the heavily doped region, the heavily doped region includes a first region and a second region, the first region covers the top of the tower, the second region covers the body of the tower, and the doping concentration of the first region is higher than that of the second region.
[0008] In some embodiments, the doping concentration in the first region is 1×10⁻⁶. 17atoms / cm 3 ~2×10 19 atoms / cm 3 ; and / or, The doping concentration in the second region is 5 × 10⁻⁶. 16 atoms / cm 3 ~1×10 19 atoms / cm 3 ; and / or, The first doped semiconductor layer further includes a third region, which is the other region of the first doped semiconductor layer excluding the heavily doped region, and the doping concentration of the third region is 1×10⁻⁶. 16 atoms / cm 3 ~5×10 17 atoms / cm 3 .
[0009] In some embodiments, there are multiple first electrodes, and one first electrode forms an electrical contact with multiple spaced-apart heavily doped regions, wherein each of the heavily doped regions of the first doped semiconductor layer is arranged in a lattice pattern.
[0010] In some embodiments, the spacing between two adjacent heavily doped regions along the length direction of the first electrode is ≥10 μm; and / or, The area of the heavily doped region is 3.14. 10 2 μm 2 ~4.9 10 4 μm 2 ; and / or, The length of the heavily doped region along the length direction of the first electrode is 20 μm to 250 μm, and the width of the heavily doped region along the width direction of the first electrode is 20 μm to 150 μm.
[0011] In some embodiments, the axial height of the first pyramid structure is 0.5 μm to 2 μm; Along the width direction of the first electrode, the width of the tower tip near the tower body is 0.2 μm to 1.5 μm, or the width of the tower body away from the tower tip is 0.7 μm to 2.8 μm.
[0012] Secondly, this application also proposes a method for preparing a photovoltaic cell, comprising the following steps: A monocrystalline silicon substrate is provided having a first surface and a second surface disposed opposite to each other, the first surface being formed with a textured surface, the textured surface including a plurality of first pyramid structures, the first pyramid structure including a pyramid body and a pyramid tip; A first semiconductor doped layer is formed such that the first semiconductor doped layer covers the textured surface; Laser treatment causes the tower tip to recrystallize into a silicon-containing material with a different crystal structure from the single-crystal silicon substrate; A first passivation layer is formed, which covers the side of the first doped semiconductor layer opposite to the textured surface; A first electrode is formed, and the portion of the first electrode corresponding to the first pyramid structure is electrically connected to the first doped semiconductor layer.
[0013] In some embodiments, the laser processing step includes: irradiating the side of the first doped semiconductor layer facing away from the single-crystal silicon substrate with a laser, so that the first doped semiconductor layer forms a heavily doped region, the heavily doped region including a first region and a second region, the first region covering the top of the tower, the second region covering the body of the tower, and the doping element concentration of the first region being higher than that of the second region. The first electrode forms an electrical contact with the heavily doped region.
[0014] In some embodiments, the power of the laser processing is 100W~800W, the wavelength of the laser processing is 400nm~2000nm, the spot diameter of the laser processing is 5μm~120μm, and the single-point dwell time of the laser processing spot is 2μs-10μs.
[0015] Compared with the prior art, this technical solution has at least the following technical advantages: In the technical solution of this application, since the material of the top of the first pyramid structure is a silicon-containing material with a different crystal structure than that of the single-crystal silicon substrate, the thermal conductivity of the top of the first pyramid structure is lower than that of its body. This increases the number of contact points formed between the first electrode and the first doped semiconductor layer region on the surface of the top of the first pyramid structure. Conversely, the number of contact points formed between the first electrode and the first doped semiconductor layer region on the surface of the body of the first pyramid structure decreases. This reduces the metal contact recombination between the first electrode and the first doped semiconductor layer, thereby increasing the open-circuit voltage of the photovoltaic cell. Attached Figure Description
[0016] The present invention will be further described below with reference to the accompanying drawings and embodiments.
[0017] Figure 1 This is a schematic diagram of the structure of the photovoltaic cell in one embodiment of the present application; Figure 2 for Figure 1 Top view; Figure 3 for Figure 1 A sectional view; Figure 4 for Figure 1 A schematic diagram of the structure of the First Pyramid of China; Figure 5 This is a schematic diagram of the structure of the photovoltaic cell in another embodiment of this application; Figure 6 This is a process flow diagram of the photovoltaic cells in this application; Figure 7 This is a schematic flowchart of the laser-enhanced contact optimization step in the photovoltaic cell fabrication method of this application.
[0018] Figure label: Detailed Implementation To better understand the technical solution of the present invention, the embodiments of the present invention will be described in detail below with reference to the accompanying drawings.
[0019] It should be understood that the described embodiments are merely some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.
[0020] The terminology used in the embodiments of this invention is for the purpose of describing particular embodiments only and is not intended to limit the invention. The singular forms “a,” “the,” and “the” as used in the embodiments of this invention and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise.
[0021] The term "and / or" used in this article is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. Additionally, the character " / " in this article generally indicates that the preceding and following related objects have an "or" relationship.
[0022] It should be noted that if the embodiments of this application involve directional indicators (such as up, down, left, right, front, back, etc.), the directional indicators are only used to explain the relative positional relationship and movement of each component in a certain specific posture (as shown in the figure). If the specific posture changes, the directional indicators will also change accordingly.
[0023] Firstly, this application proposes a photovoltaic cell 100.
[0024] Please see Figures 1-7In this embodiment of the application, the photovoltaic cell 100 includes a monocrystalline silicon substrate 110 having a first surface and a second surface disposed opposite to each other, and a first doped semiconductor layer 120, a first passivation layer 140 and a first electrode 150 sequentially disposed on the first surface in a direction away from the monocrystalline silicon substrate 110; the first surface is formed with a textured surface, the textured surface including a plurality of first pyramid structures 111, the first pyramid structure 111 including a tower body 1111 and a tower tip 1112, wherein the tower tip 1112 is a silicon-containing material with a different crystal structure from the monocrystalline silicon substrate 110, the thermal conductivity of the tower tip 1112 is lower than the thermal conductivity of the monocrystalline silicon substrate 110 (the tower body 1111), and the portion of the first electrode 150 corresponding to the first pyramid structure 111 forms an electrical contact with the first doped semiconductor layer 120.
[0025] In the technical solution of this application, since the material of the tip 1112 of the first pyramid structure 111 is a silicon-containing material with a different crystal structure than that of the single-crystal silicon substrate 110, the thermal conductivity of the tip 1112 of the first pyramid structure 111 is lower than that of its body 1111. This increases the number of contact points formed between the first electrode 150 and the first doped semiconductor layer 120 region on the surface of the tip 1112 of the first pyramid structure 111. Conversely, the number of contact points formed between the first electrode 150 and the first doped semiconductor layer 120 region on the surface of the body 1111 of the first pyramid structure 111 decreases. Consequently, the metal contact recombination between the first electrode 150 and the first doped semiconductor layer 120 is reduced, and the open-circuit voltage of the photovoltaic cell 100 is increased.
[0026] In this embodiment of the application, specifically, the body 1111 of the first pyramid structure 111 is made of monocrystalline silicon, while the tip 1112 can be made of polycrystalline silicon, microcrystalline silicon, amorphous silicon, or other silicon-containing materials with lower thermal conductivity than monocrystalline silicon. Preferably, the tip 1112 is made of polycrystalline silicon, which not only has lower thermal conductivity than monocrystalline silicon but also higher electrical conductivity, which is beneficial for improving the electrical performance of the photovoltaic cell 100.
[0027] Please see Figure 4In some embodiments, the axial height H of the first pyramid structure 111 is 0.5 μm to 2 μm, specifically 0.5 μm, 1 μm, 1.5 μm, 2 μm, or any value between them; along the width direction of the first electrode 150, the width d1 of the pyramid tip 1112 near the pyramid body 1111 is 0.2 μm to 1.5 μm, specifically 0.2 μm, 0.4 μm, 0.8 μm, 1 μm, 1.2 μm, 1.5 μm, or any value between them; or, the width d2 of the pyramid body 1111 away from the pyramid tip 1112 is 0.7 μm to 2.8 μm, specifically 0.7 μm, 1.4 μm, 2.1 μm, 2.8 μm, or any value between them. Within the above ranges, it is beneficial to reduce metal-to-metal contact recombination between the first electrode 150 and the first doped semiconductor layer 120 while maintaining the electrical performance of the photovoltaic cell 100.
[0028] In this embodiment, the first surface can be the front or back of the monocrystalline silicon substrate 110. The front of the monocrystalline silicon substrate 110 is the light-receiving surface that absorbs incident light, and the back of the monocrystalline silicon substrate 110 is the backlight surface. The monocrystalline silicon substrate 110 can be N-type or P-type.
[0029] In this embodiment of the application, the photovoltaic cell 100 can be a passivated contact cell (TOPCon cell) or a back contact cell (BC cell) or other types of photovoltaic cell 100.
[0030] Please see Figure 3 In some embodiments, the photovoltaic cell 100 is a passivated contact cell (TOPCon cell), with a first surface being the front side of the monocrystalline silicon substrate 110 and a second surface being the back side of the monocrystalline silicon substrate 110. The photovoltaic cell 100 also includes a tunneling oxide layer 160, a second doped semiconductor layer 170, a second passivation layer 180, and a second electrode 190 sequentially disposed on the back side of the monocrystalline silicon substrate 110 along a direction away from the monocrystalline silicon substrate 110, wherein the second electrode 190 forms an electrical contact with the second doped semiconductor layer 170. In a specific embodiment, the first doped semiconductor layer 120 contains an N-type dopant element, and the second doped semiconductor layer 170 contains a P-type dopant element.
[0031] In other embodiments, the photovoltaic cell is a back-contact cell (BC cell), with a first surface being the back side of a monocrystalline silicon substrate 110 and a second surface being the front side of the monocrystalline silicon substrate 110. The first surface has a first conductive region and a second conductive region. A first pyramid structure 111 is formed in the first conductive region of the first surface. A first doped semiconductor layer 120, a first passivation layer 140, and a first electrode 150 are sequentially disposed in the first conductive region of the first surface. The photovoltaic cell 100 also includes a tunneling oxide layer 160, a second doped semiconductor layer 170, a second passivation layer 180, and a second electrode 190, which are sequentially disposed in a second region of the first surface along a direction away from the monocrystalline silicon substrate 110. In one specific embodiment, the first conductive region is an N-type conductive region, the first doped semiconductor layer 120 contains N-type dopants, the second conductive region is a P-type conductive region, and the second doped semiconductor layer 170 contains P-type dopants.
[0032] The following section uses a passivated contact cell (TOPCon cell) as an example to provide a more detailed description of the photovoltaic cell 100 of this application.
[0033] In some embodiments, the N-type dopant can be a group V element such as phosphorus (P), bismuth (Bi), antimony (Sb), or arsenic (As), and the P-type dopant can be a group III element such as boron (B), aluminum (Al), gallium (Ga), or indium (In). In one specific embodiment, the single-crystal silicon substrate 110 is an N-type substrate, and the dopant element inside the first doped semiconductor layer 120 is a P-type element, which includes boron (B).
[0034] In some embodiments, in addition to the doping elements, the first doped semiconductor layer 120 / second doped semiconductor layer 170 further includes one or more of amorphous silicon, microcrystalline silicon, polycrystalline silicon, and silicon carbide.
[0035] In some embodiments, the material of the first passivation layer 140 / second passivation layer 180 includes one or more of silicon nitride, silicon oxynitride, silicon oxide, aluminum oxide, and aluminum oxynitride.
[0036] In some embodiments, the first passivation layer 140 / second passivation layer 180 can be a single-layer structure or a multi-layer structure. For a multi-layer structure, the materials of different layers can be different from each other, or some layers can be made of the same material but different from the materials of other layers. For example, the first passivation layer 140 can be a multi-layer structure of silicon nitride and aluminum oxide layers. In this way, the passivation layer has high light transmittance, balancing the passivation effect and light transmittance of the solar cell, which is beneficial for improving the light conversion efficiency of the solar cell and enhancing its performance.
[0037] In some embodiments, the thickness of the first passivation layer 140 is 50~150nm, specifically 50nm, 75nm, 100nm, 125nm, 150nm or any value between them.
[0038] In some embodiments, the first electrode 150 / second electrode 190 is sintered from a weak burn-through slurry, and the material of the first electrode 150 / second electrode 190 can be one or more of aluminum, silver, nickel, gold, molybdenum or copper.
[0039] In some embodiments, the first electrode 150 refers to a fine grid line or a finger grid line, which is different from a main grid line or a bus bar. There are multiple first electrodes 150, which are arranged sequentially at intervals along a first direction. The first electrodes 150 extend along a second direction, which is perpendicular to the first direction.
[0040] In some embodiments, the width of the first electrode 150 is 5μm to 50μm, specifically 5μm, 10μm, 20μm, 30μm, 40μm, 50μm or any value between them.
[0041] Please see Figure 4 , Figure 5 and Figure 6 In some embodiments, a weak burn-through process is used to print the first electrode 150 on the surface of the first passivation layer 140, and laser-enhanced contact optimization technology is used to enhance the electrical contact between the first electrode 150 and the first doped semiconductor layer 120. In this embodiment, a glass layer 130 is also provided on the side of the first doped semiconductor layer 120 facing away from the first pyramid structure 111, and the first glass layer 130 is located between the first electrode 150 and the first doped semiconductor layer 120. The glass layer 130 contains metal particles 131 (e.g., silver particles). During the formation of the first electrode 150, at least some of the metal particles 131 will pierce the glass layer 130 and contact the first doped semiconductor layer 120. In the subsequent laser-enhanced contact optimization process, these metal particles 131 that pierce the glass layer 130 will melt with the silicon in the first doped semiconductor layer 120 to form an alloy, i.e., metal contact points 132, thereby enabling the circuit connection between the first electrode 150 and the first doped semiconductor layer 120.
[0042] In some embodiments, the size of the silver particles is ≤20nm.
[0043] In some embodiments, the material of the glass layer 130 includes one or more compounds such as silicon oxide, silicon nitride, silicon oxynitride, silicates, lead oxide, aluminum oxide, and boric acid.
[0044] In some embodiments, the thickness of the glass layer 130 is 10nm to 500nm, specifically 10nm, 100nm, 200nm, 300nm, 400nm, 500nm or any value between them.
[0045] In this embodiment, the first electrode 150 has a metal contact area on the side facing the single-crystal silicon substrate 110. The first electrode 150 forms an electrical contact with the first doped semiconductor layer 120 through the metal contact area. The metal contact area can be the entire area of the surface of the first electrode 150 facing the single-crystal silicon substrate 110, or it can be a part of the surface of the first electrode 150 facing the single-crystal silicon substrate 110.
[0046] In some embodiments, along the length of the first electrode 150, the side of the first electrode 150 facing the single-crystal silicon substrate 110 has a plurality of spaced-apart metal contact regions, and a portion of the surface of the first electrode 150 facing the single-crystal silicon substrate 110 forms an electrical contact with the first doped semiconductor layer 120. This arrangement can reduce the number of metal contact points 132 between the first electrode 150 and the first doped semiconductor layer 120, that is, it can reduce damage to the first passivation layer 140, thereby reducing surface recombination and metal contact recombination of charge carriers and improving the open-circuit voltage of the battery.
[0047] Please see Figure 1 and Figure 2 In the above embodiment, the first passivation layer 140 has alternating gate line regions and non-gate line regions on the side opposite to the first doped semiconductor layer 120, and the first electrode 150 is disposed in the gate line region, with the first electrode 150 and the gate line region being disposed in a one-to-one correspondence.
[0048] In some embodiments, the textured surface also has a second pyramid structure, which is any pyramid structure other than the first pyramid structure 111 present on the textured surface. The body 1111 and the tip 1112 of the second pyramid structure are both made of monocrystalline silicon. Specifically, the first pyramid structure 111 is disposed opposite to the metal contact area of the first electrode 150, and the second pyramid structure is disposed offset from the metal contact area of the first electrode 150. This arrangement helps to reduce damage to the first passivation layer 140 and metal contact recombination.
[0049] Please see Figure 1 , Figure 2 and Figure 5In some embodiments, the first doped semiconductor layer 120 includes a heavily doped region 121, and the first electrode 150 forms an electrical contact with the heavily doped region 121. The heavily doped region 121 includes a first region and a second region. The first region covers the top of the tower 1112, and the second region covers the body of the tower 1111. The doping concentration of the first region is higher than that of the second region. The region with a higher doping concentration of the first doped semiconductor layer 120 is more likely to form a metal contact site 132 with the first electrode 150. By making the doping concentration of the first region higher than that of the second region, it is beneficial to further reduce the contact recombination between the first electrode 150 and the first doped semiconductor layer 120, that is, to further improve the open-circuit voltage of the photovoltaic cell 100.
[0050] In the above embodiment, a first electrode 150 forms an electrical contact with a plurality of spaced-apart heavily doped regions 121, and each heavily doped region 121 of the first doped semiconductor layer 120 is arranged in a dot matrix pattern.
[0051] In some embodiments, the difference in dopant concentration between the first region and the second region is 5 × 10⁻⁶. 16 atoms / cm 3 ~1×10 19 atoms / cm 3 Within this concentration difference range, it is beneficial to reduce the contact recombination between the first electrode 150 and the first doped semiconductor layer 120, and also beneficial to improve the electrical performance of the photovoltaic cell 100.
[0052] In some embodiments, the dopant concentration in the first region is 1×10⁻⁶. 17 atoms / cm 3 ~2×10 19 atoms / cm 3 Specifically, it can be 1×10 17 atoms / cm 3 5×10 17 atoms / cm 3 1×10 18 atoms / cm 3 5×10 18 atoms / cm 3 1×10 19 atoms / cm 3 2×10 19 atoms / cm 3 Or any value between them.
[0053] In some embodiments, the dopant concentration in the second region is 5 × 10⁻⁶. 16 atoms / cm 3 ~1×10 19 atoms / cm 3 Specifically, it can be 5×1016 atoms / cm 3 1×10 17 atoms / cm 3 5×10 17 atoms / cm 3 1×10 18 atoms / cm 3 5×10 18 atoms / cm 3 1×10 19 atoms / cm 3 Or any value between them.
[0054] Understandably, the first doped semiconductor layer 120 also includes a third region, which is the other regions of the first doped semiconductor layer 120 except for the heavily doped region 121. The doping concentration of the third region can be the same as or lower than that of the second region.
[0055] In some embodiments, the doping concentration in the third region is lower than that in the second region, and the doping concentration in the third region is 1 × 10⁻⁶. 16 atoms / cm 3 ~5×10 17 atoms / cm 3 Specifically, it can be 1×10 16 atoms / cm 3 4×10 16 atoms / cm 3 8×10 16 atoms / cm 3 2×10 17 atoms / cm 3 5×10 17 atoms / cm 3 Or any value in between. The third region, within this doping concentration range, is beneficial to improving the electrical performance of photovoltaic cell 100.
[0056] In this embodiment, the size and spacing of each heavily doped region 121 can be adjusted according to the actual situation.
[0057] In some embodiments, the spacing between two adjacent heavily doped regions 121 is ≥10 μm along the length direction of the first electrode 150. Within this spacing range, the recombination of the metal contact between the first electrode 150 and the first doped semiconductor layer 120 can be reduced relatively effectively.
[0058] In some embodiments, the area of the heavily doped region 121 is 3.14. 102μm 2~4.9 104 μm2 Specifically, it can be 3.14. 102μm 2 6.28 102μm 2 1 103μm 2 3.14 103μm 2 6.28 103μm 2 1 104μm 2 4.9 104 μm 2 Or any value between them.
[0059] In some embodiments, the length of the first region along the length direction of the first electrode 150 is 20 μm to 250 μm, specifically 20 μm, 60 μm, 100 μm, 140 μm, 180 μm, 220 μm, 250 μm or any value between them.
[0060] In some embodiments, the width of the first region along the width direction of the first electrode 150 is 20 μm to 150 μm, specifically 20 μm, 60 μm, 100 μm, 150 μm or any value between them.
[0061] Secondly, this application also proposes a method for preparing a photovoltaic cell 100, which can be used to prepare the photovoltaic cell 100 described in the first aspect.
[0062] Please see Figures 1-7 In this embodiment of the application, the preparation method includes the following steps: S100. A single-crystal silicon substrate 110 having a first surface and a second surface disposed opposite to each other is provided. The first surface is formed with a textured surface, and the textured surface includes a plurality of first pyramid structures 111, each of the first pyramid structure 111 including a pyramid body 1111 and a pyramid tip 1112. S200. Form a first semiconductor doped layer such that the first semiconductor doped layer covers the textured surface; S300. Laser processing causes the spire 1112 to recrystallize into a silicon-containing material with a different crystal structure from the single-crystal silicon substrate 110; S400. A first passivation layer 140 is formed, the first passivation layer 140 covering the side of the first doped semiconductor layer 120 facing away from the textured surface; S500. An electrode is formed, wherein the portion of the electrode corresponding to the first pyramid structure 111 is electrically connected to the first doped semiconductor layer 120.
[0063] In the preparation method of this application, laser treatment causes the apex 1112 of the first pyramid structure 111 to recrystallize into a silicon-containing material with a different crystal structure and a lower thermal conductivity than its body 1111. Since the lower the thermal conductivity, the greater the temperature rise under the same current, the first electrode 150 is more likely to form metal contact points 132 with the first doped semiconductor layer 120 in the apex 1112 region of the first pyramid structure 111. In contrast, the number of contact points formed between the first electrode 150 and the first doped semiconductor layer 120 region on the surface of the body 1111 of the first pyramid structure 111 is reduced, thereby reducing the metal contact recombination between the first electrode 150 and the first doped semiconductor layer 120 and increasing the open circuit voltage of the photovoltaic cell 100.
[0064] In this embodiment of the application, specifically, the material of the tower body 1111 is monocrystalline silicon, and the tower tip 1112 can be made of other silicon-containing materials with lower thermal conductivity than monocrystalline silicon, such as polycrystalline silicon, microcrystalline silicon, or amorphous silicon. In some preferred embodiments, the tower tip 1112 is made of polycrystalline silicon. Polycrystalline silicon not only has lower thermal conductivity than monocrystalline silicon, but it also has higher electrical conductivity, which is beneficial to improving the electrical performance of the photovoltaic cell 100.
[0065] In some embodiments, the axial height H of the first pyramid structure 111 is 0.5 μm to 2 μm, specifically 0.5 μm, 1 μm, 1.5 μm, 2 μm or any value between them; along the width direction of the first electrode 150, the width d1 of the pyramid tip 1112 near the pyramid body 1111 is 0.2 μm to 1.5 μm, specifically 0.2 μm, 0.4 μm, 0.8 μm, 1 μm, 1.2 μm, 1.5 μm or any value between them, or the width d2 of the pyramid body 1111 away from the pyramid tip 1112 is 0.7 μm to 2.8 μm, specifically 0.7 μm, 1.4 μm, 2.1 μm, 2.8 μm or any value between them.
[0066] It should be noted that the descriptions of "S100", "S200", "S300", "S400", and "S500" in the technical solution of this application are for descriptive purposes only and should not be construed as indicating or implying the order of the steps. In the preparation method of this application, step S300 can be performed before or after step S200. In some embodiments, step S300 is performed after step S200. The laser processing step includes: irradiating the side of the first doped semiconductor layer 120 facing away from the single crystal silicon substrate 110 with a laser, so that the first doped semiconductor layer 120 forms a heavily doped region 121, the heavily doped region 121 includes a first region and a second region, the first region covers the tower tip 1112, the second region covers the tower body 1111, and the doping element concentration of the first region is higher than that of the second region; the first electrode 150 forms an electrical contact with the heavily doped region 121.
[0067] In the above embodiment, laser processing causes the tip 1112 region of the first pyramid to recrystallize into a silicon-containing material with a different crystal structure than the body 1111 region. On the other hand, it causes the doping element concentration of the first doped semiconductor layer 120 on the surface of the tip 1112 of the first pyramid to be higher than the doping element concentration of the first doped semiconductor layer 120 on the surface of the body 1111, thereby reducing the metal contact recombination between the first electrode 150 and the first doped semiconductor layer 120 from multiple aspects.
[0068] In some embodiments, the difference in dopant concentration between the first region and the second region is 5 × 10⁻⁶. 16 atoms / cm 3 ~1×10 19 atoms / cm 3 Within this concentration difference range, it is beneficial to reduce the contact recombination between the first electrode 150 and the first doped semiconductor layer 120, and also beneficial to improve the electrical performance of the photovoltaic cell 100.
[0069] In some embodiments, the power of the laser processing is 100W to 800W, specifically 100W, 200W, 300W, 400W, 500W, 600W, 700W, 800W, or any value between them. Preferably, the power of the laser processing is 200W to 500W, specifically 200W, 300W, 400W, 500W, or any value between them.
[0070] The wavelength of the laser processing is 400nm to 2000nm, specifically 400nm, 800nm, 1200nm, 1600nm, 2000nm, or any value between them. Preferably, the wavelength of the laser processing is 700nm to 1400nm, specifically 700nm, 800nm, 900nm, 1000nm, 1100nm, 1200nm, 1300nm, 1400nm, or any value between them.
[0071] The laser treatment spot diameter is 5μm to 120μm, specifically 5μm, 10μm, 20μm, 30μm, 40μm, 50μm, 60μm, 70μm, 80μm, 90μm, 100μm, 110μm, 120μm, or any value between them. Preferably, the laser treatment spot diameter is 50μm to 120μm, specifically 50μm, 60μm, 70μm, 80μm, 90μm, 100μm, 110μm, 120μm, or any value between them.
[0072] The dwell time of the laser spot at a single point during laser treatment is 2μs-10μs, specifically 2μs, 4μs, 6μs, 8μs, 10μs, or any value between them. Preferably, the dwell time of the laser spot at a single point during laser treatment is 3μs-8μs, specifically 3μs, 4μs, 5μs, 6μs, 7μs, 8μs, or any value between them.
[0073] By controlling the power, spot diameter, and single-point dwell time of the laser processing within the aforementioned ranges, it is beneficial to control the doping element concentrations of the first and second regions within a suitable range, and also beneficial to control the height ratio / volume ratio of the apex 1112 and the body 1111 of the first pyramid structure 111 within a suitable range. This is beneficial to reduce the metal contact recombination between the first electrode 150 and the first doped semiconductor layer 120 while taking into account the electrical performance of the photovoltaic cell 100.
[0074] In the above embodiments, during the laser processing, when the laser spot diameter is greater than the diameter of the heavily doped region 121 or the diameter of the circumscribed circle, the single-point dwell time of the laser spot is the laser processing time of a single heavily doped region 121; when the laser spot diameter is smaller than the diameter of the heavily doped region 121 or the diameter of the circumscribed circle, the laser needs to scan a certain distance along the extension direction of the first electrode 150, and the single-point dwell time of the laser spot is the dwell time of the laser spot after each movement during the scanning process.
[0075] In some embodiments, the step of forming an electrode includes: forming a first electrode 150 on the side of the first passivation layer 140 opposite to the first doped semiconductor layer 120 using a weak burn-through process and laser-enhanced contact optimization technology.
[0076] Specifically, a weak burn-through process is first used to print a weakly burn-through metal paste on the surface of the first passivation layer 140 to form the first electrode 150 (which does not form an electrical contact with the first doped semiconductor layer 120). Then, a laser-enhanced contact optimization process is performed. The area around the first electrode 150 is irradiated with a laser to excite localized, high-density photogenerated carriers and form a localized photogenerated current under an applied reverse bias. The thermal effect of the current brings a localized high temperature, which melts the metal particles 131 (e.g., silver particles) in the first electrode 150 with the silicon in the first doped semiconductor layer 120 to form a silicon alloy (e.g., silver-silicon alloy), which is the contact point. Thus, the first electrode 150 and the first doped semiconductor layer 120 are electrically connected.
[0077] More specifically, in the process of fabricating the first electrode 150 using the weak burn-through process described above, a glass layer 130 is formed between the first electrode 150 and the first passivation layer 140. The first electrode 150 is formed by curing a metal paste, and the glass layer 130 is formed by reacting the metal paste with the first passivation layer 140. The glass layer 130 contains metal particles 131 (derived from the metal paste), and at least some of the metal particles 131 pierce the glass layer 130 to contact the first doped semiconductor layer 120. Figure 7 As shown, in the subsequent laser-enhanced contact optimization process, the metal particles 131 that pierce the glass layer 130 will melt with the silicon in the first doped semiconductor layer 120 to form metal contact points 132, thereby connecting the circuit between the first electrode 150 and the first doped semiconductor layer 120. In this embodiment, since the thermal conductivity of the tip 1112 of the first pyramid structure 111 is lower than that of its body 1111, and even the doping element concentration of the first doped semiconductor layer 120 on the surface of the tip 1112 of the first pyramid is higher than that of the first doped semiconductor layer 120 on the surface of its body 1111, the metal particles 131 are more likely to melt with the silicon located at the tip 1112 of the first pyramid structure 111 to form metal contact points 132. That is, the first electrode 150 is more likely to form metal contact points 132 with the region of the first doped semiconductor layer 120 on the surface of the tip 1112 of the first pyramid structure 111. As a result, the metal contact recombination between the first electrode 150 and the first doped semiconductor layer 120 is reduced, and the open circuit voltage of the photovoltaic cell 100 is increased.
[0078] In some embodiments, after laser treatment, the preparation method further includes the step of subjecting the laser-treated product to high-temperature annealing or high-temperature oxidation treatment.
[0079] In some embodiments, the photovoltaic cell 100 is a passivated contact cell (TOPCon cell), the first surface is the front side of the monocrystalline silicon substrate 110, and the second surface is the back side of the monocrystalline silicon substrate 110. The preparation method of this application further includes the step of: preparing the back side structure of the monocrystalline silicon substrate 110. Specifically, the back side of the monocrystalline silicon substrate 110 is etched and a tunneling oxide layer 160, a second doped semiconductor layer 170, a second passivation layer 180, and a second electrode 190 are sequentially deposited on the back side of the monocrystalline silicon substrate 110.
[0080] In the above embodiments, this application does not impose any particular limitation on the preparation method of the back structure of the single crystal silicon substrate 110. Those skilled in the art can refer to the preparation method of the back structure of passivated contact cells (TOPCon cells) known in the art.
[0081] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.
Claims
1. A photovoltaic cell, characterized in that, It includes a single-crystal silicon substrate, a first doped semiconductor layer, and a first electrode. The single-crystal silicon substrate has a first surface and a second surface disposed opposite to each other. The first doped semiconductor layer and the first electrode are disposed on the first surface. The first surface is provided with a plurality of first pyramid structures, each first pyramid structure including a body region and a apex region. The first doped semiconductor layer in the apex region is a silicon-containing material with a different crystal structure than the single-crystal silicon substrate. The first electrode forms an electrical contact with the first doped semiconductor layer.
2. The photovoltaic cell as described in claim 1, characterized in that, The first surface has a first conductive region and a second conductive region, and the first doped semiconductor layer and the first electrode are disposed in the first conductive region; The second conductive region is provided with a tunneling oxide layer, a second doped semiconductor layer and a second electrode, wherein the tunneling oxide layer is disposed on the side of the second doped semiconductor layer facing the single crystal silicon substrate.
3. The photovoltaic cell as described in claim 2, characterized in that, The first doped semiconductor layer is a doped amorphous silicon layer.
4. The photovoltaic cell as described in claim 2, characterized in that, The second doped semiconductor layer is a doped polycrystalline silicon layer.
5. The photovoltaic cell as described in claim 2, characterized in that, The material of the first electrode or the second electrode is one or more of aluminum, silver, nickel, gold, molybdenum or copper.
6. The photovoltaic cell as described in claim 1, characterized in that, Along the length of the first electrode, the side of the first electrode facing the single-crystal silicon substrate has a plurality of spaced metal contact regions, and the first electrode forms an electrical contact with the first doped semiconductor layer through the metal contact regions.
7. The photovoltaic cell according to any one of claims 1-6, characterized in that, The axial height of the first pyramid structure is 0.5 μm to 2 μm.
8. The photovoltaic cell according to any one of claims 1-6, characterized in that, Along the width direction of the first electrode, the width of the spire region on the side closer to the tower body region is 0.2 μm to 1.5 μm, or the width of the tower body region on the side farther from the spire region is 0.7 μm to 2.8 μm.
9. The photovoltaic cell according to any one of claims 1-6, characterized in that, A glass layer is formed between the first electrode and the first doped semiconductor layer, wherein the material of the glass layer includes one or more compounds such as silicon oxide, silicon nitride, silicon oxynitride, silicates, lead oxide, aluminum oxide, and boric acid.
10. The photovoltaic cell as described in claim 9, characterized in that, The thickness of the glass layer is 10 nm to 500 nm.
11. The photovoltaic cell according to any one of claims 1-6, characterized in that, The first doped semiconductor layer includes a heavily doped region, and the first electrode forms an electrical contact with the heavily doped region. The heavily doped region includes a first region and a second region. The first region covers the top of the tower, and the second region covers the body of the tower. The doping element concentration in the first region is higher than that in the second region.
12. The photovoltaic cell as described in claim 11, characterized in that, The doping concentration in the first region is 1×10 17 atoms / cm 3 ~2×10 19 atoms / cm 3 ; and / or, The doping concentration in the second region is 5 × 10⁻⁶. 16 atoms / cm 3 ~1×10 19 atoms / cm 3 ; and / or, The first doped semiconductor layer further includes a third region, which is the other region of the first doped semiconductor layer excluding the heavily doped region, and the doping concentration of the third region is 1×10⁻⁶. 16 atoms / cm 3 ~5×10 17 atoms / cm 3 .