Photovoltaic cell and preparation method thereof

Abstract

The invention relates to the field of photovoltaic technology, in particular to a photovoltaic cell and a preparation method thereof.The photovoltaic cell comprises a monocrystalline silicon substrate with a first surface and a second surface which are oppositely arranged, and a first doped semiconductor layer, a first passivation layer and a first electrode which are sequentially arranged on the first surface; a textured surface is formed on the first surface, the textured surface is provided with a plurality of first pyramid structures, each first pyramid structure comprises a tower body and a spire, the spire is a silicon-containing material with a crystal structure different from that of the monocrystalline silicon substrate, and the part, corresponding to the first pyramid structure, of the first electrode is in electric contact with the first doped semiconductor layer. In the technical scheme of the invention, the material of the spire of the first pyramid structure is the silicon-containing material with a crystal structure different from that of the monocrystalline silicon substrate, so that the number of contact points formed by the first electrode and the first doped semiconductor layer area on the surface of the spire of the first pyramid structure is increased; metal contact recombination of the first electrode and the first doped semiconductor layer is reduced.

Description

Technical Field

[0001] The present invention relates to the field of photovoltaic technology, and in particular to a photovoltaic cell and a preparation method thereof. Background Art

[0002] The current mainstream passivated contact battery (TOPCon) technology and products have an emitter formed by boron diffusion on the front of the battery, and the metal electrode penetrates the passivation layer on the emitter surface to form contact with the emitter. The metal slurry will melt and destroy the surface passivation layer during the high-temperature ablation process, increasing the surface carrier recombination, and the large number of metal contact points will also increase the metal contact recombination, making it difficult to further increase the open circuit voltage of the battery. Summary of the invention

[0003] The present application proposes a photovoltaic cell and a preparation method thereof, aiming to improve the metal contact recombination of the photovoltaic cell, thereby increasing the open circuit voltage of the photovoltaic cell.

[0004] In a first aspect, an embodiment of the present application provides a photovoltaic cell, comprising a single crystal silicon substrate having a first surface and a second surface arranged opposite to each other, and a first doped semiconductor layer, a first passivation layer, and a first electrode sequentially arranged on the first surface in a direction away from the single crystal silicon substrate;

[0005] The first surface is formed with a velvet surface, and the velvet surface has a plurality of first pyramid structures, wherein the first pyramid structure includes a tower body and a tower top, wherein the tower top is a silicon-containing material having a crystal structure different from that of the single crystal silicon substrate, and a 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 direction of the first electrode, the first electrode has a plurality of spaced-apart metal contact regions on a side facing the single crystal silicon substrate, and the electrode forms 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 tower body, and the doping element concentration of the first region is higher than the doping element concentration of the second region.

[0008] In some embodiments, the doping element concentration of the first region is 1×10 17 Atom / cm 3 ~2×10 19 Atom / cm 3 and / or,

[0009] The doping element concentration of the second region is 5×10 16 Atom / cm 3 ~1×10 19 Atom / cm 3 and / or,

[0010] The first doped semiconductor layer further includes a third region, which is other regions of the first doped semiconductor layer except the heavily doped region, and the doping element concentration of the third region is 1×10 16 Atom / cm 3 ~5×10 17 Atom / cm 3 .

[0011] In some embodiments, there are a plurality of first electrodes, one first electrode forms electrical contact with a plurality of heavily doped regions spaced apart from each other, and the heavily doped regions of the first doped semiconductor layer are sequentially arranged in a lattice.

[0012] In some embodiments, the distance between two adjacent heavily doped regions along the length direction of the first electrode is ≥10 μm; and / or,

[0013] The area of ​​the heavily doped region is 3.14*10 2 μm 2 ~4.9*10 4 μm 2 and / or,

[0014] 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.

[0015] In some embodiments, the axial height of the first pyramid structure is 0.5 μm to 2 μm;

[0016] Along the width direction of the first electrode, the width of the tower tip close to 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.

[0017] In a second aspect, the present application also proposes a method for preparing a photovoltaic cell, comprising the following steps:

[0018] Providing a single crystal silicon substrate having a first surface and a second surface arranged opposite to each other, wherein a textured surface is formed on the first surface, and the textured surface includes a plurality of first pyramid structures, and the first pyramid structures include a tower body and a tower top;

[0019] forming a first semiconductor doping layer so that the first semiconductor doping layer covers the velvet surface;

[0020] Laser processing causes the tower tip to recrystallize into a silicon-containing material with a different crystal structure from the single crystal silicon substrate;

[0021] forming a first passivation layer, wherein the first passivation layer covers a side of the first doped semiconductor layer facing away from the velvet surface;

[0022] A first electrode is formed, wherein a portion of the first electrode corresponding to the first pyramid structure is electrically connected to the first doped semiconductor layer.

[0023] In some embodiments, the laser processing step includes: irradiating a 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 includes a first region and a second region, the first region covers the top of the tower, the second region covers the tower body, and the concentration of doping elements in the first region is higher than the concentration of doping elements in the second region;

[0024] The first electrode forms an electrical contact with the heavily doped region.

[0025] In some embodiments, the power of the laser treatment is 100W to 800W, the wavelength of the laser treatment is 400nm to 2000nm, the spot diameter of the laser treatment is 5μm to 120μm, and the single-point residence time of the spot of the laser treatment is 2μs-10μs.

[0026] Compared with the prior art, this technical solution has at least the following technical effects:

[0027] In the technical solution of the present application, since the material of the top of the first pyramid structure is a silicon-containing material with a crystal structure different from that of the single-crystal silicon substrate, the thermal conductivity of the top of the first pyramid structure is lower than the thermal conductivity of the tower body, so that 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 increases, and relatively, the number of contact points formed between the first electrode and the first doped semiconductor layer region on the surface of the tower body of the first pyramid structure decreases, thereby reducing the metal contact recombination between the first electrode and the first doped semiconductor layer, and improving the open circuit voltage of the photovoltaic cell. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The present invention is further described below in conjunction with the accompanying drawings and embodiments.

[0029] Figure 1 This is a schematic diagram of the structure of a photovoltaic cell in one embodiment of the present application;

[0030] Figure 2 for Figure 1 A top view of

[0031] Figure 3 for Figure 1 A cross-sectional view of

[0032] Figure 4 for Figure 1 Schematic diagram of the structure of the first pyramid;

[0033] Figure 5 This is a schematic structural diagram of a photovoltaic cell in another embodiment of the present application;

[0034] Figure 6 A process flow chart of photovoltaic cells for this application;

[0035] Figure 7 This is a schematic flow chart of the laser enhanced contact optimization step in the photovoltaic cell preparation method of the present application.

[0036] Reference numerals:

[0037] Label name Label name 100 Photovoltaic cells 110 Single crystal silicon substrate 111 The first pyramid structure 1111 Tower 1112 Spire 120 The first doped semiconductor layer 121 Heavily doped region 130 Glass layer 131 Metal particles 132 Metal contact points 140 First passivation layer 150 First electrode 160 Tunneling oxide 170 The second doped semiconductor layer 180 Second passivation layer 190 Second electrode DETAILED DESCRIPTION

[0038] In order to better understand the technical solution of the present invention, the embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0039] It should be clear that the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0040] The terms used in the embodiments of the present invention are only for the purpose of describing specific embodiments, and are not intended to limit the present invention. The singular forms "a", "said" and "the" used in the embodiments of the present invention and the appended claims are also intended to include plural forms, unless the context clearly indicates other meanings.

[0041] The term "and / or" used in this article is only a description of the association relationship of associated objects, indicating that there can be three relationships. For example, A and / or B can mean: A exists alone, A and B exist at the same time, and B exists alone. In addition, the character " / " in this article generally indicates that the associated objects before and after are in an "or" relationship.

[0042] It should be noted that if the embodiments of the present application involve directional indications (such as up, down, left, right, front, back...), the directional indications are only used to explain the relative position relationship, movement status, etc. between the components under a certain specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indication will also change accordingly.

[0043] In a first aspect, the present application provides a photovoltaic cell 100 .

[0044] See also Figure 1-Figure 7 In the embodiment of the present application, the photovoltaic cell 100 includes a single crystal silicon substrate 110 having a first surface and a second surface arranged opposite to each other, and a first doped semiconductor layer 120, a first passivation layer 140 and a first electrode 150 arranged on the first surface in sequence in a direction away from the single crystal silicon substrate 110; the first surface is formed with a velvet surface, the velvet surface includes a plurality of first pyramid structures 111, the first pyramid structure 111 includes a tower body 1111 and a tower top 1112, wherein the tower top 1112 is a silicon-containing material with a different crystal structure from that of the single crystal silicon substrate 110, the thermal conductivity of the tower top 1112 is lower than the thermal conductivity of the single crystal 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.

[0045] In the technical solution of the present application, since the material of the top 1112 of the first pyramid structure 111 is a silicon-containing material with a different crystal structure from the single crystal silicon substrate 110, the thermal conductivity of the top 1112 of the first pyramid structure 111 is lower than the thermal conductivity of the tower body 1111 thereof, so that the number of contact points formed between the first electrode 150 and the first doped semiconductor layer 120 region on the surface of the top 1112 of the first pyramid structure 111 increases, and correspondingly, the number of contact points formed between the first electrode 150 and the first doped semiconductor layer 120 region on the surface of the tower body 1111 of the first pyramid structure 111 decreases, thereby reducing the metal contact recombination between the first electrode 150 and the first doped semiconductor layer 120, and improving the open circuit voltage of the photovoltaic cell 100.

[0046] In the embodiment of the present application, specifically, the material of the tower body 1111 of the first pyramid structure 111 is single crystal silicon, and the tower top 1112 can be made of other silicon-containing materials with lower thermal conductivity than single crystal silicon, such as polycrystalline silicon, microcrystalline silicon, amorphous silicon, etc. Preferably, the tower top 1112 is polycrystalline silicon, which not only has lower thermal conductivity than single crystal silicon, but also has higher electrical conductivity, which is beneficial to improving the electrical performance of the photovoltaic cell 100.

[0047] See also 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 therebetween; along the width direction of the first electrode 150, the width d1 of the tower tip 1112 close to the tower 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 therebetween, or the width d2 of the tower body 1111 away from the tower 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 therebetween. Within the above range, it 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.

[0048] In the embodiment of the present application, the first surface may be the front or back side of the single crystal silicon substrate 110. The front side of the single crystal silicon substrate 110 is the light receiving side for absorbing incident light, and the back side of the single crystal silicon substrate 110 is the backlight side. The single crystal silicon substrate 110 may be N-type or P-type.

[0049] In the embodiment of the present application, the photovoltaic cell 100 may be a photovoltaic cell 100 of a type such as a passivated contact cell (TOPCon cell) or a back contact cell (BC cell).

[0050] See also Figure 3 In some embodiments, the photovoltaic cell 100 is a passivation contact cell (TOPCon cell), the first surface is the front side of the single crystal silicon substrate 110, and the second surface is the back side of the single crystal silicon substrate 110; the photovoltaic cell 100 further includes a tunneling oxide layer 160, a second doped semiconductor layer 170, a second passivation layer 180, and a second electrode 190 sequentially arranged on the back side of the single crystal silicon substrate 110 in a direction away from the single crystal silicon substrate 110, and 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 doping element, and the second doped semiconductor layer 170 contains a P-type doping element.

[0051] In other embodiments, the photovoltaic cell is a back contact cell (BC cell), the first surface is the back side of the single crystal silicon substrate 110, the second surface is the front side of the single crystal silicon substrate 110, the first surface has a first conductive region and a second conductive region, the first pyramid structure 111 is formed in the first conductive region of the first surface, the first doped semiconductor layer 120, the first passivation layer 140 and the first electrode 150 are sequentially arranged in the first conductive region of the first surface; the photovoltaic cell 100 further includes a tunneling oxide layer 160, a second doped semiconductor layer 170, a second passivation layer 180 and a second electrode 190 sequentially arranged in the second region of the first surface in a direction away from the single crystal silicon substrate 110. In a specific embodiment, the first conductive region is an N-type conductive region, the first doped semiconductor layer 120 contains an N-type doping element, the second conductive region is a P-type conductive region, and the second doped semiconductor layer 170 contains a P-type doping element.

[0052] The photovoltaic cell 100 of the present application is described in more detail below by taking the photovoltaic cell 100 as a passivated contact cell (TOPCon cell) as an example.

[0053] In some embodiments, the N-type doping element may be a Group V element such as phosphorus (P), bismuth (Bi), antimony (Sb), or arsenic (As), and the P-type doping element may be a Group III element such as boron (B), aluminum (Al), gallium (Ga), or indium (In). In a specific embodiment, the single crystal silicon substrate 110 is an N-type substrate, and the doping element type inside the first doped semiconductor layer 120 is a P-type element, and the P-type element includes a boron (B) element.

[0054] In some embodiments, in addition to the doping elements, the first doped semiconductor layer 120 / the second doped semiconductor layer 170 further includes one or more of amorphous silicon, microcrystalline silicon, polycrystalline silicon, and silicon carbide.

[0055] In some embodiments, the material of the first passivation layer 140 / the second passivation layer 180 includes one or more of silicon nitride, silicon oxynitride, silicon oxide, aluminum oxide, and aluminum oxynitride.

[0056] In some embodiments, the first passivation layer 140 / the second passivation layer 180 may be a single-layer structure or a multi-layer structure. For a multi-layer structure, the materials of different layers may be different from each other, or the materials of some layers may be the same and different from the materials of other layers. For example, the first passivation layer 140 may be a multi-layer structure of a silicon nitride layer and an aluminum oxide layer. In this way, the passivation layer has high light transmittance, taking into account the passivation effect and light transmittance of the solar cell, which is beneficial to improving the light conversion efficiency of the solar cell and improving the battery performance.

[0057] In some embodiments, the thickness of the first passivation layer 140 is 50-150 nm, and specifically may be 50 nm, 75 nm, 100 nm, 125 nm, 150 nm, or any value therebetween.

[0058] In some embodiments, the first electrode 150 / the second electrode 190 is formed by sintering a weak fire-through type slurry, and the material of the first electrode 150 / the second electrode 190 can be one or more of aluminum, silver, nickel, gold, molybdenum or copper.

[0059] In some embodiments, the first electrode 150 refers to a fine grid line or a finger-shaped grid line, which is different from a main grid line or a bus bar. There are multiple first electrodes 150, and the multiple first electrodes 150 are arranged in sequence along the first direction. The first electrode 150 extends along the second direction, and the second direction is perpendicular to the first direction.

[0060] In some embodiments, the width of the first electrode 150 is 5 μm to 50 μm, and specifically may be 5 μm, 10 μm, 20 μm, 30 μm, 40 μm, 50 μm, or any value therebetween.

[0061] See also Figure 4 , Figure 5 and Figure 6 In some embodiments, a first electrode 150 is printed on the surface of the first passivation layer 140 by a weak burn-through process, and a laser enhanced contact optimization technique 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 further 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 (for example, silver particles). During the formation of the first electrode 150, at least part 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, the 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, namely, a metal contact point 132, so that the circuit between the first electrode 150 and the first doped semiconductor layer 120 is connected.

[0062] In some embodiments, the size of the silver particles is ≤ 20 nm.

[0063] In some embodiments, the material of the glass layer 130 includes one or more compounds selected from the group consisting of silicon oxide, silicon nitride, silicon oxynitride, silicate, lead oxide, aluminum oxide, boric acid, and the like.

[0064] In some embodiments, the thickness of the glass layer 130 is in the range of 10 nm to 500 nm, and specifically may be 10 nm, 100 nm, 200 nm, 300 nm, 400 nm, 500 nm, or any value therebetween.

[0065] In an embodiment of the present application, the first electrode 150 has a metal contact area on the side facing the single crystal silicon substrate 110, and the first electrode 150 forms an electrical contact with the first doped semiconductor layer 120 through the metal contact area, wherein the metal contact area can be the entire area of ​​the surface of the first electrode 150 on the side facing the single crystal silicon substrate 110, or it can be a partial area of ​​the surface of the first electrode 150 on the side facing the single crystal silicon substrate 110.

[0066] In some embodiments, along the length direction of the first electrode 150, the side of the first electrode 150 facing the single crystal silicon substrate 110 has a plurality of spaced metal contact regions, and a portion of the surface of the first electrode 150 facing the single crystal silicon substrate 110 forms electrical contact with the first doped semiconductor layer 120. This arrangement can reduce the metal contact points 132 between the first electrode 150 and the first doped semiconductor layer 120, that is, it can reduce the damage to the first passivation layer 140, thereby reducing the surface recombination and metal contact recombination of carriers, and improving the open circuit voltage of the battery.

[0067] See also Figure 1 and Figure 2 In the above embodiment, the first passivation layer 140 has alternately arranged gate line areas and non-gate line areas on the side facing away from the first doped semiconductor layer 120, and the first electrode 150 is arranged in the gate line area, and the first electrode 150 is arranged one-to-one with the gate line area.

[0068] In some embodiments, the velvet surface further has a second pyramid structure, which is another pyramid structure of the velvet surface except the first pyramid structure 111, and the tower body 1111 and the tower top 1112 of the second pyramid structure are both single crystal silicon. Specifically, the first pyramid structure 111 is arranged opposite to the metal contact area of ​​the first electrode 150, and the second pyramid structure is arranged in a staggered manner with the metal contact area of ​​the first electrode 150, which is conducive to reducing the damage of the first passivation layer 140 and the metal contact recombination.

[0069] See also Figure 1 , Figure 2 and Figure 5In some embodiments, the first doped semiconductor layer 120 includes a heavily doped region 121, 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 tower top 1112, the second region covers the tower body 1111, and the doping element concentration of the first region is higher than the doping element concentration of the second region. The region with a higher doping element concentration of the first doped semiconductor layer 120 is more likely to form a metal contact point 132 with the first electrode 150. By making the doping element concentration of the first region higher than the doping element concentration 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, further improve the open circuit voltage of the photovoltaic cell 100.

[0070] In the above embodiment, one first electrode 150 forms electrical contact with a plurality of heavily doped regions 121 disposed at intervals, and the heavily doped regions 121 of the first doped semiconductor layer 120 are sequentially arranged in a matrix.

[0071] In some embodiments, the difference in doping element concentration between the first region and the second region is 5×10 16 Atom / cm 3 ~1×10 19 Atom / 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 to improve the electrical performance of the photovoltaic cell 100 .

[0072] In some embodiments, the doping element concentration of the first region is 1×10 17 Atom / cm 3 ~2×10 19 Atom / cm 3 , specifically 1×10 17 Atom / cm 3 , 5×10 17 Atom / cm 3 , 1×10 18 Atom / cm 3 , 5×10 18 Atom / cm 3 , 1×10 19 Atom / cm 3 , 2×10 19 Atom / cm 3 or any value in between.

[0073] In some embodiments, the doping element concentration of the second region is 5×10 16 Atom / cm 3 ~1×10 19 Atom / cm 3 , specifically 5×1016 Atom / cm 3 , 1×10 17 Atom / cm 3 , 5×10 17 Atom / cm 3 , 1×10 18 Atom / cm 3 , 5×10 18 Atom / cm 3 , 1×10 19 Atom / cm 3 or any value in between.

[0074] It can be understood that the first doped semiconductor layer 120 also includes a third region, which is the other region of the first doped semiconductor layer 120 except the heavily doped region 121. The doping element concentration of the third region can be consistent with the doping element concentration of the second region, or can be lower than the doping element concentration of the second region.

[0075] In some embodiments, the doping element concentration of the third region is lower than the doping element concentration of the second region, and the doping element concentration of the third region is 1×10 16 Atom / cm 3 ~5×10 17 Atom / cm 3 , specifically 1×10 16 Atom / cm 3 , 4×10 16 Atom / cm 3 , 8×10 16 Atom / cm 3 , 2×10 17 Atom / cm 3 , 5×10 17 Atom / cm 3 The third region is within the doping concentration range, which is beneficial to improving the electrical performance of the photovoltaic cell 100 .

[0076] In the embodiment of the present application, the size and arrangement spacing of each heavily doped region 121 can be adjusted according to actual conditions.

[0077] In some embodiments, along the length direction of the first electrode 150 , the distance between two adjacent heavily doped regions 121 is ≥10 μm. Within this distance range, the metal contact between the first electrode 150 and the first doped semiconductor layer 120 can be effectively reduced.

[0078] In some embodiments, the area of ​​the heavily doped region 121 is 3.14*102μm2 to 4.9*104μm 2 , specifically 3.14*102μm2 、6.28*102μm 2 、1*103μm 2 、3.14*103μm 2 、6.28*103μm 2 、1*104μm 2 、4.9*104μm 2 or any value in between.

[0079] In some embodiments, along the length direction of the first electrode 150 , the length of the first region is 20 μm to 250 μm, specifically 20 μm, 60 μm, 100 μm, 140 μm, 180 μm, 220 μm, 250 μm or any value therebetween.

[0080] In some embodiments, along the width direction of the first electrode 150 , the width of the first region is 20 μm to 150 μm, and specifically may be 20 μm, 60 μm, 100 μm, 150 μm, or any value therebetween.

[0081] In a second aspect, the present application further proposes a method for preparing a photovoltaic cell 100 , and the photovoltaic cell 100 of the first aspect mentioned above can be prepared by using the preparation method.

[0082] See also Figure 1-Figure 7 In the embodiment of the present application, the preparation method comprises the following steps:

[0083] S100. A single crystal silicon substrate 110 having a first surface and a second surface disposed opposite to each other is provided, wherein a velvet surface is formed on the first surface, wherein the velvet surface includes a plurality of first pyramid structures 111, wherein the first pyramid structure 111 includes a tower body 1111 and a tower top 1112;

[0084] S200. forming a first semiconductor doping layer so that the first semiconductor doping layer covers the velvet surface;

[0085] S300. Laser treatment causes the spire 1112 to recrystallize to form a silicon-containing material with a different crystal structure from the single crystal silicon substrate 110;

[0086] S400. forming a first passivation layer 140, wherein the first passivation layer 140 covers a side of the first doped semiconductor layer 120 facing away from the velvet surface;

[0087] S500 . Forming an electrode, wherein a portion of the electrode corresponding to the first pyramid structure 111 is electrically connected to the first doped semiconductor layer 120 .

[0088] In the preparation method of the present application, laser treatment causes the top 1112 of the first pyramid structure 111 to recrystallize to form a silicon-containing material with a different crystal structure having a lower thermal conductivity than the body 1111 thereof. Since the lower the thermal conductivity, the greater the temperature rise under the same current, the first electrode 150 is more likely to form a metal contact point 132 with the first doped semiconductor layer 120 in the top 1112 region of the first pyramid structure 111. Relatively speaking, 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 improving the open circuit voltage of the photovoltaic cell 100.

[0089] In the embodiment of the present application, specifically, the material of the tower body 1111 is single crystal silicon, and the tower top 1112 can be made of other silicon-containing materials with lower thermal conductivity than single crystal silicon, such as polycrystalline silicon, microcrystalline silicon, amorphous silicon, etc. In some preferred embodiments, the tower top 1112 is polycrystalline silicon, which not only has lower thermal conductivity than single crystal silicon, but also has higher electrical conductivity, which is beneficial to improving the electrical performance of the photovoltaic cell 100.

[0090] 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 therebetween; along the width direction of the first electrode 150, the width d1 of the tower top 1112 close to the tower 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 therebetween, or the width d2 of the tower body 1111 away from the tower top 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 therebetween.

[0091] It should be noted that the descriptions of "S100", "S200", "S300", "S400", and "S500" in the technical solution of this application are only for descriptive purposes and cannot be understood as indicating or implying the order of the steps. In the preparation method of this application, step S300 can be performed before step S200 or after step S200.

[0092] In some embodiments, step S300 is performed after step S200, and the laser processing step includes: using laser to irradiate the side of the first doped semiconductor layer 120 facing away from the single crystal silicon substrate 110, so that the first doped semiconductor layer 120 forms a heavily doped region 121, and the heavily doped region 121 includes a first area and a second area, the first area covers the top of the tower 1112, and the second area covers the tower body 1111, and the doping element concentration of the first area is higher than the doping element concentration of the second area; the first electrode 150 forms an electrical contact with the heavily doped region 121.

[0093] In the above embodiment, laser processing is used to recrystallize the top 1112 region of the first pyramid to form a silicon-containing material with a different crystal structure from that of the body 1111 region thereof. On the other hand, the doping element concentration of the first doped semiconductor layer 120 on the surface of the top 1112 of the first pyramid is higher than the doping element concentration of the first doped semiconductor layer 120 on the surface of the body 1111 thereof, so as to reduce the metal contact recombination between the first electrode 150 and the first doped semiconductor layer 120 from multiple aspects.

[0094] In some embodiments, the difference in doping element concentration between the first region and the second region is 5×10 16 Atom / cm 3 ~1×10 19 Atom / 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 to improve the electrical performance of the photovoltaic cell 100 .

[0095] In some embodiments, the power of the laser treatment is 100W to 800W, specifically 100W, 200W, 300W, 400W, 500W, 600W, 700W, 800W or any value therebetween. Preferably, the power of the laser treatment is 200W to 500W, specifically 200W, 300W, 400W, 500W or any value therebetween.

[0096] The wavelength of the laser treatment is 400nm to 2000nm, specifically 400nm, 800nm, 1200nm, 1600nm, 2000nm or any value therebetween. Preferably, the wavelength of the laser treatment is 700nm to 1400nm, specifically 700nm, 800nm, 900nm, 1000nm, 1100nm, 1200nm, 1300nm, 1400nm or any value therebetween.

[0097] The diameter of the laser spot is 5 μm to 120 μm, and can be 5 μm, 10 μm, 20 μm, 30 μm, 40 μm, 50 μm, 60 μm, 70 μm, 80 μm, 90 μm, 100 μm, 110 μm, 120 μm or any value therebetween. Preferably, the diameter of the laser spot is 50 μm to 120 μm, and can be 50 μm, 60 μm, 70 μm, 80 μm, 90 μm, 100 μm, 110 μm, 120 μm or any value therebetween.

[0098] The single-point dwell time of the laser-processed light spot is 2μs-10μs, specifically 2μs, 4μs, 6μs, 8μs, 10μs or any value therebetween. Preferably, the single-point dwell time of the laser-processed light spot is 3μs-8μs, specifically 3μs, 4μs, 5μs, 6μs, 7μs, 8μs or any value therebetween.

[0099] By controlling the power, spot diameter and single-point dwell time of the laser processing within the above ranges, it is beneficial to control the concentration of doping elements in the first region and the second region within an appropriate range, and it is beneficial to control the height ratio / volume ratio of the top 1112 and the tower body 1111 of the first pyramid structure 111 within an appropriate range, which 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.

[0100] In the above embodiment, during the laser processing, when the spot diameter of the laser is larger than the diameter of the heavily doped region 121 or the diameter of the circumscribed circle, the single-point residence time of the spot is the laser processing time of the single heavily doped region 121; when the spot diameter of the laser 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 residence time of the spot is the residence time of the spot after each movement during the scanning process.

[0101] In some embodiments, the step of forming the electrode includes: forming the first electrode 150 on a side of the first passivation layer 140 facing away from the first doped semiconductor layer 120 by using a weak burn-through process and a laser enhanced contact optimization technique.

[0102] Specifically, a weak burn-through process is first used to print a metal paste with weak burn-through properties on the surface of the first passivation layer 140 to form a first electrode 150 (without forming an electrical contact with the first doped semiconductor layer 120); then a laser enhanced contact optimization process is performed to irradiate the surrounding area of ​​the first electrode 150 with a laser to excite localized, high-density photogenerated carriers, and form a localized photogenerated current under an external reverse bias condition. The thermal effect of the current brings about a local high temperature, and the metal particles 131 (for example, silver particles) in the first electrode 150 and the silicon in the first doped semiconductor layer 120 are melted to form a silicon alloy (for example, a silver-silicon alloy), i.e., the contact point, so that the formed first electrode 150 is electrically connected to the first doped semiconductor layer 120.

[0103] More specifically, in the process of preparing the first electrode 150 by the weak burn-through process, a glass layer 130 is formed between the first electrode 150 and the first passivation layer 140, the first electrode 150 is formed by solidifying the metal paste, the glass layer 130 is generated by the reaction of the metal paste and the first passivation layer 140, the glass layer 130 contains metal particles 131 (derived from the metal paste), and at least part of the metal particles 131 pierces the glass layer 130 and contacts 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 the embodiment of the present application, since the thermal conductivity of the top 1112 of the first pyramid structure 111 is lower than the thermal conductivity of the body 1111 thereof, and even the concentration of the doping element in the first doped semiconductor layer 120 on the surface of the top 1112 of the first pyramid is higher than the concentration of the first doped semiconductor layer 120 on the surface of the body 1111 thereof, the metal particles 131 are more likely to melt with the silicon located at the top 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 first doped semiconductor layer 120 region on the surface of the top 1112 of the first pyramid structure 111, thereby reducing the metal contact recombination between the first electrode 150 and the first doped semiconductor layer 120, and improving the open circuit voltage of the photovoltaic cell 100.

[0104] In some embodiments, after the laser treatment, the preparation method further comprises the step of: performing high temperature annealing or high temperature oxidation treatment on the laser treated product.

[0105] In some embodiments, the photovoltaic cell 100 is a passivated contact cell (TOPCon cell), the first surface is the front side of the single crystal silicon substrate 110, and the second surface is the back side of the single crystal silicon substrate 110. The preparation method of the present application also includes the steps of: preparing the back side structure of the single crystal silicon substrate 110, specifically, etching the back side of the single crystal silicon substrate 110 and depositing a tunneling oxide layer 160, a second doped semiconductor layer 170, a second passivation layer 180, and a second electrode 190 in sequence on the back side of the single crystal silicon substrate 110.

[0106] In the above embodiments, the present application does not impose any particular limitation on the method for preparing the back structure of the single crystal silicon substrate 110, and those skilled in the art may refer to the method for preparing the back structure of a passivated contact cell (TOPCon cell) known in the art.

[0107] The above are only 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 in the scope of protection of the present invention.

Claims

1. A photovoltaic cell, characterized in that: The invention comprises a single crystal silicon substrate having a first surface and a second surface arranged opposite to each other, and a first doped semiconductor layer, a first passivation layer and a first electrode arranged on the first surface in sequence in a direction away from the single crystal silicon substrate; The first surface is formed with a velvet surface, and the velvet surface has a plurality of first pyramid structures, wherein the first pyramid structure includes a tower body and a tower top, wherein the tower top is a silicon-containing material having a crystal structure different from that of the single crystal silicon substrate, and a portion of the first electrode corresponding to the first pyramid structure forms an electrical contact with the first doped semiconductor layer.

2. The photovoltaic cell according to claim 1, characterized in that Along the length direction of the first electrode, a side of the first electrode facing the single crystal silicon substrate has a plurality of spaced metal contact regions, and the electrode forms electrical contact with the doped semiconductor layer through the metal contact regions.

3. The photovoltaic cell according to claim 1, characterized in that 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 tower body, and the doping element concentration of the first region is higher than the doping element concentration of the second region.

4. The photovoltaic cell according to claim 3, characterized in that: The doping element concentration of the first region is 1×10 17 Atom / cm 3 ~2×10 19 Atom / cm 3 and / or, The doping element concentration of the second region is 5×10 16 Atom / cm 3 ~1×10 19 Atom / cm 3 and / or, The first doped semiconductor layer further includes a third region, which is other regions of the first doped semiconductor layer except the heavily doped region, and the doping element concentration of the third region is 1×10 16 Atom / cm 3 ~5×10 17 Atom / cm 3 .

5. The photovoltaic cell according to claim 3, characterized in that: There are multiple electrodes, one of which forms electrical contact with multiple heavily doped regions that are spaced apart from each other, and the heavily doped regions of the first doped semiconductor layer are sequentially arranged in a lattice.

6. The photovoltaic cell according to claim 5, characterized in that: The distance 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.

7. The photovoltaic cell according to any one of claims 1 to 6, characterized in that: 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 close to 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.

8. A method for preparing a photovoltaic cell, characterized in that: The steps include: Providing a single crystal silicon substrate having a first surface and a second surface arranged opposite to each other, wherein a textured surface is formed on the first surface, and the textured surface includes a plurality of first pyramid structures, and the first pyramid structures include a tower body and a tower top; forming a first semiconductor doping layer so that the first semiconductor doping layer covers the velvet surface; Laser processing causes the tower tip to recrystallize into a silicon-containing material with a different crystal structure from the single crystal silicon substrate; forming a first passivation layer, wherein the first passivation layer covers a side of the first doped semiconductor layer facing away from the velvet surface; A first electrode is formed, wherein a portion of the first electrode corresponding to the first pyramid structure is electrically connected to the first doped semiconductor layer.

9. The preparation method according to claim 8, characterized in that: The laser processing step comprises: using laser to irradiate the side of the first doped semiconductor layer facing away from the single crystal silicon substrate, so that the first doped semiconductor layer forms a heavily doped region, the heavily doped region comprises a first region and a second region, the first region covers the tower top, the second region covers the tower body, and the doping element concentration of the first region is higher than the doping element concentration of the second region; The first electrode forms an electrical contact with the heavily doped region.

10. The preparation method according to any one of claims 8 to 9, characterized in that: The power of the laser processing is 100W-800W, the wavelength of the laser processing is 400nm-2000nm, the diameter of the laser spot is 5μm-120μm, and the single-point residence time of the laser spot is 2μs-10μs.

Images