A solar cell and a photovoltaic module
By forming a barrier layer and a multi-layer doped passivation structure on the front surface of the solar cell substrate, the problem of high-temperature diffusion depth of silver-aluminum paste was solved, thereby improving the conversion efficiency and on-voltage performance of the cell.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- ZHEJIANG JINKO SOLAR CO LTD
- Filing Date
- 2022-07-27
- Publication Date
- 2026-07-31
AI Technical Summary
In existing N-type TOPCon batteries, the high-temperature diffusion depth of silver-aluminum paste is relatively deep, which leads to a decrease in battery conversion efficiency, and conventional improvement measures have limited effect.
A barrier layer is formed on the front surface of the substrate of the solar cell, a non-uniform light spot is formed by laser processing, an amorphous silicon layer is prepared to suppress aluminum diffusion, and a multilayer doped and passivation layer structure is combined to optimize the electrode contact and form a selective emitter.
It effectively reduces metallization loss, improves battery opening voltage and fill factor, and enhances battery conversion efficiency, especially by suppressing the diffusion depth of aluminum, achieving a depth reduction of 8-20%.
Smart Images
Figure CN117153925B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of photovoltaic cell technology, and in particular to a solar cell and a photovoltaic module. Background Technology
[0002] TOPCon (Tunnel Oxide Passivating Contacts) cells are a type of solar cell based on the selective carrier principle, using tunneled oxide passivating contacts. N-type TOPCon cells employ boron diffusion on the front side, requiring matching silver-aluminum paste for sintering. Aluminum diffuses relatively deeply into silicon at high temperatures, typically exceeding 0.5 micrometers. Summary of the Invention
[0003] The purpose of this invention is to provide a solar cell and a photovoltaic module to solve the problems in the prior art.
[0004] This invention provides a solar cell, comprising:
[0005] A substrate having a front surface and a back surface, wherein the front surface and the back surface are disposed opposite to each other along a first direction;
[0006] A first doped layer of a first doping type is located on the front surface of the substrate;
[0007] A second doped layer with a second doping type located on the back surface of the substrate, the second doping type being the opposite of the first doping type;
[0008] The dielectric layer located between the substrate and the second doped layer;
[0009] A first electrode that forms an electrical contact with the first doped layer;
[0010] The first doped layer includes a first doped region with a first doping concentration and a second doped region with a second doping concentration, wherein the first doped region forms an electrical contact with the first electrode, and the first doping concentration is greater than the second doping concentration;
[0011] A plurality of protruding structures are formed on one side of the front surface of the substrate. The first doped region is located inside the surface of the plurality of protruding structures. At least a portion of the sidewalls of the protruding structures are partially covered with a barrier layer. The crystal structure of the barrier layer is different from the crystal structure of the second doped layer.
[0012] In a solar cell as described above, preferably, the substrate comprises a monocrystalline silicon substrate and the barrier layer comprises an amorphous silicon layer.
[0013] In a solar cell as described above, preferably, the crystal structure of the barrier layer differs from the crystal structure of the second doped layer.
[0014] In a solar cell as described above, preferably, the second doped layer comprises at least one of microcrystalline silicon, polycrystalline silicon, or monocrystalline silicon.
[0015] In a solar cell as described above, preferably, the barrier layer comprises a silicon-containing material with a different crystal structure than the substrate.
[0016] In a solar cell as described above, preferably, the ratio of the height of the barrier layer to the height of the protrusion structure along the first direction is 20%-35%.
[0017] In a solar cell as described above, preferably, the protrusion structure includes a pyramidal texture structure, a frustum-shaped texture structure, or a linear texture structure.
[0018] In a solar cell as described above, preferably, the barrier layer is located on the sidewall of the pyramidal textured structure, the frustum textured structure, or the linear textured structure.
[0019] In the solar cell described above, preferably, the thickness of the barrier layer is no greater than 30 nm.
[0020] In a solar cell as described above, preferably, a first passivation layer is formed on the surface of the first doped layer facing away from the substrate, and the first electrode forms an electrical contact with the first doped region after penetrating the first passivation layer.
[0021] In a solar cell as described above, preferably, a second passivation layer is formed on the surface of the second doped layer facing away from the substrate, and the second electrode penetrates the second passivation layer and forms an electrical contact with the second doped layer.
[0022] The present invention also provides a photovoltaic module, comprising:
[0023] A battery string, wherein the battery string is formed by connecting the aforementioned solar cells;
[0024] Encapsulation layer, the encapsulation layer being used to cover the surface of the battery string;
[0025] A cover plate for covering the surface of the encapsulation layer away from the battery string.
[0026] Compared with the prior art, the present invention forms a barrier layer on the front surface of the substrate, thereby suppressing the influence of metallization, especially the silver-aluminum paste system, on the emitter stage, thereby reducing metal recombination loss, increasing the cell opening voltage and fill factor, and ultimately improving the cell conversion efficiency. Attached Figure Description
[0027] Figure 1 This is a schematic diagram of the structure of the solar cell provided in this application;
[0028] Figure 2 This is a SEM image of the front surface of the substrate of the solar cell provided in this application;
[0029] Figure 3 This is a schematic diagram of the laser spot used to fabricate the solar cell provided in this application;
[0030] Figure 4 This is a schematic diagram of the structure of the photovoltaic module provided in this application.
[0031] Explanation of reference numerals in the attached drawings: 1-substrate, 2-front surface, 3-back surface, 4-first doped layer, 41-first doped region, 42-second doped region, 5-second doped layer, 6-dielectric layer, 7-first electrode, 8-second electrode, 9-first passivation layer, 10-second passivation layer, 11-protrusion structure, 12-barrier layer, 13-cell string, 14-encapsulation layer, 15-cover plate.
[0032] S-laser spot;
[0033] D1 - First direction. Detailed Implementation
[0034] The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.
[0035] In existing technologies, N-type TOPCon (Tunnel Oxide Passing Contacts) batteries use silver-aluminum paste to form the electrode and emitter layer contact. The diffusion depth of aluminum in the emitter layer is relatively deep, usually above 0.5 micrometers, which reduces the conversion efficiency of the battery.
[0036] Common improvement measures include:
[0037] (1) Metallization damage is reduced by using low-temperature sintering, but the fill factor is generally low. There is almost no gain in battery efficiency.
[0038] (2) Generally, a relatively deep PN junction is used to reduce metallization damage. Among the related technologies, laser SE process is attempted to dope boron. The problem is that the laser damage is relatively heavy, resulting in voltage loss and thus the improvement of battery efficiency is limited.
[0039] To solve the above technical problems, such as Figure 1 and Figure 2 As shown, an embodiment of the present invention provides a solar cell, comprising:
[0040] The substrate 1 has a front surface 2 and a back surface 3, which are disposed opposite to each other along a first direction D1. In this embodiment, the first direction D1 is... Figure 1 As shown in the figure, the first direction D1 extends along the direction of gravity. When the substrate 1 is not placed horizontally, the first direction D1 also forms an angle with the direction of gravity. The front surface 2 is the light-receiving surface facing the direction of sunlight, and the back surface 3 is the surface opposite to the front surface 2. For bifacial cells, the back surface 3 can also serve as a light-receiving surface. The substrate 1 can be, for example, a crystalline semiconductor (e.g., crystalline silicon) containing dopants of a first conductivity type. The crystalline semiconductor can be single-crystal silicon, and the first conductivity type dopant can be an N-type dopant such as those containing group V elements such as phosphorus (P), arsenic (As), bismuth (Bi), and antimony (Sb), or a P-type dopant such as those containing group III elements such as boron (B), aluminum (Al), gallium (Ga), and indium (In).
[0041] In one feasible embodiment, the first doped layer 4, which has a first doping type, is located on the front surface 2 of the substrate 1. When the substrate 1 is an N-type crystalline silicon substrate 1, the first doping element of the first doped layer 4 is boron; when the substrate 1 is a P-type crystalline silicon substrate 1, the first doping element of the first doped layer 4 is phosphorus.
[0042] A second doped layer 5 with a second doping type located on the back surface 3 of the substrate 1, the second doping type being opposite to the first doping type, and the first doping element of the second doped layer 5 being compatible with the first conductivity type dopant of the substrate 1; in a feasible embodiment, when the substrate 1 is an N-type crystalline silicon substrate 1, the first doping element of the second doped layer 5 is phosphorus; when the substrate 1 is a P-type crystalline silicon substrate 1, the second doping element of the second doped layer 5 is boron.
[0043] The dielectric layer 6 is located between the substrate 1 and the second doped layer 5. The dielectric layer 6 is used to passivate the back surface 3 of the substrate 1, reduce the recombination of charge carriers at the interface, and ensure the carrier transport efficiency. In a feasible embodiment, both the second doped layer 5 and the dielectric layer 6 are provided in multiple layers. The multiple layers of the second doped layer 5 and the multiple layers of the dielectric layer 6 are alternately arranged along the first direction D1. By depositing multiple layers of the second doped layer 5, the layered passivation of the substrate 1 is achieved, the field effect passivation effect is improved, the carrier recombination at the interface of the substrate 1 is reduced, and the selective transport of charge carriers is achieved by blocking minority carriers through the multiple layers of the dielectric layer 6, thereby reducing the carrier recombination at the interface of the substrate 1 and improving the working efficiency of the solar cell.
[0044] The first electrode 7 forms an electrical contact with the first doped layer 4. The material of the first electrode 7 includes at least one conductive metal material such as silver, aluminum, copper, and nickel.
[0045] The second electrode 8 forms an electrical contact with the second doped layer 5. The material of the second electrode 8 includes at least one conductive metal material such as silver, aluminum, copper, and nickel.
[0046] The first doped layer 4 includes a first doped region 41 with a first doping concentration and a second doped region 42 with a second doping concentration. The first doped region 41 forms an electrical contact with the first electrode 7, and the first doping concentration is greater than the second doping concentration. Thus, a selective emitter structure is formed on the surface of the first doped layer 4.
[0047] In one feasible implementation, after boron expansion, a laser is irradiated onto the surface of substrate 1 to melt the borosilicate glass, forming a first doped region 41 heavily doped with boron ions in the laser-irradiated area, and a second doped region 42 lightly doped in the unirradiated area, thereby reducing surface carrier recombination caused by heavy doping.
[0048] The second doped region 42 without metal grid lines (first electrode 7) has a large sheet resistance, a low surface doping concentration, and less recombination, which can improve the open-circuit voltage and short-circuit current of the cell. The first doped region 41 where the metal grid lines (first electrode 7) are located has a high doping concentration and a deep junction, which can effectively reduce the contact resistance and improve the fill factor.
[0049] A plurality of protruding structures 11 are formed on one side of the front surface 2 of the substrate 1. The first doped region 41 is located inside the surface of the plurality of protruding structures 11. The protruding structures 11 can be formed by texturing (or etching) process. The texturing process can be chemical etching, laser etching, mechanical etching, plasma etching, etc. The structure has good light trapping and anti-reflection effects, increases the effective contact area of light, realizes further utilization of light energy, and improves power generation efficiency.
[0050] To suppress the influence of metallization, especially the silver-aluminum paste system, on the emitter (first doped layer 4), several barrier layers 12 are formed on the sidewall of each protrusion structure 11. The barrier layer 12 includes a silicon-containing material with a different crystal structure from the substrate 1. The barrier layer 12 allows some aluminum elements to enter the PN junction formed between the first doped layer 4 and the substrate 1 at a shallow depth during the sintering process, suppressing the diffusion depth of some aluminum elements. This achieves the goal of reducing the average penetration depth of aluminum spikes by 8-20% without adjusting the sintering temperature, which can further reduce the recombination of metal grid lines and improve the conversion efficiency of the battery.
[0051] In the embodiments provided in this application, the substrate 1 includes a monocrystalline silicon substrate 1, and the barrier layer 12 includes an amorphous silicon layer, as shown in the reference. Figure 2 As shown, Figure 2 This is a SEM image of the front surface 2 of the substrate 1 of the solar cell provided in this application, wherein... Figure 2 The lower left corner shows a magnified portion of the barrier layer 12. In one feasible implementation, a non-uniform, extremely thin amorphous silicon layer is generated on the surface of the first doped layer 4 (top of the protrusion structure 11) of the single-crystal silicon substrate 1 by laser induction, suppressing the diffusion depth of some aluminum elements. Specifically, the laser uses a non-uniform spot to process a local area of the protrusion structure 11 on the first doped layer 4 into micropores and an amorphous state, thereby forming the barrier layer 12. The laser spot S is a non-uniform spot, and the laser uses a mirror patterning process to bring non-uniform reflection to prepare a complex internal pattern of a single spot, thereby forming a non-uniform spot; see reference. Figure 3 As shown, the pattern of the laser spot S includes, but is not limited to, triangles, rectangles, ellipses, circles, line segments, or linear combinations of irregular shapes.
[0052] In the embodiments provided in this application, the crystal structure of the barrier layer 12 differs from the crystal structure of the second doped layer 5. The second doped layer 5 comprises at least one of microcrystalline silicon, polycrystalline silicon, or monocrystalline silicon. The second doped layer 5 is formed by doping microcrystalline silicon, polycrystalline silicon, or monocrystalline silicon with an N-type dopant. The N-type dopant can be any dopant having the same conductivity type as the substrate 1. That is, group V elements such as phosphorus (P), arsenic (As), bismuth (Bi), or antimony (Sb) can be used.
[0053] In one feasible implementation, the second doped layer 5 is a phosphorus-doped polycrystalline silicon layer. The crystal structure of the second doped layer 5 is different from that of the barrier layer 12, which is a partially microporous silicon-based amorphous silicon layer locally generated in the protrusion structure 11 by processing the first doped region 41 of the first doped layer 4 with a special non-homogeneous spot of a femtosecond laser.
[0054] In the embodiments provided in this application, the barrier layer 12 partially covers the sidewall of the protrusion structure 11, and the laser processing area is limited to the local surface of the first doped layer 4, and is restricted only to the sidewall surface of the protrusion structure 11 away from the substrate 1. This can avoid the laser spot S causing heavy damage to the surface of the substrate 1, resulting in voltage loss and limiting the improvement of battery efficiency.
[0055] In the embodiments provided in this application, along the first direction D1, the ratio of the height of the barrier layer 12 to the height of the protrusion structure 11 includes 20%-35%, including endpoint values. Specifically, the ratio ranges from 20%, 25%, 30%, 35%, etc., and of course, other values within the above range are also possible and are not limited here. Within this range, the deeper the barrier layer 12 covers, the stronger the barrier effect and the higher the conversion efficiency of the battery. When it exceeds this range, if the height of the barrier layer 12 is too large, it will reduce the light-trapping effect and anti-reflection effect of the protrusion structure 11; if the height of the barrier layer 12 is too small, it will reduce the diffusion inhibition effect of aluminum.
[0056] In the embodiments provided in this application, reference is made to Figure 2 As shown, the protruding structure 11 includes a pyramid-shaped texture structure, a frustum-shaped texture structure, or a linear texture structure. The linear texture structure is a strip or line texture structure arranged at intervals. Several strip or line texture structures are parallel to each other. All of the above structures can have good light trapping and anti-reflection effects, increase the effective contact area of light, realize further utilization of light energy, and improve the power generation efficiency of the battery.
[0057] The barrier layer 12 is located on the sidewall of the pyramidal textured structure, the frustum-shaped textured structure, or the linear textured structure. Those skilled in the art will understand that the protrusion structure 11 is not limited to the above types, or it can be a mixture of multiple structures. Forming multiple protrusion structures 11 of various shapes on the first doped layer 4 can reduce interfacial recombination and improve photoelectric conversion efficiency.
[0058] In the embodiments provided in this application, the thickness of the barrier layer 12 is no more than 30nm. If the barrier layer 12 is too thick, it will cause more severe laser damage, resulting in voltage loss and thus limited improvement in battery efficiency.
[0059] As an optional technical solution in this application, the dielectric layer 6 includes one or more of silicon oxide, aluminum oxide, hafnium oxide, silicon nitride, or silicon oxynitride. These materials have good interfacial dangling passivation and tunneling effects.
[0060] The dielectric layer 6 allows majority carriers to tunnel into the second doped layer 5 while blocking minority carriers. The majority carriers then undergo lateral transport within the second doped layer 5 and are collected by the second electrode 8. The dielectric layer 6 and the second doped layer 5 form a tunneling oxide passivation contact structure, achieving excellent interface passivation and selective carrier collection, reducing carrier recombination, and improving the photoelectric conversion efficiency of the solar cell. It should be noted that the dielectric layer 6 may not actually possess a perfect tunneling barrier, as it may contain defects such as pinholes. This can cause other charge carrier transport mechanisms (such as drift and diffusion) to dominate over the tunneling effect.
[0061] In the embodiments provided in this application, reference is made to Figure 1 As shown, a first passivation layer 9 is formed on the surface of the first doped layer 4 facing away from the substrate 1. After the first electrode 7 penetrates the first passivation layer 9, it forms an electrical contact with the first doped layer 4. The first passivation layer 9 includes at least one of a silicon oxide layer, a silicon nitride layer, an aluminum oxide layer, and a silicon oxynitride layer.
[0062] The first passivation layer 9 can passivate the front surface 2 of the battery, reduce the carrier recombination velocity on the front surface 2, and improve the photoelectric conversion efficiency. The first passivation layer 9 is located on the surface of the first doped layer 4. After the first electrode 7 penetrates the first passivation layer 9, it forms an electrical contact with the first doped layer 4. As an optional technical solution of this application, the first passivation layer 9 may be provided with an opening so that the first electrode 7 can pass through and make electrical contact with the first doped layer 4, thereby reducing the contact area between the metal electrode and the first doped layer 4, further reducing the contact resistance, and improving the open circuit voltage.
[0063] Optionally, the first passivation layer 9 includes a stacked structure of at least one or more of the following: a silicon oxide layer, a silicon nitride layer, an aluminum oxide layer, and a silicon oxynitride layer. In some embodiments, the thickness of the first passivation layer 9 ranges from 10 nm to 120 nm, specifically 10 nm, 20 nm, 30 nm, 40 nm, 50 nm, 60 nm, 70 nm, 80 nm, 90 nm, 100 nm, or 120 nm, or other values within the above range, which are not limited here.
[0064] Optionally, a second passivation layer 10 is formed on the surface of the second doped layer 5 facing away from the substrate 1. After the second electrode 8 penetrates the second passivation layer 10, it forms an electrical contact with the second doped layer 5. The second passivation layer 10 can passivate the back surface 3 of the substrate 1, reduce the recombination of charge carriers at the interface, improve the transport efficiency of charge carriers, and thus improve the photoelectric conversion efficiency of the solar cell.
[0065] Optionally, the second passivation layer 10 includes a stacked structure of at least one or more of the following: silicon oxide layer, silicon nitride layer, aluminum oxide layer, and silicon oxynitride layer.
[0066] Based on the above embodiments, referring to Figure 4 As shown, this application also provides a photovoltaic module, including: a battery string 13, which is formed by connecting the aforementioned solar cells, and adjacent battery strings 13 are connected by a conductive strip such as a solder ribbon; an encapsulation layer 14, which is used to cover the surface of the battery string 13; and a cover plate 15, which is used to cover the surface of the encapsulation layer 14 away from the battery string 13.
[0067] In some embodiments, the number of battery strings 13 is at least two, and the battery strings 13 are electrically connected by means of parallel and / or series connection.
[0068] In some embodiments, the encapsulation layer 14 includes encapsulation layers 14 disposed on the front and back sides of the battery string 13, and the material of the encapsulation layer 14 includes, but is not limited to, EVA, POE or PET films.
[0069] In some embodiments, the cover plate 15 includes a cover plate 15 disposed on the front and back of the battery string 13, and the cover plate 15 is made of a material with good light transmittance, including but not limited to glass, plastic and the like.
[0070] The above description, based on the embodiments shown in the figures, details the structure, features, and effects of the present invention. The above description is only a preferred embodiment of the present invention, but the present invention is not limited to the scope of implementation shown in the figures. Any changes made in accordance with the concept of the present invention, or equivalent embodiments modified to have equivalent changes, that do not exceed the spirit covered by the specification and figures, should be within the protection scope of the present invention.
Claims
1. A solar cell, characterized in that: include: A substrate having a front surface and a back surface, wherein the front surface and the back surface are disposed opposite to each other along a first direction; A first doped layer of a first doping type is located on the front surface of the substrate; A second doped layer with a second doping type located on the back surface of the substrate, the second doping type being the opposite of the first doping type; The dielectric layer located between the substrate and the second doped layer; A first electrode that forms an electrical contact with the first doped layer; The first doped layer includes a first doped region with a first doping concentration and a second doped region with a second doping concentration, wherein the first doped region forms an electrical contact with the first electrode, and the first doping concentration is greater than the second doping concentration; A plurality of protruding structures are formed on one side of the front surface of the substrate. The first doped region is located inside the surface of the plurality of protruding structures. At least a portion of the sidewalls of the protruding structures are partially covered with a barrier layer. The crystal structure of the barrier layer is different from the crystal structure of the second doped layer. The laser induces a non-uniform, extremely thin amorphous silicon layer on the surface of the first doped layer of the single-crystal silicon substrate, thereby suppressing the diffusion depth of some aluminum elements. The laser uses a non-uniform spot to process local areas of the protruding structure on the first doped layer into micropores and an amorphous state, thereby forming the barrier layer. The thickness of the barrier layer is no greater than 30 nm.
2. The solar cell according to claim 1, characterized in that: The substrate includes a monocrystalline silicon substrate, and the barrier layer includes an amorphous silicon layer.
3. The solar cell according to claim 1, characterized in that: The crystal structure of the barrier layer differs from that of the second doped layer.
4. The solar cell according to claim 3, characterized in that: The second doped layer includes at least one of microcrystalline silicon, polycrystalline silicon, or monocrystalline silicon.
5. The solar cell according to claim 1, characterized in that: The barrier layer comprises a silicon-containing material with a different crystal structure than the substrate.
6. The solar cell according to claim 1, characterized in that: Along the first direction, the ratio of the height of the barrier layer to the height of the protrusion structure includes 20%-35%.
7. The solar cell according to claim 1, characterized in that: The raised structure includes a pyramid-shaped texture structure, a frustum-shaped texture structure, or a linear texture structure.
8. The solar cell according to claim 7, characterized in that: The barrier layer is located on the sidewall of the pyramid-shaped texture structure, the frustum-shaped texture structure, or the linear texture structure.
9. The solar cell according to claim 1, characterized in that: A first passivation layer is formed on the surface of the first doped layer facing away from the substrate, and the first electrode forms an electrical contact with the first doped region after penetrating the first passivation layer.
10. The solar cell according to claim 1, characterized in that: A second passivation layer is formed on the surface of the second doped layer that is away from the substrate, and the second electrode forms an electrical contact with the second doped layer after penetrating the second passivation layer.
11. A photovoltaic module, characterized in that, include: A battery string, wherein the battery string is formed by connecting solar cells according to any one of claims 1 to 10; Encapsulation layer, the encapsulation layer being used to cover the surface of the battery string; A cover plate for covering the surface of the encapsulation layer away from the battery string.