CN218769554U - Solar cell and photovoltaic module - Google Patents

Abstract

The utility model discloses a solar cell and photovoltaic module, solar cell includes: the back surface is provided with a first area and a second area which are arranged in a staggered and spaced mode along a second direction, and the first area and the second area have a height difference in the first direction; a back side silicon oxide layer on the first region; the doped polycrystalline silicon layer is positioned on the surface of the back silicon oxide layer; the back passivation layer is positioned on the surface of the doped polycrystalline silicon layer; a first electrode in electrical contact with the doped polysilicon layer; a front side doping layer located on the front surface of the substrate; a front passivation layer on the front doped layer; a second electrode in electrical contact with the front doped layer. Compared with the prior art, the utility model discloses a do not set up the doping polycrystalline silicon layer in the second region to reduce the optical absorption, reduced the optical loss of doping polycrystalline silicon layer, improved positive battery efficiency and increased two-sided generated power.

Description

Solar cell and photovoltaic module

Technical Field

The utility model relates to a photovoltaic cell technical field, especially a solar cell and photovoltaic module.

Background

The TOPCon (Tunnel Oxide Passivating Contacts) cell is a solar cell with a passivated contact of a tunneling Oxide layer based on the selective carrier principle. The back surface of the metal electrode is usually in a structure of combining an ultrathin tunneling silicon oxide layer and a doped polycrystalline silicon layer, so that a passivation contact effect is realized, the metal electrode and c-Si are not in direct contact, the reduction of the recombination of carriers is facilitated, and the separation and collection of the carriers are realized.

How to further improve the efficiency of the TOPCon battery is a technical problem to be solved.

SUMMERY OF THE UTILITY MODEL

The utility model aims at providing a solar cell and photovoltaic module to solve the technical problem among the prior art, it can reduce the optical loss of doping polycrystalline silicon, improves positive battery efficiency and increases two-sided generated power.

The utility model provides a solar cell, include:

a substrate having a front surface and a back surface, the front surface and the back surface being disposed opposite to each other along a first direction, the back surface having first and second areas alternately arranged along a second direction, the first and second areas having a height difference in the first direction, the first area being farther from the front surface than the second area;

a back side silicon oxide layer on the first region;

the doped polycrystalline silicon layer is positioned on the surface of the back silicon oxide layer;

the back passivation layer is positioned on the surface of the doped polycrystalline silicon layer;

a first electrode penetrating the back passivation layer and forming an electrical contact with the doped polysilicon layer;

a front side doping layer located on the front surface of the substrate;

a front side passivation layer on the front side doped layer;

and the second electrode penetrates through the front passivation layer and then forms electric contact with the front doped layer.

In the solar cell, it is preferable that a silicon doped layer is disposed on the second region, and the silicon doped layer and the doped polysilicon layer have a height difference in the first direction.

A solar cell as described above, wherein preferably the difference in height between the doped polysilicon layer and the doped silicon layer in the first direction comprises 1-10um.

In the solar cell, it is preferable that the doping element of the silicon doping layer is the same as that of the substrate, and the doping concentration of the silicon doping layer is greater than that of the substrate.

The solar cell as described above, wherein preferably, the doping element of the doped polysilicon layer is the same as the doping element of the silicon doped layer.

A solar cell as described above, wherein preferably, the ratio of the thickness of the doped polysilicon layer to the silicon doped layer along the first direction comprises: 1:5-2:1.

A solar cell as above, wherein preferably the thickness of said doped polysilicon layer along said first direction comprises 30-300nm and the thickness of said silicon doped layer along said first direction comprises 15-1500nm.

A solar cell as described above, wherein preferably, a ratio of the widths of the first region and the second region in the second direction includes: 1:15-3:1.

A solar cell as described above, wherein preferably, the width of the first region in the second direction comprises 60-1000um, and the width of the second region in the second direction comprises 100-1400um.

The present application further provides a photovoltaic module, including:

the solar cell comprises a cell string and a solar cell, wherein the cell string is formed by connecting the solar cells;

an encapsulation layer for covering a surface of the battery string;

and the cover plate is used for covering the surface of the packaging layer far away from the battery string.

Compared with the prior art, the utility model discloses a do not set up the doping polycrystalline silicon layer in the second region to reduce the optical absorption, reduced the optical loss of doping polycrystalline silicon layer, improved positive battery efficiency and increased two-sided generated power.

Drawings

Fig. 1 is a schematic structural diagram of the present invention.

Fig. 2 is a schematic structural diagram of a photovoltaic module provided in the present application.

Description of reference numerals:

1-substrate, 2-front surface, 3-back surface, 4-back silicon oxide layer, 5-doped polysilicon layer, 6-back passivation layer, 7-first electrode, 8-front doped layer, 9-front passivation layer, 10-second electrode, 11-silicon doped layer, 12-battery string, 13-packaging layer and 14-cover plate.

D1-a first direction, D2-a second direction;

l1-the first region, L2-the second region.

Detailed Description

Reference will now be made in detail to the embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to the same or similar elements or elements having the same or similar functions throughout. The embodiments described below by referring to the drawings are exemplary only for explaining the present invention, and should not be construed as limiting the present invention.

In the prior art, a TOPCon (Tunnel Oxide passivation Contacts) cell generally includes a silicon wafer, and a silicon Oxide layer, a doped polysilicon layer and a back passivation film on the back of the silicon wafer, wherein the silicon Oxide (SiOx) layer is generally 1-2nm, and mainly functions as a tunneling layer for majority carriers, and simultaneously performs chemical passivation on the surface of the silicon wafer to reduce interface states. The Doped polycrystalline silicon (polysilicon poly-Si) layer is mainly used as a field passivation layer, and forms energy band bending on the surface of the silicon wafer, so that selective transmission of current carriers is realized, and recombination loss is reduced. In the metal electrode covering region of the back silicon oxide/doped polysilicon, the metal electrode will penetrate through the back passivation film and contact with the doped polysilicon layer, but not penetrate through the silicon oxide layer. To maintain good interfacial passivation. In the non-metal electrode coverage area, the recombination current on the surface of the silicon wafer can reach a very low level. The back passivation film is generally made of silicon nitride (SiNx) and serves as a hydrogen passivation layer and an optical matching layer.

Since doped polysilicon has light absorption capability, it will cause some optical loss and decrease the efficiency of the front cell. Sunlight mainly has a long-wave band spectrum after reaching the back surface, and the long-wave band spectrum can be absorbed by back-surface doped polycrystalline silicon, so that short-circuit current loss and the efficiency of a front-surface cell are reduced. The reason for the difference in light absorption capacity of doped polysilicon is as follows: (1) The higher the extinction coefficient a, the stronger the absorption capacity, the relationship of extinction coefficient k: α =4 × k × pi/λ; (2) the longer the absorption optical path d, the more absorption. Meanwhile, because the doped polysilicon has light absorption capability, the efficiency of the back cell is reduced, namely the double-sided rate of the cell (the double-sided rate of the cell: the wallpaper of the back efficiency and the front efficiency of the cell) is reduced, so that when the cell is used for the double-sided power generation function, the double-sided power generation power is reduced.

The thickness of the doped polysilicon layer is reduced, so that the absorption optical path d is reduced, the light absorption capacity can be reduced, and the short-circuit current and the cell efficiency are improved. Therefore, there has been a trend to reduce the thickness of doped polysilicon layers. However, as the thickness of the doped polysilicon layer is reduced, the applicants have found that the following problems arise: 1) In order to satisfy the requirement that the metal electrode penetrates through the back passivation film and contacts the doped polysilicon layer but does not penetrate through the silicon oxide layer, the method puts high demands on the mass production process matched with the method.

In order to match the thinning of the doped polysilicon layer thickness, the applicant believes that the existing improvement mainly includes: a. the thickness of the back passivation film is increased, but the time of a process for preparing the back passivation film is obviously increased, and the productivity is influenced; b. adjustment of the back electrode paste and the sintering process is very difficult to control, and particularly, the electrode paste does not have a product matched with the thickness of the doped polysilicon layer of 50nm on the market. 2) The doped polysilicon layer is thinned, so that the square resistance is increased, the transverse transmission capability of current is reduced, the filling factor of the battery is reduced, and the efficiency of the battery is influenced.

In order to solve the above technical problem, the present application provides a solar cell, including:

the solar cell module comprises a substrate 1 having a front surface 2 and a back surface 3, wherein the front surface 2 and the back surface 3 are disposed opposite to each other along a first direction D1, in the embodiment of the present invention, the first direction D1 is a direction extending along gravity as shown in fig. 1, the front surface 2 is a light receiving surface facing a sunlight irradiation direction, the back surface 3 is a surface opposite to the front surface 2, in the embodiment provided in the present invention, the solar cell is a bifacial cell, and the back surface 3 also serves as a light receiving surface. The substrate 1 may be, for example, a substrate including a crystalline semiconductor (e.g., crystalline silicon) containing a dopant of the first conductivity type. The crystalline semiconductor may be single crystalline silicon, and the first conductive type dopant may be an N-type dopant such As a V-group element including phosphorus (P), arsenic (As), bismuth (Bi), antimony (Sb), or a P-type dopant including a III-group element such As boron (B), aluminum (Al), gallium (Ga), indium (In).

The back surface 3 has first areas L1 and second areas L2 alternately arranged along a second direction D2, the second direction D2 is a horizontal extending direction shown in fig. 1, the first areas L1 and the second areas L2 have a height difference in the first direction D1, and the first areas L1 are farther from the front surface 2 than the second areas L2.

The back silicon oxide layer 4 is located on the first region L1, and the back silicon oxide layer 4 is used for performing interface passivation on the back surface 3 of the substrate 1, so that recombination of carriers at an interface is reduced, and the transmission efficiency of the carriers is ensured.

A doped polycrystalline silicon layer 5 positioned on the surface of the back silicon oxide layer 4, wherein a first doping element of the doped polycrystalline silicon layer 5 is matched with a conductive type dopant of the substrate 1; in a possible embodiment, when the substrate 1 is an N-type crystalline silicon substrate 1, the first doping element of the doped polysilicon layer 5 is phosphorus; when the substrate 1 is a P-type crystalline silicon substrate 1, the first doping element of the doped polysilicon layer 5 is boron.

And the back passivation layer 6 is positioned on the surface of the doped polycrystalline silicon layer 5, and the back passivation layer 6 comprises at least one of a silicon oxide layer, a silicon nitride layer, an aluminum oxide layer and a silicon oxynitride layer. The back passivation layer 6 can passivate the back surface 3 of the cell, reduce the carrier recombination speed of the back surface 3 and improve the photoelectric conversion efficiency.

A first electrode 7 penetrating the back passivation layer 6 and making electrical contact with the doped polysilicon layer 5, wherein in some embodiments, the material of the first electrode 7 includes at least one conductive metal material such as silver, aluminum, copper, nickel, etc. As an optional technical solution of the present application, the back passivation layer 6 may be provided with an opening for the first electrode 7 to electrically contact with the doped polysilicon layer 5 after passing through, so as to reduce the contact area between the metal electrode and the doped polysilicon layer 5, further reduce the contact resistance, and improve the open-circuit voltage.

The front doped layer 8 is positioned on the front surface 2 of the substrate 1, and a second doping element of the front doped layer 8 is opposite to a first conductive type dopant of the substrate 1; in one possible embodiment, when the substrate 1 is an N-type crystalline silicon substrate 1, the second doping element of the front-side doping layer 8 is boron; when the substrate 1 is a P-type crystalline silicon substrate 1, the second doping element of the front-side doping layer 8 is phosphorus.

The front passivation layer 9 is located on the front doped layer 8, and the front passivation layer 9 can play a role in passivating the front surface 2 of the substrate 1, so that the recombination of carriers at an interface is reduced, the transmission efficiency of the carriers is improved, and the photoelectric conversion efficiency of the cell is further improved. Optionally, the front passivation layer 9 includes a stacked structure of at least one or more of a silicon oxide layer, a silicon nitride layer, an aluminum oxide layer, and a silicon oxynitride layer.

And a second electrode 10 that penetrates the front passivation layer 9 and makes electrical contact with the front doped layer 8, wherein in some embodiments, the material of the second electrode 10 includes at least one conductive metal material such as silver, aluminum, copper, nickel, and the like.

Based on the solar cell provided in the above embodiment, since the first connection is electrically connected only in the first region L1, and the back surface silicon oxide layer 4 is only disposed on the back surface 3 of the first region L1 of the substrate 1, in the first region L1, the structure of the back surface silicon oxide layer 4/doped polysilicon layer 5/back passivation layer 6 is adopted, and the main function is to perform TOPCon structural passivation on the high recombination region of the first electrode 7 contact region; in the second region L2, the TOPCon structure is not used, because this region does not use the doped polysilicon layer 5, the optical absorption is reduced, the optical loss of the doped polysilicon layer 5 is reduced, the front cell efficiency is improved, and the double-sided power generation power is increased.

Referring to fig. 1, in the embodiment of the present application, a silicon doped layer 11 is disposed on a second region L2, the silicon doped layer 11 and the doped polysilicon layer 5 have a height difference in a first direction D1, the second region L2 adopts a structure of the silicon doped layer 11/the back passivation layer 6, and the doped polysilicon layer 5 is not adopted in the second region L2, so that optical absorption is reduced, and the lateral transmission capability of current is not affected due to the adoption of the silicon doped layer 11. Because the silicon doped layer 11 and the doped polysilicon layer 5 have a height difference in the first direction D1, the diffusion path of the photogenerated carriers separated by the built-in electric field of the PN junction in the second region L2 can be greatly shortened, and the recombination probability of the photogenerated carriers can be reduced.

In the embodiment of the present application, the height difference between the doped polysilicon layer 5 and the silicon doped layer 11 in the first direction D1 includes 1-10um, including an end point value, specifically, the range of the height difference may be 1um, 2um, 3um, 4um, 5um, 6um, 7um, 8um, 9um, 10um, etc., and may also be other values within the above range, which is not limited herein. In a preferred embodiment, 3 μm is most preferred.

In the embodiment of the application, the doping elements of the silicon doping layer 11 and the substrate 1 are the same, the doping concentration of the silicon doping layer 11 is greater than that of the substrate 1, the concentration of the silicon doping layer 11 is higher, the minority carrier lifetime is longer, and the passivation effect is better, so that the open-circuit voltage and the short-circuit current of a battery piece can be improved, meanwhile, the contact resistance can be effectively reduced, and the filling factor is improved.

In the embodiments provided herein, the doped polysilicon layer 5 and the doped silicon layer 11 have the same doping elements. The doped polysilicon layer 5 and the silicon doped layer 11 are formed by doping amorphous silicon, microcrystalline silicon, polysilicon, etc. with N-type dopants. The N-type dopant may be any dopant having the same conductivity type as the substrate 1. That is, a group V element such As phosphorus (P), arsenic (As), bismuth (Bi), or antimony (Sb) may be used.

In the embodiments provided herein, the ratio of the thicknesses of the doped polysilicon layer 5 and the doped silicon layer 11 along the first direction D1 includes: 1-5-2, the thickness ratio is not too small, and too small can lead to the composite increase of the second region L2; the transmission effect is not obvious, and the ratio of 1. The advantage of this structure is that it provides a lateral transport channel for the photo-generated carriers of the second region L2.

In the embodiment of the application, the thickness of the doped polycrystalline silicon layer 5 in the first direction D1 comprises 30-300nm, 150nm is used as the optimum, the thickness of the silicon doped layer 11 in the first direction D1 comprises 15-1500nm, 300nm is used as the optimum, the thinner doped polycrystalline silicon layer 5 can reduce the parasitic adsorption to long-wave band light, the long-wave response and the double-side rate of the solar cell are effectively improved, the burning-through depth of the metal slurry of the first electrode 7 is greatly reduced, the first electrode is not in contact with the substrate 1, and the composition of a metal contact area is reduced.

In the embodiment of the present application, the ratio of the widths of the first region L1 and the second region L2 along the second direction D2 includes: 1:15-3:1. The structure is optimized by 1. If the doped polysilicon layer 5 of the first region L1 is too narrow, the structure fails; the doped polysilicon layer 5 of the first region L1 is too wide, the area of the collection sites is too small, and even though the lateral transport capability is excellent, the doped polysilicon layer cannot be sufficiently collected by the too narrow collection sites.

In the embodiment of the present application, the width of the first region L1 along the second direction D2 includes 60-1000um, and 500um is the optimum, and the width of the second region L2 along the second direction D2 includes 100-1400um, and 1000um is the optimum, so as to obtain the optimum lateral transmission capability and collection site area.

In one possible embodiment, the solar cell is produced by:

1. and (3) double-sided texturing of the N-type substrate 1, and reacting the N-type substrate in KOH and a texturing additive to obtain a double-sided texturing sheet with the reflectivity of 7-15%.

2. After texturing, reacting a boron source (BCl 3, trimethyl borate, BBr3 and the like) with oxygen atmosphere at the temperature of 900 ℃ by using a boron diffusion process to obtain a silicon wafer with the sheet resistance of 60-250 omega;

3. etching the back surface of the silicon wafer after boron diffusion by using HF with the mass fraction of 15-45%, and removing the borosilicate glass layer on the back surface;

4. placing the substrate in a chemical cleaning machine of KOH and polishing additives to form a pyramid-based polished surface on the back, wherein the reflectivity is 35-50%;

5. placing the silicon wafer in a furnace tube at the temperature of more than 500 ℃, and introducing oxygen and silane atmosphere to form a combined structure of a back silicon oxide layer 4 and a doped polycrystalline silicon layer 5, wherein the thicknesses of the silicon oxide layer and the doped polycrystalline silicon layer are respectively 0.8-2.2nm and 30-300nm;

6. is arranged at>Introducing oxygen and phosphorus sources (usually phosphorus oxychloride and the like) into a furnace tube at 800 ℃ to diffuse phosphorus on the back, wherein the square resistance is 50-200 omega after diffusion, and the surface ECV concentration is 5E +19-6E +20/cm ³ ；

7. Forming a second region L2 by using laser technology processing;

8. placing the pyramid-shaped substrate in a chemical cleaning machine of KOH and polishing additives, and removing groove damage to form a polished surface of the pyramid base, wherein the reflectivity is 40% -55%;

9. is arranged at>Introducing oxygen and a phosphorus source (usually phosphorus oxychloride and the like) into a furnace tube at 700 ℃ to diffuse phosphorus in a second region L2 on the back surface, wherein the surface ECV concentration is 1E +17-1E +19/cm ³ ；

10. Using HNO in sequence ₃ /HF, KOH, HF treatment, removing residues on the front surface of the substrate 1Doping the polycrystalline silicon layer 5 and borosilicate glass, and phosphorus-silicon glass on the back;

11. forming an aluminum-containing passivation film layer with the thickness of 2-10nm on the front surface by using an atomic layer deposition technology;

12. and forming a SiNx anti-reflection layer on the front surface and the back surface by PECVD (plasma enhanced chemical vapor deposition), wherein the thicknesses of the SiNx anti-reflection layer are 60-130nm and 50-120nm respectively.

13. The screen printing method forms the first electrode 7 and the second electrode 10 on the front and back surfaces.

Based on the above embodiment, referring to fig. 2, the present application further provides a photovoltaic module, including: a cell string 12, the cell string 12 being formed by connecting the aforementioned solar cells, adjacent cell strings 12 being connected to each other via a conductive tape such as a solder ribbon; the packaging layer 13 is used for covering the surface of the battery string 12; and the cover plate 14 is used for covering the surface of the packaging layer 13 far away from the battery string 12.

In some embodiments, the number of battery strings 12 is at least two, and the battery strings 12 are electrically connected in parallel and/or in series.

In some embodiments, the encapsulant layer 13 includes encapsulant layers 13 disposed on the front and back sides of the battery string 12, and the material of the encapsulant layer 13 includes, but is not limited to, EVA, POE, or PET.

In some embodiments, the cover plates 14 include cover plates 14 disposed on the front and back sides of the battery string 12, and the cover plates 14 are selected from materials having good light transmission capacity, including but not limited to glass, plastic, and the like.

The structure, features and effects of the present invention have been described in detail above according to the embodiments shown in the drawings, and the above description is only the preferred embodiment of the present invention, but the present invention is not limited to the implementation range shown in the drawings, and all the modifications made according to the concepts of the present invention or equivalent embodiments modified to the same variations should be within the protection scope of the present invention when the spirit covered by the description and drawings is not exceeded.

Claims (8)

1. A solar cell, comprising:

a substrate having a front surface and a back surface, the front surface and the back surface being disposed opposite to each other along a first direction, the back surface having first and second areas alternately arranged along a second direction, the first and second areas having a height difference in the first direction, the first area being farther from the front surface than the second area;

a back side silicon oxide layer on the first region;

the doped polycrystalline silicon layer is positioned on the surface of the back silicon oxide layer;

the back passivation layer is positioned on the surface of the doped polycrystalline silicon layer;

a first electrode penetrating the back passivation layer and forming an electrical contact with the doped polysilicon layer;

a front side doping layer located on the front surface of the substrate;

a front side passivation layer on the front side doped layer;

and the second electrode penetrates through the front passivation layer and then forms electric contact with the front doped layer.

2. The solar cell of claim 1, wherein: and a silicon doped layer is arranged on the second region, and the silicon doped layer and the doped polycrystalline silicon layer have a height difference in the first direction.

3. The solar cell of claim 2, wherein: the difference in height between the doped polysilicon layer and the doped silicon layer in the first direction comprises 1-10um.

4. The solar cell of claim 2, wherein: the ratio of the thicknesses of the doped polysilicon layer and the silicon doped layer along the first direction comprises: 1:5-2:1.

5. The solar cell of claim 3, wherein: the thickness of the doped polysilicon layer along the first direction comprises 30-300nm, and the thickness of the silicon doped layer along the first direction comprises 15-1500nm.

6. The solar cell of claim 1, wherein: the ratio of the widths of the first and second regions in the second direction includes: 1:15-3:1.

7. The solar cell of claim 6, wherein: the width of the first area in the second direction comprises 60-1000um, and the width of the second area in the second direction comprises 100-1400um.

8. A photovoltaic module, comprising:

a battery string formed by connecting the solar cells according to any one of claims 1 to 7;

an encapsulation layer for covering a surface of the battery string;

and the cover plate is used for covering the surface of the packaging layer far away from the battery string.

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