Back contact solar cell

Abstract

The utility model provides a back contact solar cell, which comprises a crystalline silicon substrate, a first intrinsic amorphous silicon layer and a silicon nitride anti-reflection layer which are sequentially formed on the front surface of the crystalline silicon substrate, and a plurality of n-type heavily doped regions which are formed on the back surface of the crystalline silicon substrate and are distributed at intervals, the silicon oxide thin film and the phosphorus-doped polycrystalline silicon layer are sequentially formed on the back faces of the n-type heavily-doped regions, and the second intrinsic amorphous silicon layer and the borohydride-doped microcrystalline silicon layer are sequentially formed on the back face of a part of the phosphorus-doped polycrystalline silicon layer and the back face of the crystalline silicon substrate between every two adjacent n-type heavily-doped regions. The transparent conductive thin film is formed on the back surface of the residual part of the phosphorus-doped polycrystalline silicon layer and the back surface of the boron-doped hydrogenated microcrystalline silicon layer; the plurality of metal electrodes are formed on the transparent conductive thin film; and an opening area is formed on the transparent conductive film between two adjacent metal electrodes. According to the utility model, the open-circuit voltage and current density of the back contact solar cell are improved, and the product performance is improved.

Description

Technical Field

[0001] This utility model belongs to the field of solar cell module technology, specifically relating to a back-contact solar cell. Background Technology

[0002] With the development of solar cell technology, heterojunction back contact cells, which combine silicon-based heterojunction solar cell technology and back contact technology, are receiving increasing attention from the industry. The front side of the heterojunction back contact cell is not blocked by metal electrodes, eliminating the problem of light loss due to shading of the front electrode, and can receive more sunlight. The silicon substrate surface is passivated with intrinsic amorphous silicon or tunnel oxide layer passivation, which reduces surface recombination and can improve the open circuit voltage, making it a very efficient solar cell technology solution.

[0003] CN117410385B discloses a method for fabricating a combined passivated back contact cell with partial mask layer removal, comprising the following steps: S1, providing a double-sided polished silicon wafer; S2, sequentially forming a first semiconductor layer and a mask layer on the back side of the silicon wafer obtained in S1, wherein the first semiconductor layer includes a tunneling oxide layer and a first doped polycrystalline layer; S3, performing a first etching on the first semiconductor layer in a predetermined area on the back side of the silicon wafer obtained in S2 to form spaced second semiconductor opening regions; S4, forming a textured surface simultaneously on the back side and the front side by texturing and cleaning; S5, then removing part of the mask layer to reduce the thickness D of the mask layer formed in S2, wherein the thickness of the removed mask layer is... d satisfies: 50% ≤ d / D < 100%; S6, then a second semiconductor layer is formed on the back side obtained in S5, the second semiconductor layer includes an intrinsic amorphous silicon layer and a second doped silicon layer; a front passivation layer and an anti-reflection layer are formed on the front side of the silicon wafer; S7, a second etching is performed on the polished area on the back side of the silicon wafer obtained in S6 using a laser to form a first semiconductor opening region; S8, a conductive film layer is formed on the back side of the silicon wafer obtained in S7; S9, a third etching is performed on the conductive film layer on the back side of the silicon wafer obtained in S8 to form an insulating trench located between the first semiconductor opening region and the second semiconductor opening region; S10, metal electrodes are formed at the first semiconductor opening region and the second semiconductor opening region on the back side of the silicon wafer obtained in S9, respectively.

[0004] The open-circuit voltage and current density of the solar cells prepared by this method still need to be further improved. Utility Model Content

[0005] The purpose of this invention is to provide a back-contact solar cell with higher open-circuit voltage and current density.

[0006] To achieve the above objectives, the technical solution adopted by this utility model is as follows:

[0007] This invention provides a back-contact solar cell, comprising a crystalline silicon substrate, a first intrinsic amorphous silicon layer and a silicon nitride antireflection layer sequentially formed on the front side of the crystalline silicon substrate, a plurality of n-type heavily doped regions formed on the back side of the crystalline silicon substrate and spaced apart, a silicon oxide thin film and a phosphorus-doped polycrystalline silicon layer sequentially formed on the back side of the n-type heavily doped regions, a second intrinsic amorphous silicon layer and a borohydride microcrystalline silicon layer sequentially formed on the back side of a portion of the phosphorus-doped polycrystalline silicon layer and between two adjacent n-type heavily doped regions on the back side of the crystalline silicon substrate, a transparent conductive film formed on the back side of the remaining portion of the phosphorus-doped polycrystalline silicon layer and the back side of the borohydride microcrystalline silicon layer, and a plurality of metal electrodes formed on the transparent conductive film; wherein, an opening region is formed on the transparent conductive film between two adjacent metal electrodes.

[0008] According to some specific implementations, the doping depth of the n-type heavily doped region is 0.5 to 1 micrometer.

[0009] According to some specific embodiments, the thickness of the crystalline silicon substrate is 80 micrometers to 130 micrometers, the thickness of the silicon oxide film is 1 to 2.5 nanometers, the thickness of the phosphorus-doped polycrystalline silicon layer is 120 to 150 nanometers, the thickness of the first intrinsic amorphous silicon layer is 4 to 6 nanometers, the thickness of the silicon nitride antireflection layer is 60 to 80 nanometers, the thickness of the second intrinsic amorphous silicon layer is 4 to 6 nanometers, the thickness of the boron-doped microcrystalline silicon layer is 15 to 25 nm, and the thickness of the transparent conductive film is 100 to 110 nm.

[0010] According to some specific implementations, the distance between two adjacent heavily doped n-type regions is 0.5 to 1.5 mm.

[0011] According to some specific embodiments, each of the n-type heavily doped regions extends along the length direction of the crystalline silicon substrate.

[0012] According to some specific implementations, a spacer region is formed between two adjacent n-type heavily doped regions, and the number of spacer regions on the back side of the crystalline silicon substrate is 40 to 70.

[0013] According to some specific embodiments, the transparent conductive film is made of indium oxide.

[0014] According to some specific embodiments, the metal electrode includes a plurality of first metal electrodes and a plurality of second metal electrodes. A first metal electrode is disposed on a transparent conductive film outside the phosphorus-doped polycrystalline silicon layer, and a second metal electrode is disposed on a transparent conductive film outside the boron-doped hydride microcrystalline silicon layer. The first metal electrodes and the second metal electrodes are distributed alternately.

[0015] According to some specific embodiments, the opening region extends through the transparent conductive film.

[0016] According to some specific embodiments, the crystalline silicon substrate is N-type monocrystalline silicon.

[0017] Due to the application of the above technical solution, this utility model has the following advantages compared with the prior art:

[0018] The battery of this invention has an n-type heavily doped region formed only on the front side of the silicon oxide thin film. Through improvements to other structures of the back contact solar cell, the metallic impurities of the silicon wafer are reduced, the lifespan of the silicon wafer is improved, the resistivity of the back side of the silicon wafer is reduced, the conductivity of the thin film is improved, and thus the open-circuit voltage and current density of the back contact solar cell are increased, thereby improving the product performance. Attached Figure Description

[0019] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 This is a schematic cross-sectional view of the back-contact solar cell of this utility model;

[0021] In the above figures, 10 is an n-type heavily doped region; 11 is a crystalline silicon substrate; 12 is a first intrinsic amorphous silicon layer; 13 is a silicon nitride antireflection layer; 14 is a silicon oxide thin film; 15 is a phosphorus-doped polycrystalline silicon layer; 16 is a second intrinsic amorphous silicon layer; 17 is a boron-hydrogen-doped microcrystalline silicon layer; 18 is a transparent conductive thin film; 19 is a first metal electrode; 20 is multiple second metal electrodes; and 24 is an opening region. Detailed Implementation

[0022] In the following description, only certain exemplary embodiments are briefly described. As those skilled in the art will recognize, the described embodiments can be modified in various ways without departing from the spirit or scope of the present invention. Therefore, the drawings and description are considered to be exemplary in nature and not restrictive.

[0023] In the description of this utility model, it should be understood that the front side refers to the side of the solar cell facing the sun, and the back side refers to the side of the solar cell facing away from the sun, that is, the side opposite to the front side; wherein, the attached... Figure 1 The top is the front, and the bottom is the back. The above description of directional terms is only for the convenience of describing the embodiments of this utility model and simplifying the description, and is not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on the embodiments of this utility model.

[0024] In the description of this utility model, unless otherwise explicitly specified and limited, the terms "connected," "fixed," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part. Those skilled in the art can understand the specific meaning of the above terms in the embodiments of this utility model according to the specific circumstances. The terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this utility model, "multiple" means two or more, unless otherwise explicitly specified.

[0025] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the ranges, the endpoint values ​​of the ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein. The terms "optional" and "discretionary" mean that they may or may not be included (or may or may not be present).

[0026] Unless otherwise specified, all components of this invention can be manufactured using materials conventionally used in the field. All raw materials used in this invention are existing materials and can be provided by suppliers.

[0027] The embodiments of this utility model will now be described in detail with reference to the accompanying drawings.

[0028] like Figure 1 As shown, this utility model provides a back-contact solar cell, including a crystalline silicon substrate 11, a first intrinsic amorphous silicon layer 12 and a silicon nitride antireflection layer 13 sequentially formed on the front side of the crystalline silicon substrate 11, a plurality of n-type heavily doped regions 10 formed on the back side of the crystalline silicon substrate 11 and spaced apart, a silicon oxide thin film 14 and a phosphorus-doped polycrystalline silicon layer 15 sequentially formed on the back side of the n-type heavily doped regions 10, a second intrinsic amorphous silicon layer 16 and a borohydride microcrystalline silicon layer 17 sequentially formed on the back side of a portion of the phosphorus-doped polycrystalline silicon layer 15 and between two adjacent n-type heavily doped regions 10, a transparent conductive film 18 formed on the back side of the remaining portion of the phosphorus-doped polycrystalline silicon layer 15 and the back side of the borohydride microcrystalline silicon layer 17, and a plurality of metal electrodes formed on the transparent conductive film 18. An opening region 24 is formed on the transparent conductive film 18 between two adjacent metal electrodes.

[0029] The crystalline silicon substrate 11 can be any monocrystalline silicon wafer, such as N-type monocrystalline silicon. The size of the crystalline silicon substrate 11 can also be arbitrary, such as 210mm×105mm or 182mm×91mm, and the thickness is 80 micrometers to 130 micrometers.

[0030] According to some specific implementations, the doping depth of the n-type heavily doped region 10 is 0.5 to 1 micrometer.

[0031] According to some specific embodiments, the thickness of the silicon oxide thin film 14 is 1 to 2.5 nanometers.

[0032] According to some specific embodiments, the thickness of the phosphorus-doped polycrystalline silicon layer 15 is 120–150 nanometers.

[0033] According to some specific embodiments, the thickness of the first intrinsic amorphous silicon layer 12 is 4 to 6 nanometers.

[0034] According to some specific embodiments, the thickness of the silicon nitride antireflection layer 13 is 60-80 nanometers.

[0035] According to some specific embodiments, the thickness of the second intrinsic amorphous silicon layer 16 is 4 to 6 nanometers.

[0036] According to some specific embodiments, the thickness of the boron-doped hydrogenated microcrystalline silicon layer 17 is 15–25 nm.

[0037] According to some specific embodiments, the thickness of the transparent conductive film 18 is 100-110 nm.

[0038] According to some specific embodiments, a spacer region is formed between two adjacent heavily doped n-type regions 10, and the number of spacer regions on the back side of the silicon substrate 11 is 40 to 70. The distance between two adjacent heavily doped n-type regions 10 (i.e., the width of a spacer region) is 0.5 to 1.5 mm. The second intrinsic amorphous silicon layer 16 and the boron-doped microcrystalline silicon layer 17 formed on the back side of the silicon substrate 11 between two adjacent heavily doped n-type regions 10 are formed on the back side of the silicon substrate 11 within the spacer region.

[0039] According to some specific embodiments, each n-type heavily doped region 10 extends along the length direction of the silicon substrate 11. The spacer regions also extend along the length direction of the silicon substrate 11.

[0040] According to some specific embodiments, the transparent conductive film 18 is made of indium oxide.

[0041] According to some specific embodiments, the metal electrode includes a plurality of first metal electrodes 19 and a plurality of second metal electrodes 20. A first metal electrode 19 is disposed on a transparent conductive film 18 outside a phosphorus-doped polycrystalline silicon layer 15, and a second metal electrode 20 is disposed on a transparent conductive film 18 outside a boron-doped microcrystalline silicon layer 17. The first metal electrodes 19 and the second metal electrodes 20 are alternately distributed. The first metal electrodes 19 and the second metal electrodes 20 have different polarities.

[0042] According to some specific embodiments, the opening region 24 penetrates the transparent conductive film 18, that is, the boron-doped hydrogen crystalline silicon layer 17 at the opening region 24 is connected to the outside.

[0043] The back-contact solar cell of this invention can be prepared by the following method, which specifically includes the following steps:

[0044] (1) Phosphorus diffusion is performed on the crystalline silicon substrate 11 in a tube furnace to form an n-type heavily doped region 10;

[0045] (2) On the back side of the crystalline silicon substrate 11 with the n-type heavily doped region 10 formed, a silicon oxide thin film 14, a phosphorus-doped polycrystalline silicon layer 15 and a silicon nitride mask layer are deposited sequentially by PECVD or LPCVD and then annealed.

[0046] (3) Laser etching is performed on the first preset area on the back side of the silicon substrate 11 after the treatment in step (2) to remove the silicon oxide film 14, the phosphorus-doped polycrystalline silicon layer 15 and the mask layer 21 in the first preset area, forming an interspersed interval area.

[0047] (4) The silicon substrate 11 after step (3) is cleaned and texturized with an alkaline solution to form a pyramid textured surface on the front side of the silicon substrate 11, while removing the damage on the back side of the silicon substrate and the n-type heavily doped regions 10 in the interstices to form multiple n-type heavily doped regions 10 spaced apart.

[0048] (5) The silicon substrate 11 after step (4) is cleaned with HF solution to remove the mask layer;

[0049] (6) A first intrinsic amorphous silicon layer 12 and a silicon nitride antireflection layer 13 are sequentially deposited on the front side of the crystalline silicon substrate 11 after step (5) using CVD process, and a second intrinsic amorphous silicon layer 16 and a boron-doped hydrogen crystalline silicon layer 17 are sequentially deposited on the back side.

[0050] (7) Laser etching is performed on the second preset area on the back side of the silicon substrate 11 after the processing in step (6) to remove the second intrinsic amorphous silicon layer 16 and the boron-doped microcrystalline silicon layer 17 in the second preset area, forming an interspersed interval region. The interval region is located on the outer surface of the phosphorus-doped polycrystalline silicon layer 15, and the width of the interval region is smaller than the width of the phosphorus-doped polycrystalline silicon layer 15.

[0051] (8) PVD is used to deposit an indium oxide transparent conductive film 18 on the back side of the silicon substrate 11 after step (7), and then laser etching is used to remove part of the transparent conductive film 18 to form an open area 24 with spacing on the outside of the boron-doped microcrystalline silicon layer 17.

[0052] (9) A metal electrode is prepared on the outside of the transparent conductive film 18 on the back side of the silicon substrate 11 after step (8) by means of screen printing or electroplating.

[0053] Compared to a back-contact solar cell without an n-type heavily doped region 10, the open-circuit voltage of this novel back-contact solar cell is increased by 1 mV, the fill factor is increased by 0.1%, and the efficiency is increased by 0.06%. In one embodiment of this novel back-contact solar cell, the open-circuit voltage is 0.744 V and the current density is 42.5 mA / cm². 2 The battery's photoelectric conversion efficiency is 26.5%.

[0054] The battery of this invention has an n-type heavily doped region formed only on the front side of the silicon oxide thin film. Through improvements to other structures of the back contact solar cell, the metallic impurities of the silicon wafer are reduced, the lifespan of the silicon wafer is improved, the resistivity of the back side of the silicon wafer is reduced, the conductivity of the thin film is improved, and thus the open-circuit voltage and current density of the back contact solar cell are increased, thereby improving the product performance.

[0055] The above are merely preferred embodiments of this utility model and are not intended to limit the scope of this utility model. Various modifications and variations can be made to this utility model by those skilled in the art. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of this utility model should be included within the protection scope of this utility model.

Claims

1. A back-contact solar cell, characterized in that: The structure includes a crystalline silicon substrate (11), a first intrinsic amorphous silicon layer (12) and a silicon nitride antireflection layer (13) sequentially formed on the front side of the crystalline silicon substrate (11), a plurality of n-type heavily doped regions (10) formed on the back side of the crystalline silicon substrate (11) and spaced apart, a silicon oxide thin film (14) and a phosphorus-doped polycrystalline silicon layer (15) sequentially formed on the back side of the n-type heavily doped regions (10), and a portion of the phosphorus-doped polycrystalline silicon layer (15) and two adjacent n-type heavily doped regions. A second intrinsic amorphous silicon layer (16) and a boron-doped microcrystalline silicon layer (17) are formed on the back side of the crystalline silicon substrate (11) between the doped regions (10), and a transparent conductive film (18) is formed on the back side of the remaining portion of the phosphorus-doped polycrystalline silicon layer (15) and the back side of the boron-doped microcrystalline silicon layer (17). A plurality of metal electrodes are formed on the transparent conductive film (18); wherein an opening region (24) is formed on the transparent conductive film (18) between two adjacent metal electrodes.

2. The back-contact solar cell according to claim 1, characterized in that: The doping depth of the n-type heavily doped region (10) is 0.5 to 1 micrometer.

3. The back-contact solar cell according to claim 1, characterized in that: The thickness of the crystalline silicon substrate (11) is 80 micrometers to 130 micrometers, the thickness of the silicon oxide thin film (14) is 1 to 2.5 nanometers, the thickness of the phosphorus-doped polycrystalline silicon layer (15) is 120 to 150 nanometers, the thickness of the first intrinsic amorphous silicon layer (12) is 4 to 6 nanometers, the thickness of the silicon nitride antireflection layer (13) is 60 to 80 nanometers, the thickness of the second intrinsic amorphous silicon layer (16) is 4 to 6 nanometers, the thickness of the boron-doped microcrystalline silicon layer (17) is 15 to 25 nm, and the thickness of the transparent conductive film (18) is 100 to 110 nm.

4. The back-contact solar cell according to claim 1, characterized in that: The distance between two adjacent n-type heavily doped regions (10) is 0.5 to 1.5 mm.

5. The back-contact solar cell according to claim 1, characterized in that: Each of the n-type heavily doped regions (10) extends along the length direction of the crystalline silicon substrate (11).

6. The back-contact solar cell according to claim 1, characterized in that: An interspacer region is formed between two adjacent n-type heavily doped regions (10), and the number of interspacer regions on the back side of the crystalline silicon substrate (11) is 40 to 70.

7. The back-contact solar cell according to claim 1, characterized in that: The transparent conductive film (18) is made of indium oxide.

8. The back-contact solar cell according to claim 1, characterized in that: The metal electrodes include a plurality of first metal electrodes (19) and a plurality of second metal electrodes (20). A first metal electrode (19) is disposed on a transparent conductive film (18) outside a phosphorus-doped polycrystalline silicon layer (15), and a second metal electrode (20) is disposed on a transparent conductive film (18) outside a boron-doped hydrocrystalline silicon layer (17). The first metal electrodes (19) and the second metal electrodes (20) are distributed alternately.

9. The back-contact solar cell according to claim 1, characterized in that: The opening region (24) penetrates the transparent conductive film (18).

10. The back-contact solar cell according to claim 1, characterized in that: The silicon substrate (11) is an N-type monocrystalline silicon.

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