Solar cell and preparation method therefor

Abstract

A solar cell and a preparation method therefor. The solar cell comprises: a P-type region and an N-type region, which are located on the back side of the solar cell; an isolation region, which is located between the P-type region and the N-type region; a first electrode, which in contact with the P-type region; and a second electrode, which is in contact with the N-type region. The solar cell further comprises an electrical connecting member, which is used for electrically connecting part of the P-type region and part of the N-type region. In the solar cell and the preparation method therefor, an electrical connecting member is provided to connect part of the P-type region and part of the N-type region, such that a bypass path is formed for the situation in which some solar cell pieces are shaded, thereby reducing power loss of the cell.

Description

Solar cells and their preparation methods Technical Field

[0001] This invention relates to the field of photovoltaics, and more particularly to a solar cell and its preparation method. Background Technology

[0002] Photovoltaic modules are typically installed in sunny locations, such as rooftops, hillsides, deserts, and Gobi deserts. The outdoor environment is complex, and during use, they are often obstructed by dust, leaves, and other debris. If localized shading occurs, the modules can suffer significant damage.

[0003] In view of this, it is necessary to provide an improved solar cell and its fabrication method to solve the above-mentioned technical problems. Summary of the Invention

[0004] This invention provides a solar cell and its fabrication method to solve problems such as cell efficiency loss caused by shading.

[0005] To achieve one of the above-mentioned objectives, the present invention adopts the following technical solution:

[0006] A solar cell includes a P-region and an N-region located on its back side, an isolation region located between the P-region and the N-region, a first electrode in contact with the P-region, and a second electrode in contact with the N-region. The solar cell also includes an electrical connector that electrically connects a portion of the P-region and a portion of the N-region.

[0007] In one optional embodiment, the resistance of the electrical connector is less than the resistance of the isolation region, the resistance of the electrical connector is not less than the resistance of the P region, or the resistance of the electrical connector is the same as the resistance of the N region.

[0008] In one optional implementation, the electrical connector is located in the isolation area, and the electrical connector is made of the same material as the N area, or the electrical connector is made of the same material as the P area.

[0009] In one optional embodiment, the electrical connector extends from the N region to the isolation region, or the electrical connector extends from the P region to the isolation region.

[0010] In one optional implementation, a plurality of the P regions and a plurality of the N regions are arranged alternately along the OY direction, the electrical connector is located in the isolation region, and each N region is electrically connected to its P region on one side of the OY direction only through the electrical connector, or each P region is electrically connected to its N region on one side of the OY direction only through the electrical connector.

[0011] In one optional embodiment, the P region includes a plurality of first main gate regions extending along the OX direction and a plurality of first sub-gate regions extending along the OY direction. The plurality of first sub-gate regions are arranged along the OX direction and are connected to the first main gate regions.

[0012] The N region includes a plurality of second main gate regions extending along the OX direction and a plurality of second sub-gate regions extending along the OY direction. The plurality of second sub-gate regions are arranged along the OX direction and are connected to the second main gate regions. The first main gate region and the second main gate region are alternately arranged along the OY direction, and the first sub-gate region and the second sub-gate region are alternately arranged along the OX direction.

[0013] The electrical connector is located in an isolation zone surrounding the first sub-gate region, or the electrical connector is located in an isolation zone surrounding the second sub-gate region.

[0014] In one optional embodiment, the electrical connector connects the first main gate region and the second sub-gate region; or the electrical connector connects the second main gate region and the first sub-gate region; or the electrical connector connects the first sub-gate region and the second sub-gate region.

[0015] In one optional implementation, several first sub-gate regions connected to the first main gate region are all connected to the same N region via electrical connectors. Two adjacent first sub-gate regions are connected to different positions in the second main gate region via the electrical connectors, or two adjacent first sub-gate regions are connected to different second sub-gate regions via the electrical connectors.

[0016] In one optional embodiment, there is at least one isolation zone without an electrical connector between the two isolation zones having the electrical connector; and / or, in the isolation zone between each P zone and N zone, the area of ​​the electrical connector accounts for 0.1% to 2%.

[0017] A method for preparing a solar cell includes the following steps:

[0018] Patterned P-regions are formed on the back side of the silicon substrate;

[0019] A patterned N-region is formed on the back side of a silicon substrate, and an isolation region is provided between the N-region and the P-region;

[0020] An electrical connector is formed on the back side of a silicon substrate, electrically connecting a portion of the P-region and a portion of the N-region;

[0021] The first electrode and the second electrode are formed in the P region and the N region, respectively.

[0022] In one alternative implementation, the electrical connection is formed at a portion of the isolation zone.

[0023] In one optional embodiment, the method for preparing the solar cell includes the following steps in sequence:

[0024] A boron diffusion layer is formed on the entire back side of the silicon substrate, and laser ablation is performed, leaving only the boron diffusion layer at the location of the P-region.

[0025] A tunneling layer and an N-type polysilicon layer are formed on the entire back side. Laser delamination is then performed, leaving only the tunneling layer and N-type polysilicon layer at the N-region and the location of the electrical connector.

[0026] In one optional embodiment, the method for preparing the solar cell includes the following steps in sequence:

[0027] A boron diffusion layer is formed on the entire back side of the silicon substrate, and laser ablation is performed, leaving only the boron diffusion layer at the P-region and the location of the electrical connectors.

[0028] A tunneling layer and N-type polysilicon are formed on the entire back side, and laser delamination is performed, leaving only the tunneling layer and N-type polysilicon layer at the location of the N region.

[0029] In an optional embodiment, the P region includes a plurality of first main gate regions extending along the OX direction and a plurality of first sub-gate regions extending along the OY direction, the plurality of first sub-gate regions being arranged along the OX direction and communicating with the first main gate regions; the N region includes a plurality of second main gate regions extending along the OX direction and a plurality of second sub-gate regions extending along the OY direction, the plurality of second sub-gate regions being arranged along the OX direction and communicating with the second main gate regions; the first main gate regions and the second main gate regions are alternately arranged along the OY direction, and the first sub-gate regions and the second sub-gate regions are alternately arranged along the OX direction; the electrical connector is located in an isolation area surrounding the first sub-gate regions, or the electrical connector is located in an isolation area surrounding the second sub-gate regions.

[0030] In one optional embodiment, the electrical connector is located between the first main gate region and the second sub-gate region; or the electrical connector is located between the second main gate region and the first sub-gate region; or the electrical connector is located between the first sub-gate region and the second sub-gate region.

[0031] In an optional embodiment, the P-region is a boron diffusion region with a doping concentration of 5E18cm⁻¹. -3 ~5E19cm -3 The sheet resistance is 250 ohm / sq to 350 ohm / sq, and the junction depth is 0.5 μm to 0.1 μm; the N-region is phosphorus-, carbon-, or nitrogen-doped with a doping concentration of 3E20cm⁻¹. -3 ~5E20cm -3The process of “forming a tunneling layer and N-type polycrystalline silicon” includes the following steps: growing a tunneling layer and an N-type amorphous silicon layer by in-situ doping using PECVD; and annealing the N-type amorphous silicon layer at 850℃~980℃ to transform it into an N-type polycrystalline silicon layer.

[0032] In an optional embodiment, after forming the electrical connector, the method for fabricating the solar cell further includes the following steps:

[0033] A passivation layer is formed on the entire back and the entire front.

[0034] An anti-reflective layer is formed on the entire back and the entire front.

[0035] A first electrode and a second electrode are formed in the P-region and the N-region, respectively. The first electrode passes through the anti-reflection layer and passivation layer on the back side and contacts the P-region; the second electrode passes through the anti-reflection layer and passivation layer on the back side and contacts the N-type polysilicon layer.

[0036] The beneficial effects of the present invention are: the solar cell and its preparation method of the present invention, by setting an electrical connector to connect part of the P region and part of the N region, serve as a bypass path when the cell is partially shaded, thereby reducing the power loss of the cell. Attached Figure Description

[0037] Figure 1 is a schematic diagram of the structure of a solar cell according to an embodiment of the present invention;

[0038] Figure 2 is a schematic diagram of the structure of the back side of a solar cell according to an embodiment of the present invention;

[0039] Figure 3 is a magnified view of a unit in Figure 1;

[0040] Figure 4 is a schematic diagram of a unit in another embodiment;

[0041] Figure 5 is a schematic diagram of a unit in another embodiment;

[0042] Figure 6 is a schematic diagram of the structure of a solar cell according to one embodiment of the present invention;

[0043] Figure 7 is a flowchart of a method for preparing a solar cell according to an embodiment of the present invention;

[0044] Figure 8 is a schematic diagram of a patterned P-region formed on the back side of a silicon substrate based on the method shown in Figure 7.

[0045] Figure 9 is a schematic diagram of the deposition of the tunneling layer and the N-type amorphous silicon layer based on Figure 8;

[0046] Figure 10 is a schematic diagram of laser-induced film opening to form the N-region and electrical connector based on Figure 9;

[0047] Figure 11 is a flowchart of a method for preparing a solar cell according to another embodiment of the present invention;

[0048] Figure 12 is a schematic diagram of forming patterned P-regions and electrical interconnects on the back side of a silicon substrate based on the method shown in Figure 11;

[0049] Figure 13 is a schematic diagram of the deposition of the tunneling layer and the N-type amorphous silicon layer based on Figure 12;

[0050] Figure 14 is a schematic diagram of laser-induced film opening to form the N-region, based on Figure 13.

[0051] Among them, 100-solar cell, 101-silicon substrate, 102-front passivation layer, 103-front antireflection layer, 104-back passivation layer, 105-back antireflection layer, 1-P region, 11-first main gate region, 12-first sub-gate region, 2-N region, 21-second main gate region, 22-second sub-gate region, 3-isolation region, 4-electrical connector, 5-first electrode, 6-second electrode. Detailed Implementation

[0052] The present invention will now be described in detail with reference to the specific embodiments shown in the accompanying drawings. However, these embodiments do not limit the present invention, and any structural, methodological, or functional modifications made by those skilled in the art based on these embodiments are included within the scope of protection of the present invention.

[0053] In the various figures of this invention, for ease of illustration, some dimensions of structures or parts may be exaggerated relative to other structures or parts; therefore, only the basic structure of the subject matter of this invention is used to illustrate the invention.

[0054] Please refer to Figures 1 to 5, which show the solar cell 100 of the present invention, which includes a silicon substrate 101, a P region 1 and an N region 2 located on the back side of the silicon substrate 101, an isolation region 3 located between the P region 1 and the N region 2, an electrical connector 4 connecting a portion of the P region 1 and a portion of the N region 2, a first electrode 5 in contact with the P region 1, and a second electrode 6 in contact with the N region 2.

[0055] The silicon substrate 101 is an N-type silicon wafer, the P region 1 is a patterned region formed by boron diffusion on the back side of the silicon substrate 101, the N region 2 is also patterned and includes a tunneling layer and an N-type polysilicon layer, and the second electrode 6 is in contact with the N-type polysilicon layer.

[0056] The P region 1 includes a plurality of first main gate regions 11 extending along the OX direction and a plurality of first sub-gate regions 12 extending along the OY direction. The plurality of first sub-gate regions 12 are arranged along the OX direction, and the first sub-gate regions 12 are connected to the first main gate regions 11.

[0057] Specifically, the first sub-gate region 12 spans the first main gate region 11 along the OY direction, that is, the first sub-gate region 12 extends from the first main gate region 11 to both sides in the OY direction. In an optional embodiment, the first sub-gate region 12 is perpendicular to the first main gate region 11.

[0058] The N region 2 includes a plurality of second main gate regions 21 extending along the OX direction and a plurality of second sub-gate regions 22 extending along the OY direction. The plurality of second sub-gate regions 22 are arranged along the OX direction, and the second sub-gate regions 22 are connected to the second main gate regions 21.

[0059] Specifically, the second sub-gate region 22 spans the second main gate region 21 along the OY direction, that is, the second sub-gate region 22 extends from the second main gate region 21 to both sides in the OY direction. In an optional embodiment, the second sub-gate region 22 and the second main gate region 21 are perpendicular to each other.

[0060] The first main gate region 11 and the second main gate region 21 are alternately arranged along the OY direction, and the first sub-gate region 12 and the second sub-gate region 22 are alternately arranged along the OX direction. The entire P region 1 and the entire N region 2 are distributed in a forked shape, which is beneficial for the collection of charge carriers.

[0061] In this invention, the first main gate region 11 and the second main gate region 21 are considered as the main components, and the P region 1 and the N region 2 are considered to be arranged alternately along the OY direction.

[0062] In this process, the width of the first sub-gate region 12 is greater than the width of the second sub-gate region 22. The P-region 1 forms a PN junction with the silicon substrate 101. The wider P-region 1 is more conducive to generating a large number of charge carriers and improving the battery efficiency.

[0063] In this invention, the width ratio of the first sub-gate region 12 to the width ratio of the second sub-gate region 22 is 2:1 to 4:1, preferably 3:1, which optimizes electrical parameters such as open-circuit voltage, short-circuit current, and fill factor, thereby improving battery efficiency.

[0064] Specifically, the width of the first sub-gate region is 540nm~660nm, and the width of the second sub-gate region is 180nm~220nm. In one embodiment, the width of the first sub-gate region is 600nm, and the width of the second sub-gate region is 200nm.

[0065] The isolation region 3 is located between region P 1 and region N 2, separating region P 1 and region N 2 and preventing them from connecting to each other. In an optional embodiment, the width of the isolation region 3 is 50μm~100μm; if it is too small, the preparation process is difficult, and if it is too large, it wastes effective area.

[0066] This invention breaks away from the limitation of complete isolation between P-region 1 and N-region 2 in traditional back-side batteries (BC batteries) by providing an electrical connector 4 to connect a portion of P-region 1 and a portion of N-region 2. When a part of the battery cell is partially shaded, the electrical connector 4 bypasses and connects P-region 1 and N-region 2, reducing power loss of the battery.

[0067] From an electrical perspective, the resistance of the electrical connector 4 is less than the resistance of the isolation region 3, and the resistance of the electrical connector 4 is not less than the resistance of the P region 1, or the resistance of the electrical connector 4 is equal to the resistance of the N region 2. Under normal conditions without shadow obstruction, holes and electrons are collected by the first electrode located in the P region 1 and the second electrode located in the N region 2, respectively, and will not bypass through the electrical connector 4; however, under shadow obstruction, the resistance of the P region 1 and the N region 2 increases, and the P region 1 and the N region 2 become conductive through the electrical connector 4.

[0068] In one embodiment, the electrical connector 4 is made of the same material as the N region 2, and the electrical connector 4 and the N region 2 can be manufactured together, simplifying the process. In an optional embodiment, the electrical connector 4 extends from the N region 2 towards the isolation region 3, that is, the electrical connector 4 is a part of the N region 2 extending to the P region 1.

[0069] In another embodiment, the electrical connector 4 is made of the same material as the P region 1, and the electrical connector 4 and the P region 1 can be manufactured together, simplifying the process. In an optional embodiment, the electrical connector 4 is formed by extending the P region 1 into the isolation region 3, that is, the electrical connector 4 is a part of the P region 1 extending into the N region 2.

[0070] In this application, the electrical connector 4 is located in the isolation region 3, but does not cover the entire isolation region 3. Specifically, the electrical connector 4 is located only in a portion of the isolation region 3, or in a portion of any isolation region 3. Therefore, the P region 1 and the N region 2 on the back side are not fully connected as a single conductor, but only partially electrically connected through the electrical connector 4. The electrical connector 4 constitutes the electrical connection point or leakage point between the P region 1 and the N region 2, and can be considered as a bypass diode. When a portion of the battery cell is partially shaded, it reduces the power loss of the battery; and when there is no shading, the leakage is very weak and will not affect normal current collection.

[0071] In this invention, the isolation zone 3 with the electrical connector 4 accounts for 1% to 50% of all isolation zones 3. That is, some isolation zones 3 are not equipped with electrical connector 4, which can avoid serious leakage in N zone 2 and P zone 1 and reduce battery efficiency.

[0072] In an optional embodiment, there is at least one isolation zone 3 without electrical connector 4 between the two isolation zones 3 having the electrical connector 4, so as to prevent the P zone 1 from being connected to the surrounding N zone 2 as a whole, and also to prevent the N zone 2 from being connected to the surrounding P zone 1 as a whole.

[0073] In one optional embodiment, several P-regions 1 and several N-regions 2 are arranged alternately along the OY direction. Each N-region 2 is electrically connected only to one P-region 1 in the OY direction via an electrical connector 4, and not to the P-region 1 on the other side. Similarly, each P-region 1 is electrically connected only to one N-region 2 in the OY direction via an electrical connector 4. Therefore, electrical connection occurs only between adjacent P-regions 1 and N-regions 2, rather than all P-regions 1 and N-regions 2 on the back side being electrically connected as one unit.

[0074] In one optional embodiment, each isolation zone 3 may include a plurality of electrical connectors 4. In another optional embodiment, the plurality of electrical connectors 4 are spaced apart along the OX direction within the isolation zone 3. This design reduces the area of ​​each electrical connector 4, resulting in a low leakage rate; and the multi-point distribution forms multiple small bypass paths, enabling rapid bypassing even when any area is shaded.

[0075] Specifically, the electrical connector 4 is located within the isolation region 3 surrounding the first sub-gate region 12, or the electrical connector 4 is located within the isolation region 3 surrounding the second sub-gate region 22. In an optional embodiment, the electrical connector 4 is located at the end of the P region 1 or the N region 2, so that the CT (cycle time) of laser ablation can be optimized.

[0076] Several first sub-gate regions 12 connected to the first main gate region 11 are all connected to the same N region 2 through electrical connectors 4. Two adjacent first sub-gate regions 12 are connected to different positions of the second main gate region 21 through the electrical connectors 4, or two adjacent first sub-gate regions 12 are connected to different second sub-gate regions 22 through the electrical connectors 4.

[0077] In an optional embodiment, as shown in Figures 3 and 4, the electrical connector 4 connects the first sub-gate region 12 and the second sub-gate region 22. The current in the sub-gate region is less than the current in the main gate region, so the probability of leakage is small when there is no obstruction.

[0078] In an optional embodiment, the electrical connector 4 connects the first main gate region 11 and the second sub-gate region 22; or as shown in FIG5, the electrical connector 4 connects the second main gate region 21 and the first sub-gate region 12, which can quickly bypass when blocked by shadows to avoid generating hot spots.

[0079] In addition, the total area of ​​all the electrical connectors 4 in the entire battery cell accounts for 0.1% to 1% of the total area of ​​all the isolation areas 3. This design ensures that the battery can bypass through the electrical connectors 4 when shaded, while avoiding serious leakage under normal conditions.

[0080] In one optional implementation, the area of ​​the electrical connector 4 in each isolation zone 3 accounts for 0.1% to 2%.

[0081] The first electrode 5 in contact with the P region 1 includes a first main gate and a first sub-gate. The first main gate is located in the first main gate region, and the width of the first main gate is smaller than the width of the first main gate region. The first sub-gate is located in the first sub-gate region, and the width of the first sub-gate is smaller than the width of the first sub-gate region. In this invention, the first main gate is a non-essential gate line, and the width of the first sub-gate is 30μm~40μm.

[0082] The second electrode 6, which contacts the N-region 2, includes a second main gate and a second sub-gate. The second main gate is located in the second main gate region, and its width is smaller than the width of the second main gate region. The second sub-gate is located in the second sub-gate region, and its width is smaller than the width of the second sub-gate region. In this invention, the second main gate is a non-essential gate line, and the width of the second sub-gate is 30 μm to 40 μm.

[0083] In an optional embodiment, the solar cell 100 further includes a back passivation layer 104 and a back antireflection layer 105 located on the back sides of P region 1 and N region 2. The first electrode 5 passes through the back antireflection layer 105 and the back passivation layer 104 to contact the boron diffusion layer of P region 1; the second electrode 6 passes through the back antireflection layer 105 and the back passivation layer 104 to contact the N-type crystalline silicon layer of N region 2.

[0084] It should be noted that, in order to clearly show the positional relationship between P region 1, N region 2, spacer region 3 and electrical connector 4, the back passivation layer 104 and the back antireflection layer 105 are not shown in Figure 1.

[0085] Additionally, the solar cell 100 further includes a front passivation layer 102 located on the front side of the silicon substrate 101. The front passivation layer 102 passivates the front side, reducing interfacial recombination. The front passivation layer 102 is an aluminum oxide layer with a thickness of 3nm to 6nm, preferably 3nm to 5nm.

[0086] The solar cell 100 also includes a front antireflection layer 103 located on the front side of the front passivation layer 102, which reduces reflectivity and improves light absorption. The front antireflection layer 103 is selected from one or more stacked films of silicon nitride, silicon oxynitride, and silicon oxide, and has a thickness of 60nm~130nm, preferably 70nm~80nm.

[0087] Please refer to Figures 7-12. This invention also provides a method for preparing a solar cell, comprising the following steps:

[0088] A patterned P-region 1 is formed on the back side of the silicon substrate 101;

[0089] A patterned N-region 2 is formed on the back side of the silicon substrate 101, and an isolation region 3 is provided between the N-region 2 and the P-region 1;

[0090] An electrical connector 4 is formed on the back side of a silicon substrate 101, the electrical connector 4 electrically connecting a portion of the P region 1 and a portion of the N region 2.

[0091] The structure and positional relationship of the P region 1, the N region 2, the isolation region 3 and the electrical connector 4 are the same as those of the solar cell 100 described above, and will not be repeated here. The following will focus on the formation process.

[0092] The electrical connector 4 is formed at a portion of the isolation zone 3 without additionally occupying the effective area on the back side and without affecting the rear structural arrangement of the battery.

[0093] In the first embodiment, please refer to Figures 7 to 9. The electrical connector 4 is made of the same material as the N region 2, and the electrical connector 4 and the N region 2 are formed synchronously.

[0094] The method for preparing the solar cell is as follows: first, a patterned P-region 1 is formed, and then a patterned N-region 2 and the electrical connector 4 are formed simultaneously.

[0095] Specifically, forming the patterned P region 1 includes the following steps:

[0096] A boron diffusion layer is formed by boron diffusion across the entire back side of the silicon substrate 101; wherein the doping concentration of the boron diffusion layer is 5E18cm⁻¹. -3 ~5E19cm -3 The sheet resistance is 250 ohm / sq to 350 ohm / sq, and the junction depth is 0.5 μm to 0.1 μm.

[0097] The process involves opening the film, removing the boron diffusion layer outside region P1, leaving only the boron diffusion layer at the location of region P1, thus forming a patterned region P1. Laser film opening is preferred, using a green laser with a power of 50W~120W; or a violet laser with a power of 30W~60W. Ultraviolet picosecond or green picosecond lasers are preferred due to their low damage and cost; femtosecond lasers can also be used.

[0098] Forming the patterned N region 2 includes the following steps:

[0099] A tunneling layer and an N-type amorphous silicon layer are formed on the entire back side, preferably with phosphorus-doped amorphous silicon layer grown by PECVD in-situ doping.

[0100] Annealing transforms the N-type amorphous silicon layer into an N-type polycrystalline silicon layer.

[0101] The film is opened up, leaving only the tunneling layer and N-type polysilicon layer at the locations of N-region 2 and the electrical connector 4. N-region 2 and electrical connector 4 are formed simultaneously, and the material of electrical connector 4 is the same as that of N-region 2. The film opening process here is the same as the film opening process when forming P-region 1, and will not be described again here.

[0102] Specifically, the tunneling layer is selected from silicon oxide (SiOx) or silicon carbide (SiC), with a thickness of 1nm to 3nm, preferably 1nm to 2.5nm, more preferably 1nm to 2nm, or 1.5nm to 2nm, or 1.5nm to 2.5nm. The thickness of the tunneling layer 31 is optimized according to its density. When the tunneling layer 31 is SiOx, the thickness is 1.4nm to 2.3nm; when the tunneling layer 31 is SiC, the film is more dense, with a thickness of 1nm to 1.8nm.

[0103] The N-type polysilicon layer is a phosphorus-doped, carbon-doped, or nitrogen-doped polysilicon layer; the following explanation will use phosphorus doping as an example. The annealing temperature is 850℃~980℃, and the doping concentration of the N-type polysilicon layer is 3E20cm⁻¹. -3 ~5E20cm -3 The thickness is 80nm~130nm, and can be set to 90nm, 95nm, 100nm, 105nm, 110nm, 115nm, or 120nm.

[0104] In an optional embodiment, the method for preparing the solar cell further includes:

[0105] A passivation layer 102 is formed on the front side and a passivation layer 104 is formed on the back side. This invention uses the ALD process to deposit aluminum oxide passivation layers on both sides, which can form a good passivation effect on both P region 1 and N region 2, with a thickness of 3nm~6nm, preferably 3nm~5nm.

[0106] A front antireflection layer 103 and a back antireflection layer 105 are formed on the entire front and back sides, respectively, to reduce the reflectivity of both sides. This invention uses PECVD process to deposit a stacked film composed of one or more of silicon nitride, silicon oxynitride, and silicon oxide on both sides. The thickness of the front antireflection layer 103 and the back antireflection layer 105 is 60nm~130nm, preferably 70nm~80nm.

[0107] A first electrode 5 and a second electrode 6 are formed in P-region 1 and N-region 2, respectively. Specifically, the first electrode 5 and the second electrode 6 can be formed by screen printing and sintering. The first electrode 5 passes through the back antireflection layer 105 and the back passivation layer 104 and contacts P-region 1; the second electrode 6 passes through the back antireflection layer 105 and the back passivation layer 104 and contacts the N-type polycrystalline silicon layer.

[0108] Specifically, the process of forming the first electrode 5 and the second electrode 6 is as follows: screen printing the second sub-gate → drying → screen printing the first sub-gate → drying → screen printing the first main gate and the second main gate → sintering.

[0109] In an optional embodiment, the method for fabricating the solar cell further includes post-processing and testing / sorting.

[0110] In the second type of embodiment, please refer to Figures 10-12. The electrical connector 4 is made of the same material as the P area 1, and the electrical connector 4 and the P area 1 are formed synchronously.

[0111] The method for fabricating the solar cell is as follows: first, a patterned P-region 1 and an electrical connector 4 are formed simultaneously, and then a patterned N-region 2 is formed. The difference from the first type of embodiment lies only in the following step description.

[0112] The process of forming the patterned P region 1 includes the following steps:

[0113] Boron diffusion is performed on the entire back side of the silicon substrate 101;

[0114] The film is opened, leaving only the boron diffusion layer at the location of P region 1 and electrical connector 4, and patterned P region 1 and electrical connector 4 are formed simultaneously, with the electrical connector 4 being made of the same material as P region 1.

[0115] Forming the patterned N region 2 includes the following steps:

[0116] A tunneling layer and an N-type amorphous silicon layer are formed on the entire back side;

[0117] Annealing transforms the N-type amorphous silicon layer into an N-type polycrystalline silicon layer.

[0118] The film is opened, leaving only the tunneling layer and the N-type polycrystalline silicon layer at the location of N region 2.

[0119] The other steps are the same as in the first type of embodiment, and will not be repeated here.

[0120] In summary, the solar cell 100 of the present invention, by providing an electrical connector 4 to electrically connect part of the P region 1 and part of the N region 2, can reduce the power loss of the cell when a part of the cell is partially shaded, and can basically retain about 70% of the original power.

[0121] It should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This way of describing the specification is only for clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

[0122] The detailed descriptions listed above are merely specific descriptions of feasible embodiments of the present invention, and are not intended to limit the scope of protection of the present invention. All equivalent embodiments or modifications made without departing from the spirit of the present invention should be included within the scope of protection of the present invention.

Claims

1. A solar cell, comprising a P-region and an N-region located on its back side, an isolation region located between the P-region and the N-region, a first electrode in contact with the P-region, and a second electrode in contact with the N-region, characterized in that, The solar cell also includes an electrical connector that electrically connects a portion of the P region and a portion of the N region.

2. The solar cell according to claim 1, characterized in that: The resistance of the electrical connector is less than the resistance of the isolation region, the resistance of the electrical connector is not less than the resistance of the P region, or the resistance of the electrical connector is the same as the resistance of the N region.

3. The solar cell according to claim 1, characterized in that: The electrical connector is located in the isolation area, and the electrical connector is made of the same material as the N area, or the electrical connector is made of the same material as the P area.

4. The solar cell according to claim 3, characterized in that: The electrical connector is formed by extending from the N region to the isolation region, or the electrical connector is formed by extending from the P region to the isolation region.

5. The solar cell according to claim 1, characterized in that: The P-regions and N-regions are arranged alternately along the OY direction. The electrical connector is located in the isolation area. Each N-region is electrically connected to its P-region on one side of the OY direction only through the electrical connector, or each P-region is electrically connected to its N-region on one side of the OY direction only through the electrical connector.

6. The solar cell according to claim 5, characterized in that: The P region includes a plurality of first main gate regions extending along the OX direction and a plurality of first sub-gate regions extending along the OY direction. The plurality of first sub-gate regions are arranged along the OX direction and are connected to the first main gate regions. The N region includes a plurality of second main gate regions extending along the OX direction and a plurality of second sub-gate regions extending along the OY direction. The plurality of second sub-gate regions are arranged along the OX direction and are connected to the second main gate regions. The first main gate region and the second main gate region are alternately arranged along the OY direction, and the first sub-gate region and the second sub-gate region are alternately arranged along the OX direction. The electrical connector is located in an isolation zone surrounding the first sub-gate region, or the electrical connector is located in an isolation zone surrounding the second sub-gate region.

7. The solar cell according to claim 6, characterized in that: The electrical connector connects the first main gate region and the second sub-gate region; or the electrical connector connects the second main gate region and the first sub-gate region; or the electrical connector connects the first sub-gate region and the second sub-gate region.

8. The solar cell according to claim 7, characterized in that: Several first sub-gate regions connected to the first main gate region are all connected to the same N region through electrical connectors. Two adjacent first sub-gate regions are connected to different positions in the second main gate region through the electrical connectors, or two adjacent first sub-gate regions are connected to different second sub-gate regions through the electrical connectors.

9. The solar cell according to any one of claims 3 to 8, characterized in that: There is at least one isolation zone without an electrical connector between the two isolation zones having the electrical connector; and / or, in the isolation zone between each P zone and N zone, the area of ​​the electrical connector accounts for 0.1% to 2%; There is at least one isolation zone without an electrical connection between the two isolation zones having the electrical connection.

10. A method for preparing a solar cell, characterized in that: Includes the following steps: Patterned P-regions are formed on the back side of the silicon substrate; A patterned N-region is formed on the back side of a silicon substrate, and an isolation region is provided between the N-region and the P-region; An electrical connector is formed on the back side of a silicon substrate, electrically connecting a portion of the P-region and a portion of the N-region; The first electrode and the second electrode are formed in the P region and the N region, respectively.

11. The method for preparing a solar cell according to claim 10, characterized in that: The electrical connector is formed at a portion of the isolation zone.

12. The method for preparing a solar cell according to claim 10, characterized in that: The method for preparing the solar cell includes the following steps in sequence: A boron diffusion layer is formed on the entire back side of the silicon substrate, and laser ablation is performed, leaving only the boron diffusion layer at the location of the P-region. A tunneling layer and an N-type polysilicon layer are formed on the entire back side. Laser delamination is then performed, leaving only the tunneling layer and N-type polysilicon layer at the N-region and the location of the electrical connector.

13. The method for preparing a solar cell according to claim 10, characterized in that: The method for preparing the solar cell includes the following steps in sequence: A boron diffusion layer is formed on the entire back side of the silicon substrate, and laser ablation is performed, leaving only the boron diffusion layer at the P-region and the location of the electrical connectors. A tunneling layer and N-type polysilicon are formed on the entire back side, and laser delamination is performed, leaving only the tunneling layer and N-type polysilicon layer at the location of the N region.

14. The method for preparing a solar cell according to any one of claims 10 to 13, characterized in that: The P region includes a plurality of first main gate regions extending along the OX direction and a plurality of first sub-gate regions extending along the OY direction. The plurality of first sub-gate regions are arranged along the OX direction and are connected to the first main gate regions. The N region includes a plurality of second main gate regions extending along the OX direction and a plurality of second sub-gate regions extending along the OY direction. The plurality of second sub-gate regions are arranged along the OX direction and are connected to the second main gate regions. The first main gate region and the second main gate region are alternately arranged along the OY direction, and the first sub-gate region and the second sub-gate region are alternately arranged along the OX direction. The electrical connector is located in an isolation zone surrounding the first sub-gate region, or the electrical connector is located in an isolation zone surrounding the second sub-gate region.

15. The method for preparing a solar cell according to claim 14, characterized in that: The electrical connector is located between the first main gate region and the second sub-gate region; or the electrical connector is located between the second main gate region and the first sub-gate region; or the electrical connector is located between the first sub-gate region and the second sub-gate region.

16. The method for preparing a solar cell according to any one of claims 10 to 13, characterized in that: The P-region is a boron diffusion region with a doping concentration of 5E18cm⁻¹. -3 ~5E19cm -3 Or the sheet resistance is 250 ohm / sq~350 ohm / sq, and the junction depth is 0.5 μm~0.1 μm; The N-region is doped with phosphorus, carbon, or nitrogen at a concentration of 3E20cm⁻¹. -3 ~5E20cm -3 The process of "forming a tunneling layer and N-type polycrystalline silicon" includes the following steps: growing a tunneling layer and an N-type amorphous silicon layer by in-situ doping using PECVD; and annealing the N-type amorphous silicon layer at 850℃~980℃ to transform it into an N-type polycrystalline silicon layer.

17. The method for preparing a solar cell according to any one of claims 10 to 13, characterized in that: After forming the electrical connectors, the method for fabricating the solar cell further includes the following steps: A passivation layer is formed on the entire back and the entire front. An anti-reflective layer is formed on the entire back and the entire front. A first electrode and a second electrode are formed in the P-region and the N-region, respectively. The first electrode passes through the anti-reflection layer and passivation layer on the back side and contacts the P-region; the second electrode passes through the anti-reflection layer and passivation layer on the back side and contacts the N-type polysilicon layer.

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