Back contact battery and photovoltaic module

Abstract

The invention discloses a back contact battery and a photovoltaic module, relates to the technical field of photovoltaics, and is used for solving the problem that the patterning of a hot spot prevention design is complicated and the battery efficiency is influenced. The back contact battery comprises a substrate having a first surface and a second surface which are opposite to each other; the first doping parts and the second doping parts are alternately arranged in the first direction and arranged on the first face at intervals, the first doping parts and the second doping parts extend in the second direction, the conduction types of the first doping parts and the second doping parts are opposite, and the first direction and the second direction intersect; the third doping part is arranged on the first face and located between the first doping part and the second doping part, the third doping part extends in the second direction, the conduction type of the third doping part is the same as that of the second doping part, and the third doping part is communicated with the first doping part and the second doping part; the thickness of the third doped part is smaller than that of the second doped part and / or the doping concentration of the third doped part is smaller than that of the second doped part.

Description

Technical Field

[0001] The present invention relates to the technical field of solar cells, and in particular to a back contact cell. Background Art

[0002] Back-contact cells refer to cells where both the P-region metal electrode and the N-region metal electrode are on the back of the cell, and there is no metal electrode blocking the front. Compared with cells with blocked fronts, back-contact cells have higher short-circuit current and photoelectric conversion efficiency, and are currently one of the technical directions for achieving high-efficiency crystalline silicon cells.

[0003] Under certain conditions, the shaded back contact cell in a series branch of a photovoltaic module does not generate electricity, and the other illuminated back contact cells apply a reverse bias to the shaded back contact cell. The shaded back contact cell acts as a load to consume the energy generated by other illuminated back contacts. The temperature of the shaded back contact cell will be significantly higher than that of other back contact cells, forming a hot spot effect. The hot spot effect will seriously damage the back contact cell and pose a very serious hidden danger to the safety of photovoltaic modules. For this reason, the existing anti-hot spot design is used to reduce the risk of hot spots. The existing anti-hot spot design is to directly connect the local areas of the adjacent N and P zones to form multiple spaced connecting channels.

[0004] However, the existing anti-hot spot design has complex patterning, is limited by the size of the laser spot, requires high processing accuracy, and the matching between the connecting channel for anti-hot spot and the P-region and N-region affects the battery efficiency. Summary of the invention

[0005] The object of the present invention is to provide a back contact cell and a photovoltaic module to simplify the patterning of anti-hot spot design and improve cell efficiency.

[0006] In a first aspect, the present invention provides a back contact battery, comprising:

[0007] a substrate having opposing first and second surfaces;

[0008] The first doped portion and the second doped portion are alternately arranged along the first direction and are disposed at intervals on the first surface, the first doped portion and the second doped portion extend along the second direction, the first doped portion and the second doped portion have opposite conductivity types, and the first direction and the second direction intersect;

[0009] A third doping portion is arranged on the first surface and located between the first doping portion and the second doping portion, the third doping portion extends along the second direction, the third doping portion and the second doping portion have the same conductivity type, the third doping portion is connected to the first doping portion and the second doping portion, the thickness of the third doping portion is less than the thickness of the second doping portion and / or the doping concentration of the third doping portion is less than the doping concentration of the second doping portion.

[0010] In the case of adopting the above technical solution, the first doping part, the second doping part and the third doping part all extend along the second direction, the third doping part is located between the first doping part and the second doping part, the first doping part and the second doping part of opposite conductivity type are connected through the third doping part located between the two, the second doping part and the third doping part have the same conductivity type, then the third doping part and the first doping part have opposite conductivity types, and the thickness of the third doping part is less than the thickness of the second doping part and / or the doping concentration of the third doping part is less than the doping concentration of the second doping part. The first doping part and the second doping part form a reverse leakage channel through the third doping part. When the solar cell is blocked and does not work, and other unblocked solar cells apply a reverse bias to the blocked solar cell, the reverse leakage current will be bypassed through the reverse leakage channel, thereby reducing the risk of forming a hot spot on the blocked solar cell. Since the thickness of the third doping part is less than the thickness of the second doping part and / or the doping concentration of the third doping part is less than the doping concentration of the second doping part, the third doping part can meet the anti-hot spot requirement, and can reduce the leakage loss of the solar cell when it is not blocked and works normally, thereby improving the power generation efficiency. In addition, in the second direction, the first doped part, one entire side of the second doped part and one entire side of the third doped part are connected. Compared with the existing anti-hot spot design through multiple discrete channels, the anti-hot spot design pattern is simplified, and there is no need to be limited to the size of the laser spot, which reduces the processing accuracy and improves the preparation efficiency.

[0011] In some possible implementations, the thickness of the third doping portion is 10 nm to 300 nm, and the thickness of the second doping portion is 100 nm to 400 nm.

[0012] In the case of adopting the above technical solution, when the thickness of the third doped part is less than 10nm, the square resistance of the third doped part is too large, the current transmission capacity is too small, when the reverse bias is applied, the reverse leakage current is too small, and the anti-hot spot effect is not ideal. If the thickness of the third doped part is greater than 300nm, the square resistance of the third doped part is too small, the current transmission capacity is too large, when the solar cell works normally, the leakage current of the third doped part is too large, and the adverse effect on the battery efficiency is relatively large. Therefore, in order to balance the anti-hot spot effect and battery efficiency, the thickness of the third doped part is selected to be 10nm to 300nm.

[0013] In some possible implementations, the doping concentration of the third doping portion is 1×10 18 cm -3 ~1×10 21 cm -3 .

[0014] When the above technical solution is adopted, the doping concentration of the third doping part is 1×10 18 cm -3When the doping concentration of the third doped part is greater than 1×10 21 cm -3 The resistivity of the third doping part is too large, the square resistance is too small, and the current transmission capacity is too large. When the solar cell is working normally, the leakage current of the third doping part is too large, which has a great adverse effect on the battery efficiency. Therefore, in order to balance the anti-hot spot effect and battery efficiency, the doping concentration of the third doping part is selected to be 1×10 18 cm -3 ~1×10 21 cm -3 .

[0015] In some possible implementations, in the first direction, a width of the third doping portion is 50 μm to 1500 μm.

[0016] When the above technical solution is adopted, if the width of the third doped portion is less than 50 μm, the distance between the first doped portion and the second doped portion is too small, and the leakage of the solar cell is serious during normal operation, which affects the battery efficiency. If the width of the third doped portion is greater than 1500 μm, the width of the third doped portion is too large. Under the condition of the same battery area, the width of the first doped portion and the second doped portion is too small, which affects the carrier collection ability and thus reduces the battery efficiency.

[0017] In some possible implementations, a surface of the third doping portion facing away from the substrate is recessed toward a side of the substrate relative to a surface of the second doping portion facing away from the substrate.

[0018] When the above technical solution is adopted, the third doping part and the second doping part can first form the same doping layer of the same thickness in the same step, and then the third doping part is thinned so that the surface of the third doping part facing away from the substrate is recessed toward the substrate side relative to the surface of the second doping part facing away from the substrate, thereby simplifying the process.

[0019] In some possible implementations, the third doped portion and the first doped portion are overlapped at a joint portion, and the third doped portion is overlapped on the first doped portion.

[0020] When the above technical solution is adopted, during the preparation process, for the case where the first doping part is deposited first and then the second doping part is deposited, the third doping part and the second doping part can be formed in the same deposition step, and the third doping part covering the first doping part needs to be etched away. If the third doping part has an area overlapping the first doping part, the area of ​​etching the third doping part can be reduced, thereby improving the etching efficiency. At the same time, it can ensure that the third doping part is reliably connected to the first doping part.

[0021] In some possible implementations, an isolation trench is formed in the third doping portion, the isolation trench exposes the substrate, and a projection of the isolation trench on the third doping portion is located within a boundary of the third doping portion.

[0022] When adopting the above technical solution, an isolation groove is reasonably opened on the third doped part, and the first doped part and the second doped part are isolated by the isolation groove, so as to reduce carrier recombination and improve conversion efficiency. At the same time, the third doped part is maintained to have a reverse leakage channel formed with the first doped part and the second doped part, so as to play a role in preventing hot spots.

[0023] In some possible implementations, a third doped portion has a plurality of isolation trenches arranged at intervals along the second direction.

[0024] When adopting the above technical solution, a plurality of isolation grooves are provided in the same third doped part, and the plurality of isolation grooves are arranged at intervals along the second direction. By reasonably arranging the isolation grooves, the first doped part and the second doped part are isolated, carrier recombination is reduced, and conversion efficiency is improved. At the same time, the part of the third doped part located between two adjacent isolation grooves serves as the main reverse leakage channel, playing a role in preventing hot spots.

[0025] In some possible implementations, a third doped portion has an isolation trench extending along the second direction, and in the second direction, a first distance exists between two ends of the isolation trench and a boundary of the third doped portion.

[0026] When adopting the above technical solution, there is only one isolation trench extending along the second direction in the same third doped part. In the second direction, the parts of the third doped part located at both ends of the isolation trench serve as the main reverse leakage channel, playing a role in preventing hot spots. At the same time, the length of the isolation trench is relatively large, which can effectively isolate the first doped part and the second doped part, reduce carrier recombination, and improve conversion efficiency.

[0027] In some possible implementations, in the first direction, a side of the isolation trench close to the second doping portion is connected to the second doping portion, and a first distance exists between a side of the isolation trench close to the first doping portion and the first doping portion.

[0028] When the above technical solution is adopted, one side of the isolation trench is connected to the second doping part, and the other side has a second spacing with the first doping part, so that one side of the third doping part is connected to the first doping part. In the second direction, the parts of the third doping part located at both ends of the isolation trench and the parts with the second spacing serve as the main reverse leakage channels, playing a role in preventing hot spots. At the same time, the reasonable setting of the isolation trench can effectively isolate the first doping part and the second doping part, reduce carrier recombination, and improve conversion efficiency.

[0029] In some possible implementations, in the first direction, a width of the isolation trench is greater than 50 μm and less than 1500 μm.

[0030] In some possible implementations, the materials of the first doped part, the second doped part and the third doped part all include doped polysilicon. Then the first doped part and the second doped part both form a back contact cell with a tunnel passivation contact structure, which has the advantages of high conversion efficiency, good stability and low Auger recombination of the tunnel passivation contact structure.

[0031] Or, the material of the first doping part includes doped polysilicon, and the material of the second doping part and the third doping part includes one of doped amorphous silicon, doped microcrystalline silicon, and doped nanocrystalline silicon. In this way, a hybrid back contact cell is formed in which a region of one conductivity type on the first surface is a heterojunction structure and a region of another conductivity type is a tunnel passivation contact structure, and has the advantages of high conversion efficiency, good stability, and low Auger recombination of the tunnel passivation contact structure and good passivation effect, high conversion efficiency, long service life, and low preparation energy consumption of the heterojunction structure.

[0032] In some possible implementations, the materials of the first doped portion, the second doped portion, and the third doped portion all include doped polysilicon, the back contact cell further includes a first tunneling oxide layer and a second tunneling oxide layer, the first tunneling oxide layer is disposed in a region of the first surface corresponding to the first doped portion, and the first doped portion is disposed on the first tunneling oxide layer;

[0033] The second tunneling oxide layer is disposed in a region of the first surface at least corresponding to the second doping portion and the third doping portion, and the second doping portion and the third doping portion are both disposed on the second tunneling oxide layer.

[0034] When the above technical solution is adopted, the first doped part and the first tunneling oxide layer form a tunneling passivation contact structure of one conductivity type, and the second doped part and the second tunneling oxide layer form a tunneling passivation contact structure of another conductivity type. The back contact cell has the advantages of high conversion efficiency, good stability and low Auger recombination of the tunneling passivation contact structure.

[0035] In a second aspect, the present invention further provides a photovoltaic module, comprising a back contact cell as described in any one of the above items.

[0036] Since the photovoltaic module adopts the back-contact cell in the first aspect and any technical solution, it has the same beneficial effects as the first aspect and any technical solution, and will not be described in detail. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] The drawings described herein are used to provide a further understanding of the present invention and constitute a part of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0038] Figure 1 A schematic structural diagram of a back contact battery without a passivation layer and an anti-reflection layer provided in an embodiment of the present invention;

[0039] Figure 2 A schematic structural diagram of a back contact battery provided by an embodiment of the present invention;

[0040] Figure 3 A schematic structural diagram of a back contact battery provided by an embodiment of the present invention having no passivation layer and anti-reflection layer on the first surface;

[0041] Figure 4 A schematic structural diagram of a second back contact battery provided by an embodiment of the present invention having no passivation layer and anti-reflection layer on the first surface;

[0042] Figure 5 A schematic structural diagram of a third back contact battery provided by an embodiment of the present invention having no passivation layer and anti-reflection layer on the first surface;

[0043] Figure 6 A schematic structural diagram of a fourth back contact battery provided in an embodiment of the present invention having no passivation layer and anti-reflection layer on the first surface.

[0044] Figure numerals: 1 is a substrate, 2 is a first tunneling oxide layer, 3 is a first doping portion, 4 is a second tunneling oxide layer, 5 is a second doping portion, 6 is a third doping portion, 61 is an isolation trench, 7 is a first passivation layer, 8 is a first anti-reflection layer, 9 is a second passivation layer, and 10 is a second anti-reflection layer. DETAILED DESCRIPTION

[0045] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0046] It should be noted that when an element is referred to as being "fixed to" or "disposed on" another element, it can be directly on the other element or indirectly on the other element. When an element is referred to as being "connected to" another element, it can be directly connected to the other element or indirectly connected to the other element.

[0047] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, the meaning of "multiple" is two or more, unless otherwise clearly and specifically defined. The meaning of "several" is one or more, unless otherwise clearly and specifically defined.

[0048] In the description of the present invention, it is necessary to understand that the directions or positional relationships indicated by the terms "up", "down", "front", "back", "left", "right", etc. are based on the directions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore cannot be understood as a limitation on the present invention.

[0049] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0050] like Figure 1-Figure 3 As shown, an embodiment of the present invention provides a back contact battery, including a substrate 1, a first doping part 3, a second doping part 5 and a third doping part 6; wherein the substrate 1 has a first surface and a second surface opposite to each other, the first surface may be a backlight surface, and the second surface may be a light receiving surface, i.e., a front surface. The first doping part 3, the second doping part 5 and the third doping part 6 may all be arranged on the first surface along the second direction in a strip shape; the first doping part 3 and the second doping part 5 are alternately arranged and arranged at intervals along the first direction, the third doping part 6 is arranged on the first surface and is located between the first doping part 3 and the second doping part 5, the third doping part 6 is connected to the first doping part 3 and the second doping part 5, the first doping part 3 and the second doping part 5 have opposite conductivity types, the third doping part 6 and the second doping part 5 have the same conductivity type, the thickness of the third doping part 6 is less than the thickness of the second doping part 5 and / or the doping concentration of the third doping part 6 is less than the doping concentration of the second doping part 5. wherein the first direction intersects with the second direction, for example, may be perpendicular.

[0051] It should be noted that the third doping part 6 is connected with the first doping part 3 and the second doping part 5, and the connection can be achieved by direct contact between the third doping part 6 and the first doping part 3 at least partially, or the third doping part 6 is indirectly connected with the first doping part 3 through a semiconductor layer or an extremely thin dielectric layer. Since the dielectric layer is extremely thin and has an inner expansion area, it can be conductive. The semiconductor layer or dielectric layer here can be a tunneling oxide layer, an intrinsic amorphous silicon layer, an amorphous silicon layer, a microcrystalline silicon layer, or a nanocrystalline silicon layer, as long as the conductive connection between the third doping part 6 and the first doping part 3 can be achieved. Similarly, the connection between the third doping part 6 and the second doping part 5 can also be achieved by direct contact or indirectly through a semiconductor layer or an extremely thin dielectric layer.

[0052] In the case of adopting the above technical solution, the first doping part 3, the second doping part 5 and the third doping part 6 all extend along the second direction, the first doping part 3 and the second doping part 5 are arranged alternately and spaced along the first direction, the third doping part 6 is located between the first doping part 3 and the second doping part 5, the first doping part 3 and the second doping part 5 of opposite conductivity types are connected through the third doping part 6 located therebetween, the second doping part 5 and the third doping part 6 have the same conductivity type, and the third doping part 6 and the first doping part 3 have opposite conductivity types. The first doping part 3 and the second doping part 5 form a reverse leakage channel through the third doping part 6, and when the solar cell is blocked and does not work, and other unblocked solar cells apply a reverse bias to the blocked solar cell, the reverse leakage current will be bypassed through the reverse leakage channel, thereby reducing the risk of forming a hot spot on the blocked solar cell. Since the thickness of the third doping part 6 is less than the thickness of the second doping part 5 and / or the doping concentration of the third doping part 6 is less than the doping concentration of the second doping part 5, the doping concentration and the thickness of the doping part have an impact on the resistivity and the square resistance (abbreviated as square resistance). The smaller the doping concentration of the doping part, the greater the resistivity, the greater the square resistance, and the thinner the thickness of the doping part, the greater the square resistance. On the basis that the third doping part 6 can meet the requirements of anti-hot spot, it can reduce the leakage loss of the solar cell when it is not blocked and working normally, and improve the power generation efficiency. In addition, in the second direction, the first doping part 3 and one side of the second doping part 5 are connected to one side of the third doping part 6, and the size of the entire reverse leakage channel in the second direction is relatively large. The first doping part 3 and the second doping part 5 can conduct reverse leakage current at any position in the second direction, and the anti-hot spot effect is significant. Compared with the existing anti-hot spot channels through multiple discrete anti-hot spot channels, the pattern of the anti-hot spot design is simplified, and it does not need to be limited by the size of the laser spot, which reduces the processing accuracy and improves the preparation efficiency.

[0053] By comparing the parameters of a conventional back contact battery with an anti-hot spot structure with the back contact battery in this application, a table showing the parameter values ​​of the conventional back contact battery minus the parameter values ​​of the back contact battery in this application is obtained.

[0054] Table 1 The difference between the parameter values ​​of the conventional back contact battery and the parameter values ​​of the back contact battery of this application

[0055] Eff(%) Voc(mV) Isc(A) FF(%) Rs(mΩ) Rsh(Ω) -0.045 0.99 -0.011 -0.19 0.028 -355.58

[0056] It can be seen from Table 1 that the battery efficiency of the back contact battery using the anti-hot spot structure in this application is 0.045% higher than that of the conventional back contact battery with the anti-hot spot structure, and the short-circuit current, fill factor and parallel resistance are all improved. While achieving the anti-hot spot effect, the battery efficiency is improved.

[0057] For example, the substrate 1 may be a silicon substrate. Alternatively, the substrate 1 may be a substrate made of any semiconductor material such as a germanium silicon substrate, a germanium substrate or a gallium arsenide substrate. The conductivity type of the substrate 1 may be an N-type semiconductor substrate, a P-type semiconductor substrate or an intrinsic semiconductor substrate. The first doping portion 3 may be a P-type doping portion, the second doping portion 5 may be an N-type doping portion, and the conductivity type of the third doping portion 6 may be an N-type. The P-type doping portion and the N-type doping portion are connected by the third doping portion 6 to form a reverse leakage channel. Of course, the first doping portion 3 may also be an N-type doping portion, the second doping portion 5 may be a P-type doping portion, and the conductivity type of the third doping portion 6 may be a P-type.

[0058] The first doping part 3, the second doping part 5 and the third doping part 6 may be in a strip structure. Of course, the first doping part 3 and the second doping part 5 may also be part of the cross-finger doping part. In this case, the first doping part 3 and the second doping part 5 refer to the strip-shaped part of the corresponding auxiliary gate electrode. The cross-finger doping part also has a first main gate region doping part connected to the first doping part 3, and a second main gate region doping part connected to the second doping part 5. The first main gate region doping part and the second main gate region doping part both extend along the first direction and are alternately arranged in the second direction. Similarly, the third doping part 6 is also arranged between the first main gate region doping part and the adjacent second doping part 5, and between the second main gate region doping part and the adjacent first doping part 3. The third doping part 6 is connected, so that the first main gate region doping part, the second doping part 5 and the third doping part 6 also form a reverse leakage channel, so that the second main gate region doping part, the first doping part 3 and the third doping part 6 also form a reverse leakage channel, and the reverse leakage channel here has the same principle and effect as the reverse leakage channel described above, which will not be repeated.

[0059] In some embodiments, the thickness of the third doping portion 6 is 10 nm to 300 nm. For example, the thickness of the third doping portion 6 can be 10 nm, 20 nm, 30 nm, 40 nm, 50 nm, 60 nm, 70 nm, 80 nm, 90 nm, 100 nm, 110 nm, 120 nm, 130 nm, 140 nm, 150 nm, 160 nm, 170 nm, 180 nm, 190 nm, 200 nm, 210 nm, 220 nm, 230 nm, 240 nm, 250 nm, 260 nm, 270 nm, 280 nm, 290 nm, 300 nm, etc. The thickness of the second doping portion 6 can be 10 nm, 20 nm, 30 nm, 40 nm, 50 nm, 60 nm, 70 nm, 80 nm, 90 nm, 100 nm, 110 nm, 120 nm, 130 nm, 140 nm, 150 nm, 160 nm, 170 nm, 180 nm, 190 nm, 200 nm, 210 nm, 220 nm, 230 nm, 240 nm, 250 nm, 260 nm, 270 nm, 280 nm, 290 nm, 300 nm, etc. The thickness of the third doped portion 6 is 100 nm to 400 nm. For example, the thickness of the second doped portion 5 can be 100 nm, 110 nm, 120 nm, 130 nm, 140 nm, 150 nm, 160 nm, 170 nm, 180 nm, 190 nm, 200 nm, 210 nm, 220 nm, 230 nm, 240 nm, 250 nm, 260 nm, 270 nm, 280 nm, 290 nm, 300 nm, 310 nm, 320 nm, 330 nm, 340 nm, 350 nm, 360 nm, 370 nm, 380 nm, 390 nm, 400 nm, etc. As long as the thickness of the third doped portion 6 is less than the thickness of the second doped portion 5, it is acceptable.

[0060] In the case of adopting the above technical solution, when the thickness of the third doping part 6 is less than 10nm, the square resistance of the third doping part 6 is too large, the current transmission capacity is too small, when the reverse bias is applied, the reverse leakage current is too small, and the anti-hot spot effect is not ideal. If the thickness of the third doping part 6 is greater than 300nm, the square resistance of the third doping part 6 is too small, the current transmission capacity is too large, when the solar cell works normally, the leakage current of the third doping part 6 is too large, and the adverse effect on the battery efficiency is relatively large. Therefore, in order to balance the anti-hot spot effect and the battery efficiency, the thickness of the third doping part 6 is selected to be 10nm to 300nm.

[0061] In some embodiments, the doping concentration of the third doping portion 6 is 1×10 18 cm -3 ~1×10 21 cm -3 For example, the doping concentration of the third doping portion 6 may be 1×10 18 cm -3 , 3×10 18 cm -3 , 5×10 18 cm -3 ,7×10 18 cm -3 ,9×10 18 cm -3 , 1×10 19 cm-3 , 3×10 19 cm -3 , 5×10 19 cm -3 ,7×10 19 cm -3 ,9×10 19 cm -3 , 1×10 20 cm -3 , 3×10 20 cm -3 , 5×10 20 cm -3 ,7×10 20 cm -3 ,9×10 20 cm -3 , 1×10 21 cm -3 As long as the doping concentration of the third doping portion 6 is lower than the doping concentration of the second doping portion 5 , it will be sufficient.

[0062] When the above technical solution is adopted, the doping concentration of the third doping part 6 is 1×10 18 cm -3 When the doping concentration of the third doped portion 6 is greater than 1×10 21 cm -3 The resistivity of the third doping part 6 is too large, the square resistance is too small, and the current transmission capacity is too large. When the solar cell works normally, the leakage current of the third doping part 6 is too large, which has a great adverse effect on the cell efficiency. Therefore, to balance the anti-hot spot effect and cell efficiency, the doping concentration of the third doping part 6 is selected to be 1×10 18 cm -3 ~1×10 21 cm -3 .

[0063] It should be noted that the second doping part 5 and the third doping part 6 have the same conductivity type. Therefore, when preparing the second doping part 5 and the third doping part 6, they can be prepared in the same process step to simplify the process steps. According to the different doping concentrations, a suitable doping method is selected. For example, when in-situ doping is used, the doping concentration of the doping source layer located on the second doping part 5 is greater than the doping concentration of the doping source layer located on the third doping part 6. After that, in the same doping advancement step, the second doping part 5 and the third doping part 6 are obtained. Alternatively, when diffusion doping is used, a mask is formed on the surface of the third doping part 6 to be diffused. When diffusion doping is performed in a diffusion furnace, the mask partially blocks the diffused elements, so that the doping concentration in the third doping part 6 provided with the mask is smaller, while the doping concentration in the second doping part 5 without the mask is larger. Of course, the second doping part 5 and the third doping part 6 can also be formed by doping in different steps.

[0064] In some embodiments, in the first direction, the width of the third doping portion 6 is 50 μm to 1500 μm. For example, the width of the third doping portion 6 can be 50 μm, 100 μm, 150 μm, 200 μm, 250 μm, 300 μm, 350 μm, 500 μm, 600 μm, 700 μm, 800 μm, 900 μm, 1000 μm, 1100 μm, 1200 μm, 1300 μm, 1400 μm, 1500 μm, etc., so that the third doping portion 6 occupies 5% to 80% of the entire backlight surface area, and the first doping portion 3 and the second doping portion 5 occupies 15% to 45% of the entire backlight surface area. If the width of the third doping portion 6 is less than 50 μm, the distance between the first doping portion 3 and the second doping portion 5 is too small, and the leakage of the solar cell is serious during normal operation, affecting the battery efficiency. If the width of the third doping portion 6 is greater than 1500 μm, the width of the third doping portion 6 is too large. Under the condition of the same battery area, the width of the first doping portion 3 and the second doping portion 5 is too small, which affects the carrier collection capacity and thus reduces the battery efficiency.

[0065] like Figure 1 and Figure 2 As shown, in some embodiments, the surface of the third doping portion 6 facing away from the substrate 1 is recessed toward the side of the substrate 1 relative to the surface of the second doping portion 5 facing away from the substrate 1. That is, when there is no height difference on the first surface of the substrate 1 as a whole, the surfaces of the second doping portion 5 and the third doping portion 6 formed on the first surface close to the substrate are located in the same plane, then the distance between the surface of the third doping portion 6 facing away from the substrate 1 and the first surface of the substrate 1 is smaller than the distance between the surface of the second doping portion 5 facing away from the substrate 1 and the first surface of the substrate 1, that is, the thickness of the third doping portion 6 is smaller than the thickness of the second doping portion 5.

[0066] In the case of adopting the above technical solution, the third doping part 6 and the second doping part 5 can first form the same doping layer of the same thickness in the same step, and then the area corresponding to the second doping part 5 is protected, such as mask protection, and only the area corresponding to the third doping part 6 is thinned, for example, laser etching thinning, chemical etching thinning, etc., and the surface of the third doping part 6 facing away from the substrate 1 is concave toward the side of the substrate 1 relative to the surface of the second doping part 5 facing away from the substrate 1, which simplifies the process. Of course, the second doping part 5 and the third doping part 6 can also directly form doping layers of different thicknesses separately in different steps without the need for subsequent etching thinning. In this way, the surface of the third doping part facing away from the substrate and the surface of the second doping part facing away from the substrate can be located in the same plane, as long as the thickness of the third doping part is less than the thickness of the second doping part.

[0067] In some embodiments, the third doping part 6 forms an overlap with the first doping part 3 at the joint part, and the third doping part 6 overlaps the first doping part 3. In the preparation process, for the case where the first doping part is deposited first and then the second doping part is deposited, specifically, the first doping part of the entire surface can be prepared on the first surface of the substrate first, and then the first doping part is removed in the area where the second doping part and the third doping part are to be prepared, and then a whole doping layer is prepared on the first surface of the substrate, and the doping layer covers the area of ​​the substrate where the second doping part and the third doping part are to be formed and the surface of the first doping part retained on the substrate, and then the doping layer is thinned in the area corresponding to the third doping part, and then the doping layer covering the first doping part needs to be etched and removed to expose the first doping part. If in this step, the doping layer retains a part covering the area on the first doping part to form a third doping part overlapping the first doping part, the area of ​​etching the doping layer can be reduced, and the etching efficiency can be improved. At the same time, it can ensure reliable connection between the third doping part and the first doping part, and realize reliable connection of the reverse leakage channel.

[0068] like Figure 4-Figure 6 As shown, in some embodiments, the third doping portion 6 is provided with an isolation groove 61, the isolation groove 61 exposes the substrate 1, and the projection of the isolation groove 61 on the third doping portion 6 is located within the boundary of the third doping portion 6, that is, the projection boundary of the isolation groove 61 does not exceed the boundary of the third doping portion 6, and at least an area capable of connecting the first doping portion 3 and the second doping portion 5 is retained on the third doping portion 6.

[0069] When the above technical solution is adopted, an isolation groove 61 is reasonably opened on the third doping part 6, and the first doping part 3 and the second doping part 5 are isolated by the isolation groove 61, so as to reduce carrier recombination and improve conversion efficiency. At the same time, the third doping part 6 is maintained to have a reverse leakage channel formed with the first doping part 3 and the second doping part 5, so as to play a role in preventing hot spots.

[0070] like Figure 4 As shown, this embodiment provides a first arrangement of the isolation grooves 61, wherein a plurality of isolation grooves 61 are arranged in the second direction in the same strip-shaped third doped portion 6. The shape of the orthographic projection of the isolation grooves 61 on the third doped portion 6 can be rectangular, circular, triangular, etc., and is not limited to the shapes listed in this embodiment. In order to facilitate the laser grooving process, the shape of the isolation grooves 61 is preferably to simplify the scanning process of the laser spot and reduce the restriction on the size of the laser spot.

[0071] It should be noted that the number of isolation grooves 61 on the third doped portions 6 of different strips can be the same or different, and the isolation grooves 61 on the first surface are arranged in an array in a regular pattern to simplify the pattern and facilitate processing. Of course, the isolation grooves 61 can also be arranged randomly.

[0072] When the above technical solution is adopted, a plurality of isolation grooves 61 are provided in the same third doped portion 6, and the plurality of isolation grooves 61 are arranged at intervals along the second direction. By reasonably arranging the isolation grooves 61, the first doped portion 3 and the second doped portion 5 are locally isolated, carrier recombination is reduced, and conversion efficiency is improved. At the same time, the portion of the third doped portion 6 located between two adjacent isolation grooves 61 serves as the main reverse leakage channel, thereby playing a role in preventing hot spots.

[0073] like Figure 5 As shown, in some embodiments, a second arrangement of the isolation trench 61 is provided, and the same strip-shaped third doping portion 6 has an isolation trench 61 extending along the second direction, and in the second direction, there is a first spacing D between the two ends of the isolation trench 61 and the boundary of the third doping portion 6. That is, there is only one strip-shaped isolation trench 61 in a third doping portion 6, and there is a first spacing D between the two ends of the isolation trench 61 and the boundary of the third doping portion 6, respectively. The first spacing D can be greater than or equal to 50μm and less than or equal to 500μm. When the first spacing D is less than 50μm, the reverse leakage channel formed is too narrow, the reverse leakage current is too small, and the anti-hot spot effect is not ideal. The first spacing D at both ends of the isolation trench 61 can be equal or unequal. When it is equal, the reverse leakage current at both ends can be more balanced.

[0074] When adopting the above technical solution, there is only one isolation groove 61 extending along the second direction in the same third doped part 6. In the second direction, the parts of the third doped part 6 located at both ends of the isolation groove 61 serve as the main reverse leakage channel, playing a role in preventing hot spots. At the same time, the length of the isolation groove 61 is relatively large, which can effectively isolate the first doped part 3 and the second doped part 5, reduce carrier recombination, and improve battery efficiency.

[0075] like Figure 6As shown, in some embodiments, a third arrangement of the isolation groove 61 is provided, and the third doping portion 6 of the same strip has an isolation groove 61 extending along the second direction, and in the first direction, the side of the isolation groove 61 close to the second doping portion 5 is connected to the second doping portion 5, and the side of the isolation groove 61 close to the first doping portion 3 is separated from the first doping portion 3 by a second spacing E. That is, one side of the third doping portion 6 is connected to the first doping portion 3, and the other side is separated from the second doping portion 5 by the isolation groove 61. In the second direction, the parts of the third doping portion 6 located at both ends of the isolation groove 61 and the parts with the second spacing E serve as the main reverse leakage channel, which plays the role of preventing hot spots. At the same time, the reasonable arrangement of the isolation groove 61 can effectively isolate the first doping portion 3 and the second doping portion 5, reduce carrier recombination, and improve conversion efficiency. The second spacing E can be greater than or equal to 50μm and less than or equal to 500μm. When the second spacing E is less than 50μm, the reverse leakage channel formed is too narrow, the reverse leakage current is too small, and the anti-hot spot effect is not ideal.

[0076] Of course, if Figure 5 As shown, in the first direction, the third doped portion 6 located on both sides of the isolation trench 61 respectively has a long strip region connected to the first doped portion 3 and the second doped portion 5. Of course, when there are multiple isolation trenches 61 arranged at intervals in the same strip of the third doped portion 6, in the first direction, only one side of the multiple isolation trenches 61 may have the second spacing E with the first doped portion 3, and the isolation and hot spot prevention effects can also be achieved.

[0077] like Figure 3-Figure 6 As shown, in some possible implementations, in the first direction, the width of the isolation trench 61 is greater than 50μm and less than 1500μm, that is, less than the width of the third doping portion 6. For example, the width of the isolation trench 61 can be 60μm, 100μm, 150μm, 200μm, 250μm, 300μm, 350μm, 500μm, 600μm, 700μm, 800μm, 900μm, 1000μm, 1100μm, 1200μm, 1300μm, 1400μm, 1450μm, etc. If the width of the isolation groove 61 is less than 50 μm, the leakage current will be too large, which is not conducive to battery efficiency. If the width of the isolation groove 61 is greater than 1500 μm, the area occupied by the first surface is too large. Accordingly, the area proportion of the first doped part 3 and the second doped part 5 is too small, and the carrier collection ability is weak, which is also not conducive to battery efficiency.

[0078] like Figure 1 and Figure 2As shown, in some embodiments, the materials of the first doping part 3, the second doping part 5 and the third doping part 6 all include doped polysilicon. In this way, the first doping part 3 and the second doping part 5 can be combined with the tunneling oxide layer to form a tunneling passivation contact structure. The back contact cell has the advantages of high conversion efficiency, good stability and low Auger recombination of the tunneling passivation contact structure.

[0079] For example, in the case where the materials of the first doping part 3, the second doping part 5 and the third doping part 6 all include doped polysilicon, the back contact cell further includes a first tunneling oxide layer 2 and a second tunneling oxide layer 4, the first tunneling oxide layer 2 is arranged in a region of the first surface corresponding to the first doping part 3, and the first doping part 3 is arranged on the first tunneling oxide layer 2; the second tunneling oxide layer 4 is arranged in a region of the first surface at least corresponding to the second doping part 5 and the third doping part 6, and the second doping part 5 and the third doping part 6 are both arranged on the second tunneling oxide layer 4. The first doping part 3 forms a tunneling passivation contact structure of one conductivity type with the first tunneling oxide layer 2, the second doping part 5 forms a tunneling passivation contact structure of another conductivity type with the second doping part 4, the third doping part 6 forms a reverse leakage channel of the tunneling passivation contact structure with the second tunneling oxide layer 4, the third doping part 6 and the first doping part 3 can be directly in contact and connected or indirectly conductively connected through the second tunneling oxide layer 4, and the third doping part 6 is directly in contact and connected with the second doping part 5. It should be noted that since the thickness of the second tunneling oxide layer 4 is very thin, it can serve as a dielectric layer to indirectly connect the third doped part 6 and the first doped part 3. Therefore, during preparation, the second tunneling oxide layer 4 under the third doped part 6 can be retained without being removed, so that the second tunneling oxide layer 4 corresponding to the third doped part 6 is in contact with the first doped part 3, and the third doped part 6 and the first doped part 3 can also be conductively connected.

[0080] In other embodiments, the material of the first doping part 3 includes doped polysilicon, and the material of the second doping part 5 and the third doping part 6 includes one of doped amorphous silicon, doped microcrystalline silicon, and doped nanocrystalline silicon. In this way, the first doping part 3 can be combined with the tunneling oxide layer to form a tunneling passivation contact structure, the second doping part 5 can be combined with the intrinsic amorphous silicon to form a heterojunction structure, and the third doping part 6 can be combined with the intrinsic amorphous silicon to form a reverse leakage channel of the heterojunction structure, thereby forming a hybrid back contact cell in which one conductive type region of the first surface is a heterojunction structure and another conductive type region is a tunneling passivation contact structure, and at the same time has the advantages of high conversion efficiency, good stability, and low Auger recombination of the tunneling passivation contact structure and good passivation effect, high conversion efficiency, long service life, and low preparation energy consumption of the heterojunction structure.

[0081] It should be noted that, in the case where the third doped portion 6 is doped amorphous silicon, doped microcrystalline silicon, or doped nanocrystalline silicon, the third doped portion 6 and the first doped portion 3 can be directly in contact and connected or indirectly conductively connected through intrinsic amorphous silicon, and the third doped portion 6 and the second doped portion 5 can be directly in contact and connected. The thickness of intrinsic amorphous silicon is extremely thin, and it can be used as a dielectric layer to indirectly conductively connect the third doped portion 6 and the first doped portion 3. Therefore, during preparation, the intrinsic amorphous silicon of a certain thickness below the third doped portion 6 can be retained without being completely removed, so that the intrinsic amorphous silicon corresponding to the third doped portion 6 is in contact with the first doped portion 3, and the third doped portion 6 and the first doped portion 3 can also be conductively connected.

[0082] like Figure 2 As shown, in some possible implementations, the back contact cell further includes a first passivation layer 7 and a first anti-reflection layer 8, wherein the first passivation layer 7 is disposed on the first doped portion 3, the second doped portion 5 and the third doped portion 6, and the first anti-reflection layer 8 is disposed on the first passivation layer 7. The first passivation layer 7 is used to improve the passivation effect, reduce carrier recombination, and improve cell efficiency, and the first anti-reflection layer 8 is used to reduce reflection of incident light.

[0083] Similarly, the back contact cell can also sequentially arrange a second passivation layer 9 and a second anti-reflection layer 10 on the second side, ie, the front side, of the substrate 1 , which have the same functions as the first passivation layer 7 and the first anti-reflection layer 8 .

[0084] In a second aspect, based on the back-contact cell described in any one of the above embodiments, an embodiment of the present invention further provides a photovoltaic module, comprising the back-contact cell described in any one of the above embodiments.

[0085] Since the photovoltaic module adopts the back-contact cell in the first aspect and any possible implementation method above, it has the same beneficial effects as the first aspect and any technical solution, and will not be described in detail.

[0086] In the description of the above embodiments, specific features, structures, materials or characteristics may be combined in a suitable manner in any one or more embodiments or examples.

[0087] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art can easily think of changes or substitutions within the technical scope disclosed by the present invention, which should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A back contact battery, characterized in that: include: a substrate having opposing first and second surfaces; The first doped portion and the second doped portion are alternately arranged along a first direction and are disposed at intervals on the first surface, the first doped portion and the second doped portion extend along a second direction, the first doped portion and the second doped portion have opposite conductivity types, and the first direction and the second direction intersect; A third doping portion is arranged on the first surface and located between the first doping portion and the second doping portion, the third doping portion extends along the second direction, the third doping portion and the second doping portion have the same conductivity type, the third doping portion is connected to the first doping portion and the second doping portion, the thickness of the third doping portion is less than the thickness of the second doping portion and / or the doping concentration of the third doping portion is less than the doping concentration of the second doping portion.

2. The back contact cell according to claim 1, characterized in that: The thickness of the third doping portion is 10 nm to 300 nm, and the thickness of the second doping portion is 100 nm to 400 nm.

3. The back contact cell according to claim 1, characterized in that: The doping concentration of the third doping part is 1×10 18 cm -3 ~1×10 21 cm -3 .

4. The back contact cell according to claim 1, characterized in that: In the first direction, a width of the third doping portion is 50 μm to 1500 μm.

5. The back contact cell according to claim 1, characterized in that: A surface of the third doping portion facing away from the substrate is recessed toward a side of the substrate relative to a surface of the second doping portion facing away from the substrate.

6. The back contact cell according to claim 1, characterized in that: The third doping portion and the first doping portion are overlapped at a joint portion, and the third doping portion is overlapped on the first doping portion.

7. The back contact cell according to claim 1, characterized in that: An isolation trench is formed in the third doping portion, the isolation trench exposes the substrate, and a projection of the isolation trench on the third doping portion is located within a boundary of the third doping portion.

8. The back contact battery according to claim 7, characterized in that: A plurality of the isolation trenches are arranged at intervals along the second direction.

9. The back contact battery according to claim 7, characterized in that: The third doped portion has an isolation trench extending along the second direction, and in the second direction, a first distance exists between two ends of the isolation trench and a boundary of the third doped portion.

10. The back contact cell according to claim 9, characterized in that: In the first direction, a side of the isolation trench close to the second doping portion is connected to the second doping portion, and a second distance exists between a side of the isolation trench close to the first doping portion and the first doping portion.

11. The back contact battery according to any one of claims 7 to 10, characterized in that: In the first direction, a width of the isolation trench is greater than 50 μm and less than 1500 μm.

12. The back contact cell according to claim 1, characterized in that: The materials of the first doping part, the second doping part and the third doping part all include doped polysilicon; Alternatively, the material of the first doping part includes doped polycrystalline silicon, and the material of the second doping part and the third doping part includes one of doped amorphous silicon, doped microcrystalline silicon, and doped nanocrystalline silicon.

13. The back contact cell according to claim 1, characterized in that: The materials of the first doped part, the second doped part and the third doped part all include doped polysilicon, the back contact cell further includes a first tunneling oxide layer and a second tunneling oxide layer, the first tunneling oxide layer is arranged in a region of the first surface corresponding to the first doped part, and the first doped part is arranged on the first tunneling oxide layer; The second tunneling oxide layer is disposed in a region of the first surface at least corresponding to the second doping portion and the third doping portion, and the second doping portion and the third doping portion are both disposed on the second tunneling oxide layer.

14. A photovoltaic module, characterized in that: Comprising a back contact battery as described in any one of claims 1-13.

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