Back contact cell, back contact cell string and photovoltaic module

Abstract

The invention discloses a back contact cell, a back contact cell string and a photovoltaic module, the back contact cell comprises first doped layers, second doped layers and isolation grooves which are arranged on the back surface of a semiconductor substrate, the first doped layers and the second doped layers are alternately arranged, the isolation grooves are arranged between the first doped layers and the second doped layers, and the first doped layers and the second doped layers are alternately arranged. The doping types of the first doping layer and the second doping layer are different; the passivation layer is arranged on the first doping layer, the second doping layer and the isolation groove; the passivation layer on the first side wall, close to the isolation groove, of the first doping layer is provided with a concave-convex structure. By implementing the invention, the isolation effect and passivation effect of the isolation groove can be improved, thereby reducing the electric leakage risk of the battery and improving the reliability of the battery.

Description

Technical Field

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

[0002] The positive and negative electrodes of the back-contact solar cell are both set on the back of the cell. There is no metal electrode blocking the front, and the entire area is used to absorb sunlight, which can minimize the short-circuit current loss caused by the front of the cell. It has the advantages of high conversion efficiency, large short-circuit current, and high fill factor, and has received extensive attention from academia and industry. Since the positive and negative electrodes of the back-contact solar cell are set on one side of the cell, there is a contact position between the N region and the P region, and the lateral movement of the current will form a leakage channel, an isolation groove is generally set between the N region and the P region and a back passivation layer is deposited to isolate and insulate the N region and the P region. However, the subsequent production process will have an adverse effect on the quality of the passivation layer on the isolation groove, thereby affecting the performance of the back-contact solar cell. Summary of the invention

[0003] The technical problem to be solved by the present invention is to provide a back-contact battery, a back-contact battery string and a photovoltaic module, which can improve the isolation effect and passivation effect of the isolation groove, reduce the risk of battery leakage, and improve the reliability of the battery.

[0004] In order to solve the above problems, the present invention discloses a back contact battery, comprising a first doping layer, a second doping layer and an isolation groove arranged on the back side of a semiconductor substrate, wherein the first doping layer and the second doping layer are alternately arranged, the isolation groove is arranged between the first doping layer and the second doping layer, and the first doping layer and the second doping layer have different doping types;

[0005] A passivation layer, the passivation layer being disposed on the first doping layer, the second doping layer and the isolation trench;

[0006] The passivation layer on the first side wall of the first doping layer close to the isolation trench has a concave-convex structure.

[0007] As an improvement of the above technical solution, the passivation layer on the second side wall of the second doping layer close to the isolation groove has a concave-convex structure.

[0008] As an improvement of the above technical solution, the concave-convex structure includes a concave portion and a convex portion arranged along a first direction, and the concave portion and the convex portion are connected in sequence.

[0009] As an improvement of the above technical solution, the concave-convex structure includes periodically repeated concave portions and convex portions arranged along the first direction, and the concave portions and convex portions are connected in sequence.

[0010] As an improvement of the above technical solution, the repetition period of the recessed portions and the raised portions is 2 to 6.

[0011] As an improvement of the above technical solution, the concave-convex structure is located on the passivation layer of the first side wall, the distance between the concave portion and the first side wall is D1, the distance between the convex portion and the first side wall is D2, and D1 and D2 satisfy: D2 = (1.5-4) D1;

[0012] As an improvement of the above technical solution, the D1 is 2 μm to 5 μm, and the D2 is 7 μm to 15 μm.

[0013] As an improvement of the above technical solution, the concave-convex structure is located on the passivation layer of the second side wall, the distance between the concave portion and the second side wall is D3, the distance between the convex portion and the second side wall is D4, and D3 and D4 satisfy: D4 = (1.5-4) D3;

[0014] As an improvement of the above technical solution, the D3 is 2 μm to 5 μm, and the D4 is 7 μm to 15 μm.

[0015] As an improvement of the above technical solution, along the first direction, the depth of the recessed portion is H1, the height of the raised portion is H2, and H1 and H2 satisfy: H2 = (0.8-1.5) H1.

[0016] As an improvement of the above technical solution, H1 is 2 μm to 5 μm, and H2 is 2 μm to 5 μm.

[0017] As an improvement of the above technical solution, along the second direction, the width of the isolation groove is 20 μm to 100 μm.

[0018] As an improvement of the above technical solution, the shapes of the recessed portion and the raised portion are one or more of rectangular, triangular, trapezoidal, and arc-shaped.

[0019] As an improvement of the above technical solution, the passivation layer includes a first passivation layer and a second passivation layer that are periodically and alternately stacked;

[0020] A concave portion is formed on the first passivation layer, and a convex portion is formed on the second passivation layer;

[0021] Alternatively, a protrusion is formed on the first passivation layer, and a depression is formed on the second passivation layer.

[0022] As an improvement of the above technical solution, the first passivation layer and the second passivation layer are made of different materials.

[0023] As an improvement of the above technical solution, the number of stacking periods of the passivation layer is 1 to 6.

[0024] As an improvement of the above technical solution, the thickness of the passivation layer is 5 μm to 50 μm, and the thickness ratio of the first passivation layer to the second passivation layer is 1:(0.8 to 1.5).

[0025] As an improvement of the above technical solution, the passivation layer is one or more of an intrinsic amorphous silicon layer, an intrinsic polycrystalline silicon layer, an intrinsic nanocrystalline silicon layer, an intrinsic mixed crystal silicon layer, a silicon oxide layer, an aluminum oxide layer, a silicon oxynitride layer, a silicon nitride layer, and a carbon nitride silicon oxide layer.

[0026] As an improvement of the above technical solution, the passivation layer includes a silicon nitride layer and a silicon oxide layer stacked in sequence.

[0027] As an improvement of the above technical solution, the first doped layer includes a first tunneling layer and a first polarity doped layer stacked on the first tunneling layer, and the second doped layer includes a second tunneling layer and a second polarity doped layer stacked on the second tunneling layer;

[0028] The first tunneling layer and the second tunneling layer are one or more of a silicon oxide layer, an aluminum oxide layer, a titanium oxide layer, a zinc oxide layer, an intrinsic amorphous silicon layer, an intrinsic polycrystalline silicon layer, an intrinsic nanocrystalline silicon layer, and an intrinsic mixed crystal silicon layer;

[0029] The first polarity doped layer and the second polarity doped layer are one or more of a doped polysilicon layer, a doped amorphous silicon layer, and a doped microcrystalline silicon layer, and the polarity of the first polarity doped layer is opposite to that of the second polarity doped layer.

[0030] Correspondingly, the present invention also discloses a back-contact battery string, including the above-mentioned back-contact battery.

[0031] Correspondingly, the present invention also discloses a photovoltaic module, comprising the above-mentioned back-contact cell string.

[0032] The implementation of the present invention has the following beneficial effects: the passivation layer of the first side wall and / or the second side wall of the present invention has a concave-convex structure, and the setting of the concave-convex structure can increase the surface area of ​​the passivation layer, and further increase the isolation between the first doped layer and the second doped layer; secondly, the concave-convex structure can block the sputtered metal during the electrode manufacturing process, and avoid the electrode metal from being coated on the passivation layer of the first side wall during the electrode manufacturing process on the first doped layer, thereby reducing the damage to the passivation layer caused by the electrode manufacturing, thereby reducing the risk of leakage; in addition, the concave-convex structure on the passivation layer can effectively reduce the risk of stress concentration in the isolation groove, prevent the battery from cracking, and thus improve the reliability of the battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 is a schematic structural diagram of a back contact battery provided by an embodiment of the present invention;

[0034] Figure 2 is a schematic structural diagram of a back contact battery provided by another embodiment of the present invention;

[0035] Figure 3 is a schematic structural diagram of a back contact battery provided by another embodiment of the present invention;

[0036] Figure 4 is a schematic diagram of the dimensions of a passivation layer on the side wall of an isolation groove of a back contact battery provided by an embodiment of the present invention;

[0037] Figure 5 is a schematic diagram of the structure of the isolation groove of the back contact battery provided by an embodiment of the present invention after the passivation layer is deposited;

[0038] Figure 6 It is a schematic diagram of the process of etching the side wall of the passivation layer of the isolation trench of the back contact battery provided by an embodiment of the present invention;

[0039] Figure 7 It is a schematic diagram of the process of etching the sidewall of the passivation layer of the isolation trench of the back contact battery provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0040] In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention is described in further detail below.

[0041] See also Figure 1 The present invention provides a back contact battery, comprising a first doping layer 11, a second doping layer 12 and an isolation groove 13 arranged on the back side of a semiconductor substrate 1, a plurality of the first doping layers 11 and the second doping layers 12 are arranged alternately, and the isolation groove 13 is arranged between adjacent first doping layers 11 and second doping layers 12. Specifically, the doping type of the first doping layer 11 can be different from or the same as the doping type of the semiconductor substrate 1, and the second doping layer 12 and the first doping layer 11 have different conductivity types. Therefore, the back side of the back contact battery has a first doping layer 11 and a second doping layer 12 of opposite conductivity types, and an isolation groove 13 is arranged between the first doping layer 11 and the second doping layer 12 of opposite conductivity types. The first doping layer 11 and the second doping layer 12 distributed at intervals can prevent the first doping layer 11 and the second doping layer 12 from contacting and causing a short circuit. A passivation layer 2 is arranged on each of the first doping layer 11, the second doping layer 12 and the isolation groove 13, and the passivation layer 2 is used to chemically passivate the back side of the semiconductor substrate 1 to reduce the carrier recombination rate on the back side. The passivation layer 2 on the first sidewall 111 of the first doping layer 11 close to the isolation trench 13 has a concave-convex structure 3 .

[0042] Compared with the passivation layer with a flat surface on the existing isolation groove, the present invention also sets a concave-convex structure 3 on the passivation layer 2 of the first side wall 111 of the first doping layer 11 near the isolation groove 13. The setting of the concave-convex structure 3 can increase the surface area of ​​the passivation layer 2 and further increase the isolation between the first doping layer 11 and the second doping layer 12; secondly, during the electrode manufacturing process, metal ions or particles may be deposited on the passivation layer 2 of the isolation groove 13, causing damage to the passivation layer 2 and reducing the passivation effect. The concave-convex structure 3 can block the sputtered metal to avoid the electrode metal from being coated on the passivation layer 2 of the first side wall 111 during the electrode manufacturing process on the first doping layer 11, reducing the damage to the passivation layer 2 caused by the electrode manufacturing, thereby reducing the risk of leakage; in addition, the channel-shaped recessed isolation groove 13 will also increase the risk of hidden cracks in the battery cell. The concave-convex structure 3 on the passivation layer 2 can effectively reduce the stress concentration risk of the isolation groove 13 and prevent the battery from cracking, thereby improving the reliability of the battery.

[0043] Specifically, the concave-convex structure 3 includes a concave portion 31 and a convex portion 32 arranged along a first direction, and the concave portion 31 and the convex portion 32 are connected in sequence. In a preferred embodiment, the concave-convex structure 3 includes a periodically repeated concave portion 31 and a convex portion 32 arranged along a first direction, and the concave portion 31 and the convex portion 32 are connected in sequence. The repetition period of the concave portion 31 and the convex portion 32 is 2 to 6, and 3, 4, and 5 are exemplary. The periodically repeated concave-convex structure 3 can further increase the surface area of ​​the passivation layer 2, thereby improving the passivation effect on the surface of the isolation groove 13. If the repetition period of the concave portion 31 and the convex portion 32 is greater than 6, the complexity of the preparation process will be increased, and the thickness of the passivation layer 2 will be too large, thereby increasing the overall thickness of the battery. Among them, the first direction can be a direction perpendicular to the front and / or back of the solar cell, and the second direction can be a direction parallel to the alternating arrangement of the first doping layer 11 and the second doping layer 12 of the solar cell, and the two are perpendicular to each other.

[0044] In a preferred embodiment, Figure 4As shown, the distance between the recessed portion 31 and the first side wall 111 is D1, and the distance between the protruding portion 32 and the first side wall 111 is D2, and D1 and D2 satisfy: D2 = (1.5 ~ 4) D1. It can be understood that the distance D1 between the recessed portion 31 and the first side wall 111, and the distance D2 between the protruding portion 32 and the first side wall 111 are both the maximum distances between the recessed portion 31 or the protruding portion 32 and the first side wall 111. If the ratio of D2 to D1 is less than 1.5, the concave-convex amplitude of the concave-convex structure 3 formed by the recessed portion 31 and the protruding portion 32 is not large, and the performance improvement is not large compared with the passivation layer 2 structure with a flat surface; if the ratio of D2 to D1 is greater than 4, the concave-convex amplitude of the concave-convex structure 3 formed by the recessed portion 31 and the protruding portion 32 is too large, which increases the complexity of the preparation process. Specifically, D1 is 2μm to 5μm, exemplarily 2.5μm, 3μm, 3.5μm, 4μm or 4.5μm, but not limited thereto. D2 is 7μm to 15μm, exemplarily 8μm, 10μm, 11μm, 12μm or 14μm, but not limited thereto. If D1 is too small, the passivation performance of the passivation layer 2 is reduced, which is not conducive to the improvement of battery performance; if D2 is too large, the width of the isolation groove 13 needs to be increased accordingly, resulting in a reduction in the area of ​​the first doping layer 11 and / or the second doping layer 12, thereby affecting the collection of carriers.

[0045] In a preferred embodiment, along the first direction, the depth of the recessed portion 31 is H1, and the height of the raised portion 32 is H2, and H1 and H2 satisfy: H2 = (0.8-1.5) H1. If the ratio between the depth H1 of the recessed portion 31 and the height H2 of the raised portion 32 is too large or too small, it is not conducive to improving the passivation performance of the passivation layer 2. More preferably, the depth H1 of the recessed portion 31 and the height H2 of the raised portion 32 are the same. Specifically, H1 is 2μm to 5μm, and exemplary ones are 2.5μm, 3μm, 3.5μm, 4μm or 4.5μm, but not limited thereto. H2 is 2μm to 5μm, and exemplary ones are 2.5μm, 3μm, 3.5μm, 4μm or 4.5μm, but not limited thereto.

[0046] It is understandable that the shapes of the recessed portion 31 and the raised portion 32 may be the same or different. Specifically, the shapes of the recessed portion 31 and the raised portion 32 may be one or more of rectangular, triangular, trapezoidal, and arc-shaped, but are not limited thereto. Specifically, D1 and D2 are the distances between the vertex on the recessed portion 31 or the raised portion 32 that is farthest from the first side wall 111 and the first side wall 111. Preferably, the shapes of the recessed portion 31 and the raised portion 32 are arc-shaped, and the edge of the passivation layer 2 composed of the recessed portion 31 and the raised portion 32 forms a wavy structure. The requirements for process accuracy for preparing a passivation layer with a wavy structure are lower, which is conducive to reducing the process difficulty. It should be noted that in the actual production process, it is difficult to achieve complete consistency in the structural dimensions of the recessed portions in different cycles and the raised portions in different cycles, but in general, the dimensional deviation can be controlled within 5%.

[0047] It is understandable that if Figure 3 As shown, in order to avoid damaging the passivation layer on the bottom of the isolation groove 13 during the formation of the concavo-convex structure, thereby exposing the bottom of the isolation groove 13, the bottom of the isolation groove 13 is generally provided with a bottom passivation layer 20. The bottom passivation layer 20 can be made of a dense anti-etching material. The bottom passivation layer 20 is not sensitive to selective etching. Therefore, the bottom of the isolation groove 13 still maintains good passivation performance during the formation of the concavo-convex structure. In some embodiments, the bottom passivation layer is an Al2O3 passivation layer or a TiO2 passivation layer.

[0048] In a preferred embodiment, Figure 2 As shown, the passivation layer 2 on the second side wall 121 of the second doping layer 12 near the isolation groove 13 also has a concavo-convex structure 3, and the concavo-convex structure 3 includes a recessed portion 31 and a protruding portion 32 arranged along the first direction, and the recessed portion 31 and the protruding portion 32 are connected in sequence. The passivation layer 2 on the second side wall 121 of the second doping layer 12 near the isolation groove 13 is also provided with a concavo-convex structure, which can reduce the adverse effect of the deposited electrode metal on the passivation layer of the second side wall 121, and further increase the isolation performance of the isolation groove 13. Optionally, the concavo-convex structure 3 of the passivation layer 2 on the second side wall 121 can be the same as or different from the concavo-convex structure 3 of the passivation layer 2 on the first side wall 111. Preferably, the concavo-convex structure 3 on the passivation layer 2 on both side walls is the same, which can simplify the preparation process and improve the preparation efficiency.

[0049] Along the second direction, the width D5 of the isolation groove 13 is 20 μm to 100 μm, and is exemplarily 30 μm, 40 μm, 60 μm, 80 μm or 90 μm, but not limited thereto. If the width of the isolation groove 13 is less than 20 μm, it cannot play a good isolation role for the first doping layer 11 and the second doping layer 12; if the width of the isolation groove 13 is greater than 100 μm, it will cause the cross-sectional area of ​​at least one of the first doping layer 11 and the second doping layer 12 to decrease, thereby affecting the carrier collection capacity, and the carriers generated after the semiconductor substrate 1 absorbs photons cannot be promptly conducted out by the first doping layer 11 and / or the second doping layer 12, affecting the photoelectric conversion efficiency of the back contact battery.

[0050] It can be understood that the first doping layer 11 and the second doping layer 12 are arranged on the semiconductor substrate 1. Optionally, the semiconductor substrate is an N-type silicon substrate, the first doping layer 11 is an N-type doping layer, and the second doping layer 12 is a P-type doping layer, or the semiconductor substrate is an N-type silicon substrate, the first doping layer 11 is a P-type doping layer, and the second doping layer 12 is an N-type doping layer, which is not specifically limited here. Optionally, the first doping layer 11 can be located in the semiconductor substrate 1, or it can be located on a partial area of ​​the backlight surface of the semiconductor substrate 1, and the second doping layer 12 can be located in the semiconductor substrate 1, or it can be located on a partial area of ​​the backlight surface of the semiconductor substrate 1. The first doping layer 11 and the second doping layer 12 can be rectangular strip areas, wavy strip areas, etc. that match the morphology of the electrode structure printed thereon, which are not specifically limited here. In addition, for the first doping layer 11 and the second doping layer 12, since the range of the first doping layer 11 and the second doping layer 12 affects the junction area range of the PN junction in the back contact battery, and thus affects the strength of the built-in electric field in the back contact battery, the area ratio between the first doping layer 11 and the second doping layer 12 can be determined according to the requirements for the junction area range of the PN junction in the actual application scenario, and no specific limitation is made here.

[0051] Specifically, the material of the semiconductor substrate 1 may be a semiconductor material such as silicon, silicon germanium, germanium or gallium arsenide. When the first doped layer 11 is formed on a partial area of ​​the backlight surface of the semiconductor substrate 1, the first doped layer 11 includes a first doped semiconductor layer 111, and the material of the first doped semiconductor layer 113 may be a semiconductor material such as silicon, silicon germanium, germanium or gallium arsenide; the crystal orientation of the first doped semiconductor layer 111 may be amorphous, nanocrystalline, microcrystalline, single crystal or polycrystalline, etc. When the second doped layer 12 is formed on a partial area of ​​the backlight surface of the semiconductor substrate 1, the second doped layer 12 includes a second doped semiconductor layer 123, and the material of the second doped semiconductor layer 123 may be a semiconductor material such as silicon, silicon germanium, germanium or gallium arsenide; the crystal orientation of the second doped semiconductor layer 123 may be amorphous, nanocrystalline, microcrystalline, single crystal or polycrystalline, etc. The materials of the first doped semiconductor layer 113 and the second doped semiconductor layer 123 may be the same or different, and are not specifically limited here.

[0052] In a preferred embodiment, a first tunneling layer 121 is formed between the first doped semiconductor layer 113 and the semiconductor substrate 1, and / or a second tunneling layer 122 is formed between the second doped semiconductor layer 123 and the semiconductor substrate 1. The material of the first tunneling layer 121 and / or the second tunneling layer 122 can be silicon oxide, aluminum oxide, titanium oxide or the like.

[0053] In addition to the above structure, the back contact battery also includes a first electrode 41 and a second electrode 42. The first electrode 41 penetrates the passivation layer 2 and is electrically connected to the first doping layer 11; the second electrode 42 penetrates the passivation layer 2 and is electrically connected to the second doping layer 12. The first electrode 41 and the second electrode 42 are fine grids (sub-grids) of the solar cell, which are used to collect and aggregate the current of the solar cell. The first electrode 41 and the second electrode 42 can be sintered by a burn-through slurry or a non-burn-through slurry. The material of the first electrode 41 and the second electrode 42 can be one or more of aluminum, silver, gold, nickel, molybdenum or copper.

[0054] In order to form the concave-convex structure 3 of the passivation layer 2, the passivation layer 2 includes a first passivation layer 21 and a second passivation layer 22 stacked in sequence, wherein the materials of the first passivation layer 21 and the second passivation layer 22 are different. Specifically, the first passivation layer 21 and the second passivation layer 22 have different etching rates under the same etching conditions. The passivation layer structure is formed alternately by using materials with different etching rates. Under the same etching conditions, the first passivation layer and the second passivation layer are selectively etched respectively to form different etching surfaces, and finally a passivation layer 2 with a concave-convex structure is obtained. Specifically, the thickness of the passivation layer 2 is 5 μm to 50 μm, and is exemplarily 10 μm, 15 μm, 20 μm, 30 μm or 40 μm, but not limited thereto. If the thickness of the passivation layer 2 is less than 5 μm, it cannot provide sufficient passivation effect, resulting in a higher surface recombination rate, affecting the open circuit voltage, and is easily damaged in the subsequent preparation process, affecting stability and reliability; if the thickness of the passivation layer 2 is greater than 50 μm, it will cause unnecessary parasitic absorption, reduce the short-circuit current density of the battery, and increase the series resistance of the battery, affecting the fill factor of the battery. In a preferred embodiment, the thickness ratio of the first passivation layer 21 to the second passivation layer 22 is 1:(0.8-1.5), and is exemplarily 1:0.9, 1:1, 1:1.2, 1:1.3 or 1:1.4, but not limited thereto. Optionally, a recessed portion 31 is formed on the first passivation layer 21, and a convex portion 32 is formed on the second passivation layer 22; or, a convex portion 32 is formed on the first passivation layer 21, and a recessed portion 31 is formed on the second passivation layer 22. In a preferred embodiment, the passivation layer 2 includes a first passivation layer 21 and a second passivation layer 22 that are periodically and alternately stacked, and the stacking period number of the first passivation layer 21 and the second passivation layer 22 is 1 to 6, and exemplarily 2, 3, 4, and 5. In addition, different passivation layer materials can also be used to form the first passivation layer, the second passivation layer, the third passivation layer, etc., respectively, and the concave-convex structure can be formed by selective etching of different passivation layer materials.

[0055] Optionally, the passivation layer 2 is one or more of an intrinsic amorphous silicon layer, an intrinsic polycrystalline silicon layer, an intrinsic nanocrystalline silicon layer, an intrinsic mixed crystal silicon layer, a silicon oxide layer, an aluminum oxide layer, a silicon oxynitride layer, a silicon nitride layer, and a carbon nitride silicon oxide layer. Regarding the formation of the passivation layer 2, the aluminum oxide layer can be prepared by chemical vapor deposition (CVD), plasma chemical vapor deposition (PECVD), atomic layer deposition (ALD), plasma assisted ALD, molecular beam epitaxy and the like, which are not specifically limited here; the silicon nitride layer, silicon oxide layer, silicon oxynitride layer, etc. can be prepared by chemical vapor deposition (CVD), plasma chemical vapor deposition (PECVD), low pressure chemical vapor deposition (LPCVD), magnetron sputtering technology and the like, which are not specifically limited here. Wherein silicon nitride and aluminum oxide will produce a large amount of hydrogen at the same time of thin film deposition, which can form good hydrogen passivation. In a preferred embodiment, the passivation layer 2 includes a silicon nitride layer and a silicon oxide layer stacked in sequence.

[0056] Specifically, the method for forming the passivation layer 2 includes the following steps:

[0057] S1, forming a first passivation layer and a second passivation layer stacked in sequence on the isolation groove of the back contact battery;

[0058] In a preferred embodiment, Figure 5 As shown, a first passivation layer and a second passivation layer are periodically stacked on the isolation groove of the back contact battery, and the stacking period is 2 to 6;

[0059] S2, selectively etching the first passivation layer and the second passivation layer of the first side wall or the second side wall to obtain a concave-convex structure.

[0060] In a preferred embodiment, Figure 6 and Figure 7 As shown, the passivation layer on the first side wall and the second side wall is selectively etched to obtain a concave-convex structure.

[0061] The specific selective etching method can be dry etching, wet etching, etc. In one embodiment, remote plasma dry etching is used to selectively etch the first passivation layer and the second passivation layer. Exemplarily, when the first passivation layer is a silicon nitride layer and the second passivation layer is a silicon oxide layer, the etching rate ratio of the silicon nitride layer and the silicon oxide layer is greater than 30:1, and during the etching process of the silicon nitride layer, the silicon oxide layer or the silicon substrate is basically not etched. Specifically, the dry etching gas uses O2 and N2, the flow rate of O2 is 700sccm~900sccm, the flow rate of N2 is 100sccm~120sccm, preferably, the flow rate of O2 is 800sccm, and the flow rate of N2 is 110sccm; the silicon nitride etching gas uses NF3, the flow rate is 30sccm~50sccm, preferably, the flow rate of NF3 is 40sccm.

[0062] In one embodiment, wet etching is used to selectively etch the first passivation layer and the second passivation layer. For example, when the first passivation layer is a silicon nitride layer and the second passivation layer is a silicon oxide layer, HF solution diluted with NH4F is used for selective etching, and the HF solution is determined to be etched to SiO2 and SiN x :H has different etching rates. The etching rate of HF solution on SiO2 depends on HF 2- SiOH 2+ The effect of HF solution on SiN x :H is etched through F - SiNH 3+ By properly adjusting the pH value of the solution, the HF 2- With F - The relative content between them ensures the SiO2 etching rate while reducing the HF to SiN x :H etching, thereby improving the etching of SiO2 / SiN x :H selectivity. Preferably, the pH value of the etching solution is 4 to 7, which can obtain a better SiO2 / SiN x :H selectivity, better, the pH value of the etching solution is 5.

[0063] It is understandable that the structure of the passivation layer on the first doping layer 11 and the second doping layer 12 may be the same as or different from the structure of the passivation layer on the isolation trench 13 , and the structure is selected according to specific circumstances.

[0064] Correspondingly, an embodiment of the present invention further provides a solar cell string, including the above-mentioned solar cells, each solar cell string includes a plurality of solar cells connected in series, and the plurality of solar cells can be partially overlapped to form a solar cell string, and the contact area between the overlaps is not conductively connected, that is, no conductive glue or other adhesive is required between the overlapped areas, and the solar cells are simply overlapped together. Optionally, the solar cell can be a whole-piece back contact cell, or a sliced ​​back contact cell (such as a half-sliced ​​back contact cell or a third-sliced ​​back contact cell, etc.). Among them, the above-mentioned whole-piece back contact cell can be a whole-piece cell that does not require slice processing; or, the above-mentioned whole-piece back contact cell can also include at least two slice units with a symmetrical electrode design; or, the above-mentioned whole-piece back contact cell can also include at least two slice units with an asymmetric electrode design. The overlapping areas of adjacent solar cells in the solar cell string are provided with series welding strips to fix the adjacent solar cells, and the series welding strips connect the adjacent solar cells in series. Different solar cell strings are obtained by series connection and / or parallel connection.

[0065] Correspondingly, an embodiment of the present invention further provides a battery assembly, including the above-mentioned solar cell string. The battery assembly may also include a metal frame, a back plate, a photovoltaic glass and an adhesive film. The adhesive film may be filled between the front and back of the solar cell string, the photovoltaic glass, the back plate, etc. The adhesive film may be a transparent colloid with good light transmittance and aging resistance, such as an EVA adhesive film or a POE adhesive film, which may be selected according to actual conditions and is not specifically limited here.

[0066] Photovoltaic glass can cover the front of the solar cell string. Photovoltaic glass can be ultra-white glass, which has high light transmittance, high transparency, and excellent physical, mechanical and optical properties. For example, the light transmittance of ultra-white glass can reach more than 92%, which can protect the solar cell string without affecting its efficiency as much as possible. At the same time, the adhesive film can bond the photovoltaic glass and the solar cell string together. The presence of the adhesive film can seal and insulate the solar cell string to achieve waterproof and moisture-proof.

[0067] The backplane can be attached to the back of the solar cell string. The backplane can protect and support the solar cell string. The backplane has reliable insulation, water resistance and aging resistance. The backplane can be tempered glass, organic glass, aluminum alloy TPT composite film, etc., which can be selected according to actual conditions and are not specifically limited here. The whole composed of the backplane, solar cell string, film and photovoltaic glass can be set on a metal frame. The metal frame serves as the main external support structure of the entire battery assembly and provides stable support and installation for the battery assembly.

[0068] The present invention will be further described below with specific embodiments:

[0069] Example 1

[0070] This embodiment provides a back contact battery, including an N-type doping layer, a P-type doping layer and an isolation groove arranged on the back of an N-type silicon substrate, wherein a plurality of N-type doping layers and P-type doping layers are alternately arranged, and the isolation groove is arranged between adjacent N-type doping layers and P-type doping layers. A passivation layer is arranged on the N-type doping layer, the P-type doping layer and the isolation groove, and the passivation layer on the first side wall of the N-type doping layer close to the isolation groove has a concave-convex structure.

[0071] The concave-convex structure includes a concave portion and a convex portion arranged in a direction perpendicular to the back side of the solar cell, the distance between the concave portion and the first side wall is 2μm, the distance between the convex portion and the first side wall is 12μm, the depth of the concave portion is 2μm, and the height of the convex portion is 5μm.

[0072] Example 2

[0073] This embodiment provides a back contact battery, including an N-type doping layer, a P-type doping layer and an isolation groove arranged on the back of an N-type silicon substrate, wherein a plurality of N-type doping layers and P-type doping layers are alternately arranged, and the isolation groove is arranged between adjacent N-type doping layers and P-type doping layers. A passivation layer is arranged on the N-type doping layer, the P-type doping layer and the isolation groove, and the passivation layer on the first side wall of the N-type doping layer close to the isolation groove has a concave-convex structure.

[0074] The concave-convex structure includes periodically repeated concave portions and convex portions arranged in a direction perpendicular to the back side of the solar cell, with a repetition period of 3, a distance between the concave portion and the first side wall of 2 μm, a distance between the convex portion and the first side wall of 12 μm, a depth of the concave portion of 2 μm, and a height of the convex portion of 5 μm.

[0075] Example 3

[0076] This embodiment provides a back contact battery, including an N-type doping layer, a P-type doping layer and an isolation groove arranged on the back of an N-type silicon substrate, wherein a plurality of N-type doping layers and P-type doping layers are alternately arranged, and the isolation groove is arranged between adjacent N-type doping layers and P-type doping layers. A passivation layer is arranged on the N-type doping layer, the P-type doping layer and the isolation groove, and the passivation layer on the first side wall of the N-type doping layer close to the isolation groove has a concave-convex structure.

[0077] The concave-convex structure includes periodically repeated concave portions and convex portions arranged in a direction perpendicular to the back side of the solar cell, with a repetition period of 3, a distance between the concave portion and the first side wall of 3 μm, a distance between the convex portion and the first side wall of 10 μm, a depth of the concave portion of 2 μm, and a height of the convex portion of 5 μm.

[0078] Example 4

[0079] This embodiment provides a back contact battery, including an N-type doping layer, a P-type doping layer and an isolation groove arranged on the back of an N-type silicon substrate, wherein a plurality of N-type doping layers and P-type doping layers are alternately arranged, and the isolation groove is arranged between adjacent N-type doping layers and P-type doping layers. A passivation layer is arranged on the N-type doping layer, the P-type doping layer and the isolation groove, and the passivation layer on the first side wall of the N-type doping layer close to the isolation groove has a concave-convex structure.

[0080] The concave-convex structure includes periodically repeated concave portions and convex portions arranged in a direction perpendicular to the back side of the solar cell, with a repetition period of 3, a distance between the concave portion and the first side wall of 2 μm, a distance between the convex portion and the first side wall of 12 μm, a depth of the concave portion of 4 μm, and a height of the convex portion of 4 μm.

[0081] Example 5

[0082] This embodiment provides a back contact battery, including an N-type doping layer, a P-type doping layer and an isolation groove arranged on the back of an N-type silicon substrate, wherein a plurality of N-type doping layers and P-type doping layers are alternately arranged, and the isolation groove is arranged between adjacent N-type doping layers and P-type doping layers. A passivation layer is arranged on the N-type doping layer, the P-type doping layer and the isolation groove, and the passivation layer on the first side wall of the N-type doping layer close to the isolation groove has a concave-convex structure.

[0083] The concave-convex structure includes periodically repeated concave portions and convex portions arranged in a direction perpendicular to the back side of the solar cell, with a repetition period of 3, a distance between the concave portion and the first side wall of 3 μm, a distance between the convex portion and the first side wall of 10 μm, a depth of the concave portion of 4 μm, and a height of the convex portion of 4 μm.

[0084] Example 6

[0085] This embodiment provides a back contact battery, including an N-type doped layer, a P-type doped layer and an isolation groove arranged on the back of an N-type silicon substrate, wherein a plurality of N-type doped layers and P-type doped layers are alternately arranged, and the isolation groove is arranged between adjacent N-type doped layers and P-type doped layers. A passivation layer is arranged on the N-type doped layer, the P-type doped layer and the isolation groove, and the passivation layer on the first side wall of the N-type doped layer close to the isolation groove and the passivation layer on the second side wall of the P-type doped layer close to the isolation groove both have a concave-convex structure.

[0086] The concave-convex structure includes periodically repeated concave portions and convex portions arranged in a direction perpendicular to the back side of the solar cell, with a repetition period of 3, a distance between the concave portion on the first side wall and the first side wall of 3 μm, a distance between the convex portion and the first side wall of 10 μm, a distance between the concave portion on the second side wall and the second side wall of 3 μm, a distance between the convex portion and the second side wall of 10 μm, a depth of the concave portion of 4 μm, and a height of the convex portion of 4 μm.

[0087] Performance testing:

[0088] The back contact cells prepared in Examples 1 to 6 were subjected to printed electrodes, sintered and alloyed, and then annealed to obtain finished solar cells. The short-circuit current density and photoelectric conversion efficiency of the finished solar cells were measured. The results are shown in the following table.

[0089]

[0090] The above is a preferred embodiment of the present invention. It should be pointed out that a person skilled in the art can make several improvements and modifications without departing from the principle of the present invention. These improvements and modifications are also considered to be within the scope of protection of the present invention.

Claims

1. A back contact battery, characterized in that: The method comprises a first doping layer, a second doping layer and an isolation groove arranged on the back side of a semiconductor substrate, wherein a plurality of the first doping layers and the second doping layers are alternately arranged, the isolation groove is arranged between the first doping layer and the second doping layer, and the first doping layer and the second doping layer have different doping types; A passivation layer, the passivation layer being disposed on the first doping layer, the second doping layer and the isolation trench; The passivation layer on the first side wall of the first doping layer close to the isolation trench has a concave-convex structure.

2. The back contact cell according to claim 1, characterized in that The passivation layer on the second side wall of the second doping layer close to the isolation trench has a concave-convex structure.

3. The back contact cell according to claim 1 or 2, characterized in that: The concave-convex structure includes a concave portion and a convex portion arranged along a first direction, and the concave portion and the convex portion are connected in sequence.

4. The back contact cell according to claim 3, characterized in that The concave-convex structure includes periodically repeated concave portions and convex portions arranged along a first direction, and the concave portions and convex portions are connected in sequence.

5. The back contact cell according to claim 4, characterized in that The repetition period of the concave portion and the convex portion is 2 to 6.

6. The back contact cell according to claim 3, characterized in that The concave-convex structure is located on the passivation layer of the first side wall, the distance between the concave portion and the first side wall is D1, the distance between the convex portion and the first side wall is D2, and D1 and D2 satisfy: D2=(1.5-4)D1.

7. The back contact cell according to claim 6, characterized in that The D1 is 2 μm to 5 μm, and the D2 is 7 μm to 15 μm.

8. The back contact battery according to claim 3, characterized in that The concave-convex structure is located on the passivation layer of the second side wall, the distance between the concave portion and the second side wall is D3, the distance between the convex portion and the second side wall is D4, and D3 and D4 satisfy: D4=(1.5-4)D3.

9. The back contact cell according to claim 8, characterized in that The D3 is 2 μm to 5 μm, and the D4 is 7 μm to 15 μm.

10. The back contact cell according to claim 3, characterized in that Along the first direction, the depth of the concave portion is H1, the height of the convex portion is H2, and H1 and H2 satisfy: H2 = (0.8-1.5) H1.

11. The back contact cell according to claim 10, characterized in that The H1 is 2 μm to 5 μm, and the H2 is 2 μm to 5 μm.

12. The back contact cell according to claim 1, characterized in that Along the second direction, the width of the isolation groove is 20 μm to 100 μm.

13. The back contact cell according to claim 3, characterized in that The shapes of the concave portion and the convex portion are one or more of a rectangle, a triangle, a trapezoid, and an arc.

14. The back contact cell according to claim 1, characterized in that The passivation layer comprises a first passivation layer and a second passivation layer which are periodically and alternately stacked; A concave portion is formed on the first passivation layer, and a convex portion is formed on the second passivation layer; Alternatively, a protrusion is formed on the first passivation layer, and a depression is formed on the second passivation layer.

15. The back contact cell according to claim 14, characterized in that The first passivation layer and the second passivation layer are made of different materials.

16. The back contact cell according to claim 14, characterized in that The number of stacking cycles of the passivation layer is 1-6.

17. The back contact cell according to claim 14, characterized in that The thickness of the passivation layer is 5 μm to 50 μm, and the thickness ratio of the first passivation layer to the second passivation layer is 1:(0.8 to 1.5).

18. The back contact cell according to claim 1, characterized in that The passivation layer is one or more of an intrinsic amorphous silicon layer, an intrinsic polycrystalline silicon layer, an intrinsic nanocrystalline silicon layer, an intrinsic mixed crystal silicon layer, a silicon oxide layer, an aluminum oxide layer, a silicon oxynitride layer, a silicon nitride layer, and a carbon nitride silicon oxide layer.

19. The back contact cell according to claim 18, characterized in that The passivation layer includes a silicon nitride layer and a silicon oxide layer stacked in sequence.

20. The back contact cell according to claim 1, characterized in that The first doped layer includes a first tunneling layer and a first polarity doped layer stacked on the first tunneling layer, and the second doped layer includes a second tunneling layer and a second polarity doped layer stacked on the second tunneling layer; The first tunneling layer and the second tunneling layer are one or more of a silicon oxide layer, an aluminum oxide layer, a titanium oxide layer, a zinc oxide layer, an intrinsic amorphous silicon layer, an intrinsic polycrystalline silicon layer, an intrinsic nanocrystalline silicon layer, and an intrinsic mixed crystal silicon layer; The first polarity doped layer and the second polarity doped layer are one or more of a doped polysilicon layer, a doped amorphous silicon layer, and a doped microcrystalline silicon layer, and the polarity of the first polarity doped layer is opposite to that of the second polarity doped layer.

21. A back contact battery string, characterized in that: Comprising a back contact battery as claimed in any one of claims 1 to 20.

22. A photovoltaic module, characterized in that: Comprising a back-contact cell string as claimed in claim 21.

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