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 silicon 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 layers of the first doping layer and the second doping layer are provided with through holes used for depositing electrodes, and the side walls of the through holes of the first doping layer and / or the second doping layer are provided with concave-convex structures. According to the back contact cell, the passivation performance of the passivation layer is ensured, the transverse contact area between the electrode and the doping layer domain can be increased, the resistivity is reduced, and the efficiency of the back contact cell is improved.

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 attracted extensive attention from academia and industry. The positive and negative electrodes of the back-contact solar cell are connected to different doping layer domains through the through holes on the passivation layer. The contact area between the electrode and the doping layer domain determines the resistivity of the cell, but the increase in contact area will correspondingly lead to a decrease in the passivation performance of the passivation layer, which ultimately leads to a decrease in the efficiency 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 cell, a back-contact cell string and a photovoltaic module, which increase the contact area between the electrode and the doping layer, reduce the resistivity and improve the efficiency of the back-contact cell while ensuring the passivation performance of the passivation layer.

[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 silicon substrate, wherein the first doping layer and the second doping layer are arranged alternately, 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] Through holes for depositing electrodes are provided on the passivation layers of the first doping layer and the second doping layer, and side walls of the through holes of the first doping layer and / or the second doping layer have a concave-convex structure.

[0007] As an improvement of the above technical solution, the concave-convex structure includes a concave portion and a convex portion arranged in a first direction, and the concave portion and the convex portion are connected in sequence.

[0008] 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.

[0009] As an improvement of the above technical solution, the repetition period of the recessed portions and the raised portions is 2 to 6.

[0010] As an improvement of the above technical solution, both side walls of the through hole are provided with a concave-convex structure;

[0011] Along the second direction, the distance between the recessed portions on the two side walls of the through hole is D1, and the distance between the raised portions on the two side walls of the through hole is D2, and D1 and D2 satisfy: D1 = (1.5-2.5) D2.

[0012] As an improvement of the above technical solution, the D1 is 60 μm to 120 μm, and the D2 is 30 μm to 50 μm.

[0013] As an improvement of the above technical solution, 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.

[0014] As an improvement of the above technical solution, H1 is 2 μm to 5 μm, and H2 is 2 μm to 5 μm.

[0015] 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.

[0016] 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; a recessed portion is formed on the first passivation layer, and a protruding portion is formed on the second passivation layer.

[0017] As an improvement of the above technical solution, the first passivation layer and the second passivation layer are made of different materials.

[0018] As an improvement of the above technical solution, the number of stacking periods of the passivation layer is 1 to 6.

[0019] As an improvement of the above technical solution, the thickness of the passivation layer is 50 μm to 150 μm, and the thickness ratio of the first passivation layer to the second passivation layer is 1:(0.8 to 1.5).

[0020] 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.

[0021] As an improvement of the above technical solution, the passivation layer includes a silicon nitride layer and a silicon oxide layer stacked in sequence.

[0022] 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;

[0023] 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;

[0024] 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.

[0025] Correspondingly, the present invention also discloses a back-contact battery string, including the above-mentioned back-contact battery.

[0026] Correspondingly, the present invention also discloses a photovoltaic module, comprising the above-mentioned back-contact cell string.

[0027] The implementation of the present invention has the following beneficial effects: through holes for depositing electrodes are provided on the passivation layers of the first doping layer and the second doping layer of the present invention, and the side walls of the through holes on the first doping layer and / or the second doping layer have a concave-convex structure, the concave portion increases the lateral area of ​​the electrode, which is beneficial to reducing the resistivity, and the convex portion can reduce the amount of electrode metal slurry while ensuring the passivation performance of the passivation layer, ultimately improving the efficiency of the back contact battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 is a schematic structural diagram of a back contact battery provided in Example 1 of the present invention;

[0029] Figure 2 is a schematic structural diagram of a back contact battery provided in Example 2 of the present invention;

[0030] Figure 3 is a schematic structural diagram of a back contact battery provided in Example 6 of the present invention;

[0031] Figure 4 is a schematic diagram of the dimensions of the passivation layer on the side wall of the through hole of the back contact battery provided in Example 2 of the present invention;

[0032] Figure 5 is a schematic diagram of the structure of a back contact battery after a passivation layer is deposited provided in Example 2 of the present invention;

[0033] Figure 6 is a schematic structural diagram of a back contact battery provided in Example 2 of the present invention after a through hole for depositing an electrode is opened;

[0034] Figure 7 is a schematic structural diagram of a back contact battery provided in Example 2 of the present invention after a concavo-convex structure is formed on the side wall of the through hole;

[0035] Figure 8It is a schematic diagram of the structure of the back contact battery after electrode deposition provided in Example 2 of the present invention. DETAILED DESCRIPTION

[0036] 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.

[0037] 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 with different conductivity types, and an isolation groove 13 is arranged between the first doping layer 11 and the second doping layer 12 with different 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 of the first doping layer 11 and the second doping layer 12 is provided with a through hole 3 for depositing an electrode, and the sidewall of the through hole 3 of the first doping layer 11 and / or the second doping layer 12 has a concave-convex structure.

[0038] Compared with the existing through holes of regular shape, the present invention further provides a concave-convex structure 4 on the side wall of the through hole 3 of the first doping layer 11. The concave-convex structure 4 includes a concave portion 41 and a convex portion 42. The concave portion 41 increases the lateral contact area between the electrode and the doping layer, which is beneficial to reduce the resistivity and ultimately improve the efficiency of the back contact battery. The provision of the convex portion 42 can reduce the amount of electrode slurry used overall, saving costs.

[0039] Specifically, a first through hole for depositing the first electrode 51 is provided on the passivation layer 2 of the first doping layer 11, and the sidewall of the first through hole has a concave-convex structure 4. It can be understood that the first doping layer 11 can be an emitter or a back surface field, preferably an emitter. Exemplarily, the semiconductor substrate 1 is an N-type silicon substrate, and the first doping layer 11 is a P-type doping layer, which collects holes and transfers them to the first electrode 51. The sidewall of the first through hole for depositing the first electrode 51 is set as a non-straight surface with a concave-convex structure, which increases the lateral area of ​​the first electrode 51, reduces the resistivity, and more holes can be transferred to the first electrode 51. The concave-convex structure 4 includes a concave portion 41 and a convex portion 42 arranged along the first direction, and the concave portion 41 and the convex portion 42 are connected in sequence. Along the second direction, the distance between the recessed portion 41 located on one side wall of the first through hole and the other side wall is 60μm to 120μm, exemplarily 70μm, 80μm, 90μm, 100μm or 110μm, but not limited thereto, and the distance between the protruding portion 42 located on one side wall of the first through hole and the other side wall is 30μm to 50μm, exemplarily 32μm, 35μm, 38μm, 42μm or 48μm, but not limited thereto. Preferably, the ratio between the two satisfies 1.5 to 2.5. It can be understood that the distance between the recessed portion 41 located on one side wall and the other side wall, and the distance between the protruding portion 42 located on one side wall and the other side wall are both the minimum distances between the recessed portion 41 or the protruding portion 42 and the other side wall.

[0040] In a preferred embodiment, the concave-convex structure 4 includes a periodically repeated concave portion 41 and a convex portion 42 arranged along a first direction, the concave portion 41 and the convex portion 42 are connected in sequence, and the repetition period of the concave portion 41 and the convex portion 42 is 2 to 6, and 3, 4, and 5 are exemplary. The periodically repeated concave-convex structure 4 can further increase the surface area of ​​the passivation layer 2, thereby improving the passivation effect. If the repetition period of the concave portion 41 and the convex portion 42 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.

[0041] In a preferred embodiment, both side walls of the first through hole are provided with a concave-convex structure 4 to further increase the lateral area of ​​the first electrode 11. Figure 2 and Figure 4As shown, along the second direction, the distance between the recessed portions 41 located on the two side walls of the first through hole is D1, and the distance between the raised portions 42 located on the two side walls of the first through hole is D2, and D1 and D2 satisfy: D1 = (1.5 ~ 2.5) D2. It can be understood that the distance D1 between the recessed portions 41 located on the two side walls of the through hole and the distance D2 between the raised portions 42 located on the two side walls of the through hole are both the minimum distances between the two recessed portions 41 or the two raised portions 42 located on the two side walls. If the ratio of D1 to D2 is less than 1.5, the concave-convex amplitude of the concave-convex structure 4 formed by the recessed portions 41 and the raised portions 42 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 2.5, the concave-convex amplitude of the concave-convex structure 4 formed by the recessed portions 41 and the raised portions 42 is too large, which increases the complexity of the preparation process. Specifically, D1 is 60μm to 120μm, and exemplary ones are 70μm, 80μm, 90μm, 100μm or 110μm, but not limited thereto. D2 is 30μm to 50μm, and exemplary ones are 32μm, 35μm, 38μm, 42μm or 48μm, but not limited thereto. If D1 is too large, the width of the first through hole needs to be increased accordingly, resulting in an increase in the amount of electrode metal used, and also increasing the contact recombination loss between the electrode and the doping layer; if D2 is too small, the contact area between the first electrode 51 and the first doping layer 11 is too small, which is not conducive to improving the battery performance.

[0042] In a preferred embodiment, along the first direction, the height of the recessed portion 41 is H1, and the depth of the raised portion 42 is H2, and H1 and H2 satisfy: H2 = (0.8-1.5) H1. If the ratio between the height H1 of the recessed portion 41 and the depth H2 of the raised portion 42 is too large or too small, it is not conducive to improving the passivation performance of the passivation layer 2. More preferably, the height H1 of the recessed portion 41 and the depth H2 of the raised portion 42 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.

[0043] It is understandable that the shapes of the recessed portion 41 and the raised portion 42 may be the same or different. Specifically, the shapes of the recessed portion 41 and the raised portion 42 may be one or more of rectangular, triangular, trapezoidal, and arc-shaped, but are not limited thereto. Preferably, the shapes of the recessed portion 41 and the raised portion 42 are arc-shaped, and the edge of the passivation layer 2 composed of the recessed portion 41 and the raised portion 42 forms a wavy structure. The wavy structure has lower requirements on process precision, which helps to reduce 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%.

[0044] In a preferred embodiment, Figure 4 As shown, a second through hole for depositing the second electrode 52 is provided on the passivation layer 2 of the second doping layer 12, and the side wall of the second through hole has a concave-convex structure 4, and the concave-convex structure 4 includes a recessed portion 41 and a raised portion 42 arranged along a first direction, and the recessed portion 41 and the raised portion 42 are connected in sequence. The side wall of the electrode through hole on the second doping layer 12 is also set to a concave-convex structure, which can increase the lateral area of ​​the second electrode 52, increase the carrier collection efficiency, and further improve the conversion efficiency of the battery. Optionally, the concave-convex structure 4 of the first through hole can be the same as or different from the concave-convex structure 4 of the second through hole. Preferably, the concave-convex structure 4 on the first through hole and the second through hole is the same, which can simplify the preparation process and improve the preparation efficiency.

[0045] 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.

[0046] 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 112 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 122, and the material of the second doped semiconductor layer 122 may be a semiconductor material such as silicon, silicon germanium, germanium or gallium arsenide; the crystal orientation of the second doped semiconductor layer 122 may be amorphous, nanocrystalline, microcrystalline, single crystal or polycrystalline, etc. The materials of the first doped semiconductor layer 112 and the second doped semiconductor layer 122 may be the same or different, and are not specifically limited here.

[0047] In a preferred embodiment, a first tunneling layer 111 is formed between the first doped semiconductor layer 112 and the semiconductor substrate 1, and / or a second tunneling layer 121 is formed between the second doped semiconductor layer 122 and the semiconductor substrate 1. The material of the first tunneling layer 111 and / or the second tunneling layer 121 can be silicon oxide, aluminum oxide, titanium oxide or the like.

[0048] In addition to the above structure, the back contact battery also includes a first electrode 51 and a second electrode 52. The first electrode 51 is at least arranged in a first through hole on the first doping layer 11, and the first electrode 51 is electrically connected to the first doping layer 11; the second electrode 52 is at least arranged in a second through hole on the second doping layer 12, and the second electrode 52 is electrically connected to the second doping layer 12. The first electrode 51 and the second electrode 52 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 51 and the second electrode 52 can be sintered by a burn-through slurry or a non-burn-through slurry. The material of the first electrode 51 and the second electrode 52 can be one or more of aluminum, silver, gold, nickel, molybdenum or copper.

[0049] In order to form the concave-convex structure 4 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 5μm to 50μm, and is exemplarily 10μm, 15μm, 20μm, 30μm or 40μm, but not limited thereto. If the thickness of the passivation layer 2 is less than 5μm, 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 50μm, 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. Specifically, a recessed portion 41 is formed on the first passivation layer 21, and a convex portion 42 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 is 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 selectively etching different passivation layer materials.

[0050] 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.

[0051] Specifically, the method for forming the passivation layer 2 includes the following steps:

[0052] S1, such as Figure 5 As shown, a first passivation layer and a second passivation layer stacked in sequence are formed on the first doping layer and the second doping layer;

[0053] In a preferred embodiment, a first passivation layer and a second passivation layer are periodically stacked on the first doped layer and the second doped layer of the back contact cell, and the stacking period is 2 to 6;

[0054] S2, such as Figure 6 As shown, a through hole penetrating the passivation layer is opened on the passivation layer of the first doping layer. Specifically, the through hole can be opened by using a laser;

[0055] S3, such as Figure 7 As shown, the side wall of the through hole is selectively etched to obtain a concave-convex structure;

[0056] In a preferred embodiment, it also includes:

[0057] S4, opening a through hole penetrating the passivation layer on the passivation layer of the second doping layer;

[0058] S5. Selectively etch the sidewall of the through hole to obtain a concave-convex structure.

[0059] 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 to 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 is O 2 and N 2 , O 2 The flow rate is 700sccm~900sccm, N 2 The flow rate is 100 sccm to 120 sccm, preferably, O 2 The flow rate is 800sccm, N 2 The flow rate is 110sccm; the silicon nitride etching gas is NF 3 , the flow rate is 30sccm~50sccm, preferably, NF 3 The flow rate is 40sccm.

[0060] 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, NH 4 F diluted HF solution for selective etching, determines the HF solution to SiO 2 and SiN x :H has different etching rates. HF solution has different etching rates for SiO 2 The etching is based 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 that SiO 2 While reducing the etching rate, HF can also reduce the effect of HF on SiN x :H etching, thereby improving the etching of SiO 2 / SiN x :H selectivity. Preferably, the pH value of the etching solution is 4 to 7, which can obtain better SiO 2 / SiN x :H selectivity, better, the pH value of the etching solution is 5.

[0061] S6, such as Figure 8As shown, metal is deposited at least in the through hole to form an electrode; specifically, the metal can be deposited by physical vapor deposition, thermal evaporation, magnetron sputtering, etc.;

[0062] It is understandable that the structure of the passivation layer on the isolation trench 13 may be the same as or different from the structure of the passivation layer on the first doping layer 11 and / or the second doping layer 12 , and the structure is selected according to specific circumstances.

[0063] 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.

[0064] 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.

[0065] 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.

[0066] 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.

[0067] The present invention will be further described below with specific embodiments:

[0068] Example 1

[0069] 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, the N-type doping layer and the P-type doping layer are alternately arranged, and the isolation groove is arranged between the N-type doping layer and the P-type doping layer. A passivation layer is arranged on the N-type doping layer, the P-type doping layer and the isolation groove, and a through hole for depositing an electrode is opened on the passivation layer of the P-type doping layer and the N-type doping layer, and a side wall of the through hole of the P-type doping layer has a concave-convex structure.

[0070] 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 located on one side wall of the through hole and the other side wall is 100μm, the distance between the convex portion located on one side wall of the through hole and the other side wall is 30μm, the depth of the concave portion is 2μm, and the height of the convex portion is 5μm.

[0071] Example 2

[0072] 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, the N-type doped layer and the P-type doped layer are alternately arranged, and the isolation groove is arranged between the N-type doped layer and the P-type doped layer. A passivation layer is arranged on the N-type doped layer, the P-type doped layer and the isolation groove, and a through hole for depositing an electrode is opened on the passivation layer of the P-type doped layer and the N-type doped layer, and both side walls of the through hole of the P-type doped layer have a concave-convex structure.

[0073] 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 portions on the two side walls of the through hole is 120 μm, the distance between the convex portions on the two side walls of the through hole is 40 μm, the depth of the concave portion is 2 μm, and the height of the convex portion is 5 μm.

[0074] Example 3

[0075] 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, the N-type doped layer and the P-type doped layer are alternately arranged, and the isolation groove is arranged between the N-type doped layer and the P-type doped layer. A passivation layer is arranged on the N-type doped layer, the P-type doped layer and the isolation groove, and a through hole for depositing an electrode is opened on the passivation layer of the P-type doped layer and the N-type doped layer, and both side walls of the through hole of the P-type doped layer have a concave-convex structure.

[0076] 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. The distance between the concave portions on the two side walls of the through hole is 120 μm, the distance between the convex portions on the two side walls of the through hole is 40 μm, the depth of the concave portions is 5 μm, and the height of the convex portions is 2 μm.

[0077] Example 4

[0078] 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, the N-type doped layer and the P-type doped layer are alternately arranged, and the isolation groove is arranged between the N-type doped layer and the P-type doped layer. A passivation layer is arranged on the N-type doped layer, the P-type doped layer and the isolation groove, and a through hole for depositing an electrode is opened on the passivation layer of the P-type doped layer and the N-type doped layer, and both side walls of the through hole of the P-type doped layer have a concave-convex structure.

[0079] 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. The distance between the concave portions on the two side walls of the through hole is 90 μm, the distance between the convex portions on the two side walls of the through hole is 40 μm, the depth of the concave portions is 5 μm, and the height of the convex portions is 2 μm.

[0080] Example 5

[0081] 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, the N-type doped layer and the P-type doped layer are alternately arranged, and the isolation groove is arranged between the N-type doped layer and the P-type doped layer. A passivation layer is arranged on the N-type doped layer, the P-type doped layer and the isolation groove, and a through hole for depositing an electrode is opened on the passivation layer of the P-type doped layer and the N-type doped layer, and both side walls of the through hole of the P-type doped layer have a concave-convex structure.

[0082] 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. The distance between the concave portions on the two side walls of the through hole is 90 μm, the distance between the convex portions on the two side walls of the through hole is 40 μm, the depth of the concave portions is 4 μm, and the height of the convex portions is 4 μm.

[0083] Example 6

[0084] 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, the N-type doping layer and the P-type doping layer are alternately arranged, and the isolation groove is arranged between the N-type doping layer and the P-type doping layer. A passivation layer is arranged on the N-type doping layer, the P-type doping layer and the isolation groove, and a through hole for depositing an electrode is opened on the passivation layer of the P-type doping layer and the N-type doping layer, and both side walls of the through hole of the P-type doping layer and the N-type doping layer have a concave-convex structure.

[0085] 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. The distance between the concave portions on the two side walls of the through hole is 90 μm, the distance between the convex portions on the two side walls of the through hole is 40 μm, the depth of the concave portions is 4 μm, and the height of the convex portions is 4 μm.

[0086] Performance testing:

[0087] The back contact cells prepared in Examples 1 to 5 were subjected to annealing treatment after printing electrodes, sintering and alloying to obtain finished solar cells. The photoelectric properties of the finished solar cells were measured. The results are shown in the following table.

[0088]

[0089] 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 silicon substrate, wherein the first doping layer and the second doping layer are arranged alternately, 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; Through holes for depositing electrodes are provided on the passivation layers of the first doping layer and the second doping layer, and side walls of the through holes of the first doping layer and / or the second doping layer have a concave-convex structure.

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

3. The back contact cell according to claim 2, 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.

4. The back contact cell according to claim 3, characterized in that The repetition period of the concave portion and the convex portion is 2 to 6.

5. The back contact battery according to claim 2, characterized in that Both side walls of the through hole are provided with concave-convex structures; Along the second direction, the distance between the recessed portions on the two side walls of the through hole is D1, and the distance between the raised portions on the two side walls of the through hole is D2, and D1 and D2 satisfy: D1 = (1.5-2.5) D2.

6. The back contact cell according to claim 5, characterized in that The D1 is 60 μm to 120 μm, and the D2 is 30 μm to 50 μm.

7. The back contact cell according to claim 2, characterized in that 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.

8. The back contact cell according to claim 7, characterized in that The H1 is 2 μm to 5 μm, and the H2 is 2 μm to 5 μm.

9. The back contact cell according to claim 1, 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.

10. The back contact cell according to claim 1, characterized in that The passivation layer includes 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.

11. The back contact cell according to claim 10, characterized in that The first passivation layer and the second passivation layer are made of different materials.

12. The back contact cell according to claim 10, characterized in that The number of stacking cycles of the passivation layer is 1-6.

13. The back contact cell according to claim 10, characterized in that The thickness of the passivation layer is 50 μm to 150 μm, and the thickness ratio of the first passivation layer to the second passivation layer is 1:(0.8 to 1.5).

14. 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.

15. The back contact cell according to claim 14, characterized in that The passivation layer includes a silicon nitride layer and a silicon oxide layer stacked in sequence.

16. 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.

17. A back contact battery string, characterized in that: Comprising a back contact battery as claimed in any one of claims 1 to 16.

18. A photovoltaic module, characterized in that: Comprising a back-contact cell string as claimed in claim 17.

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