Back contact battery piece and photovoltaic module

Abstract

The utility model discloses a back contact battery piece and a photovoltaic assembly, and the back contact battery piece comprises a silicon substrate which is provided with a front surface and a back surface; the back surface of the silicon substrate is provided with a groove, and the groove divides the back surface of the silicon substrate into a first area and a second area; a first transport layer disposed on the first region; the barrier layer is arranged on the end part, close to the second region, of the first transmission layer; the insulating layer is arranged on the side wall of the groove, extends downwards to cover part of the bottom of the groove, and extends upwards to the first transmission layer to cover the barrier layer; the second transmission layer is arranged at the bottom of the groove and extends upwards along the side wall of the groove to cover the insulating layer; a back surface passivation layer disposed on the first transport layer and the second transport layer; a conductive layer disposed on the back passivation layer; and the front passivation layer and the front anti-reflection layer are stacked on the front surface of the silicon substrate. According to the structural design, the transmission isolation effect is good, and the efficiency of the battery piece is improved.

Description

Technical Field

[0001] The utility model belongs to the technical field of solar cells, and in particular relates to a back contact cell sheet and a photovoltaic module. Background Art

[0002] Photovoltaic solar cells generally use silicon as the cell substrate, which is formed through a manufacturing process. Through continuous technological progress, they have developed rapidly in recent years.

[0003] Currently, the main types of crystalline silicon cells on the market include: PERC (Passivated Emitter and Rear Cell), TOPCON (Tunnel Oxide Passivating Contact), BC (back contact), and HJT (heterojunction) cells. TOPCON cells have replaced PERC cells as the mainstream, achieving efficiencies exceeding 26.4%. However, due to gridline shading, their light utilization is low, limiting their development potential. BC cells, on the other hand, effectively address this issue by concentrating the electrodes on a single side, maximizing light utilization on the front side.

[0004] Existing BC cells primarily use ink as an insulating layer to separate the different semiconductor layers, or laser grooving to isolate the transmission layer. However, using graphite as an insulating layer provides poor isolation and can introduce contamination issues. Laser grooving, which disconnects the contacts, is difficult to control, affecting isolation effectiveness. Furthermore, the increasing application of photovoltaic solar cells in a variety of fields is placing higher demands on cell efficiency. Utility Model Content

[0005] In order to solve the above problems existing in the prior art, the present invention provides a back-contact solar cell and photovoltaic module. The technical problems to be solved by the present invention are achieved through the following technical solutions:

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

[0007] The silicon substrate has a front surface and a back surface; a groove is provided on the back surface of the silicon substrate, and the groove divides the back surface of the silicon substrate into a first area and a second area, the first area being the protruding areas on both sides, and the second area being the groove area in the middle;

[0008] a first transmission layer, disposed on the first area;

[0009] a barrier layer, disposed on the first transmission layer at an end position close to the second region;

[0010] an insulating layer, disposed on a sidewall of the groove and extending downward to cover a portion of the bottom of the groove, while extending upward to the first transmission layer and covering the barrier layer;

[0011] a second transmission layer, disposed at the bottom of the groove and extending upward along the sidewalls of the groove to cover the insulating layer;

[0012] a back passivation layer, disposed on the first transmission layer and the second transmission layer;

[0013] A conductive layer is provided on the back passivation layer;

[0014] The front passivation layer and the front anti-reflection layer are stacked on the front side of the silicon substrate.

[0015] In a second aspect, the present invention provides a photovoltaic module, which includes several back-contact solar cells provided by the first aspect of the present invention.

[0016] Beneficial effects of the utility model:

[0017] The utility model provides a back-contact solar cell, comprising a silicon substrate having a front side and a back side; a groove is provided on the back side of the silicon substrate, the groove dividing the back side of the silicon substrate into a first area and a second area, the first area being the protruding areas on both sides, and the second area being the groove area in the middle; a first transmission layer is arranged on the first area; a barrier layer is arranged on the first transmission layer at an end position close to the second area; an insulating layer is arranged on the side wall of the groove and extends downward to cover the bottom of the groove, and at the same time extends upward to the first transmission layer and covers the barrier layer; a second transmission layer is arranged at the bottom of the groove and extends upward along the side wall of the groove to cover the insulating layer; a back passivation layer is arranged on the first transmission layer and the second transmission layer; a conductive layer is arranged on the back passivation layer; a front passivation layer and a front anti-reflection layer are stacked and arranged on the front side of the silicon substrate. This device structure increases the surface area of ​​the silicon substrate by creating grooves on the backside of the silicon substrate. The insulating layer is cleverly designed on the groove walls of the silicon substrate, avoiding the problem of direct contact between the first and second transmission layers, which could cause short circuits. This also increases the coverage area of ​​the first and second transmission layers, thereby increasing the carrier collection area within the cell and improving cell efficiency. Furthermore, this insulating layer structure design avoids the potential contamination caused by using ink as the insulating layer, as well as the difficulty in controlling laser precision when using laser grooving to disconnect contacts.

[0018] The present invention will be described in further detail below with reference to the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is a schematic structural diagram of a back-contact solar cell provided by an embodiment of the present utility model;

[0020] Figure 2 This is a schematic flow chart of a method for preparing a back-contact solar cell provided by an embodiment of the present utility model;

[0021] Figures 3a-3i This is a schematic diagram of a process for preparing a back-contact solar cell provided in an embodiment of the present invention.

[0022] Description of reference numerals:

[0023] 1-silicon substrate, 2-first tunneling polysilicon layer, 3-first doped layer, 4-back passivation layer, 5-first electrode, 6-second electrode, 7-blocking layer, 8-insulating layer, 9-second tunneling polysilicon layer, 10-second doped layer, 11-transparent conductive film, 12-front passivation layer, 13-front anti-reflection layer; T1-first transmission layer, T2-second transmission layer, C-conductive layer. DETAILED DESCRIPTION

[0024] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0025] The first aspect of the present invention provides a back contact solar cell. Figure 1 , Figure 1 This is a schematic diagram of the structure of a back-contact solar cell provided by an embodiment of the present invention. The back-contact solar cell specifically includes:

[0026] The silicon substrate 1 has a front surface and a back surface; a groove is provided on the back surface of the silicon substrate 1, and the groove divides the back surface of the silicon substrate 1 into a first area and a second area, the first area being the protruding areas on both sides, and the second area being the groove area in the middle;

[0027] A first transmission layer T1, provided on the first area;

[0028] The barrier layer 7 is provided on the first transmission layer T1 and close to the end of the second region;

[0029] an insulating layer 8 disposed on the sidewalls of the groove and extending downward to cover a portion of the bottom of the groove, while extending upward to the first transmission layer T1 and covering the barrier layer 7;

[0030] The second transmission layer T2 is provided at the bottom of the groove and extends upward along the sidewall of the groove to cover the insulating layer 8;

[0031] A back passivation layer 4 is provided on the first transmission layer T1 and the second transmission layer T2;

[0032] Conductive layer C, provided on the back passivation layer 4;

[0033] The front passivation layer 12 and the front anti-reflection layer 13 are stacked on the front surface of the silicon substrate 1 .

[0034] In order to more clearly represent the first area and the second area, in this embodiment Figure 1 Four dotted lines L1, L2, L3, and L4 are added. It is understandable that the dotted lines L1, L2, L3, and L4 do not actually exist, but are used to distinguish the first area, the second area, the first transmission layer, and the second transmission layer. Specifically, Figure 1 As shown, the first area is the portion between L1 and L2 and between L3 and L4, and the second area is the portion between L2 and L3.

[0035] As a preferred implementation, the first and second regions of this embodiment are symmetrically distributed around the midpoint of the groove, and the width ratio of the first and second regions is 1:1 to 1.5:1. For example, if the width of the second region is 1 mm to 10 mm, the width of the first region is 1.5 mm to 15 mm.

[0036] Furthermore, the depth of the groove in the silicon substrate 1 is 10 μm-100 μm.

[0037] Optionally, in this embodiment, the first transmission layer T1 includes a first tunneling polysilicon layer 2 and a first doping layer 3 arranged in a stacked manner; the thickness of the first tunneling polysilicon layer 2 is 3nm-10nm; the first doping layer 3 is a P-type doped polysilicon layer with a thickness of 50nm-100nm; the second transmission layer T2 includes a second tunneling polysilicon layer 9 and a second doping layer 10 arranged in a stacked manner, and the thickness of the second tunneling polysilicon layer 9 is 3nm-10nm; the second doping layer 10 is an N-type doped polysilicon layer with a thickness of 50nm-100nm.

[0038] It is understood that the first tunneling polysilicon layer 2 is closer to the silicon substrate than the first doped layer 3, and the second tunneling polysilicon layer 9 is closer to the silicon substrate than the second doped layer 10. Under illumination, carriers are generated and transferred through the first and second doped layers 3, 10 within the cell. The tunneling polysilicon layer has a selective tunneling property for carriers, allowing electrons to pass through while blocking holes, thus reducing carrier recombination.

[0039] Optionally, in this embodiment, the material of the barrier layer 7 includes silicon dioxide and doping substances, and the thickness is not less than 100 nm.

[0040] For further information, please see Figure 1The insulating layer 8 has a portion located on the groove wall of the second region and a portion extending from the surface of the first region to the bottom of the groove of the second region. The portion of the insulating layer 8 extending on the first transmission layer T1 is one-tenth of the width of the first region, and the portion extending on the bottom of the groove is one-tenth of the width of the second region. The insulating layer 8 serves to separate the first transmission layer T1 and the second transmission layer T2, preventing direct contact between the two, which would cause carriers to short-circuit at the doped layer and prevent effective carrier collection.

[0041] Optionally, as an implementation manner, the material of the insulating layer 8 is one of SiO 2 and SiC, and the thickness is 100 nm-1000 nm.

[0042] In this embodiment, the back passivation layer 4 and the front passivation layer 12 are made of AlxOy (x, y ≠ 0) with a thickness of 1nm-5nm. Alternatively, this embodiment uses Al2O3 as the material for both passivation layers. The front passivation layer 12 protects the front of the cell from damage and oxidation. The Al2O3 / Si interface formed between the front passivation layer 12 and the silicon substrate 1 has a negative charge effect, which encourages electrons to leave and reduces electron loss.

[0043] Furthermore, the material of the front anti-reflection layer 13 is SiNx (x≠0) with a thickness of 20nm-120nm, which can effectively protect the surface of the battery cell from damage. At the same time, the hydrogen bonds generated by the reaction can replace the dangling bonds of the carrier-saturated Si interface to avoid carrier loss.

[0044] For further information, please see Figure 1 , wherein the conductive layer C includes a transparent conductive film 11 and a metal electrode; the material of the transparent conductive film is a conductive polymer material or a conductive plastic, and the thickness is 10nm-100nm;

[0045] The metal electrodes include a first electrode 5 and a second electrode 6 ; the first electrode 5 is disposed on the transparent conductive film 11 above the first transmission layer T1 , and the second electrode 6 is disposed on the transparent conductive film 11 above the second transmission layer T2 , which can effectively collect carriers.

[0046] Optionally, in this embodiment, both the first electrode 5 and the second electrode 6 are printed electrodes.

[0047] The back-contact cell provided by this utility model increases the surface area of ​​the silicon substrate by creating grooves on the back side of the silicon substrate. The insulating layer is cleverly designed on the groove walls of the silicon substrate, avoiding the problem of direct contact between the first and second transmission layers, which could cause a short circuit. This also increases the coverage area of ​​the first and second transmission layers, thereby increasing the carrier collection area within the cell and improving cell efficiency. Furthermore, this insulating layer structure design avoids the potential contamination caused by using ink as the insulating layer, as well as the difficulty in controlling laser precision when using laser grooving to disconnect the contacts.

[0048] Based on the same utility model concept, the second aspect of the utility model further provides a photovoltaic module, which includes several back contact cells provided by the first aspect of the utility model.

[0049] Specifically, a plurality of back contact cells are arranged in an array, with the first region and the second region spaced apart. Figure 1 The direction parallel to the middle section is the first direction, Figure 1 The vertical direction of the middle cross section is the second direction, and the first area and the second area are spaced apart and distributed along the first direction. The photovoltaic module also has high efficiency.

[0050] The third aspect of the present invention also provides a method for preparing a back contact solar cell. Figure 2 , Figure 2 This is a schematic flow chart of a method for preparing a back-contact solar cell according to an embodiment of the present invention. The method mainly includes the following steps:

[0051] Step 1: Deposit a first transmission layer and a barrier layer in sequence on the back side of the silicon substrate.

[0052] The first transmission layer includes a first tunneling polysilicon layer and a first doping layer.

[0053] Step 2: Based on the division effect of the first area and the second area on the back of the silicon substrate, the barrier layer, the first transmission layer and part of the silicon substrate in the second area are removed by laser to form a groove on the back of the silicon substrate.

[0054] Step 3: Covering the surfaces of the first region and the second region with an insulating layer, and then removing most of the insulating layer, leaving the groove wall portion of the second region and the portion extending to the bottom of the groove and the surface of the first region.

[0055] Step 4: forming a second transmission layer on the surfaces of the first region and the second region, and then removing the second transmission layer and the barrier layer on the first region not covered by the insulating layer.

[0056] The second transmission layer includes a second tunneling polysilicon layer and a second doping layer.

[0057] Step 5: forming a front passivation layer and a front anti-reflection layer in sequence on the front surface of the silicon substrate, and forming a back passivation layer on the first transmission layer and the second transmission layer.

[0058] Step 6: Making a conductive layer on the back passivation layer; wherein the conductive layer includes a transparent conductive film and a metal electrode, and the metal electrode includes a first electrode and a second electrode; the first electrode is arranged on the transparent conductive film above the first transmission layer, and the second electrode is arranged on the transparent conductive film above the second transmission layer.

[0059] At this point, the preparation of the back contact cell is completed.

[0060] The preparation method provided in this embodiment can prepare the device provided in the first aspect above. Therefore, the prepared back-contact cell has the same beneficial effects as the back-contact cell of the first aspect.

[0061] The following combination Figures 3a-3i The preparation process diagram shown in FIG1 is used to introduce the above preparation method in detail.

[0062] S1: depositing a first transmission layer and a barrier layer in sequence on the back side of the silicon substrate.

[0063] First, a single crystal silicon material is selected and polished and cleaned to form a silicon substrate 1. Any one side of the silicon substrate 1 is defined as the back side, and the other side is defined as the front side. Figure 3a shown.

[0064] Then, PECVD (Plasma Enhanced Chemical Vapor Deposition) or LPCVD (Low Pressure Chemical Vapor Deposition) is used to sequentially deposit 3nm-10nm of SiO2 and 50nm-100nm of P-type doped polysilicon layers as the first tunneling polysilicon layer 2 and the first doped layer 3 on the back side of the silicon substrate 1 to form a first transmission layer. Subsequently, 120nm of silicon dioxide is deposited on the first doped layer 3 to serve as a barrier layer 7. The deposition reaction temperature is 400-600°C.

[0065] After processing in step S1, the obtained sample is as follows Figure 3b shown.

[0066] S2: For the sample obtained in step S1, a laser combined with chemical etching method is used to remove the first transmission layer T1 and the barrier layer 7 located on the second area, and a portion of the silicon substrate is removed to form a groove on the back side of the silicon substrate.

[0067] Specifically, first, a mask is attached to the part that does not need to be removed. The part with the mask is the first area. A laser is used to remove the barrier layer 7, the first doping layer 3, the first tunneling polysilicon layer 2 and part of the silicon substrate at the part without the mask. The depth of the silicon substrate removed is 10μm-100μm.

[0068] Subsequently, the mask was removed by wet cleaning and polishing, and the obtained sample was as shown in FIG. Figure 3c It is worth noting that the mask is not marked in the figure because it needs to be cleaned.

[0069] Optionally, the laser can be at least one of infrared, green, and ultraviolet lasers. The laser spot shape is square, with a size of 250-310 μm and an overlap ratio of 40%-50%. The laser power can be 88W-200W; the wavelength can be 300nm, 500nm, 700nm, or 1000nm; and the laser pulse energy can be 400μJ-600μJ. Chemical etching chemicals include hydrofluoric acid, sodium hydroxide, hydrogen peroxide, and hydrochloric acid.

[0070] S3: A layer of silicon dioxide with a thickness of 100 nm to 1000 nm is formed on the surface of the first region and the second region by high temperature annealing, so as to facilitate the subsequent formation of the insulating layer 8, such as Figure 3d shown.

[0071] S4: For the sample obtained in step S3, a laser combined with chemical etching method is used to remove part of the silicon dioxide to form an insulating layer at the junction of the first region and the second region.

[0072] Specifically, a mask is used to cover a portion of the connection between the first region and the second region, that is, the insulating layer on the groove wall portion of the second region and a portion of the insulating layer extending to the groove bottom of the first region and the second region are retained, and the remaining insulating layer on the insulating layer in the first region and the groove bottom of the second region is removed by laser, and then the mask is removed by wet cleaning to form the insulating layer 8, as shown in FIG. Figure 3e As shown, the insulating layer 8 extends over the first region and the second region to a length of 100 μm-1000 μm.

[0073] S5: Using PECVD or LPCVD, 3nm-10nm SiO2 is sequentially deposited on the sample obtained in step S4 as the second tunneling polysilicon layer 9 and 50nm-100nm N-type doped polysilicon layer as the second doping layer 10. Figure 3f It can be understood that the second tunneling polysilicon layer 9 completely covers the bottom of the groove and the insulating layers on both sides thereof.

[0074] S6: For the sample obtained in step S5, the second doping layer 10, the second tunneling polysilicon layer 9 and the barrier layer 7 on the first region not covered by the insulating layer are removed by laser combined with chemical etching to form a second transmission layer.

[0075] Specifically, a mask is used to cover the second region and the barrier layer 7 in the first region, and a laser is used to remove the second doped layer 10 and the second tunneling polysilicon layer 9 and the barrier layer 7 in the remaining portion of the first region. Subsequently, wet back polishing is performed and the mask is removed to form a second transmission layer. Figure 3g shown.

[0076] S7: PECVD is used to sequentially deposit the front passivation layer 12, the front anti-reflection layer 13 and the back passivation layer 4.

[0077] Specifically, first, 2nm-50nm of Al2O3 is deposited on the front surface of the silicon substrate 1 as a front passivation layer 12; then 50nm-500nm of SiNx (x≠0) is deposited on the front passivation layer 12 as a front anti-reflection layer 13; finally, 50nm-500nm of SiNx (x≠0) is deposited on the back surface of the entire sample as a back passivation layer 4. The obtained sample is as follows Figure 3h shown.

[0078] S8: forming a conductive layer on the back passivation layer 4 .

[0079] First, a 10nm-100nm transparent conductive film 11 is deposited on the back passivation layer 4 by PVD (Physical Vapor Deposition) method. Figure 3i shown.

[0080] Finally, a metal conductive paste is printed by a printing method and cured to form the first electrode 5 and the second electrode 6 .

[0081] At this point, the preparation of the back contact cell is completed.

[0082] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise" and the like to indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present invention.

[0083] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of the technical features being referred to. Thus, a feature specified as "first" or "second" may explicitly or implicitly include one or more of such features. In the description of this utility model, "plurality" means two or more, unless otherwise specifically defined.

[0084] In the present invention, unless otherwise expressly specified or limited, a first feature being "above" or "below" a second feature may include the first and second features being in direct contact, or may include the first and second features being in contact not directly but through another feature between them. Moreover, a first feature being "above," "above," and "above" a second feature may include the first feature being directly above or obliquely above the second feature, or may simply mean that the first feature is higher in level than the second feature. A first feature being "below," "below," and "below" a second feature may include the first feature being directly below or obliquely below the second feature, or may simply mean that the first feature is lower in level than the second feature.

[0085] In the description of the present invention, the reference terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" mean that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art can combine and combine different embodiments or examples described in this specification.

[0086] The above content is a further detailed description of the present invention in conjunction with specific preferred embodiments, and the specific implementation of the present invention cannot be considered to be limited to these descriptions. For those skilled in the art of the present invention, without departing from the concept of the present invention, several simple deductions or substitutions can be made, which should be considered to fall within the scope of protection of the present invention.

Claims

1. A back contact solar cell, characterized in that: include: A silicon substrate having a front surface and a back surface; a groove is provided on the back surface of the silicon substrate, wherein the groove divides the back surface of the silicon substrate into a first area and a second area, wherein the first area is a protruding area on both sides, and the second area is a groove area in the middle; a first transmission layer, disposed on the first area; a barrier layer, disposed on the first transmission layer at an end position close to the second region; an insulating layer, disposed on a sidewall of the groove and extending downward to cover a portion of the bottom of the groove, and extending upward to the first transmission layer and covering the barrier layer; a second transmission layer, disposed at the bottom of the groove and extending upward along the sidewall of the groove to cover the insulating layer; a back passivation layer, disposed on the first transmission layer and the second transmission layer; A conductive layer is provided on the back passivation layer; A front passivation layer and a front anti-reflection layer are stacked and arranged on the front side of the silicon substrate.

2. The back contact solar cell according to claim 1, characterized in that: The first region and the second region are symmetrically distributed with respect to the midpoint of the groove; and a width ratio between the first region and the second region is 1:1 to 1.5:

1.

3. The back contact solar cell according to claim 1, characterized in that: The depth of the groove in the silicon substrate is 10 μm-100 μm.

4. The back contact solar cell according to claim 1, characterized in that: The extending portion of the insulating layer on the first transmission layer is one tenth of the width of the first region, and the extending portion of the insulating layer on the bottom surface of the groove is one tenth of the width of the second region.

5. The back contact solar cell according to any one of claims 1 to 4, characterized in that: The insulating layer is made of SiO2 or SiC, and has a thickness of 100 nm to 1000 nm.

6. The back contact solar cell according to claim 1, characterized in that: The first transmission layer includes a first tunneling polysilicon layer and a first doping layer stacked together; the first tunneling polysilicon layer has a thickness of 3nm-10nm; the first doping layer is a P-type doped polysilicon layer with a thickness of 50nm-100nm; The second transmission layer includes a second tunneling polysilicon layer and a second doping layer which are stacked. The thickness of the second tunneling polysilicon layer is 3nm-10nm. The second doping layer is an N-type doped polysilicon layer with a thickness of 50nm-100nm.

7. The back contact solar cell according to claim 1, characterized in that: The barrier layer comprises silicon dioxide and doping substances, and has a thickness of no less than 100 nm.

8. The back contact solar cell according to claim 1, characterized in that: The material of the back passivation layer and the front passivation layer is AlxOy, and the thickness is 1nm-5nm; the material of the front anti-reflection layer is SiNx, and the thickness is 20nm-120nm.

9. The back contact solar cell according to claim 1, characterized in that: The conductive layer includes a transparent conductive film and a metal electrode; the material of the transparent conductive film is a conductive polymer material or a conductive plastic, and the thickness is 10nm-100nm; The metal electrode includes a first electrode and a second electrode; the first electrode is arranged on the transparent conductive film above the first transmission layer, and the second electrode is arranged on the transparent conductive film above the second transmission layer.

10. A photovoltaic module, characterized in that: The photovoltaic module comprises the back-contact cells according to any one of claims 1 to 9.

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