Back contact solar cell and preparation method thereof

Abstract

The invention discloses a back contact solar cell and a preparation method thereof, and relates to the technical field of solar cell manufacturing, and the back contact solar cell comprises a silicon substrate; a first carrier collection layer, a heavily doped layer and a second carrier collection layer which are stacked from inside to outside are arranged in a first region of the first main surface of the silicon substrate; the doping type of the first carrier collection layer is opposite to that of the heavily doped layer; the second carrier collection layer is arranged in a second region of the first main surface of the silicon substrate; a spacer region is arranged between the first region and the second region, and the doping type of the second carrier collection layer is opposite to the doping type of the first carrier collection layer. According to the embodiment, the heavily doped layer is arranged in the first region, and current conduction between the first carrier collection layer and the heavily doped layer and current conduction between the heavily doped layer and the second carrier collection layer are achieved at the same time. Meanwhile, the technological process is simplified, laser damage is reduced, and the photoelectric conversion efficiency of the solar cell is effectively improved.

Description

Technical Field

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

[0002] For back-contact solar cells, after absorbing sunlight, the silicon substrate will generate electron and hole carriers, and collect electrons and holes through the P region and N region respectively to form an electric potential. Among them, in the existing back-contact solar cells with full back electrodes, the P region and the N region will respectively set the first carrier collection layer and the second carrier collection layer, and through doping with different doping types, opposite doping types are obtained, thereby obtaining the positive and negative poles of the solar cell.

[0003] However, in order to prepare the first carrier collection layer and the second carrier collection layer in different regions, the existing technology inevitably uses a laser film opening process, and the film is opened and removed in some regions after the entire surface is prepared, thereby retaining the first carrier collection layer and the second carrier collection layer in some regions. High-energy laser beams can cause laser damage to the silicon substrate, junction region, and field region, greatly affecting the photoelectric conversion efficiency of solar cells. Summary of the invention

[0004] In view of this, an embodiment of the present invention provides a back-contact solar cell and a method for preparing the same. By arranging a heavily doped layer outside the first carrier collection layer in the first region, current conduction between the first carrier collection layer and the heavily doped layer can be achieved when the doping types are opposite. At the same time, there is no need to perform laser film opening on the second carrier collection layer. A high-low junction is formed between the heavily doped layer and the second carrier collection layer of the same doping type, and the current is conducted between the heavily doped layer and the second carrier collection layer. Laser damage to the silicon substrate caused by the laser film opening process is avoided, and the photoelectric conversion efficiency of the solar cell is effectively improved.

[0005] In order to solve the above technical problems, the present invention provides the following technical solutions:

[0006] In a first aspect, the present invention provides a back-contact solar cell, comprising: a silicon substrate; a first carrier collection layer, a heavily doped layer, and a second carrier collection layer stacked from inside to outside in a first region of a first main surface of the silicon substrate; wherein the doping type of the first carrier collection layer is opposite to the doping type of the heavily doped layer; and a second carrier collection layer arranged in a second region of the first main surface of the silicon substrate; wherein a spacing region is provided between the first region and the second region, and the doping type of the second carrier collection layer is opposite to the doping type of the first carrier collection layer.

[0007] Optionally, the doping concentration of the heavily doped layer is not less than 1E 19atoms / cm 3 .

[0008] Optionally, the back-contact solar cell further includes: a conductive film layer disposed outside the second carrier collection layer.

[0009] Optionally, the first carrier collection layer includes a stacked tunneling oxide layer and a first doping layer doped with a first element; or, the first carrier collection layer includes a stacked first intrinsic silicon-containing thin film layer and a first doping layer doped with a first element.

[0010] Optionally, the second carrier collection layer includes a second intrinsic silicon-containing thin film layer and a second doping layer doped with a second element which are stacked.

[0011] Optionally, the doping concentration of the heavily doped layer is greater than the doping concentration of the second doped layer; and / or the first intrinsic silicon-containing thin film layer and / or the second intrinsic silicon-containing thin film layer is a thin film structure composed of one or more of microcrystalline silicon, nanosilicon, amorphous silicon, silicon oxide or silicon carbide; and / or the first doped layer and / or the second doped layer and / or the heavily doped layer is a thin film structure composed of one or more of microcrystalline silicon, nanosilicon, amorphous silicon, silicon oxide or silicon carbide.

[0012] Optionally, the back-contact solar cell further includes: a passivation layer and an anti-reflection layer sequentially arranged from the inside to the outside on the second main surface of the silicon substrate; and / or metal electrodes respectively arranged in the first region and the second region.

[0013] Optionally, a passivation layer is provided on the second main surface of the silicon substrate, and the passivation layer includes a combination of at least one or more of an intrinsic silicon-containing film and a doped silicon-containing film; and / or an anti-reflection layer is provided on the second main surface of the silicon substrate, and the anti-reflection layer includes one or more of aluminum oxide, silicon nitride, silicon oxynitride and silicon oxide.

[0014] Optionally, the thickness of the tunnel oxide layer is 0.5 nm to 3.0 nm; and / or the thickness of the first doped layer and / or the second doped layer and / or the heavily doped layer is 1 nm to 250 nm.

[0015] Optionally, the conductive film layer is a multilayer structure of metal oxides and / or nitrides doped with one or more doping elements; wherein the metal oxide includes at least one of the following: indium oxide, tin oxide, zinc oxide, cadmium oxide, titanium nitride; the metal nitride is titanium nitride; the doping elements include at least one of the following: indium, tin, calcium, aluminum, cadmium, zinc, cerium, fluorine.

[0016] In a second aspect, the present invention provides a method for preparing a back-contact solar cell, comprising:

[0017] Step 1, preparing a first carrier collection layer and a heavily doped layer in sequence from inside to outside in a first region of a first main surface of a silicon substrate;

[0018] Step 2, preparing a second carrier collection layer in the first region and the second region of the first main surface of the silicon substrate;

[0019] The first regions and the second regions are arranged alternately, and a spacing region is provided between adjacent first regions and second regions; and the doping type of the first carrier collection layer is opposite to the doping type of the heavily doped layer.

[0020] The technical solution of the first aspect of the above invention has the following advantages or beneficial effects: by arranging a heavily doped layer outside the first carrier collection layer in the first region, current conduction between the first carrier collection layer and the heavily doped layer can be achieved when the doping types are opposite. At the same time, there is no need to perform laser film opening on the second carrier collection layer, and a high-low junction is formed between the heavily doped layer and the second carrier collection layer of the same doping type, and the current is conducted between the heavily doped layer and the second carrier collection layer. Laser damage to the silicon substrate caused by the laser film opening process is avoided, the photoelectric conversion efficiency of the solar cell is effectively improved, and the preparation process is simplified, making the process more stable and reliable. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The accompanying drawings are used to better understand the present invention and do not constitute an improper limitation of the present invention.

[0022] Figure 1 is a schematic cross-sectional structure diagram of a back-contact solar cell according to an embodiment of the present invention;

[0023] Figure 2 It is a schematic diagram of the cross-sectional structure of a back contact solar cell in the prior art;

[0024] Figure 3 It is a schematic diagram of the cross-sectional structure of a back contact solar cell in the prior art when the second carrier collection layer in the first region is not removed and the heavily doped layer is not provided;

[0025] Figure 4 is a schematic cross-sectional structure diagram of a back-contact solar cell with spacing regions arranged at different positions according to an embodiment of the present invention;

[0026] Figure 5 It is a schematic diagram of the main process of a method for preparing a back-contact solar cell provided in accordance with an embodiment of the present invention;

[0027] Figure 6 The silicon substrate structure is obtained after texturing and polishing according to an embodiment of the present invention;

[0028] Figure 7 is a structural schematic diagram of forming a mask layer outside the first carrier collection layer while preparing the first carrier collection layer on the entire surface of the first main surface according to an embodiment of the present invention;

[0029] Figure 8 is a schematic diagram of a cross-sectional structure of a silicon substrate obtained after the mask layer in the second region and the spacing region is regionally removed by a laser process according to an embodiment of the present invention;

[0030] Fig. 9 It is a schematic diagram of the cross-sectional structure of a silicon substrate obtained after removing the first carrier collection layer in the second region and the spacer region by using an alkaline solution and removing the mask layer in the first region by using an acid solution according to an embodiment of the present invention;

[0031] Fig.10 is a schematic diagram of a cross-sectional structure of a silicon substrate after step S501 provided in an embodiment of the present invention;

[0032] Fig.11 It is a schematic diagram of a cross-sectional structure obtained after a second carrier collection layer is prepared on the entire first main surface of a silicon substrate according to an embodiment of the present invention;

[0033] Fig.12 It is a schematic diagram of the cross-sectional structure of a silicon substrate obtained after preparing a full-surface conductive film layer outside the second carrier collection layer according to an embodiment of the present invention;

[0034] Fig.13 It is a schematic diagram of a silicon substrate structure formed after the second carrier collection layer and the conductive film layer in the spacing area are grooved by laser technology according to an embodiment of the present invention.

[0035] The reference numerals are as follows:

[0036] 1-silicon substrate; 11-first region; 12-second region; 13-spacer region; 2-first carrier collection layer; 3-heavily doped layer; 4-second carrier collection layer; 5-conductive film layer; 6-passivation layer; 7-anti-reflection layer; 8-metal electrode; 100-mask layer. DETAILED DESCRIPTION

[0037] A solar cell is a photoelectric semiconductor sheet that uses sunlight to generate electricity directly. It is also called a "solar chip" or "photovoltaic cell". As long as it is illuminated by light that meets certain illumination conditions, it can instantly output voltage and generate current in the presence of a circuit. In physics, it is called solar photovoltaic (PV), or photovoltaic for short. In order to conveniently and clearly describe the method for preparing a solar cell and the solar cell of the present invention, the following exemplary embodiments of the present invention are described in conjunction with the accompanying drawings, which include various details of the embodiments of the present invention to facilitate understanding, and they should be considered as merely exemplary. Therefore, those of ordinary skill in the art should recognize that various changes and modifications can be made to the embodiments described herein without departing from the scope and spirit of the present invention. Similarly, for the sake of clarity and conciseness, the description of well-known functions and structures is omitted in the following description.

[0038] In recent years, with the development of monocrystalline solar cells, especially the successful industrialization of passivated emitter and back field (PERC) technology, the efficiency improvement of mass-produced cells on P-type silicon wafers has reached a bottleneck. More attention has been paid to N-type cells with higher body minority carrier lifetime and lower attenuation. Three types of cell structures, including N-type PERT, heterojunction (HJT) and tunneling oxide passivated contact (TOPCon), have also gradually attracted attention from the industry. Among them, in order to further improve the efficiency of traditional heterojunction cells, people have made further improvements to the structure of heterojunction cells, and heterojunction cells with a full back electrode structure have emerged, which can remove the shielding of sunlight by the grid lines and increase the absorption efficiency of incident light.

[0039] However, in order to prepare the first carrier collection layer and the second carrier collection layer in different areas, the existing technology inevitably uses a laser film opening process, and the film is opened and removed in some areas after the entire surface is prepared, so as to retain the first carrier collection layer and the second carrier collection layer in some areas. High-energy laser beams can cause laser damage to the silicon substrate, junction area, and field area, greatly affecting the photoelectric conversion efficiency of solar cells.

[0040] In one embodiment of the present invention, Figure 1 As shown, this embodiment provides a back-contact solar cell, which includes: a silicon substrate 1; a first carrier collection layer 2, a heavily doped layer 3, and a second carrier collection layer 4 stacked from inside to outside in a first area 11 of a first main surface of the silicon substrate 1; wherein the doping type of the first carrier collection layer 2 is opposite to the doping type of the heavily doped layer 3; a second carrier collection layer 4 is arranged in a second area 12 of the first main surface of the silicon substrate 1; wherein a spacing area 13 is provided between the first area 11 and the second area 12, and the doping type of the second carrier collection layer 4 is opposite to the doping type of the first carrier collection layer 2.

[0041] For example, in Figure 1 The first main surface is the back side of the silicon substrate, and the purpose of the spacing region 13 is to block the electrical connection between the first region 11 and the second region 12. Since the doping type of the first carrier collection layer 2 is opposite to the doping type of the heavily doped layer 3, and the doping types of the first carrier collection layer 2 and the second carrier collection layer 4 are also opposite, the heavily doped layer 3 is actually the same as the doping type of the second carrier collection layer 4. Among them, the second carrier collection layer 4 is usually lightly doped, and the doping concentration is different from that of the heavily doped layer 3. Therefore, the embodiment of the present invention forms a high-low junction between the heavily doped layer 3 and the second carrier collection layer 4 to achieve current transmission. As for the first carrier collection layer 2 and the heavily doped layer 3, although the doping types of the two are opposite, due to the high doping concentration of the heavily doped layer 3, it will quickly recombine with the electron holes in the first carrier collection layer 2 to form a composite junction, thereby achieving current conduction.

[0042] Below Figure 2 and Figure 3 For example, it is explained that if the second carrier collection layer 4 of the first region 11 is not removed and the heavily doped layer 3 is not provided on the silicon substrate structure of the prior art, carrier transport cannot be achieved. Figure 2 is a schematic diagram of the cross-sectional structure of a back-contact solar cell in the prior art, Figure 3 FIG. 1 is a schematic diagram of a cross-sectional structure of a back contact solar cell in the prior art when the second carrier collection layer 4 of the first region 11 is not removed and the heavily doped layer 3 is not provided. Figure 2 From the structure, it can be seen that in the prior art, taking the N-type silicon substrate as an example, since the doping types of the first carrier collection layer 2 and the second carrier collection layer 4 are opposite, a P region (second region) and an N region (first region) are formed in the left and right regions of the silicon substrate 1, respectively, wherein the first region 11 is doped with n-type and the second region 12 is doped with p-type, then a pn junction will be formed in the second region 12. After the silicon substrate 1 is irradiated by sunlight, the energy of the photons is absorbed, and electrons are excited from the atoms to form electron-hole pairs, which are affected by the electric field of the pn junction and move to the N region and the P region respectively, forming a solar cell with the N region as the negative pole and the P region as the positive pole. If the second carrier collection layer 4 of the first region 11 is not removed, then Figure 3 As shown, based on the formation of a pn junction in the second region, a pn junction is also formed between the first carrier collection layer 2 and the second carrier collection layer 4 in the first region 11. At this time, part of the carriers move toward the second region 12, and part move toward the first region 11. The collection efficiency is low, resulting in reduced battery efficiency.

[0043] In the embodiment of the present invention, by providing the heavily doped layer 3, the pn junction of the first region 11 is transformed into a composite junction, which will not compete with the pn junction of the second region 12 for carriers, thereby achieving normal collection of carriers.

[0044] In an optional embodiment, the doping concentration of the heavily doped layer 3 is not less than 1E 19 atoms / cm 3 It should be noted that, as the doping concentration in the heavily doped layer 3 continues to increase, the recombination rate between the heavily doped layer 3 and the first carrier collection layer 2 also accelerates. Therefore, it is only necessary to define the critical concentration at which a pn junction will not be formed between the heavily doped layer 3 and the first carrier collection layer 2. In theory, the higher the doping concentration of the heavily doped layer 3, the better.

[0045] In an optional embodiment, the back-contact solar cell provided by the present invention also includes: a conductive film layer 5 arranged on the outside of the second carrier collection layer 4, wherein the conductive film layer 5 is used to respectively conduct the carriers of the first region 11 and the second region 12 to the corresponding metal electrodes 8 to realize current conduction.

[0046] For the first carrier collection layer 2, two different stacking results can be achieved. In an optional embodiment, the first carrier collection layer 2 includes a stacked tunneling oxide layer and a first doped layer doped with a first element; and in another optional embodiment, the first carrier collection layer 2 includes a stacked first intrinsic silicon-containing thin film layer and a first doped layer doped with a first element. Among them, the preparation processes of the tunneling oxide layer and the first intrinsic silicon-containing thin film layer are different. At different preparation temperatures, the preparation of the corresponding structure can be carried out according to actual conditions. For the second carrier collection layer 4, in an optional embodiment, it includes a stacked second intrinsic silicon-containing thin film layer and a second doped layer doped with a second element. Among them, the first element and the second element can be boron and phosphorus, respectively. For example, when the silicon substrate 1 is an n-type silicon substrate, the first element is phosphorus and the second element is boron.

[0047] In addition, in the embodiment of the present invention, the doping concentration of the heavily doped layer 3 needs to be greater than the doping concentration of the second doped layer to ensure that a high-low junction structure is formed between the heavily doped layer 3, the second intrinsic silicon-containing thin film layer, and the second doped layer.

[0048] In an optional embodiment, the first intrinsic silicon-containing thin film layer and / or the second intrinsic silicon-containing thin film layer is a thin film structure composed of one or more of microcrystalline silicon, nano silicon, amorphous silicon, silicon oxide or silicon carbide. As for the first doped layer and / or the second doped layer and / or the heavily doped layer 3, it can also be a thin film structure composed of one or more of microcrystalline silicon, nano silicon, amorphous silicon, silicon oxide or silicon carbide. Among them, the thickness of the tunneling oxide layer is 0.5nm~3.0nm, for example, 0.5nm, 1.0nm, 1.5nm, 2.0nm, 3.0nm, etc.; the thickness of the first doped layer and / or the second doped layer and / or the heavily doped layer 3 is 1 nm~250nm, for example, 1nm, 50nm, 100nm, 150nm, 200nm, 250nm, etc.

[0049] The back contact solar cell provided by the present invention is as follows Figure 1 As shown, it also includes: a passivation layer 6 and an anti-reflection layer 7 are sequentially arranged on the second main surface of the silicon substrate 1 from the inside to the outside. Figure 1 The front side of the silicon substrate 1. Specifically, the passivation layer 6 can be a combination of at least one or more of an intrinsic silicon-containing film and a doped silicon-containing film; in terms of thickness setting, the thickness of the intrinsic silicon-containing film can be 1nm to 15nm, such as 1nm, 5nm, 10nm, 15nm, etc., and the thickness of the doped silicon-containing film can be 0nm to 15nm, such as 0nm, 5nm, 10nm, 15nm, etc. The anti-reflection layer 7 can be one or more of aluminum oxide, silicon nitride, silicon oxynitride and silicon oxide. In terms of thickness setting, the thickness of the anti-reflection layer 7 can be 40nm to 200nm, such as 40nm, 80nm, 100nm, 150nm, 180nm, 200nm, etc.

[0050] As for the conductive film layer 5, in an optional embodiment, the conductive film layer 5 is a multilayer structure of metal oxides and / or nitrides doped with one or more doping elements; wherein the metal oxide includes at least one of the following: indium oxide, tin oxide, zinc oxide, cadmium oxide, titanium nitride; the metal nitride is titanium nitride; the doping elements include at least one of the following: indium, tin, calcium, aluminum, cadmium, zinc, cerium, fluorine.

[0051] In a further optional embodiment, metal electrodes 8 are respectively provided in the first region 11 and the second region 12, wherein the metal electrodes 8 may be one or more stacks of silver electrodes, silver alloy electrodes, copper electrodes, copper alloy electrodes, and nickel / copper / silver multilayer electrodes.

[0052] It can be understood that, in the embodiment of the present invention, the purpose of the spacer region 13 is to block the conduction of carriers between the first region 11 and the second region 12, so the location of the spacer region 13 can be adjusted according to actual conditions, for example Figure 4 The cross-sectional structure of the silicon substrate is shown. Figure 1 and Figure 4 It can be seen that the spacing region 13 can be set in the spacing region of the silicon substrate 1, or can be set biased towards the second region 12. It should be noted that the second intrinsic silicon-containing thin film layer in the second carrier collection layer 4 has a very high square resistance, which is higher than the square resistance of the silicon substrate 1, so it will not conduct the current between the first region 11 and the second region 12.

[0053] In summary, the back-contact solar cell provided by the embodiment of the present invention can achieve current conduction between the first carrier collection layer and the heavily doped layer when the doping types are opposite by arranging a heavily doped layer outside the first carrier collection layer in the first region. At the same time, there is no need to perform laser film opening on the second carrier collection layer, and a high-low junction is formed between the heavily doped layer and the second carrier collection layer of the same doping type, and the current is conducted between the heavily doped layer and the second carrier collection layer. Laser damage to the silicon substrate caused by the laser film opening process is avoided, and the photoelectric conversion efficiency of the solar cell is effectively improved.

[0054] Figure 5 A method for preparing a back-contact solar cell provided by an embodiment of the present invention is shown, such as Figure 5 As shown, the preparation method provided by the present invention comprises:

[0055] Step S501, preparing a first carrier collection layer 2 and a heavily doped layer 3 in sequence from inside to outside in a first region 11 of a first main surface of a silicon substrate 1;

[0056] Step S502 , preparing a second carrier collection layer 4 in the first region 11 and the second region 12 of the first main surface of the silicon substrate 1 ;

[0057] The first regions 11 and the second regions 12 are arranged alternately, and a spacing region 13 is provided between adjacent first regions 11 and second regions 12 ; the doping type of the first carrier collection layer 2 is opposite to the doping type of the heavily doped layer 3 .

[0058] The specific preparation process of step S501 and step S502 is described in detail below:

[0059] In an optional embodiment, before step S501, the silicon substrate 1 needs to be textured and polished to remove damage to the silicon substrate 1 itself caused during the cutting process, so as to ensure the overall performance of the solar cell prepared subsequently. Specifically, before step S501, it includes: performing alkali texture on the first main surface and the second main surface of the silicon substrate 1, and polishing the first main surface using a mask layer provided on the second main surface of the silicon substrate 1. The texture can be performed using a commonly used alkali texture method. Exemplarily, the silicon substrate structure obtained after texture and polishing is as follows: Figure 6 As shown, in an optional embodiment, an oxide layer can be prepared on the second main surface after texturing as a mask layer to protect the velvet structure of the second main surface during the polishing process, and after polishing, the oxide layer can be removed using an acidic solution such as a hydrofluoric acid solution.

[0060] In an optional embodiment, based on the different structures of the first carrier collection layer 2, the process of preparing the first carrier collection layer 2 in step S501 may specifically include: preparing a tunneling oxide layer and a first doping layer doped with a first element on the first main surface of the silicon substrate 1 from the inside to the outside, to obtain the first carrier collection layer 2; or, preparing a first intrinsic silicon-containing thin film layer and a first doping layer doped with a first element on the first main surface of the silicon substrate 1 from the inside to the outside, to obtain the first carrier collection layer 2. Exemplarily, the process of preparing the first carrier collection layer 2 is as follows: Figures 7 to 9 As shown, Figure 7 A schematic structural diagram of forming a mask layer 100 outside the first carrier collection layer 2 while preparing the first carrier collection layer 2 entirely on the first main surface. Figure 8 is a schematic diagram of a cross-sectional structure of a silicon substrate obtained after the mask layer 100 in the second region 12 and the spacing region 13 is removed regionally by laser technology, Fig. 9 Then in Figure 8 FIG. 1 is a schematic diagram of a cross-sectional structure of a silicon substrate obtained after removing the first carrier collection layer 2 of the second region 12 and the spacer region 13 by using an alkaline solution, and removing the mask layer 100 of the first region 11 by using an acid solution. The mask layer 100 of the first region 11 needs to be used to protect the structure of the first region 11 from being corroded by the alkaline solution, so that only the first carrier collection layer 2 of the second region 12 and the spacer region 13 is removed, and then the mask layer 100 of the first region 11 is removed by using an acid solution.

[0061] After obtaining the silicon substrate structure in which the first carrier collection layer 2 is provided only in the first region 11, the heavily doped layer 3 can be prepared on the outside of the first carrier collection layer 2, that is, the structure obtained after step S501 is as follows: Fig.10 shown.

[0062] Similarly, the process of preparing the second carrier collection layer 4 in step S502 includes: preparing a second intrinsic silicon-containing thin film layer and a second doped layer doped with a second element in the first area 11 and the second area 12 of the first main surface of the silicon substrate 1 from the inside to the outside to obtain the second carrier collection layer 4.

[0063] In a further optional embodiment, after step S502 , the method further includes: step S503 , preparing a conductive film layer 5 outside the second carrier collection layer 4 in the first region 11 and the second region 12 .

[0064] Below through Figures 11 to 13 The process shown in FIG. 5 is used to specifically describe the process of preparing the second carrier collection layer 4 and the conductive film layer 5 in step S502 and step S503. Fig.11 Schematic diagram of the cross-sectional structure obtained after the second carrier collection layer 4 is prepared on the entire first main surface of the silicon substrate 1. Fig.12 Schematic diagram of the cross-sectional structure of the silicon substrate obtained after preparing the entire conductive film layer 5 outside the second carrier collection layer 4, Fig.13 It is a schematic diagram of the silicon substrate structure formed after the second carrier collection layer 4 and the conductive film layer 5 of the spacing region 13 are grooved by laser technology.

[0065] In a further optional embodiment, before preparing the second carrier collection layer 4, a passivation layer 6 and an anti-reflection layer 7 may be prepared on the second main surface of the silicon substrate 1 from the inside to the outside. After step S503, metal electrodes 8 are prepared in the first region 11 and the second region 12, respectively. Through the above process, the following can be obtained: Figure 1 The back contact solar cell structure according to the embodiment of the present invention is shown.

[0066] In summary, the back-contact solar cell provided by the embodiment of the present invention can achieve current conduction between the first carrier collection layer and the heavily doped layer when the doping types are opposite by arranging a heavily doped layer outside the first carrier collection layer in the first region. At the same time, there is no need to perform laser film opening on the second carrier collection layer, and a high-low junction is formed between the heavily doped layer and the second carrier collection layer of the same doping type, and the current is conducted between the heavily doped layer and the second carrier collection layer. Laser damage to the silicon substrate caused by the laser film opening process is avoided, and the photoelectric conversion efficiency of the solar cell is effectively improved.

[0067] Embodiment 1

[0068] Step a, polishing the first main surface and the second main surface of the silicon substrate to obtain a smooth silicon substrate surface;

[0069] Step b, sequentially preparing a tunnel oxide layer and an intrinsic polysilicon layer on the first main surface of the silicon substrate by LPCVD, and forming an n-type doped layer by doping the intrinsic polysilicon with phosphorus;

[0070] Step c, preparing a heavily doped layer outside the doped polysilicon layer, and preparing a mask layer outside;

[0071] Step d, removing the mask layer on the second area and the spacer area by laser;

[0072] Step e, etching the second area and the spacer area with an alkali solution, and performing texturing after etching, while removing the mask layer on the first area with an acid solution;

[0073] Step f, forming an intrinsic silicon-containing thin film, a p-type doped layer, and a passivation layer prepared on the second main surface on the first main surface of the silicon substrate in sequence by plate-type PECVD method;

[0074] Step g, preparing an anti-reflection layer on the second main surface of the silicon substrate;

[0075] Step h, forming a conductive film layer on the first surface by PVD method;

[0076] Step i, groove the intrinsic silicon-containing film, the p-type doped layer and the conductive film layer in the spacing region;

[0077] Step j: preparing metal electrodes in the first region and the second region respectively.

[0078] Comparative Example 1

[0079] Step a, performing a texturing treatment on the silicon substrate to form a texturing structure on the first main surface and the second main surface of the silicon substrate;

[0080] Step b, depositing an oxide layer on the second main surface of the silicon substrate by using a tubular PECVD method;

[0081] Step c, polishing the first main surface of the silicon substrate to obtain a smooth silicon substrate surface;

[0082] Step d, sequentially preparing a tunnel oxide layer and an intrinsic polysilicon layer on the first main surface of the silicon substrate by LPCVD, and forming an n-type doped layer by doping the intrinsic polysilicon with phosphorus, and simultaneously preparing a mask layer outside the n-type doped layer;

[0083] Step e, removing the mask layer on the second area and the spacer area by laser;

[0084] Step f, etching the second region and the spacer region with an alkaline solution, and removing the mask layer on the first region with an acid solution;

[0085] Step g, preparing a passivation layer and an anti-reflection layer on the second main surface of the silicon substrate in sequence from the inside to the outside;

[0086] Step h, forming an intrinsic silicon-containing thin film and a p-type doped layer in sequence on the first main surface of the silicon substrate by plate-type PECVD method;

[0087] Step i, removing the intrinsic silicon-containing film and the p-type doped layer in the first region by using a laser process;

[0088] Step j, preparing a conductive film layer on the first main surface;

[0089] Step k, slotting the conductive film layer in the spacing area;

[0090] Step 1: Prepare metal electrodes in the first region and the second region respectively.

[0091] Comparative Example 2

[0092] Step a, polishing the first main surface and the second main surface of the silicon substrate to obtain a smooth silicon substrate surface;

[0093] Step b, sequentially preparing a tunnel oxide layer and an intrinsic polysilicon layer on the first main surface of the silicon substrate by LPCVD, and forming an n-type doped layer by doping the intrinsic polysilicon with phosphorus;

[0094] Step c, removing the mask layer on the second area and the spacing area by laser; Step d, etching the second area and the spacing area with alkaline solution, and performing texturing after etching, and removing the mask layer on the first area with acid solution;

[0095] Step e: forming an intrinsic silicon-containing thin film, a p-type doped layer, and a passivation layer prepared on the second main surface on the first main surface of the silicon substrate in sequence by plate-type PECVD method;

[0096] Step f, preparing an anti-reflection layer on the second main surface of the silicon substrate;

[0097] Step g, forming an intrinsic silicon-containing thin film, a p-type doped layer, and a passivation layer prepared on the second main surface on the first main surface of the silicon substrate in sequence by using a plate-type PVD method;

[0098] Step h, preparing an anti-reflection layer on the second main surface of the silicon substrate;

[0099] Step i, forming a conductive film layer on the first surface by PVD method;

[0100] Step j, slotting the conductive film layer in the spacing area;

[0101] Step k: preparing metal electrodes in the first region and the second region respectively.

[0102] The performance of the back-contact solar cells prepared in the above examples and comparative examples was tested, and the results are shown in the following table:

[0103]

[0104] From the above performance test results, it can be seen that the performance of the solar cell in the embodiment of the present invention is almost the same as that in the prior art, but no additional laser removal process is required, which not only simplifies the process flow, but also reduces the loss of the laser to the passivation film layer below, thereby improving the battery performance. Moreover, in the case of not setting a heavily doped layer, that is, only on the basis of comparative example 1 without removing the second carrier collection layer in the first region, it is impossible to effectively form the conduction of carriers, which illustrates the key role between the heavily doped layer in the embodiment of the present invention and the first carrier collection layer and the second carrier collection layer.

[0105] The embodiment of the present invention also provides the following technical solutions:

[0106] Technical solution 1. A back-contact solar cell, characterized in that it includes: a silicon substrate 1; a first carrier collection layer 2, a heavily doped layer 3, and a second carrier collection layer 4 stacked from the inside to the outside in a first area 11 of the first main surface of the silicon substrate 1; wherein the doping type of the first carrier collection layer 2 is opposite to the doping type of the heavily doped layer 3; a second carrier collection layer 4 is arranged in a second area 12 of the first main surface of the silicon substrate 1; wherein a spacing area 13 is provided between the first area 11 and the second area 12, and the doping type of the second carrier collection layer 4 is opposite to the doping type of the first carrier collection layer 2.

[0107] Technical Solution 2. The back-contact solar cell according to Technical Solution 1 is characterized in that the doping concentration of the heavily doped layer 3 is not less than 1E 19 atoms / cm 3 .

[0108] Technical Solution 3. The back-contact solar cell according to Technical Solution 1 is characterized in that it also includes: a conductive film layer 5 arranged outside the second carrier collection layer 4.

[0109] Technical Solution 4. The back-contact solar cell according to Technical Solution 1 is characterized in that the first carrier collection layer 2 includes a stacked tunneling oxide layer and a first doping layer doped with a first element; or, the first carrier collection layer 2 includes a stacked first intrinsic silicon-containing thin film layer and a first doping layer doped with a first element.

[0110] Technical Solution 5. The back-contact solar cell according to Technical Solution 1 is characterized in that the second carrier collection layer 4 includes a second intrinsic silicon-containing thin film layer and a second doping layer doped with a second element which are stacked.

[0111] Technical Solution 6. The back-contact solar cell according to Technical Solution 5 is characterized in that the doping concentration of the heavily doped layer 3 is greater than the doping concentration of the second doped layer; and / or the first intrinsic silicon-containing thin film layer and / or the second intrinsic silicon-containing thin film layer is a thin film structure composed of one or more of microcrystalline silicon, nanosilicon, amorphous silicon, silicon oxide or silicon carbide; and / or the first doped layer and / or the second doped layer and / or the heavily doped layer 3 is a thin film structure composed of one or more of microcrystalline silicon, nanosilicon, amorphous silicon, silicon oxide or silicon carbide.

[0112] Technical Solution 7. The back-contact solar cell according to Technical Solution 1 is characterized in that it also includes: a passivation layer 6 and an anti-reflection layer 7 arranged in sequence from the inside to the outside on the second main surface of the silicon substrate 1; and / or, metal electrodes 8 respectively arranged in the first area 11 and the second area 12.

[0113] Technical Solution 8. The back-contact solar cell according to Technical Solution 7 is characterized in that a passivation layer 6 is provided on the second main surface of the silicon substrate 1, and the passivation layer 6 includes a combination of at least one or more of an intrinsic silicon-containing film and a doped silicon-containing film; and / or an anti-reflection layer 7 is provided on the second main surface of the silicon substrate 1, and the anti-reflection layer 7 includes one or more of aluminum oxide, silicon nitride, silicon oxynitride and silicon oxide.

[0114] Technical Solution 9. The back-contact solar cell according to Technical Solution 4 is characterized in that the thickness of the tunneling oxide layer is 0.5 nm to 3.0 nm; and / or the thickness of the first doped layer and / or the second doped layer and / or the heavily doped layer 3 is 1 nm to 250 nm.

[0115] Technical Solution 10. The back-contact solar cell according to Technical Solution 3 is characterized in that the conductive film layer 5 is a multilayer structure of metal oxides and / or nitrides doped with one or more doping elements; wherein the metal oxide includes at least one of the following: indium oxide, tin oxide, zinc oxide, cadmium oxide, titanium nitride; the metal nitride is titanium nitride; the doping elements include at least one of the following: indium, tin, calcium, aluminum, cadmium, zinc, cerium, and fluorine.

[0116] Technical Solution 11. A method for preparing a back-contact solar cell, comprising:

[0117] Step 1, preparing a first carrier collection layer 2 and a heavily doped layer 3 in sequence from inside to outside in a first region 11 of a first main surface of a silicon substrate 1;

[0118] Step 2, preparing a second carrier collection layer 4 in the first region 11 and the second region 12 of the first main surface of the silicon substrate 1;

[0119] The first regions 11 and the second regions 12 are arranged alternately, and a spacing region 13 is provided between adjacent first regions 11 and second regions 12 ; the doping type of the first carrier collection layer 2 is opposite to the doping type of the heavily doped layer 3 .

[0120] Technical Solution 12. The preparation method according to Technical Solution 11 is characterized in that, after step 2, it further comprises:

[0121] Step 3: preparing a conductive thin film layer 5 outside the second carrier collection layer 4 in the first region 11 and the second region 12 .

[0122] Technical Solution 13. The preparation method according to Technical Solution 11 is characterized in that step 1 comprises:

[0123] A tunneling oxide layer and a first doping layer doped with a first element are sequentially prepared on a first main surface of a silicon substrate 1 from inside to outside to obtain a first carrier collection layer 2;

[0124] or,

[0125] A first intrinsic silicon-containing thin film layer and a first doped layer doped with a first element are sequentially prepared on the first main surface of the silicon substrate 1 from inside to outside to obtain a first carrier collection layer 2.

[0126] Technical Solution 14. The preparation method according to Technical Solution 11 is characterized in that step 2 comprises:

[0127] A second intrinsic silicon-containing thin film layer and a second doped layer doped with a second element are sequentially prepared in the first region 11 and the second region 12 of the first main surface of the silicon substrate 1 from inside to outside to obtain a second carrier collection layer 4.

[0128] Technical Solution 15. The preparation method according to Technical Solution 11 is characterized in that it also includes:

[0129] A passivation layer 6 and an anti-reflection layer 7 are sequentially formed on the second main surface of the silicon substrate 1 from inside to outside;

[0130] And / or, metal electrodes 8 are prepared in the first region 11 and the second region 12 respectively.

[0131] The introduction provided in the above steps is only used to help understand the structure, method and core idea of ​​the present invention. For ordinary technicians in this technical field, without departing from the principle of the present invention, several improvements and modifications can be made to the present invention, and these improvements and modifications also belong to the scope of protection of the claims of the present invention.

Claims

1. A back contact solar cell, characterized in that: include: Silicon substrate (1); A first region (11) of the first main surface of the silicon substrate (1) comprises a first carrier collection layer (2), a heavily doped layer (3) and a second carrier collection layer (4) stacked from inside to outside; wherein the doping type of the first carrier collection layer (2) is opposite to the doping type of the heavily doped layer (3); A second carrier collection layer (4) disposed in a second region (12) of the first main surface of the silicon substrate (1); There is a spacing region (13) between the first region (11) and the second region (12), and the doping type of the second carrier collection layer (4) is opposite to the doping type of the first carrier collection layer (2).

2. The back contact solar cell according to claim 1, characterized in that: The doping concentration of the heavily doped layer (3) is not less than 1E 19 atoms / cm 3 .

3. The back contact solar cell according to claim 1, characterized in that: Also includes: A conductive film layer (5) is arranged outside the second carrier collection layer (4).

4. The back contact solar cell according to claim 1, characterized in that: The first carrier collection layer (2) comprises a stacked tunneling oxide layer and a first doping layer doped with a first element; or the first carrier collection layer (2) comprises a stacked first intrinsic silicon-containing thin film layer and a first doping layer doped with a first element.

5. The back contact solar cell according to claim 1, characterized in that: The second carrier collection layer (4) comprises a second intrinsic silicon-containing thin film layer and a second doping layer doped with a second element which are stacked.

6. The back contact solar cell according to claim 5, characterized in that: The doping concentration of the heavily doped layer (3) is greater than the doping concentration of the second doping layer; and / or, The first intrinsic silicon-containing thin film layer and / or the second intrinsic silicon-containing thin film layer is a thin film structure composed of one or more of microcrystalline silicon, nano silicon, amorphous silicon, silicon oxide or silicon carbide; and / or, The first doped layer and / or the second doped layer and / or the heavily doped layer (3) is a thin film structure composed of one or more of microcrystalline silicon, nano silicon, amorphous silicon, silicon oxide or silicon carbide.

7. The back contact solar cell according to claim 1, characterized in that: Also includes: A passivation layer (6) and an anti-reflection layer (7) are sequentially arranged on the second main surface of the silicon substrate (1) from the inside to the outside; and / or, Metal electrodes (8) are respectively arranged in the first region (11) and the second region (12).

8. The back contact solar cell according to claim 7, characterized in that: A structure in which a passivation layer (6) is provided on the second main surface of the silicon substrate (1), wherein the passivation layer (6) comprises a combination of at least one or more of an intrinsic silicon-containing film and a doped silicon-containing film; and / or, A structure in which an anti-reflection layer (7) is arranged on the second main surface of the silicon substrate (1), wherein the anti-reflection layer (7) comprises one or more of aluminum oxide, silicon nitride, silicon oxynitride and silicon oxide.

9. The back contact solar cell according to claim 4, characterized in that: The thickness of the tunnel oxide layer is 0.5nm to 3.0nm; and / or, The thickness of the first doping layer and / or the second doping layer and / or the heavily doped layer (3) is 1 nm to 250 nm.

10. A method for preparing a back contact solar cell, characterized in that: include: Step 1, preparing a first carrier collection layer (2) and a heavily doped layer (3) in sequence from the inside to the outside in a first region (11) of a first main surface of a silicon substrate (1); Step 2, preparing a second carrier collection layer (4) in the first region (11) and the second region (12) of the first main surface of the silicon substrate (1); The first regions (11) and the second regions (12) are arranged alternately, and a spacing region (13) is provided between adjacent first regions (11) and second regions (12); and the doping type of the first carrier collection layer (2) is opposite to the doping type of the heavily doped layer (3).

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