Back contact battery and preparation method thereof

Abstract

The invention discloses a back contact cell and a preparation method thereof, and relates to the technical field of solar cell manufacturing, and the preparation method comprises the steps: a first carrier collection layer and an insulation isolation layer are prepared in a partial region of a first main surface of a silicon substrate from inside to outside in sequence, and the partial region comprises a spacer region and a first functional region located at the edge; sequentially preparing a second carrier collection layer, a reflection increasing layer and a damage layer on the first main surface of the silicon substrate from inside to outside; the reflection increasing layer is of a structure of which the refractive index is gradually increased along the direction far away from the silicon substrate; removing the damaged layer corresponding to the first functional area through laser, and reflecting the laser through the reflection increasing layer; and removing the residual damage layer, the reflection increasing layer and the second carrier collecting layer corresponding to the first functional region on the first main surface in a chemical etching mode. According to the embodiment, the damaged layer is used for absorbing part of laser energy, the reflection increasing layer is used for reflecting the laser penetrating through the damaged layer, transmission of the laser is reduced, and efficiency loss in the preparation process is reduced.

Description

Technical Field

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

[0002] In the existing back contact cell preparation process, laser is usually used to open the film to prepare P and N regions in different areas of the silicon substrate. However, the existing laser process usually directly scans the removed part. Due to the strong transmittance of the laser and the high heat generated, it will cause a certain degree of thermal damage to other structures both vertically and horizontally, affecting the passivation effect of the carrier collection layer. Summary of the invention

[0003] In view of this, an embodiment of the present invention provides a back-contact battery and a method for preparing the same, wherein a reflection-enhancing layer and a damage layer are arranged on the outside of the second carrier collection layer, so that during the laser opening of the first functional area, the damage layer is used to absorb part of the laser energy, and the reflection-enhancing layer is used to reflect the laser passing through the damage layer, thereby reducing the transmission of the laser and reducing the efficiency loss in the battery preparation process.

[0004] In order to solve the above technical problems, the present invention provides the following technical solutions:

[0005] In a first aspect, the present invention provides a method for preparing a back-contact battery, comprising: step 1, preparing a first carrier collection layer and an insulating isolation layer in sequence from the inside to the outside on a partial area of ​​a first main surface of a silicon substrate, wherein the partial area includes a spacing area and a first functional area located at the edge; step 2, preparing a second carrier collection layer, a reflection enhancement layer and a damage layer in sequence from the inside to the outside on the first main surface of the silicon substrate; the reflection enhancement layer is a structure with a refractive index increasing in a direction away from the silicon substrate; step 3, removing the damage layer corresponding to the first functional area by laser, and reflecting the laser by the reflection enhancement layer; step 4, removing the remaining damage layer, the reflection enhancement layer and the second carrier collection layer corresponding to the first functional area on the first main surface by chemical etching to obtain a second functional area adjacent to the spacing area.

[0006] Optionally, the step 1 includes: step 11, preparing a first carrier collection layer and an insulating isolation layer in sequence from the inside to the outside on the first main surface of the silicon substrate; step 12, using a laser to remove the first carrier collection layer and the insulating isolation layer corresponding to the second functional area.

[0007] Optionally, step 11 includes: preparing a tunneling oxide layer and a first doping layer in sequence from the inside to the outside on the first main surface of the silicon substrate to obtain a first carrier collection layer; or, preparing a first intrinsic silicon-containing thin film layer and a first doping layer in sequence from the inside to the outside on the first main surface of the silicon substrate to obtain a first carrier collection layer.

[0008] Optionally, step 2 includes: preparing a second intrinsic silicon-containing thin film layer and a second doping layer in sequence from the inside to the outside on the first main surface of the silicon substrate to obtain a second carrier collection layer.

[0009] Optionally, the reflection enhancement layer is a multi-layer structure, including: a silicon oxide layer, a silicon oxynitride layer, and a silicon nitride layer; wherein the refractive indices of the silicon oxide layer, the silicon oxynitride layer, and the silicon nitride layer increase in sequence.

[0010] Optionally, after step 4, the method further includes: step 5, preparing a passivation layer and an anti-reflection layer on the second main surface of the silicon substrate from the inside to the outside; wherein the anti-reflection layer includes an ultraviolet conversion layer for converting ultraviolet light into visible light.

[0011] Optionally, after step 4, the method further includes: step 6, preparing a conductive film layer on the first main surface; and step 7, grooving the area of ​​the conductive film layer corresponding to the spacing area to form a first conductive film layer and a second conductive film layer that are not connected.

[0012] Optionally, before step 1, the method further includes: performing alkali texturing on the first main surface and the second main surface of the silicon substrate, and polishing the first main surface using a mask layer arranged on the second main surface of the silicon substrate.

[0013] Optionally, step 4 includes: step 41, using an acid solution to remove the reflection enhancing layer of the first functional area; step 42, using an alkaline solution to remove the second carrier collection layer corresponding to the first functional area, while removing the damaged layer of the second functional area and the spacing area; step 43, using an acid solution to remove the reflection enhancing layer corresponding to the second functional area and the spacing area, while removing the insulating isolation layer of the first functional area.

[0014] In a second aspect, the present invention provides a back-contact battery prepared by any of the above-mentioned preparation methods, comprising: a silicon substrate; a first carrier collection layer arranged in a first functional area on the first main surface of the silicon substrate; a second carrier collection layer arranged in a second functional area on the first main surface of the silicon substrate; wherein a spacing area is arranged between the first functional area and the second functional area, and the first functional area and the second functional area are arranged alternately; the conductivity type of the first carrier collection layer is opposite to the conductivity type of the second carrier collection layer; wherein the first carrier collection layer extends from the first functional area to the spacing area; an insulating isolation layer is also arranged in the spacing area, and the insulating isolation layer is arranged on the outside of the first carrier collection layer; the second carrier collection layer extends from the second functional area to the outside of the insulating isolation layer.

[0015] The technical solution of the first aspect of the above invention has the following advantages or beneficial effects: by arranging a reflection-enhancing layer and a damaged layer on the outside of the second carrier collection layer, the damaged layer is used to absorb part of the laser energy during the laser film opening of the first functional area, and the reflection-enhancing layer is used to reflect the laser passing through the damaged layer, thereby reducing the transmission of the laser and reducing the efficiency loss in the battery preparation process. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The accompanying drawings are used to better understand the present invention and do not constitute an improper limitation of the present invention.

[0017] Figure 1 is a schematic flow chart of a method for preparing a back contact battery according to an embodiment of the present invention;

[0018] Figure 2 is a schematic diagram of a cross-sectional structure of a silicon substrate obtained after polishing the first main surface according to an embodiment of the present invention;

[0019] Figure 3 is a schematic flow chart of a specific preparation method according to step S101 of an embodiment of the present invention;

[0020] Figure 4 is a schematic diagram of a cross-sectional structure of a silicon substrate obtained after step S301 according to an embodiment of the present invention;

[0021] Figure 5 is a schematic diagram of a cross-sectional structure of a silicon substrate obtained after step S302 according to an embodiment of the present invention;

[0022] Figure 6 is a schematic diagram of a cross-sectional structure of a silicon substrate obtained after step S102 according to an embodiment of the present invention;

[0023] Figure 7is a schematic diagram of a cross-sectional structure of a silicon substrate obtained after step S103 according to an embodiment of the present invention;

[0024] Figure 8 is a schematic flow chart of a specific preparation method of step S104 according to an embodiment of the present invention;

[0025] Fig. 9 is a schematic diagram of a cross-sectional structure of a silicon substrate obtained after step S803 according to an embodiment of the present invention;

[0026] Fig.10 is a schematic diagram of a cross-sectional structure of a silicon substrate after a passivation layer 7 and an anti-reflection layer 8 are prepared according to an embodiment of the present invention;

[0027] Fig.11 is a schematic flow chart of the preparation method after step S105 according to an embodiment of the present invention;

[0028] Fig.12 is a schematic diagram of a cross-sectional structure of a silicon substrate obtained after step S1101 according to an embodiment of the present invention;

[0029] Fig.13 is a schematic diagram of a cross-sectional structure of a silicon substrate obtained after step S1102 according to an embodiment of the present invention;

[0030] Fig.14 Schematic diagram of the overall structure of a back contact battery according to an embodiment of the present invention.

[0031] The reference numerals are as follows:

[0032] 1-silicon substrate; 11-spacer region; 12-first functional region; 13-second functional region;

[0033] 2-first carrier collection layer; 3-insulating isolation layer; 4-second carrier collection layer; 5-reflection enhancement layer; 6-damage layer; 7-passivation layer; 8-anti-reflection layer; 81-ultraviolet light conversion layer; 9-conductive film layer; 91-first conductive film layer; 92-second conductive film layer; 10-metal electrode;

[0034] 100 - mask layer; 200 - spacing grooves; 300 - first silicon glass layer. DETAILED DESCRIPTION

[0035] A solar cell is a photoelectric semiconductor wafer 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 to be 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.

[0036] In the existing back contact battery preparation process, it is necessary to first prepare the first carrier collection layer 2 and the insulating isolation layer 3 on the first functional area 12 and the spacing area 11, and on the basis of this structure, prepare a whole layer of the second carrier collection layer 4, and use a laser process to remove the second carrier collection layer 4 and the insulating isolation layer 3 on the first functional area 12, so as to obtain a first functional area 12 containing only the first carrier collection layer 2 and a second functional area 13 containing only the second carrier collection layer 4, and at the same time, the insulating isolation layer 3 is retained in the spacing area 11 between the first functional area 12 and the second functional area 13. However, while the laser process selectively removes the second carrier collection layer 4 and the insulating isolation layer 3 on the first functional area 12, its strong transmittance and the high heat generated will inevitably penetrate the first carrier collection layer 2 in the longitudinal direction and the second carrier collection layer 4 in the transverse direction. Specifically, the heat generated by the laser process will cause the concentration of doped elements in the first carrier collection layer 2 and the second carrier collection layer 4 to be redistributed, thereby affecting the passivation performance of the first carrier collection layer 2 and the second carrier collection layer 4. Therefore, the present invention provides a back-contact battery and a preparation method thereof that can reduce the impact of the laser process.

[0037] In one embodiment of the present invention, Figure 1 As shown, this embodiment provides a method for preparing a back contact battery, and the preparation method may include the following steps:

[0038] Step S101, preparing a first carrier collection layer 2 and an insulating isolation layer 3 in sequence from the inside to the outside on a partial area of ​​the first main surface of the silicon substrate 1, wherein the partial area includes a spacing area 11 and a first functional area 12 located at the edge;

[0039] Step S102, on the first main surface of the silicon substrate 1, a second carrier collection layer 4, a reflection enhancement layer 5 and a damaged layer 6 are sequentially prepared from the inside to the outside; the reflection enhancement layer 5 is a structure with a refractive index increasing in a direction away from the silicon substrate 1;

[0040] Step S103, removing the damaged layer 6 corresponding to the first functional area 12 by laser, and reflecting the laser by the reflection enhancement layer 5;

[0041] Step S104 , removing the remaining damaged layer 6 , the reflection enhancement layer 5 and the second carrier collection layer 4 corresponding to the first functional region 12 on the first main surface by chemical etching, to obtain the second functional region 13 adjacent to the spacing region 11 .

[0042] Among them, the reflection-enhancing layer 5 and the damaged layer 6 in step S102 and step S103 are the main inventive points of the embodiment of the present invention. Specifically, during the film opening process of the laser process, the damaged layer 6 is used to directly contact the laser and absorb most of the laser energy, and is ultimately not retained in the battery structure of the back contact battery. Therefore, the damaged layer 6 can select a material that is easier to absorb energy, such as an intrinsic amorphous silicon layer. As for the reflection-enhancing layer 5, its function is to further reflect the laser that is not absorbed by the damaged layer 6, thereby further reducing the laser energy penetrating into the second carrier collection layer 4 and the first carrier collection layer 2. Therefore, in an optional embodiment, the present invention sets the reflection-enhancing layer 5 as a multilayer structure, and the refractive index of each layer structure increases successively along the direction away from the silicon substrate 1, that is, the laser will first pass through the layer structure with the highest refractive index, and then pass through the layer structure with a lower refractive index. It can be understood that when light is incident from a high refractive index medium to a low refractive index medium, by setting a multilayer structure with a refractive index that increases successively, the reflected laser energy can be effectively increased, thereby reducing the penetration of the laser energy. In a further optional embodiment, the more layers of the reflection enhancement layer 5, the better the effect of laser reflection, and the refraction angle of the laser is affected by the material and thickness of the layer structure. According to actual needs, a specific thickness and a specific material can be set for each layer structure to achieve a better reflection effect. In a further optional embodiment, the reflection enhancement layer 5 is a multilayer structure, including: a silicon oxide layer, a silicon oxynitride layer, and a silicon nitride layer; wherein the refractive indexes of the silicon oxide layer, the silicon oxynitride layer, and the silicon nitride layer increase in sequence.

[0043] In order to remove the damage to the silicon substrate 1 formed during the cutting process, before step S101, the first main surface of the silicon substrate 1 needs to be polished to improve the quality of the overall back contact battery. Therefore, in an optional embodiment, before step S101, it also includes: performing a texturing treatment on the first main surface and the second main surface of the silicon substrate 1, and polishing the first main surface using the mask layer 100 set on the second main surface of the silicon substrate 1. Specifically, the texturing treatment can be a commonly used alkali texturing process, Figure 2 The cross-sectional structure of the silicon substrate obtained by the above process, wherein the back side of the silicon substrate is the first main surface, and the front side of the silicon substrate is the second main surface. Specifically, the mask layer 100 can be one or more of silicon oxide, silicon nitride, or silicon oxynitride.

[0044] Below, in Figure 2 In an optional embodiment, in step S101, the first carrier collection layer 2 and the insulating isolation layer 3 are usually prepared on the entire first main surface, and then the first carrier collection layer 2 and the insulating isolation layer 3 are prepared only in a part of the area by laser removal. That is, step S101 can be as follows Figure 3 As shown, specifically including:

[0045] Step S301, preparing a first carrier collection layer 2 and an insulating isolation layer 3 in sequence from the inside to the outside on the first main surface of the silicon substrate 1;

[0046] Step S302 , using laser to remove the first carrier collection layer 2 and the insulating isolation layer 3 corresponding to the second functional region 13 .

[0047] It should be noted that, while the first carrier collection layer 2 and the insulating isolation layer 3 are removed by laser in step S302, the second functional region 13 of the silicon substrate 1 is actually damaged due to the high transmittance and high energy of the laser. Therefore, in an optional embodiment, after step S302, the surface of the silicon substrate 1 exposed in the second functional region 13 is etched with an alkaline solution to form a polished surface with a tower base, so as to eliminate the damage to the surface of the silicon substrate 1 caused by the laser, and then the second carrier collection layer 4 is prepared.

[0048] For the first carrier collection layer 2, two different stacked structures can be used to form a passivation structure. In an optional embodiment, the first carrier collection layer 2 includes a stacked tunneling oxide layer and a first doping layer doped with a first element. In another optional embodiment, the first carrier collection layer 2 includes a stacked first intrinsic silicon-containing thin film layer and a first doping film doped with a first element. Specifically, when a high-temperature process is used for preparation, the first carrier collection layer 2 in the first region can be set as a tunneling oxide layer and a first doping layer doped with a first element; and when a low-temperature process is used for preparation, the first carrier collection layer 2 in the first region can be set as a first intrinsic silicon-containing thin film layer and a first doping layer doped with a first element. Therefore, the process of step S301 can specifically include: preparing a tunneling oxide layer and a first doping layer in sequence from the inside to the outside on the first main surface of the silicon substrate 1 to obtain the first carrier collection layer 2; or, preparing a first intrinsic silicon-containing thin film layer and a first doping layer in sequence from the inside to the outside on the first main surface of the silicon substrate 1 to obtain the first carrier collection layer 2. As for the preparation process of the second carrier collection layer 4, in an optional embodiment, step S102 may include: preparing a second intrinsic silicon-containing thin film layer and a second doping layer in sequence from the inside to the outside on the first main surface of the silicon substrate 1 to obtain the second carrier collection layer 4.

[0049] It can be understood that while the first element is diffused to form the first doped layer, a first silicon glass layer 300 doped with the first element is also formed synchronously outside the first doped layer, that is, in an optional embodiment, the first carrier collection layer 2 also includes a first silicon glass layer 300 disposed outside the first doped layer. That is, the cross-sectional structure of the silicon substrate obtained after step S301 is as follows: Figure 4 As shown, the cross-sectional structure of the silicon substrate obtained after step S302 is as follows Figure 5 As shown. Figure 4 and Figure 5 It can be seen that the first carrier collection layer 2 and the insulating isolation layer 3 are prepared in sequence from the inside to the outside in the spacing area 11 and the first functional area 12 of the first main surface of the silicon substrate 1, and the second functional area 13 is a smooth silicon substrate 1, which is more suitable for the preparation of the second carrier collection layer 4.

[0050] Below Figure 6 and Figure 7 Taking the structure of as an example, the process of step S102 and step S103 is described, wherein, Figure 6 is a cross-sectional structure diagram of the silicon substrate obtained after step S102, Figure 7 is a cross-sectional structure diagram of the silicon substrate obtained after step S103. Figure 6As shown, after step S102, the second carrier collection layer 4, the reflection enhancement layer 5 and the damaged layer 6 are prepared in sequence from the inside to the outside on the entire first main surface of the silicon substrate 1. Although only the first functional area 12 needs to be laser opened later, in order to remove other layer structures only by chemical etching in step S104 and reduce the transfer of lateral energy during the laser opening process, the embodiment of the present invention utilizes the reflection enhancement layer 5 and the damaged layer 6 in the second functional area 13 and the spacing area 11 to further protect the second carrier collection layer 4.

[0051] In an optional embodiment, when the reflection enhancement layer 5 is a silicon oxide layer, a silicon oxynitride layer, and a silicon nitride layer with successively increasing refractive indices, and the damaged layer 6 is an intrinsic amorphous silicon layer, the process of removing the damaged layer 6, the reflection enhancement layer 5, and the second carrier collection layer 4 by chemical etching in step S104 can be as follows: Figure 8 As shown, specifically including:

[0052] Step S801, removing the reflection enhancement layer 5 in the first functional area 12 by using an acid solution;

[0053] Step S802, using an alkaline solution to remove the second carrier collection layer 4 corresponding to the first functional region 12, while removing the damaged layer 6 in the second functional region 13 and the spacing region 11;

[0054] Step S803 , using an acid solution to remove the reflection enhancement layer 5 corresponding to the second functional region 13 and the spacing region 11 , while removing the insulating isolation layer 3 of the first functional region 12 .

[0055] The acid solution may be a hydrofluoric acid solution. The laser process in step S103 can remove only the damaged layer 6 corresponding to the first functional area 12 by setting the scanning width and scanning position, while leaving the damaged layer 6 in the remaining areas. Since the damaged layer 6 is an intrinsic amorphous silicon layer, the speed of reacting with the acid solution is very slow, so the damaged layer 6 can actually be used as a protective layer to protect the second functional area 13 and the spacing area 11, so that when the first main surface is cleaned with hydrofluoric acid, only the reflective enhancement layer 5 composed of the stacked silicon oxide layer, silicon oxynitride layer, and silicon nitride layer is washed away. Furthermore, the intrinsic amorphous silicon layer and the doped polysilicon layer are very easy to react with alkaline solution, especially sodium hydroxide solution. In step S802, when the first main surface is cleaned with alkaline solution, the second carrier collection layer 4 corresponding to the first functional area 12 and the damaged layer 6 of the second functional area 13 and the spacing area 11 are simultaneously cleaned, and the reflection enhancement layer 5 in the second functional area 13 and the spacing area 11 that cannot react with the alkaline solution is exposed, and finally cleaned with the acid solution in step S803. In step S803, the first silicon glass layer 300 of the first functional area 12 is also removed by the acid solution, leaving only the combination of the tunneling oxide layer and the first doped layer or the combination of the first intrinsic silicon-containing thin film layer and the first doped layer.

[0056] It can be seen that by repeatedly using the acid solution and the alkaline solution, the redundant structures on the first main surface of the silicon substrate 1 can be removed from the outside to the inside, so as to obtain Fig. 9 The cross-sectional structure of the silicon substrate is shown in FIG. Fig. 9 As shown, the embodiment of the present invention ultimately only needs to retain the first carrier collection layer 2 on the first functional area 12 and the second carrier collection layer 4 on the second functional area 13, while the first silicon glass layer 300 in the spacing area will be retained inside the spacing area because it cannot directly contact the acid solution. In addition, the acid solution is also corrosive to the mask layer 100 on the second main surface of the silicon substrate 1. Therefore, after being treated with the acid solution, the mask layer 200 on the second main surface of the silicon substrate 1 is also removed accordingly. Fig. 9 In the embodiment, the second main surface of the silicon substrate 1 is an exposed velvet structure.

[0057] In an optional embodiment, Fig. 9 On the basis of the structure (i.e. after step S104), the preparation method provided by the present invention also includes: step S105, preparing a passivation layer 7 and an anti-reflection layer 8 in sequence from the inside to the outside on the second main surface of the silicon substrate 1; wherein the anti-reflection layer 8 includes an ultraviolet conversion layer for converting ultraviolet light into visible light.

[0058] The silicon substrate structure with the passivation layer 7 and the anti-reflection layer 8 prepared as above is as follows Fig.10As shown. Specifically, the anti-reflection layer 8 may include a multi-layer structure, one of which is an ultraviolet conversion layer. In order to achieve the purpose of converting ultraviolet light into visible light, the ultraviolet conversion layer in the embodiment of the present invention is preferably a layer structure containing carbon quantum dots or silicon quantum dots, and the conversion of visible light is achieved through quantum dots. For the layer structure of the anti-reflection layer 8 except the ultraviolet conversion layer 81, in an optional embodiment, it can be composed of one or more of aluminum oxide, silicon nitride, silicon oxynitride and silicon oxide. As for the material of the passivation layer 7, in an optional embodiment, it can be a combination of at least one or more of an intrinsic silicon-containing film and a doped silicon-containing film.

[0059] In a further optional embodiment, after step S105, Fig.11 As shown, including:

[0060] Step S1101, preparing a conductive film layer 9 on the first main surface;

[0061] Step S1102 , grooves are formed in the conductive film layer 9 in the region corresponding to the spacing region 11 to form a first conductive film layer 91 and a second conductive film layer 92 that are not connected.

[0062] Specifically, Fig.12 FIG. 4 shows a schematic diagram of the cross-sectional structure of the silicon substrate obtained in step S1101. Fig.13 FIG. 4 shows a schematic diagram of the cross-sectional structure of the silicon substrate obtained in step S1102. Fig.12 and Fig.13 It can be seen that the first conductive film layer 91 and the second conductive film layer 92 are respectively used to lead out the carriers in the first functional area 12 and the second functional area 13, and finally they are led out by electrodes of different polarities. Therefore, the first functional area 12 and the second functional area 13 cannot be connected, and a spacing area 11 needs to be set to ensure that no short circuit occurs between the positive and negative poles.

[0063] In a further optional embodiment, after step S1102, the method further includes: metal electrodes 10 are respectively arranged in the first functional area 12 and the second functional area 13. Thus, the overall structural diagram of the back contact battery provided by the embodiment of the present invention is obtained, as shown in FIG. Fig.14 shown.

[0064] In summary, the method for preparing a back-contact battery provided in an embodiment of the present invention sets a reflection-enhancing layer and a damage layer on the outside of the second carrier collection layer, so that during the laser opening of the first functional area, the damage layer is used to absorb part of the laser energy, and the reflection-enhancing layer is used to reflect the laser passing through the damage layer, thereby reducing the transmission of the laser and reducing the efficiency loss in the battery preparation process.

[0065] Below is still Fig.14Taking the back contact battery structure provided by the present invention as an example, the structure specifically includes:

[0066] A silicon substrate 1; a first carrier collecting layer 2 is arranged in a first functional area 12 of the first main surface of the silicon substrate 1; a second carrier collecting layer 4 is arranged in a second functional area 13 of the first main surface of the silicon substrate 1; wherein a spacing area 11 is arranged between the first functional area 12 and the second functional area 13, and the first functional areas 12 and the second functional areas 13 are arranged alternately; the conductivity type of the first carrier collecting layer 2 is opposite to the conductivity type of the second carrier collecting layer 4; wherein the first carrier collecting layer 2 extends from the first functional area 12 to the spacing area 11; an insulating isolation layer 3 is also arranged in the spacing area 11, and the insulating isolation layer 3 is arranged outside the first carrier collecting layer 2; the second carrier collecting layer 4 extends from the second functional area 13 to the outside of the insulating isolation layer 3.

[0067] The insulating isolation layer 3 is used to isolate the first carrier collection layer 2 and the second carrier collection layer 4 to form a conductive channel. In an optional embodiment, the insulating isolation layer 3 is made of a dielectric material with extremely poor conductivity, specifically including one or more of silicon oxide, silicon nitride, and silicon oxynitride.

[0068] In order to guide the carriers of the first functional area 12 and the second functional area 13, in an optional embodiment, the back contact battery provided by the present invention further includes: a conductive film layer 9 arranged outside the first carrier collection layer 2 and the second carrier collection layer 4. The conductive film layer 9 is used to guide the carriers in the first carrier collection layer 2 or the second carrier collection layer 4 connected thereto to realize the transmission of current.

[0069] However, since the first functional region 12 and the second functional region 13 correspond to different electrodes respectively, the portions of the conductive film layer 9 corresponding to the first functional region 12 and the second functional region 13 cannot be connected, so the back contact battery provided by the present invention also includes: a spacing groove 200 located outside the insulating isolation layer 3; wherein the spacing groove 200 is used to separate the conductive film layer 9 into a first conductive film layer 91 and a second conductive film layer 92. Among them, the first conductive film layer 91 corresponds to the second functional region 13, and the second conductive film layer 92 corresponds to the first functional region 12. It can be understood that the purpose of the spacing groove 200 is to disconnect the first conductive film layer 91 and the second conductive film layer 92 to prevent electrical connection between the P region and the N region, so the specific slot position has little effect on the overall battery performance, so it is sufficient to ensure that the spacing groove 200 is set in the spacing region 11, and the specific slot position is not specifically limited by the present invention.

[0070] As for the specific material of the conductive film layer 9, in an optional embodiment, the conductive film layer 9 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. By doping different metal oxides or nitrides and controlling the doping concentration, conductive film layers with different work functions can be obtained, which can be specifically set according to actual needs, and the present invention does not make specific limitations.

[0071] It is understandable that, since the second carrier collection layer 4 also has a certain conductivity, in order to prevent the first functional region 12 and the second functional region 13 from being connected through the second carrier collection layer 4 of the spacing region 11, in an optional embodiment, while the spacing groove 200 separates the first conductive film layer 91 and the second conductive film layer 92, the part of the second carrier collection layer 4 extending to the outside of the insulating isolation layer 3 is also divided into two sections. It can be seen that the embodiment of the present invention can effectively isolate the electrical connection between the P region and the N region through the combination of the spacing groove 200 and the insulating isolation layer 3.

[0072] For the first carrier collection layer 2, two different stacked structures can be used to form a passivation structure. 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. 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. Specifically, when a high-temperature process is used for preparation, the first carrier collection layer 2 in the first region can be set as a tunneling oxide layer and a first doped layer doped with a first element; and when a low-temperature process is used for preparation, the first carrier collection layer 2 in the first region can be set as a first intrinsic silicon-containing thin film layer and a first doped layer doped with a first element. As 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.

[0073] Further, for the material of the first carrier collection layer 2 and the second carrier collection layer 4, in an optional embodiment, the first intrinsic silicon-containing thin film layer and / or the second intrinsic silicon-containing thin film layer can be a thin film structure composed of one or more of microcrystalline silicon, nanosilicon, amorphous silicon, silicon oxide or silicon carbide; the first doped silicon-containing thin film can be a thin film structure composed of one or more of polycrystalline silicon, microcrystalline silicon, nanosilicon, amorphous silicon, silicon oxide or silicon carbide; the second doped layer can be a thin film structure composed of one or more of microcrystalline silicon, nanosilicon, amorphous silicon, silicon oxide or silicon carbide.

[0074] In a further optional embodiment, the thickness of the tunnel oxide layer is 0.5nm to 3.0nm, such as 0.5nm, 1.0nm, 1.5nm, 2.0nm, 2.5nm, 3.0nm, etc.; and / or, the thickness of the first doped layer is 10nm to 300nm, such as 10nm, 50nm, 100nm, 150nm, 200nm, 250nm, 300nm, etc.; and / or, the thickness of the second doped layer is 10nm to 300nm, such as 10nm, 20nm, 30nm, 100nm, 200nm, 300nm, etc. In order to ensure the concentration of the doping element, the thickness of the doped polysilicon layer is usually large, but too large a thickness will cause parasitic absorption of sunlight, so it is more appropriate to set the thickness of the doped polysilicon layer to 50nm to 300nm.

[0075] In an optional embodiment, the back contact cell provided by the present invention further comprises: a passivation layer 7 and an anti-reflection layer 8 arranged sequentially from the inside to the outside on the second main surface of the silicon substrate 1, wherein the anti-reflection layer 8 comprises an ultraviolet light conversion layer for converting ultraviolet light into visible light. Fig.14 In the embodiment, the first main surface is the back side of the silicon substrate 1, and the second main surface is the front side of the silicon substrate 1. In order to reduce the reflectivity of the passivation layer 7 and the anti-reflection layer 8, in an optional embodiment, the silicon substrate 1 may be textured first, and then the passivation layer 7 and the anti-reflection layer 8 may be prepared on the textured surface.

[0076] As for the materials of the passivation layer 7 and the anti-reflection layer 8, in an optional embodiment, the passivation layer 7 can be a combination of at least one or more of an intrinsic silicon-containing film and a doped silicon-containing film; the material of the ultraviolet light conversion layer has been described in the preparation method part and will not be repeated here, and the part of the anti-reflection layer 8 other than the ultraviolet light conversion layer can include one or more of aluminum oxide, silicon nitride, silicon oxynitride and silicon oxide. The ultraviolet light conversion layer is one or more of carbon quantum dots, silicon quantum dots and germanium quantum dots, and its size is 1 to 20nm.

[0077] In an optional embodiment, the back contact battery provided by the present invention further includes: metal electrodes 10 respectively disposed in the first functional area 12 and the second functional area 13. Specifically, the metal electrodes 10 can be printed by conventional methods.

[0078] In summary, the back-contact battery prepared by the preparation method provided by the embodiment of the present invention, by setting a reflection enhancement layer and a damage layer on the outside of the second carrier collection layer, so that during the laser opening of the first functional area, the damage layer is used to absorb part of the laser energy, and the reflection enhancement layer is used to reflect the laser passing through the damage layer, thereby reducing the transmission of the laser and reducing the efficiency loss in the battery preparation process.

[0079] Embodiment 1

[0080] 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;

[0081] Step b, depositing a mask layer on the second main surface of the silicon substrate by using a tubular PECVD method; wherein the mask layer is silicon oxide;

[0082] Step c, polishing the first main surface of the silicon substrate to obtain a smooth silicon substrate surface;

[0083] Step d, sequentially preparing a tunnel oxide layer and an intrinsic polysilicon on the first main surface of the silicon substrate by LPCVD, and forming an n-type doped layer by phosphorus-doping the intrinsic polysilicon, and simultaneously forming an n-type silicon glass layer on the outside of the n-type doped layer, and preparing an insulating isolation layer on the outside of the n-type silicon glass layer by tubular PECVD;

[0084] Step e, removing the tunneling oxide layer and the n-type doping layer on the second region by laser, forming an n-type silicon glass layer and an insulating isolation layer;

[0085] Step f, etching the second area with alkaline solution;

[0086] Step g, forming an intrinsic silicon-containing thin film, a p-type doped layer, a reflection-enhancing layer and a damaged layer in sequence on the first main surface of the silicon substrate by plate-type PECVD; wherein the reflection-enhancing layer is a three-layer structure (silicon oxide layer, silicon oxynitride layer and silicon nitride layer) with a refractive index increasing in a direction away from the silicon substrate, and the refractive index ratio of the three-layer structure is 1.5:1.7:2.1;

[0087] Step h, removing the damaged layer on the first region by laser, and removing the remaining damaged layer, the reflection enhancement layer, and the intrinsic silicon-containing film and the p-type doped layer corresponding to the first functional region on the first main surface by chemical etching, to obtain a second functional region adjacent to the spacing region;

[0088] Step i, forming a passivation layer and an anti-reflection layer in sequence on the second main surface of the silicon substrate by plate-type PECVD, and preparing a conductive film layer on the first main surface of the silicon substrate; wherein the anti-reflection layer comprises an ultraviolet conversion layer for converting ultraviolet light into visible light;

[0089] Step j, groove the conductive film layer in the spacing area to form a first conductive film layer and a second conductive film layer that are not connected;

[0090] Step 1: Prepare metal electrodes on the outside of the first conductive film layer and the second conductive film layer respectively.

[0091] Embodiment 2

[0092] The only difference between Example 2 and Example 1 is that the reflection enhancement layer prepared in step g is a double-layer structure (silicon oxide layer and silicon nitride layer) with a refractive index increasing in the direction away from the silicon substrate, and the refractive index ratio of the double-layer structure is 1.5:2.1; the other steps are exactly the same.

[0093] Comparative Example 1

[0094] The only difference between Comparative Example 1 and Example 1 is that the reflection-enhancing medium layer used in step g is a conventional single-layer silicon nitride layer, and the refractive index of the silicon nitride layer is 2.1. The other steps are exactly the same.

[0095] By performing performance tests on the back contact cells respectively prepared by the methods of the above-mentioned Example 1, Example 2 and Comparative Example 1, the performance data comparison results shown in Table 1 below were obtained:

[0096] Table 1 Battery performance data comparison table

[0097] <![CDATA[Jsc(mA / cm 2 )]]> Voc(mV) FF(%) Eta(%) Embodiment 1 41.10 754.0 86.28 26.74 Embodiment 2 41.11 753.8 86.24 26.72 Comparative Example 1 41.09 753.2 86.15 26.66

[0098] According to Table 1, it can be seen that the short-circuit current density (Jsc) and open-circuit voltage (Voc), fill factor (FF), and conversion efficiency (Eta) of Example 1 and Example 2 provided by the present invention are higher than those of Comparative Example 1, and as the number of layers of the stacked structure in the reflection-enhancing layer increases, the performance of the prepared battery is better. This indicates that the setting of the reflection-enhancing layer and the damage layer effectively reduces the influence of the heat energy generated during the laser film opening process on the first carrier collection layer, and as the number of layers with increasing refractive index in the reflection-enhancing layer increases, the reflection effect on the laser is better.

[0099] 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 method for preparing a back contact battery, characterized in that: include: Step 1, preparing a first carrier collection layer (2) and an insulating isolation layer (3) in sequence from the inside to the outside in a partial area of ​​the first main surface of the silicon substrate (1), wherein the partial area includes a spacing area (11) and a first functional area (12) located at the edge; Step 2, on the first main surface of the silicon substrate (1), a second carrier collection layer (4), a reflection enhancement layer (5) and a damaged layer (6) are sequentially prepared from the inside to the outside; the reflection enhancement layer (5) is a structure with a refractive index increasing in a direction away from the silicon substrate (1); Step 3, removing the damaged layer (6) corresponding to the first functional area (12) by laser, and reflecting the laser by the reflection enhancement layer (5); Step 4, removing the remaining damaged layer (6), the reflection enhancement layer (5) and the second carrier collection layer (4) corresponding to the first functional area (12) on the first main surface by chemical etching, so as to obtain a second functional area (13) adjacent to the spacing area (11).

2. The method according to claim 1, characterized in that The step 1 comprises: Step 11, preparing a first carrier collection layer (2) and an insulating isolation layer (3) on the first main surface of the silicon substrate (1) from the inside to the outside in sequence; Step 12, removing the first carrier collection layer (2) and the insulating isolation layer (3) corresponding to the second functional area (13) by using a laser; Preferably, the step 11 comprises: A tunneling oxide layer and a first doping layer are sequentially prepared from the inside to the outside on a first main surface of a silicon substrate (1) to obtain a first carrier collection layer (2); or, A first intrinsic silicon-containing thin film layer and a first doping layer are sequentially prepared on a first main surface of a silicon substrate (1) from the inside to the outside to obtain a first carrier collection layer (2).

3. The method according to claim 1, characterized in that The step 2 comprises: A second intrinsic silicon-containing thin film layer and a second doping layer are sequentially prepared from the inside to the outside on the first main surface of the silicon substrate (1) to obtain a second carrier collection layer (4); and / or, The reflection enhancement layer (5) is a multi-layer structure, comprising: a silicon oxide layer, a silicon oxynitride layer, and a silicon nitride layer; wherein the refractive indices of the silicon oxide layer, the silicon oxynitride layer, and the silicon nitride layer increase in sequence; and / or, After step 4, the method further includes: Step 5: preparing a passivation layer (7) and an anti-reflection layer (8) on the second main surface of the silicon substrate (1) from the inside to the outside in sequence; wherein the anti-reflection layer (8) comprises an ultraviolet conversion layer for converting ultraviolet light into visible light.

4. The method according to claim 1, characterized in that: After step 4, the method further includes: Step 6, preparing a conductive film layer (9) on the first main surface; Step 7, grooves are formed in the conductive film layer (9) in the region corresponding to the spacing region (11), so as to form a first conductive film layer (91) and a second conductive film layer (92) that are not connected; Preferably, before step 1, the method further comprises: performing a texturing treatment 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 (100) arranged on the second main surface of the silicon substrate (1); and / or, After step 7, the method further includes: respectively setting metal electrodes (10) in the first functional area (12) and the second functional area (13).

5. The method according to claim 1, characterized in that: The step 4 comprises: Step 41, removing the reflection enhancement layer (5) in the first functional area (12) by using an acid solution; Step 42, using an alkaline solution to remove the second carrier collection layer (4) corresponding to the first functional region (12), while removing the damaged layer (6) of the second functional region (13) and the spacing region (11); Step 43, using an acid solution to remove the reflection enhancement layer (5) corresponding to the second functional area (13) and the spacing area (11), while removing the insulating isolation layer (3) of the first functional area (12).

6. A back contact battery prepared by any one of the preparation methods of claims 1 to 5, characterized in that: include: Silicon substrate (1); A first carrier collection layer (2) provided in a first functional region (12) of a first main surface of the silicon substrate (1); A second carrier collection layer (4) is arranged in a second functional region (13) on the first main surface of the silicon substrate (1); wherein a spacing region (11) is arranged between the first functional region (12) and the second functional region (13); the first functional region (12) and the second functional region (13) are arranged alternately; and the conductivity type of the first carrier collection layer (2) is opposite to the conductivity type of the second carrier collection layer (4); Wherein, the first carrier collection layer (2) extends from the first functional region (12) to the spacing region (11); An insulating isolation layer (3) is also provided in the spacing region (11), and the insulating isolation layer (3) is provided outside the first carrier collection layer (2); the second carrier collection layer (4) extends from the second functional region (13) to the outside of the insulating isolation layer (3).

7. The back contact cell according to claim 6, characterized in that: Also includes: A conductive film layer (9) disposed outside the first carrier collection layer (2) and the second carrier collection layer (4); Preferably, it also includes: A spacing groove (200) located outside the insulating isolation layer (3); Wherein, the spacing groove (200) is used to separate the conductive film layer (9) into a first conductive film layer (91) and a second conductive film layer (92); Preferably, The spacing groove (200) separates the first conductive film layer (91) and the second conductive film layer (92), and also divides the portion of the second carrier collection layer (4) extending outside the insulating isolation layer (3) into two sections.

8. The back contact cell according to claim 6, characterized in that: Also includes: A passivation layer (7) and an anti-reflection layer (8) are sequentially arranged from inside to outside on the second main surface of the silicon substrate (1); Wherein, the anti-reflection layer (8) comprises an ultraviolet light conversion layer for converting ultraviolet light into visible light.

9. The back contact battery according to claim 6, characterized in that: The first carrier collection layer (2) comprises a tunneling oxide layer and a first doping layer which are stacked; or the first carrier collection layer (2) comprises a first intrinsic silicon-containing thin film layer and a first doping layer which are stacked; The second carrier collection layer (5) comprises a second intrinsic silicon-containing thin film layer and a second doping layer which are stacked; Preferably, The passivation layer (7) comprises at least one or more combinations of an intrinsic silicon-containing film and a doped silicon-containing film; and / or, The anti-reflection layer (8) further comprises a layer structure composed of one or more of aluminum oxide, silicon nitride, silicon oxynitride and silicon oxide; and / or, The insulating isolation layer (3) comprises one or more of silicon oxide, silicon nitride, and silicon oxynitride; Preferably, 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 is a thin film structure composed of one or more of polycrystalline silicon, microcrystalline silicon, nano silicon, amorphous silicon, silicon oxide or silicon carbide; and / or, The second doped layer is a thin film structure composed of one or more of microcrystalline silicon, nano silicon, amorphous silicon, silicon oxide or silicon carbide; Preferably, The thickness of the tunnel oxide layer is 0.5nm to 3.0nm; and / or, The thickness of the first doping layer is 10nm to 300nm; and / or, The thickness of the second doping layer is 10 nm to 300 nm.

10. The back contact cell according to claim 6, characterized in that: The conductive film layer (9) 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 element includes at least one of the following: indium, tin, calcium, aluminum, cadmium, zinc, cerium, and fluorine.

Images