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 method comprises the steps: sequentially preparing a first carrier collection layer and an insulating layer on a first main surface of a silicon substrate from inside to outside; performing two times of laser scanning on a partial region of the insulating layer by using a laser process, and removing the remaining first carrier collection layer in a laser scanning region by using an alkaline solution; the laser power of the first-time laser scanning is greater than that of the second-time laser scanning, and the laser power of the first-time laser scanning is not greater than 380mJ / cm < 2 >; and preparing a second carrier collection layer in the laser scanning area and an edge area, close to the laser scanning area, in the residual insulating layer, and removing the insulating layer which is not covered by the second carrier collection layer by using a chemical etching process. According to the embodiment, laser damage to the silicon substrate is effectively reduced, the height difference between different areas of the silicon substrate is reduced, and the photoelectric conversion efficiency is 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] In the existing back contact battery preparation process, it is usually necessary to prepare the p-region and n-region separately. Specifically, after preparing a whole layer of carrier collection layer and insulating layer on the surface of the silicon substrate, a laser process is used to remove the insulating layer and carrier collection layer in some areas to obtain the structure of the n-region. Since the insulating layer to be opened usually has a certain thickness requirement, a higher laser power is required to effectively open the insulating layer. However, high-power laser energy can cause serious laser damage to the surface of the silicon substrate, which means that before the subsequent preparation of the p-region structure, it is necessary to use a texturing process to remove the laser damage on the surface of the silicon substrate, resulting in height differences between different areas of the silicon substrate, thereby increasing the amount of metal slurry used in the subsequent electrode preparation process. Summary of the invention

[0003] In view of this, an embodiment of the present invention provides a back-contact solar cell and a preparation method thereof. By improving the laser process for removing the insulating layer in the prior art and optimizing the laser process from one high-laser-power laser process to two low-laser-power laser processes, the laser damage to the silicon substrate can be effectively reduced, thereby reducing the etching depth of the damaged surface of the silicon substrate during the texturing process, reducing the height difference between different areas of the silicon substrate, and effectively improving the photoelectric conversion efficiency of the back-contact solar cell.

[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 solar cell, comprising: step 1, sequentially preparing a first carrier collection layer and an insulating layer from inside to outside on a first main surface of a silicon substrate;

[0006] Step 2: perform laser scanning twice on a partial area of ​​the insulating layer using a laser process, and use an alkaline solution to remove the remaining first carrier collection layer in the laser scanning area; wherein the laser power of the first laser scanning is greater than the laser power of the second laser scanning, and the laser power of the first laser scanning is not greater than 380 mJ / cm 2 ;

[0007] Step 3, preparing a second carrier collection layer in the laser scanning area and the edge area of ​​the remaining insulating layer close to the laser scanning area, and using a chemical etching process to remove the insulating layer not covered by the second carrier collection layer, to form a first functional area having the second carrier collection layer, a second functional area having the first carrier collection layer, and an isolation area stacked from the inside to the outside with the first carrier collection layer, the insulating layer and the second carrier collection layer.

[0008] Optionally, the laser power of the first laser scan is 1.2 to 4 times the laser power of the second laser scan.

[0009] Optionally, step 1 includes: preparing a first tunneling oxide layer and a first doping layer doped with a first doping element on a first main surface of a silicon substrate from the inside to the outside, to obtain the first carrier collection layer; or, preparing a first intrinsic silicon-containing thin film layer and a first doping layer doped with a first doping element on a first main surface of a silicon substrate from the inside to the outside, to obtain the first carrier collection layer.

[0010] Optionally, step 3 includes: preparing a second tunneling oxide layer and a second doping layer doped with a second doping element in sequence from the inside to the outside in the laser scanning area and the edge area of ​​the remaining insulating layer close to the laser scanning area to obtain the second carrier collection layer; or, preparing a second intrinsic silicon-containing thin film layer and a second doping layer doped with a second doping element in sequence from the inside to the outside in the laser scanning area and the edge area of ​​the remaining insulating layer close to the laser scanning area to obtain the second carrier collection layer.

[0011] Optionally, removing the insulating layer not covered by the second carrier collection layer by using a chemical etching process includes: chemically etching the insulating layer not covered by the second carrier collection layer by using a hydrofluoric acid solution.

[0012] Optionally, the laser parameters of the first laser scan are: scanning frequency of 1KHz to 1000KHz, speed of 1m / sec to 100m / sec; and / or, the laser parameters of the second laser scan are: scanning frequency of 1KHz to 1000KHz, speed of 1m / sec to 100m / sec. Optionally, step 2 includes: step 21, performing a first laser scan on a partial area of ​​the insulating layer using a laser process to remove a portion of the thickness of the insulating layer; step 22, performing a second laser scan on the remaining insulating layer in the scanned area to expose the first carrier collection layer in the scanned area; step 23, using an alkaline solution to remove the remaining first carrier collection layer and part of the silicon substrate on the scanned area.

[0013] In a second aspect, the present invention provides a back-contact solar cell prepared by the above-mentioned preparation method, comprising: a silicon substrate; wherein, the silicon substrate is provided with alternating first functional areas and second functional areas, and an isolation area located between the first functional areas and the second functional areas; a second carrier collection layer arranged on the first functional area, and a first carrier collection layer arranged on the second functional area; wherein, the first carrier collection layer extends from the second functional area to the isolation area, and the second carrier collection layer extends from the first functional area to the isolation area; the second carrier collection layer is located outside the first carrier collection layer, and an insulating layer is also provided between the first carrier collection layer and the second carrier collection layer.

[0014] The technical solution of the first aspect of the above invention has the following advantages or beneficial effects: by improving the laser process for removing the insulating layer in the prior art, optimizing the laser process with high laser power into two laser processes with low laser power, the laser damage to the silicon substrate can be effectively reduced, thereby reducing the etching depth of the damaged surface of the silicon substrate during the texturing process, reducing the height difference between different areas of the silicon substrate, and effectively improving the photoelectric conversion efficiency of the back contact solar cell. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] The accompanying drawings are used to better understand the present invention and do not constitute an improper limitation of the present invention.

[0016] Figure 1 is a schematic flow chart of a method for preparing a back-contact solar cell according to an embodiment of the present invention;

[0017] Figure 2 is a schematic flow chart of the preparation method of step S102 according to an embodiment of the present invention;

[0018] Figure 3 is a schematic diagram of a cross-sectional structure of a silicon substrate obtained after step S202 according to an embodiment of the present invention;

[0019] Figure 4 is a schematic diagram of a cross-sectional structure of a silicon substrate obtained after step S203 according to an embodiment of the present invention;

[0020] Figure 5 is a schematic diagram of the cross-sectional structure of a silicon substrate for preparing a second carrier collection layer in its entirety according to an embodiment of the present invention;

[0021] Figure 6 is a schematic diagram of a cross-sectional structure of a silicon substrate in which a second carrier collection layer is disposed only in the first functional region and the isolation region according to an embodiment of the present invention;

[0022] Figure 7is a schematic flow chart of a preparation method after step S103 according to an embodiment of the present invention;

[0023] Figure 8 4 is a schematic diagram of the cross-sectional structure of a back-contact solar cell according to an embodiment of the present invention.

[0024] The reference numerals are as follows:

[0025] 1-silicon substrate; 11-first functional area; 12-second functional area; 13-isolation area; 2-first carrier collection layer; 3-insulating layer; 4-second carrier collection layer; 5-passivation layer; 6-anti-reflection layer; 7-conductive film layer; 8-metal electrode. DETAILED DESCRIPTION

[0026] 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.

[0027] In one embodiment of the present invention, Figure 1 As shown, this embodiment provides a method for preparing a back-contact solar cell, and the preparation method may include the following steps:

[0028] Step S101, preparing a first carrier collection layer 2 and an insulating layer 3 in sequence from the inside to the outside on a first main surface of a silicon substrate 1;

[0029] Step S102, using a laser process to perform laser scanning twice on a partial area of ​​the insulating layer 3, and using an alkaline solution to remove the first carrier collection layer 2 remaining in the laser scanning area; wherein the laser power of the first laser scanning is greater than the laser power of the second laser scanning, and the laser power of the first laser scanning is not greater than 380mJ / cm 2 ;

[0030] Step S103, prepare a second carrier collection layer 4 in the laser scanning area and the edge area of ​​the remaining insulating layer 3 close to the laser scanning area, and use a chemical etching process to remove the insulating layer 3 not covered by the second carrier collection layer 4, to form a first functional area 11 with a first carrier collection layer 2, a second functional area 12 with a second carrier collection layer 4, and an isolation area 13 stacked with the first carrier collection layer 2, the insulating layer 3 and the second carrier collection layer 4 from the inside to the outside.

[0031] Among them, the steps improved by the embodiment of the present invention are mainly the laser process in step S102. In the prior art, usually only one high-power laser scan is used to remove the insulating layer 3. This is because the insulating layer 3 usually has a certain thickness. If only one low-power laser scan is performed, the insulating layer 3 may not be effectively removed. It can be understood that the reason why the insulating layer 3 is set to a certain thickness is that in the process of using an alkaline solution to remove part of the first carrier collection layer 2 corresponding to the first functional area 11 and simultaneously texturing the surface of the silicon substrate 1 to remove laser damage, the alkaline solution will simultaneously partially etch the insulating layer 3. If the insulating layer 3 is too thin, it cannot effectively resist the etching of the alkaline solution, and may damage the first carrier collection layer 2 corresponding to the second functional area 12. Therefore, a sufficiently thick insulating layer is required to protect the first carrier collection layer 2 corresponding to the second functional area 12.

[0032] However, the improvement of the laser process in the embodiment of the present invention is not only to optimize a high-power laser scan into two low-power laser scan processes, but also to further optimize the power of the two low-power laser scan processes, that is, the laser power of the first laser scan is greater than the laser power of the second laser scan, rather than selecting two laser scan processes with the same power. Through multiple experiments by the inventor, in a preferred embodiment, the laser power of the first laser scan is 1.2 to 4 times the laser power of the second laser scan, for example, 1.2 times, 2 times, 3 times, 4 times, etc. After preparing back-contact solar cells using laser processes with different laser powers, the inventor found that the morphology of the surface of the silicon substrate 1 can be changed by the first higher-power laser scan process, making the surface of the silicon substrate smoother. In this way, during the second lower-power laser scan process, the reflectivity of the laser on the surface of the silicon substrate 1 will increase, thereby effectively reducing the damage to the surface of the silicon substrate caused by the second laser scan process. At the same time, since the laser power of the first laser scan and the second laser scan is lower than that of the prior art, the heat generated during the scanning process will also be lower, that is, at a lower temperature, the extension of the laser-induced damage layer can be effectively reduced, further reducing the laser damage to the silicon substrate 1.

[0033] In addition, as the surface damage of the silicon substrate 1 decreases, the removal of the silicon substrate surface will also be reduced accordingly, that is, the height difference of the silicon substrate between the first functional area 11 and the second functional area 12 will also be reduced accordingly. In this way, in the subsequent preparation process of the metal electrode, while ensuring the level of the metal electrode surface of the first functional area 11 and the second functional area 12, the amount of slurry used in the first functional area 11 can be reduced accordingly, thereby reducing the preparation cost.

[0034] In an optional embodiment, the laser bands of the first laser scan and the second laser scan may be the same or different. Specifically, the laser parameters of the first laser scan are: scanning frequency of 1KHz to 1000KHz, such as 1KHz, 50KHz, 500KHz, 1000KHz, etc.; speed of 1m / sec to 100m / sec, such as 1m / sec, 30m / sec, 50m / sec, 80m / sec, 100m / sec, etc.; laser parameters of the second laser scan are: scanning frequency of 1KHz to 1000KHz, such as 1KHz, 50KHz, 500KHz, 1000KHz, etc.; speed of 1m / sec to 100m / sec, such as 1m / sec, 30m / sec, 50m / sec, 80m / sec, 100m / sec, etc.

[0035] In an optional embodiment, the process of preparing the first carrier collection layer 2 in step S101 includes: preparing a first tunneling oxide layer and a first doping layer doped with a first doping element 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 doped with a first doping element 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. The process conditions for preparing the tunneling oxide layer and the first intrinsic silicon-containing thin film layer are different, one is a low-temperature preparation process, and the other is a high-temperature preparation process. In the actual preparation process, the tunneling oxide layer or the first intrinsic silicon-containing thin film can be selected according to the actual process requirements.

[0036] For the process of step S102, in an optional embodiment, as Figure 2 As shown, including:

[0037] Step S201, performing a first laser scan on a partial area of ​​the insulating layer 3 using a laser process to remove a partial thickness of the insulating layer 3;

[0038] Step S202, performing a second laser scan on the remaining insulating layer 3 in the scanned area to expose the first carrier collection layer 2 in the scanned area;

[0039] Step S203 , using an alkaline solution to remove the remaining first carrier collection layer 2 and a portion of the silicon substrate 1 on the scanning area.

[0040] For example, the cross-sectional structure of the silicon substrate obtained through the above steps S201 and S202 can be as follows: Figure 3 As shown, the cross-sectional structure of the silicon substrate obtained after the above step S203 is as follows Figure 4 As shown. Through the above process, it can be seen that in the embodiment of the present invention, only a part of the thickness of the insulating layer 3 is removed during the first laser scan. Since a part of the thickness of the insulating layer 3 is still retained, the laser energy during the scanning process will be absorbed by the retained part of the insulating layer 3 and the first carrier collection layer 2 inside the insulating layer 3, that is, the first laser scan will hardly cause damage to the surface of the silicon substrate 1. With the second laser scan, the insulating layer in the scanned area is completely removed. It should be noted that in the actual operation process, it cannot be guaranteed that the second laser scan will just remove the insulating layer 3 without etching the first carrier collection layer 2. Therefore, the second laser scan will actually remove part of the first carrier collection layer 2 in the scanned area, but the etching thickness of the first carrier collection layer 2 by the second laser scan should be reduced as much as possible to minimize the laser damage to the surface of the silicon substrate 1 caused by the second laser scan.

[0041] For the process of step S103, since the structure of the second carrier collection layer 4 is similar to that of the first carrier collection layer 2, in an optional embodiment, the process of preparing the second carrier collection layer 4 in step S103 may include: preparing a second tunneling oxide layer and a second doping layer doped with a second doping element in the laser scanning area and the edge area of ​​the remaining insulating layer 3 close to the laser scanning area from the inside to the outside to obtain the second carrier collection layer 4; or, preparing a second intrinsic silicon-containing thin film layer and a second doping layer doped with a second doping element in the laser scanning area and the edge area of ​​the remaining insulating layer 3 close to the laser scanning area from the inside to the outside to obtain the second carrier collection layer 4.

[0042] Specifically, the process of preparing the second carrier collection layer 4 is actually to prepare the carrier collection layer in an entire layer first, and then remove the carrier collection layer corresponding to the second functional area 12 by laser process, so as to obtain the second carrier collection layer 4 which is only arranged in the first functional area 11 and the isolation area 13. For example, Figure 5 and Figure 6As shown, it should be noted here that although the laser process is also involved, the hardness and etching difficulty of the carrier collection layer are far less than those of the insulating layer 3. Therefore, the laser power requirement for removing the carrier collection layer is relatively low, and the overall performance of the back contact solar cell is relatively small. Therefore, the embodiment of the present invention mainly improves the laser process in step S102. It is understandable that the laser process used in preparing the second carrier collection layer 4 can also be improved according to actual needs, and the present invention does not limit this.

[0043] Regarding the process of removing the remaining insulating layer 3 in step S103 , in an optional embodiment, the process includes: chemically etching the insulating layer 3 not covered by the second carrier collection layer 4 using a hydrofluoric acid solution.

[0044] In a further optional embodiment, after step S103, Figure 7 As shown, including:

[0045] Step S701, preparing a passivation layer 5 and an anti-reflection layer 6 in sequence from the inside to the outside on the second main surface of the silicon substrate 1;

[0046] Step S702, preparing a conductive film layer 7 on the first main surface of the silicon substrate 1, and grooves the conductive film layer 7 in the isolation region 13;

[0047] Step S703 , preparing metal electrodes 8 on the first functional area 11 and the second functional area 12 respectively.

[0048] For example, the back contact solar cell structure finally obtained through step S701 to step S703 is as follows: Figure 8 The passivation layer 5 and the anti-reflection layer 6 in step S301 can be deposited by at least one of PECVD, ALD, PVD, and evaporation.

[0049] In summary, the method for preparing a back-contact solar cell provided in an embodiment of the present invention improves the laser process for removing the insulating layer in the prior art and optimizes it from a single high-laser-power laser process to two low-laser-power laser processes. This can effectively reduce the laser damage to the silicon substrate, thereby reducing the etching depth of the damaged surface of the silicon substrate during the texturing process, reducing the height difference between different areas of the silicon substrate, and effectively improving the photoelectric conversion efficiency of the back-contact solar cell.

[0050] Figure 8 FIG. 4 is a schematic cross-sectional view of a back contact solar cell prepared by the above-mentioned preparation method according to an embodiment of the present invention. Figure 8As shown, the solar cell provided by the present invention includes: a silicon substrate 1; wherein, the silicon substrate 1 is provided with a first functional area 11 and a second functional area 12 arranged alternately, and an isolation area 13 located between the first functional area 11 and the second functional area 12; a second carrier collection layer 4 is provided on the first functional area 11, and a first carrier collection layer 2 is provided on the second functional area 12; wherein, the first carrier collection layer 2 extends from the second functional area 12 to the isolation area 13, and the second carrier collection layer 4 extends from the first functional area 11 to the isolation area 13; the second carrier collection layer 4 is located outside the first carrier collection layer 2, and an insulating layer 3 is also provided between the first carrier collection layer 2 and the second carrier collection layer 4.

[0051] Since the present invention is mainly aimed at improving the laser process in the preparation method, there is no major change to the overall back-contact solar cell structure. However, the height difference between the silicon substrate 1 corresponding to the first functional area 11 and the second functional area 12 in the back-contact solar cell prepared by the existing process is generally 4μm to 10μm, and after being prepared by the preparation method provided in the embodiment of the present invention, in an optional embodiment, the height difference between the silicon substrate 1 corresponding to the first functional area 11 and the silicon substrate 1 corresponding to the second functional area 12 is 0μm to 5μm. It can be seen that the preparation method provided by the present invention can effectively reduce the height difference between the p-region and the n-region of the back-contact solar cell, thereby reducing the metal slurry consumed in the subsequent metal electrode preparation process.

[0052] For the specific structure of the first carrier collection layer 2, two different stacked structures can be used. In an optional embodiment, the first carrier collection layer 2 includes: a first tunneling oxide layer stacked and a first doped layer doped with a first doping element, or a first intrinsic silicon-containing thin film layer stacked and a first doped layer doped with a first doping element. Among them, the process conditions for preparing the tunneling oxide layer and the first intrinsic silicon-containing thin film layer are different, one is a low-temperature preparation process, and the other is a high-temperature preparation process. In the actual preparation process, the tunneling oxide layer or the first intrinsic silicon-containing thin film can be selected according to the actual process requirements. For the specific structure of the second carrier collection layer 4, similar to the first carrier collection layer 2, in an optional embodiment, the second carrier collection layer 4 includes: a second tunneling oxide layer stacked and a second doped layer doped with a second doping element, or a second intrinsic silicon-containing thin film layer stacked and a second doped layer doped with a second doping element.

[0053] The first intrinsic silicon-containing film and / or the second intrinsic silicon-containing film include at least one film layer structure selected from microcrystalline silicon, nano-silicon, amorphous silicon, silicon oxide, and silicon carbide, and the thickness may be set to be 1 nm to 50 nm, such as 1 nm, 10 nm, 15 nm, 20 nm, 30 nm, 40 nm, 45 nm, 50 nm, etc. The first doped layer and / or the second doped layer include at least one film layer structure selected from microcrystalline silicon, nano-silicon, amorphous silicon, silicon oxide, and silicon carbide.

[0054] In a further optional embodiment, the insulating layer 3 includes at least one of aluminum oxide, silicon oxide, gallium oxide, silicon nitride, aluminum nitride, silicon oxynitride, and aluminum oxynitride.

[0055] Regarding the thickness of the first carrier collection layer 2 and the second carrier collection layer 4, in an optional embodiment, the thickness of the first tunneling oxide layer and / or the second tunneling oxide layer is 0.5nm to 3nm, such as 0.5nm, 1nm, 2nm, 3nm, etc. The thickness of the first doping layer and / or the second doping layer is 30nm to 200nm, such as 30nm, 50nm, 100nm, 200nm, etc.

[0056] In an optional embodiment, if Figure 4 As shown, the back contact solar cell provided by the present invention further includes: a passivation layer 5 and an anti-reflection layer 6 arranged in sequence from the inside to the outside on the second main surface of the silicon substrate 1. The material of the passivation layer 5 can be an intrinsic silicon-containing film or a stacked structure or an aluminum oxide layer composed of an intrinsic silicon-containing film and an n-type doped silicon-containing film. In a preferred embodiment, the thickness of the intrinsic silicon-containing film is 1nm to 15nm, such as 1nm, 5nm, 8nm, 10nm, 12nm, 15nm, and the thickness of the n-type doped silicon-containing film is 0nm to 15nm, such as 0nm, 5nm, 8nm, 10nm, 12nm, 15nm. It can be understood that when the thickness of the n-type doped silicon-containing film is 0nm, the passivation layer 5 is only composed of the intrinsic silicon-containing film. As for the material of the anti-reflection layer 6, in an optional embodiment, the anti-reflection layer 6 can be at least one of aluminum oxide, silicon oxide, gallium oxide, silicon nitride, aluminum nitride, silicon oxynitride, aluminum oxynitride, magnesium fluoride, lithium fluoride, ITO, and zinc oxide, and the thickness of the anti-reflection layer 6 can be 40nm to 200nm, such as 40nm, 80nm, 100nm, 150nm, 200nm, etc. Further, the back contact solar cell provided by the present invention also includes: metal electrodes 7 respectively arranged in the first functional area 11 and the second functional area 12.

[0057] In summary, the back-contact solar cell provided in the embodiment of the present invention improves the laser process for removing the insulating layer in the prior art and optimizes it from a single high-laser-power laser process to two low-laser-power laser processes, thereby effectively reducing the laser damage caused to the silicon substrate, thereby reducing the etching depth of the damaged surface of the silicon substrate during the texturing process, reducing the height difference between different areas of the silicon substrate, and effectively improving the photoelectric conversion efficiency of the back-contact solar cell.

[0058] Example

[0059] Step a, preparing a tunneling oxide layer, a first doping layer and an insulating layer in sequence from the inside to the outside on the first main surface of the N-type silicon substrate; wherein the tunneling oxide layer is silicon oxide with a thickness of 2 nm, the first doping layer has a thickness of 200 nm, and the insulating layer is silicon oxide with a thickness of 100 nm;

[0060] Step b, using a laser process to perform laser scanning twice on a partial area of ​​the insulating layer (the first functional area); wherein the laser power P1 of the first laser scanning is 1.5 times the laser power P2 of the second laser scanning (i.e., P1=1.5P2=30W), and the specific parameters of the first laser scanning are a wavelength of green light, a power of 30W, a frequency of 500kHz, and a speed of 40m / sec, and the specific parameters of the second laser scanning are a wavelength of green light, a power of 20W, a frequency of 500kHz, and a speed of 40m / sec;

[0061] Step c, using an alkaline solution to remove the remaining tunneling oxide layer and the first doping layer in the laser scanning area, and forming a suede surface in the scanning area of ​​the silicon substrate;

[0062] Step d, preparing an intrinsic silicon-containing thin film layer and a second doped layer in sequence from the inside to the outside on the second main surface of the silicon substrate; wherein the thickness of the first doped layer is 50 nm;

[0063] Step e, scanning the intrinsic silicon-containing thin film layer and the second doped layer of the second functional area once by using a laser process; wherein the specific parameters of the laser process are a wavelength of green light, a power of 12 W, a frequency of 500 kHz, and a speed of 40 m / sec;

[0064] Step f, chemically etching the insulating layer not covered by the second doping layer using a 5% hydrofluoric acid solution;

[0065] Step g, stacking and preparing a passivation layer and an anti-reflection layer on the second main surface of the silicon substrate, and preparing a conductive film layer on the first main surface;

[0066] Step h, slotting the conductive film layer; wherein the slotting position corresponds to the isolation area;

[0067] Step i: prepare metal electrodes in the first functional area and the second functional area respectively.

[0068] Comparative Example 1

[0069] Step a, preparing a tunneling oxide layer, a first doping layer and an insulating layer in sequence from the inside to the outside on the first main surface of the N-type silicon substrate; wherein the tunneling oxide layer is silicon oxide with a thickness of 2 nm, the first doping layer has a thickness of 200 nm, and the insulating layer is silicon oxide with a thickness of 100 nm;

[0070] Step b, using a laser process to perform laser scanning twice on a partial area (the first functional area) of the insulating layer; wherein the laser power P1 of the first laser scanning is the same as the laser power P2 of the second laser scanning (i.e., P1=P2=25W), the specific parameters of the first laser scanning are 25W, the frequency is 500kHz, and the speed is 40m / sec, and the specific parameters of the second laser scanning are 25W, the frequency is 500kHz, and the speed is 40m / sec;

[0071] Step c, using an alkaline solution to remove the remaining tunneling oxide layer and the first doping layer in the laser scanning area, and forming a suede surface in the scanning area of ​​the silicon substrate;

[0072] Step d, preparing an intrinsic silicon-containing thin film layer and a second doped layer in sequence from the inside to the outside on the second main surface of the silicon substrate; wherein the thickness of the first doped layer is 50 nm;

[0073] Step e, scanning the intrinsic silicon-containing thin film layer and the second doped layer of the second functional area once by using a laser process; wherein the specific parameters of the laser process are a wavelength of green light, a power of 12 W, a frequency of 500 kHz, and a speed of 40 m / sec;

[0074] Step f, chemically etching the insulating layer not covered by the second doping layer using a 5% hydrofluoric acid solution;

[0075] Step g, stacking and preparing a passivation layer and an anti-reflection layer on the second main surface of the silicon substrate, and preparing a conductive film layer on the first main surface;

[0076] Step h, slotting the conductive film layer; wherein the slotting position corresponds to the isolation area;

[0077] Step i: prepare metal electrodes in the first functional area and the second functional area respectively.

[0078] Comparative Example 2

[0079] Step a, preparing a tunneling oxide layer, a first doping layer and an insulating layer in sequence from the inside to the outside on the first main surface of the N-type silicon substrate; wherein the tunneling oxide layer is silicon oxide with a thickness of 2 nm, the first doping layer has a thickness of 200 nm, and the insulating layer is silicon oxide with a thickness of 100 nm;

[0080] Step b, using a laser process to perform a laser scan on a partial area (first functional area) of the insulating layer; wherein the laser power of the laser scanning is twice the laser power in step b of comparative example 1 (ie, P=50W);

[0081] Step c, using an alkaline solution to remove the remaining tunneling oxide layer and the first doping layer in the laser scanning area, and forming a suede surface in the scanning area of ​​the silicon substrate;

[0082] Step d, preparing an intrinsic silicon-containing thin film layer and a second doped layer in sequence from the inside to the outside on the second main surface of the silicon substrate; wherein the thickness of the first doped layer is 50 nm;

[0083] Step e, scanning the intrinsic silicon-containing thin film layer and the second doped layer of the second functional area once by using a laser process; wherein the specific parameters of the laser process are a wavelength of green light, a power of 12 W, a frequency of 500 kHz, and a speed of 40 m / sec;

[0084] Step f, chemically etching the insulating layer not covered by the second doping layer using a 5% hydrofluoric acid solution;

[0085] Step g, stacking and preparing a passivation layer and an anti-reflection layer on the second main surface of the silicon substrate, and preparing a conductive film layer on the first main surface;

[0086] Step h, slotting the conductive film layer; wherein the slotting position corresponds to the isolation area;

[0087] Step i: prepare metal electrodes in the first functional area and the second functional area respectively.

[0088] The performance of the back-contact solar cell obtained by the above preparation process was tested, and the test results were as follows:

[0089] Minority carrier lifetime (μs) <![CDATA[Composite current density (A / cm 2 )]]> Body life (μs) Virtual opening voltage (μs) Comparative Example 1 1.008 0.97 1.121 1.002 Comparative Example 2 1 1 1 1 Example 1.117 0.902 1.139 1.007

[0090] From the above results, it can be seen that the insulating layer is removed by two laser scanning processes in the embodiment of the present invention, which effectively improves the minority carrier lifetime, body lifetime, and virtual opening voltage compared to the process of using only one high-power laser scanning process. And compared to the process of using two laser scanning processes with the same laser power, the laser power of the first laser scanning is increased and the laser power of the second laser scanning is reduced, which can further reduce the laser damage to the silicon substrate by the laser process and increase the minority carrier lifetime and body lifetime.

[0091] 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 solar cell, characterized in that: include: Step 1, preparing a first carrier collection layer (2) and an insulating layer (3) on a first main surface of a silicon substrate (1) from inside to outside in sequence; Step 2, using a laser process to perform laser scanning twice on a partial area of ​​the insulating layer (3), and using an alkaline solution to remove the first carrier collection layer (2) remaining in the laser scanning area; wherein the laser power of the first laser scanning is greater than the laser power of the second laser scanning, and the laser power of the first laser scanning is not greater than 380 mJ / cm 2 ; Step 3, preparing a second carrier collection layer (4) in the laser scanning area and in the edge area of ​​the remaining insulating layer (3) close to the laser scanning area, and removing the insulating layer (3) not covered by the second carrier collection layer (4) by a chemical etching process, to form a first functional area (11) having the second carrier collection layer (4), a second functional area (12) having the first carrier collection layer (2), and an isolation area (13) on which the first carrier collection layer (2), the insulating layer (3) and the second carrier collection layer (4) are stacked from the inside to the outside.

2. The method according to claim 1, characterized in that The laser power of the first laser scan is 1.2 to 4 times the laser power of the second laser scan.

3. The method according to claim 1, characterized in that The step 1 comprises: A first tunneling oxide layer and a first doping layer doped with a first doping element are sequentially prepared on a first main surface of a silicon substrate (1) from inside to outside to obtain the first carrier collection layer (2); or, A first intrinsic silicon-containing thin film layer and a first doping layer doped with a first doping element are sequentially prepared on a first main surface of a silicon substrate (1) from the inside to the outside to obtain the first carrier collection layer (2).

4. The method according to claim 1, characterized in that: The step 3 comprises: A second tunneling oxide layer and a second doping layer doped with a second doping element are sequentially prepared from inside to outside in the laser scanning area and in the edge area of ​​the remaining insulating layer (3) close to the laser scanning area to obtain the second carrier collection layer (4); or, A second intrinsic silicon-containing thin film layer and a second doping layer doped with a second doping element are sequentially prepared from the inside to the outside in the laser scanning area and in the edge area of ​​the remaining insulating layer (3) close to the laser scanning area to obtain the second carrier collection layer (4).

5. The method according to claim 1, characterized in that The step of removing the insulating layer (3) not covered by the second carrier collection layer (4) by using a chemical etching process comprises: The insulating layer (3) not covered by the second carrier collection layer (4) is chemically etched using a hydrofluoric acid solution.

6. The method according to claim 1, characterized in that The laser parameters of the first laser scan are: scanning frequency of 1KHz to 1000KHz, speed of 1m / sec to 100m / sec; and / or, The laser parameters of the second laser scanning are: scanning frequency of 1KHz to 1000KHz, and speed of 1m / sec to 100m / sec.

7. The method according to claim 1, characterized in that The step 2 comprises: Step 21, using a laser process to perform a first laser scan on a partial area of ​​the insulating layer (3) to remove a partial thickness of the insulating layer (3); Step 22, performing a second laser scan on the remaining insulating layer (3) in the scanning area to expose the first carrier collection layer (2) in the scanning area; Step 23, using an alkaline solution to remove the remaining first carrier collection layer (2) and a portion of the silicon substrate (1) on the scanning area.

8. A back-contact solar cell prepared by any method according to claim 1 to 7, characterized in that: include: A silicon substrate (1); wherein the silicon substrate (1) is provided with first functional areas (11) and second functional areas (12) arranged alternately, and an isolation area (13) located between the first functional areas (11) and the second functional areas (12); A second carrier collection layer (4) disposed on the first functional region (11), and a first carrier collection layer (2) disposed on the second functional region (12); Wherein, the first carrier collection layer (2) extends from the second functional region (12) to the isolation region (13), and the second carrier collection layer (4) extends from the first functional region (11) to the isolation region (13); The second carrier collection layer (4) is located outside the first carrier collection layer (2), and an insulating layer (3) is also provided between the first carrier collection layer (2) and the second carrier collection layer (4).

9. The back contact solar cell according to claim 8, characterized in that: The height difference between the silicon substrate (1) corresponding to the first functional area (11) and the silicon substrate (1) corresponding to the second functional area (12) is 0 μm to 5 μm; and / or, The first carrier collection layer (2) comprises: a first tunneling oxide layer and a first doping layer doped with a first doping element arranged in layers, or a first intrinsic silicon-containing thin film layer and a first doping layer doped with a first doping element arranged in layers; and / or, The second carrier collection layer (4) comprises: a second tunneling oxide layer and a second doping layer doped with a second doping element arranged in layers, or a second intrinsic silicon-containing thin film layer and a second doping layer doped with a second doping element arranged in layers.

10. The back contact solar cell according to claim 9, characterized in that: The thickness of the first tunneling oxide layer and / or the second tunneling oxide layer is 0.5 nm to 3 nm; and / or, The thickness of the first doping layer and / or the second doping layer is 30 nm to 200 nm.

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