Tunneling oxide layer passivation contact cell and preparation method thereof

Abstract

The present invention relates to the technical field of solar cells, and in particular to a tunneling oxide layer passivated contact cell and a preparation method thereof. The cell comprises a substrate, a tunneling oxide layer, and a first doped layer. The substrate has a front surface and a back surface that are arranged opposite to each other, and at least the back surface has a metallized region and a non-metallized region. The tunneling oxide layer and the first doped layer are sequentially formed on the back surface, wherein an inner expansion layer is formed on the side of the tunneling oxide layer that is away from the first doped layer. The ratio of the doping concentration of the substrate corresponding to the non-metallized region to the doping concentration of the inner expansion layer in the metallized region is (1×10 ‑6 ~5×10 ‑4 ) : 1. The cell improves the photoelectric conversion efficiency of the tunnel oxide layer passivation contact cell by increasing the concentration difference between the non-metallized area and the metallized area.

Description

Technical Field

[0001] The present invention relates to the technical field of solar cells, and in particular to a tunneling oxide layer passivation contact cell and a preparation method thereof. Background Art

[0002] The tunneling oxide passivated contact cell (TOPCon cell, Thin Oxide Passivated Contact) is a type of passivated contact cell that reduces minority carrier recombination (the process by which minority carriers (electrons or holes) recombine with majority carriers in a semiconductor) by isolating the metal from the silicon substrate with a thin film. An ultra-thin layer of silicon oxide is deposited on the back of the cell, followed by a thin layer of doped polysilicon, forming a passivating contact structure. The ultra-thin silicon oxide layer allows majority electrons to tunnel into the polysilicon layer and blocks minority hole recombination, allowing electrons lateral to the polysilicon layer to be collected by the metal. This significantly reduces the metal contact recombination current, increases the cell's open-circuit voltage and short-circuit current, and thus improves the cell's conversion efficiency. In short, the passivation mechanism of the tunneling silicon oxide passivated contact structure stems from the following aspects: first, the chemical passivation provided by the silicon oxide interface; second, the field passivation effect of doped polysilicon; and third, the valence band mismatch between polysilicon and silicon, which blocks hole transmission.

[0003] However, the tunnel oxide passivation contact cell provided by the related technology is still restricted in improving the photoelectric conversion efficiency due to the problems of increased Auger recombination and reduced open circuit voltage. Summary of the Invention

[0004] The present invention provides a tunneling oxide passivation contact cell and a method for preparing the same. The method can form a doping concentration difference between the metallized region and the non-metallized region of the tunneling oxide passivation contact cell. The doping concentration of the substrate corresponding to the non-metallized region is lower than the doping concentration of the inner diffusion layer of the metallized region. The high doping concentration of the inner diffusion layer of the metallized region ensures electron transmission and a high fill factor (FF), while the low doping concentration of the substrate corresponding to the non-metallized region effectively suppresses increased Auger recombination, improves the problem of large-scale electron recombination, and reduces the open circuit voltage (Voc). In short, the method of the present invention forms a doping concentration difference between the non-metallized region and the metallized region, thereby ensuring electron transmission in the metallized region and improving the fill factor (FF) while preventing a decrease in the open circuit voltage (Voc) of the non-metallized region. The power conversion efficiency (PCE) is positively correlated with both the fill factor (FF) and the open circuit voltage (Voc). Therefore, the power conversion efficiency of the tunneling oxide passivation contact cell can be improved by increasing the concentration difference between the non-metallized region and the metallized region.

[0005] The embodiments of the present invention can be implemented as follows:

[0006] In a first aspect, the present invention provides a tunneling oxide layer passivation contact cell, comprising:

[0007] A substrate having a front side and a back side disposed opposite to each other, wherein at least the back side has a metallized area and a non-metallized area;

[0008] A tunnel oxide layer is formed on the back side and is located in the metallization area;

[0009] A first doped layer is formed on a side of the tunnel oxide layer facing away from the substrate; wherein,

[0010] The tunnel oxide layer is formed on the side away from the first doped layer to form an inner expansion layer; the ratio of the doping concentration of the substrate corresponding to the non-metallized area to the doping concentration of the inner expansion layer in the metallized area is (1×10 -6 ~5×10 -4 ) :1.

[0011] In an optional embodiment, the doping concentration of the substrate corresponding to the non-metallized area is 1×10 15 ~5×10 16 atom / cm 3 The doping concentration of the inner diffusion layer in the metallized area is 1×10 20 ~1×10 21 atom / cm 3 .

[0012] In an optional embodiment, the first doped layer is a phosphorus-doped polysilicon layer.

[0013] In an optional embodiment, the thickness of the first doping layer is 90-150 nm.

[0014] In an optional embodiment, the tunneling oxide layer passivated contact cell further includes a first passivation layer, which covers the inner diffusion layer, the tunneling oxide layer and the outside of the first doping layer in the metallization region.

[0015] In an optional embodiment, the first passivation layer also covers the outside of the substrate in the non-metallized area.

[0016] In a second aspect, the present invention provides a method for preparing a tunneling oxide layer passivation contact cell, which is used to prepare the tunneling oxide layer passivation contact cell of any of the aforementioned embodiments; the method for preparing the tunneling oxide layer passivation contact cell comprises:

[0017] forming a tunnel oxide layer and a polysilicon layer on the back side of the substrate, and doping the polysilicon layer to form a first doped layer and an inner diffusion layer located on a side of the tunnel oxide layer away from the first doped layer;

[0018] The non-metallized area on the back of the substrate is processed by laser, and the area not processed by laser is the metallized area;

[0019] Pre-cleaning of non-metallized and metallized areas;

[0020] Then, the non-metallized area and the metallized area are subjected to alkali washing to remove the first doping layer, the tunneling oxide layer and the inner diffusion layer in the non-metallized area.

[0021] In an optional embodiment, the cleaning liquid for pre-cleaning is a first alkaline solution; and the cleaning liquid for alkaline washing includes a second alkaline solution and an additive.

[0022] In an alternative embodiment, the temperature of the pre-wash is lower than the temperature of the alkaline wash.

[0023] In an optional embodiment, the temperature of the pre-wash is 60-70°C; the temperature of the alkali wash is 75-85°C.

[0024] In an optional embodiment, the additive includes a surfactant; and the volume ratio of the additive to the second alkali solution is 0.5-1.5%.

[0025] In an optional embodiment, the mass concentration of at least one of the first alkali solution and the second alkali solution is 2-3%.

[0026] In an alternative embodiment, the pre-cleaning time is longer than the alkaline cleaning time.

[0027] In an optional embodiment, the pre-cleaning time is not less than 97 seconds, and the alkaline cleaning time is 90-95 seconds.

[0028] In an optional embodiment, the wavelength of the laser is 300-650 nm, the spot size is 130-420 μm, the scanning speed is greater than 30 m / s, the power is greater than or equal to 35 W, and the frequency is greater than or equal to 300 kHz.

[0029] In an optional embodiment, the width of the non-metallized area is 400-900 μm.

[0030] The tunneling oxide passivation contact cell of the embodiment of the present invention has the following beneficial effects: a doping concentration difference is formed between the metallized region and the non-metallized region of the tunneling oxide passivation contact cell provided by the embodiment of the present invention, wherein the doping concentration of the substrate corresponding to the non-metallized region is lower than the doping concentration of the inner diffusion layer of the metallized region. The high doping concentration of the inner diffusion layer of the metallized region can ensure electron transmission and ensure a high fill factor (FF), while the low doping concentration of the substrate corresponding to the non-metallized region can effectively suppress the increase of Auger recombination, improve the problem of a large number of electrons being recombined, and reduce the open circuit voltage (Voc). In short, the doping concentration difference is formed between the non-metallized region and the metallized region of the tunneling oxide passivation contact cell of the present invention, which ensures electron transmission in the metallized region, improves the fill factor (FF), and avoids a decrease in the open circuit voltage of the non-metallized region. The power conversion efficiency (PCE) is positively correlated with both the fill factor (FF) and the open circuit voltage (Voc). That is, the power conversion efficiency of the tunneling oxide passivation contact cell can be improved by increasing the concentration difference between the non-metallized region and the metallized region.

[0031] Moreover, the doping concentration of the substrate corresponding to the non-metallized area is lower than the doping concentration of the inner diffusion layer of the metallized area, which can also reduce the parasitic absorption of light and improve ISC (short circuit current).

[0032] The beneficial effects of the preparation method of the tunnel oxide layer passivation contact cell of the embodiment of the present invention include: in the preparation method provided by the embodiment of the present invention, after the tunnel oxide layer and the first doping layer are formed on the back side of the substrate, the non-metallized area of ​​the substrate is first laser treated, and then the non-metallized area and the metallized area that has not been laser treated are pre-cleaned and alkali washed in sequence, so that after the alkali washing, a concentration difference is formed between the non-metallized area and the metallized area; wherein the doping concentration of the substrate corresponding to the non-metallized area is lower than the doping concentration of the inner diffusion layer of the metallized area. The inner diffusion layer of the metallized area has a high doping concentration, which can ensure the transmission of electrons and ensure a high fill factor (FF), while the doping concentration of the substrate corresponding to the non-metallized area is low, which can effectively suppress the increase of Auger recombination, improve the problem of a large number of electrons being recombined, and reduce the open circuit voltage (Voc); in short, the preparation method of the present invention forms a doping concentration difference between the non-metallized area and the metallized area, which ensures the electron transmission of the metallized area, improves the fill factor (FF), and avoids the reduction of the open circuit voltage of the non-metallized area, thereby improving the power conversion efficiency (Power Conversion Efficiency). The PCE is positively correlated with both the fill factor (FF) and the open circuit voltage (Voc), which means that the photoelectric conversion efficiency of the tunnel oxide passivation contact cell can be improved by increasing the concentration difference between the non-metallized area and the metallized area. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments. It should be understood that the following drawings only illustrate certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without paying any creative work.

[0034] Figure 1 The present invention provides a flow chart for preparing a tunnel oxide layer passivated contact cell;

[0035] Figure 2 Schematic diagram of the structure of the tunnel oxide passivation contact cell according to Example 1 of the present invention;

[0036] Figure 3 Schematic diagram of the structure of the tunnel oxide passivation contact cell of Comparative Example 5 of the present invention;

[0037] Figure 4 This is a diagram showing the detection results of Experimental Example 1 of the present invention.

[0038] Icon: 010-tunneling oxide layer passivation contact cell; 100-substrate; 110-tunneling oxide layer; 120-first doping layer; 121-inner diffusion layer; 130-second doping layer; 141-first passivation layer; 142-second passivation layer; 151-first anti-reflection layer; 152-second anti-reflection layer; 161-back metal electrode; 162-front metal electrode. DETAILED DESCRIPTION

[0039] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings herein can be arranged and designed in various different configurations.

[0040] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention as claimed, but rather merely represents selected embodiments of the present invention. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without creative effort are intended to fall within the scope of protection of the present invention.

[0041] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, it does not need to be further defined or explained in subsequent drawings.

[0042] In the description of the present invention, it should be noted that if the terms "upper", "lower", "inside", "outside", etc. appear, the orientation or position relationship indicated is based on the orientation or position relationship shown in the accompanying drawings, or is the orientation or position relationship in which the product of the invention is usually placed when in use. It is only for the convenience of describing the present invention and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, it should not be understood as a limitation on the present invention.

[0043] In addition, the terms "first", "second", etc., if used, are merely used to distinguish and describe, and should not be understood as indicating or implying relative importance.

[0044] It should be noted that, in the absence of conflict, the features in the embodiments of the present invention may be combined with each other.

[0045] The tunneling oxide passivated contact cell (TOPCon cell, Thin Oxide Passivated Contact) provided by the related technology can reduce minority carrier recombination (the process of minority carriers (electrons or holes) and majority carriers in a semiconductor) by isolating the metal from the silicon substrate through a thin film. The tunneling oxide passivated contact cell prepares an ultra-thin layer of silicon oxide on the back of the silicon substrate (usually an n-type single-crystalline silicon substrate), and then deposits a thin layer of doped polysilicon to form a passivating contact structure. The ultra-thin silicon oxide layer allows majority electrons to tunnel into the polysilicon layer and also blocks minority carrier-hole recombination, allowing electrons to be collected by the metal during lateral transmission in the polysilicon layer. This greatly reduces the metal contact recombination current, improves the open-circuit voltage and short-circuit current of the cell, and thus improves the cell conversion efficiency. In short, the passivation mechanism of the tunneling silicon oxide passivated contact structure mainly comes from the following aspects: first, the chemical passivation provided by the silicon oxide interface, second, the field passivation effect of doped polysilicon, and third, the valence band mismatch between polysilicon and silicon, which blocks the transmission of holes.

[0046] The inventors have discovered that the thickness of the doped polysilicon film, a key component of the passivation contact structure, significantly affects parasitic absorption of long-wavelength light. If the doped polysilicon film is too thick, it can cause severe parasitic absorption of long-wavelength light, leading to a series of problems in crystalline silicon solar cells, such as poor long-wavelength response and low bifaciality, thus hindering improvements in photoelectric conversion efficiency. If the doped polysilicon film is too thin, after the sintering process, it can affect the performance of the back polysilicon layer and the tunneling oxide layer, resulting in a decrease in the cell's passivation performance. Therefore, improving the photoelectric conversion efficiency of cells with tunneling oxide passivation contacts is difficult to achieve simply by optimizing the thickness of the doped polysilicon film (increasing or reducing it).

[0047] Accordingly, in order to improve the photoelectric conversion efficiency of the tunneling oxide passivation contact cell while ensuring the passivation and contact properties of the tunneling oxide passivation contact cell (that is, ensuring that the doped polysilicon film has a relatively optimal thickness), the inventors adopted a method of suppressing the increase of Auger recombination of the tunneling oxide passivation contact cell and increasing the open circuit voltage.

[0048] The tunneling oxide layer passivation contact cell and its preparation method disclosed in the present invention will be described in detail below.

[0049] Please refer to Figure 1 The tunnel oxide passivation contact cell 010 disclosed herein includes a substrate 100 (e.g., an n-type monocrystalline silicon wafer), a tunnel oxide layer 110, and a first doped layer 120. The substrate 100 has a front side and a back side that are oppositely distributed, and at least the back side has a metallized region and a non-metallized region. The tunnel oxide layer 110 is formed on the back side and is located in the metallized region. The first doped layer 120 is formed on the side of the tunnel oxide layer 110 that is away from the substrate 100. The side of the tunnel oxide layer 110 that is away from the first doped layer 120 forms an inner extension layer 121. The ratio of the doping concentration of the non-metallized region corresponding to the substrate 100 to the doping concentration of the inner extension layer 121 in the metallized region is (1×10 -6 ~5×10 -4 ) :1.

[0050] It can be seen that the doping concentration of the substrate 100 corresponding to the non-metallized region of the tunneling oxide passivation contact cell 010 disclosed in the present invention is lower than the doping concentration of the inner diffusion layer 121 of the metallized region; wherein, the doping concentration of the inner diffusion layer 121 of the metallized region is high, which can ensure the transmission of electrons and ensure a higher fill factor (FF), while the doping concentration of the substrate 100 corresponding to the non-metallized region is low, which can effectively suppress the increase of Auger recombination, improve the problem of a large number of electrons being recombined, and reduce the open circuit voltage (Voc); in short, the battery disclosed in the present invention forms a doping concentration difference between the non-metallized region and the metallized region, which ensures the electron transmission of the metallized region, improves the fill factor (FF), and avoids the reduction of the open circuit voltage of the non-metallized region. According to the calculation formula of the photoelectric conversion efficiency (PCE): (In the formula, η is the photoelectric conversion efficiency, Voc is the open-circuit voltage, Isc is the short-circuit current, FF is the fill factor, and Pin is the input optical power of the incident light) It can be seen that the photoelectric conversion efficiency is positively correlated with both the fill factor (FF) and the open-circuit voltage (Voc). That is, the photoelectric conversion efficiency of the tunneling oxide layer passivation contact cell 010 can be improved by increasing the concentration difference between the non-metallized area and the metallized area.

[0051] Moreover, the doping concentration of the substrate 100 corresponding to the non-metallized area is lower than the doping concentration of the inner extension layer 121 in the metallized area, which can also reduce parasitic absorption of light and improve ISC (short circuit current).

[0052] It should be noted that the doping concentration of the substrate 100 corresponding to the non-metallized area may refer to the highest concentration of the substrate 100 in the corresponding area; accordingly, the doping concentration of the inner expansion layer 121 in the metallized area may also refer to the highest concentration of the inner expansion layer 121.

[0053] Of course, in other embodiments, the doping concentration of the substrate 100 corresponding to the non-metallized area may also refer to the middle value of the doping concentration of the substrate 100 in the corresponding area; correspondingly, the doping concentration of the inner expansion layer 121 in the metallized area may also refer to the middle value of the doping concentration of the inner expansion layer 121.

[0054] Optionally, the doping concentration of the substrate 100 corresponding to the non-metallized area is 1×10 15 ~5×10 16 atom / cm 3 , for example: 1×10 15 atom / cm 3 , 2×10 15 atom / cm 3 , 5×10 15 atom / cm 3 , 7×10 15 atom / cm 3 , 1×10 16 atom / cm 3 , 2×10 16 atom / cm 3 , 3×10 16 atom / cm 3 , 5×10 16 atom / cm 3 etc.; the doping concentration of the inner expansion layer 121 in the metallized area is 1×10 20 ~1×10 21 atom / cm 3 , for example: 1×10 20 atom / cm 3 , 2×10 20 atom / cm 3 , 3×10 20 atom / cm 3 , 4×10 20 atom / cm 3 , 5×10 20 atom / cm 3 , 6×10 20atom / cm 3 , 7×10 20 atom / cm 3 , 8×10 20 atom / cm 3 , 9×10 20 atom / cm 3 , 1×10 21 atom / cm 3 By optimizing the doping concentrations of the metallized and non-metallized regions, on the one hand, the non-metallized regions can effectively reduce carrier recombination, increase minority carrier lifetime and open-circuit voltage, thereby improving the overall efficiency of the battery, that is, directly improving the energy conversion efficiency of the battery. On the other hand, the metallized regions can optimize charge carrier transport, ensure good ohmic contact, reduce contact resistance, improve charge carrier collection efficiency, increase current density (Jsc), and further improve the overall performance of the battery. On the other hand, it can provide an optimized concentration difference between the metallized and non-metallized regions, optimize the carrier transmission path, reduce energy loss, and further enhance the performance and stability of the battery.

[0055] At the same time, optimizing the doping concentrations in the metallized and non-metallized regions can also reduce the series resistance and the non-radiative recombination centers to improve the fill factor (FF) and further ensure the improvement of the photoelectric conversion efficiency; it can also improve the stability and reliability of the tunneling oxide passivation contact cell 010, that is, it is not only beneficial to improve the initial efficiency of the tunneling oxide passivation contact cell 010, but also to enhance its long-term stability and reliability, so that it can maintain a high energy output under different working environments.

[0056] The inventors further discovered that if the doping concentration of the inner extension layer 121 in the metallization region is further increased (i.e., greater than 1×10 21 atom / cm 3), will instead have a negative impact on various properties of the tunnel oxide passivation contact cell 010. For example, excessively high doping concentrations will significantly increase Auger recombination, causing more carriers to recombine in the metallization area, reducing the minority carrier lifetime, thereby affecting the cell's open circuit voltage and reducing the photoelectric conversion efficiency; excessively high doping concentrations are likely to introduce more crystal defects and stress, damaging the crystal quality of the material, such as causing crystal structure deformation or defects such as dislocations, increasing non-radiative recombination centers, further reducing cell performance and stability; although high doping can reduce contact resistance, after exceeding a certain concentration, the resistance improvement will tend to saturate, and may even increase resistance due to impurity scattering effects, and may even easily damage the substrate 100, and even cause contact quality degradation during the metallization process; excessive doping may also cause band structure distortion, leading to the formation of excessive deep energy level defects or non-radiative recombination centers, which act as carrier traps, increase the recombination probability of electrons and holes, affect the carrier transport characteristics, and reduce the cell's open circuit voltage, short-circuit current density, fill factor, and conversion efficiency.

[0057] Moreover, if the doping concentration is too high, a more complex process is required, the cost is difficult to control, and the manufacturing is more difficult.

[0058] Optionally, the first doped layer 120 is a phosphorus-doped polysilicon layer. The phosphorus-doped polysilicon layer plays a vital role in surface passivation, carrier selectivity, tunneling effect, and optical performance optimization. The phosphorus-doped polysilicon layer, combined with the tunneling oxide layer 110, provides excellent surface passivation, significantly reducing the carrier recombination rate on the back surface, thereby improving the minority carrier lifetime and open-circuit voltage. Phosphorus doping enables the polysilicon layer to act as an electron-selective contact layer, allowing electrons to pass efficiently while blocking holes, reducing recombination losses. At the same time, the high doping concentration reduces contact resistance and improves carrier collection efficiency. Furthermore, the phosphorus-doped polysilicon layer and the tunneling oxide layer 110 work together to achieve efficient electron transmission through the quantum tunneling effect, avoiding the recombination problem of traditional metal-semiconductor contacts. The phosphorus-doped polysilicon layer also optimizes the optical properties of the back surface of the cell, enhancing the reflection of long-wavelength light and further improving the cell's light absorption efficiency.

[0059] Optionally, the thickness of the first doping layer 120 is 90-150 nm, for example, 90 nm, 95 nm, 100 nm, 110 nm, 120 nm, 130 nm, 140 nm, 150 nm, etc. In this way, on the one hand, the parasitic absorption problem caused by the excessive thickness of the first doped layer 120 can be improved. If the thickness is greater than 150nm, it will cause serious parasitic absorption of long-wave light, increase the absorption loss of the incident light, and lead to poor long-wave response and low bifaciality of the tunnel oxide passivation contact cell 010. That is, optimizing the thickness of the first doped layer 120 can reduce the absorption loss of the incident light and enhance the reflection of long-wavelength light, further improving the photoelectric conversion efficiency of the cell; on the other hand, it can also improve the problem of decreased passivation performance of the tunnel oxide passivation contact cell 010 caused by the thickness of the first doped layer 120 being too thin. That is, within the above thickness range, it can effectively balance the surface passivation performance and carrier transport efficiency, ensure the synergistic effect of the polysilicon layer and the tunnel oxide layer 110, significantly reduce the carrier recombination rate on the back surface, thereby improving the minority carrier lifetime and open-circuit voltage, and at the same time form a high-quality electron-selective contact layer, allowing electrons to tunnel and pass efficiently, while blocking holes, reducing recombination losses, reducing contact resistance, and improving carrier collection efficiency.

[0060] The tunnel oxide passivation contact cell 010 disclosed herein further includes a first passivation layer 141, which covers the inner extension layer 121 of the metallization region, the tunnel oxide layer 110, and the exterior of the first doped layer 120. This significantly improves the performance and reliability of the tunnel oxide passivation contact cell 010. The first passivation layer 141 effectively reduces the carrier recombination rate at the interface between the metallization region and the semiconductor, reducing recombination losses caused by surface states, thereby increasing the minority carrier lifetime and open-circuit voltage. The first passivation layer 141 provides additional protection for the tunnel oxide layer 110 and the first doped layer 120, acting as a physical barrier to reduce impurity diffusion and the impact of the external environment on the device. It also enhances interfacial stability, preventing damage to the oxide layer during subsequent processes, and ensuring the high efficiency of the tunneling effect, as well as long-term stability and durability. Furthermore, the first passivation layer 141 optimizes the contact performance of the metallization region, reducing contact resistance and improving carrier collection efficiency.

[0061] Furthermore, the first passivation layer 141 also covers the outside of the substrate 100 in the non-metallized area. This not only effectively reduces the carrier recombination rate on the surface of the non-metallized area and reduces the recombination loss caused by surface states, thereby improving the minority carrier lifetime and open-circuit voltage, but also helps improve the carrier transmission characteristics in the substrate 100 by reducing leakage current, further improving the fill factor and conversion efficiency of the battery. In addition, the first passivation layer 141 also optimizes the optical performance of the non-metallized area, reduces surface reflection, improves light absorption efficiency, and provides additional protection for the substrate 100, preventing corrosion of the material by the external environment (such as moisture and impurities), thereby enhancing the long-term reliability of the device.

[0062] The tunnel oxide passivated contact cell 010 disclosed herein also includes a second doped layer 130. This second doped layer 130, formed on the front surface of the substrate 100, can be a boron diffusion layer serving as a p+ emitter. This second doped layer 130 (p+ emitter) not only helps improve the separation efficiency of photogenerated carriers but also reduces the surface recombination rate, thereby increasing the open-circuit voltage (Voc) and short-circuit current density (Jsc), ultimately boosting the overall conversion efficiency of the cell.

[0063] Furthermore, the tunnel oxide passivation contact cell 010 further includes a second passivation layer 142, which is formed on the side of the second doped layer 130 facing away from the substrate 100. The second passivation layer 142 can not only further reduce the surface recombination rate, but also protect the diffusion layer from being affected by subsequent process steps.

[0064] Optionally, the first passivation layer 141 and the second passivation layer 142 may be Al 2 O 3 . In other embodiments, the second passivation layer 142 may also be silicon oxide or silicon nitride, etc., which is not specifically limited here.

[0065] Furthermore, the tunneling oxide passivation contact cell 010 also includes a first anti-reflection layer 151 and a second anti-reflection layer 152; wherein, the first anti-reflection layer 151 is formed on the side of the first passivation layer 141 facing away from the substrate 100, and the second anti-reflection layer 152 is formed on the side of the second passivation layer 142 facing away from the substrate 100.

[0066] The present disclosure also provides a method for preparing a tunneling oxide layer passivation contact cell 010, which is used to prepare the tunneling oxide layer passivation contact cell 010. The preparation method comprises:

[0067] Performing a texturing process on the front surface of a substrate 100 (for example, an n-type silicon substrate 100 ) to form a texturing surface on the front surface of the substrate 100 ;

[0068] Boron diffusion is performed on the front surface of the substrate 100 after the texturing process to form a front boron diffusion layer (i.e., the second doping layer 130);

[0069] Etching is performed on the back side of the substrate 100 to remove the borosilicate glass (BSG) layer on the back side, and the back side of the substrate 100 is alkaline polished;

[0070] A tunnel oxide layer 110 and a polysilicon layer (i.e., a Poly layer) are formed on the back side of the substrate 100, and the polysilicon layer is doped to form a first doped layer 120 and an inner extension layer 121 located on a side of the tunnel oxide layer 110 away from the first doped layer 120;

[0071] The non-metallized area on the back side of the substrate 100 is treated with a laser to modify the protective layer (e.g., phosphorus-silicon glass layer) on the doped surface of the polysilicon layer in the non-metallized area; the area not treated with the laser is the metallized area;

[0072] Use chain pickling to remove the protective layer (e.g., phosphosilicate glass layer, PSG) on the front and side surfaces and expose the polysilicon layer of the winding;

[0073] Pre-cleaning of non-metallized and metallized areas;

[0074] Then, the non-metallized area and the metallized area are subjected to alkaline washing to remove the first doped layer 120, the tunneling oxide layer 110 and the inner diffusion layer 121 in the non-metallized area, so that the first doped layer 120 (i.e., the phosphorus-doped polysilicon layer) and the tunneling oxide layer 110 in the metallized area are retained;

[0075] Then, the second passivation layer 142, the first passivation layer 141, the second anti-reflection layer 152 and the first anti-reflection layer 151 are prepared in sequence, as well as the front metal electrode 162 and the back metal electrode 161. The electrodes are then made into good contact through sintering, light injection and laser-assisted sintering.

[0076] After forming the tunneling oxide layer 110 and the first doping layer 120 on the back side of the substrate 100, the non-metallized area of ​​the substrate 100 is first laser treated to ensure that the protective layer corresponding to the non-metallized area is modified, and then the non-metallized area and the metallized area that has not been laser treated are pre-cleaned and alkali washed in sequence, so that after the alkali washing, a concentration difference is formed between the non-metallized area and the metallized area; wherein the doping concentration of the substrate 100 corresponding to the non-metallized area is lower than the doping concentration of the inner diffusion layer 121 in the metallized area. The inner diffusion layer 121 in the metallized area has a high doping concentration, which can ensure the transmission of electrons and ensure a high fill factor (FF), while the doping concentration of the substrate 100 corresponding to the non-metallized area is low, which can effectively suppress the increase of Auger recombination, improve the problem of a large number of electrons being recombined, and reduce the open circuit voltage (Voc); in short, the preparation method of the present invention forms a doping concentration difference between the non-metallized area and the metallized area, that is, it ensures the electron transmission in the metallized area, improves the fill factor (FF), and avoids the reduction of the open circuit voltage in the non-metallized area, thereby improving the photoelectric conversion efficiency (Power Conversion Efficiency). The PCE) is positively correlated with both the fill factor (FF) and the open circuit voltage (Voc), which means that the photoelectric conversion efficiency of the tunnel oxide passivation contact cell 010 can be improved by increasing the concentration difference between the non-metallized area and the metallized area.

[0077] It should be noted that the aforementioned inner expansion layer 121 formed on the side of the tunneling oxide layer 110 away from the first doped layer 120 is formed when the first doped layer 120 is prepared by a phosphorus diffusion process, and the doping atoms phosphorus diffuse through the polysilicon layer into the silicon substrate 100; the retention of the inner expansion layer 121 in the metallized area ensures a high doping concentration of the expansion layer 121 in the metallized area, and the inner expansion layer 121 is distributed on the side of the tunneling oxide layer 110 away from the first doped layer 120, that is, the inner expansion layer 121 has a certain depth, that is, the doping has a certain depth, and a higher doping concentration and depth are conducive to the transmission of electrons, thereby ensuring a higher fill factor (FF).

[0078] It should also be noted that after pre-cleaning and alkaline washing, the polysilicon coating on the front and side surfaces will also be removed.

[0079] In the present disclosure, the metallized area includes not only the back metal electrode 161 and the first doped layer 120 around it, but also includes the back metal electrode 161 and all the first doped layers 120, tunneling oxide layer 110, and inner expansion layer 121 corresponding to the back metal electrode 161. It can even be understood as the first passivation layer 141 and the first anti-reflection layer 151 wrapped around the outside of the above structure.

[0080] Optionally, the wavelength of the laser is 300-650 nm (for example, 300 nm, 325 nm, 350 nm, 375 nm, 400 nm, 425 nm, 450 nm, 475 nm, 500 nm, 525 nm, 550 nm, 575 nm, 600 nm, 625 nm, 650 nm, etc.), and the spot size is 130-420 μm (for example, 130 μm, 150 μm, 180 μm, 200 μm, 240 μm, 28 0μm, 300μm, 320μm, 350μm, 380μm, 400μm, 420μm, etc.), scanning speed greater than 30m / s (for example: 31m / s, 32m / s, 35m / s, 38m / s, 40m / s, etc.), power greater than or equal to 35W (for example: 35W, 38W, 41W, 42W, 45W, 47W, 50W, etc.), frequency greater than or equal to 300kHz (for example: 300kHz, 400kHz, etc.). Under the above-mentioned laser processing parameters, on the one hand, it is possible to ensure that the protective layer formed in the non-metallized region is reliably modified into a structure that can react with the subsequent pre-cleaning and alkali washing, so that the protective layer can be efficiently and reliably removed during the pre-cleaning and alkali washing processes. On the other hand, it is possible to also cause at least a portion of the first doped layer 120, the tunneling oxide layer 110, and the inner expansion layer 121 in the non-metallized region to be laser-modified into a structure that is more easily eluted (corroded) by the subsequent pre-cleaning and alkali washing steps (for example, by causing the first doped layer 120 to undergo a phase change and oxidation, thereby reducing its chemical stability and making it more easily eluted; for example, by causing the interface between the inner expansion layer 121 and the substrate 100 to change, thereby reducing the adhesion strength of the inner expansion layer 121 to the substrate 100; for example, by causing the crystal structure of the tunneling oxide layer 110 to become unstable), thereby ensuring that the subsequent pre-cleaning and alkali washing steps can efficiently and reliably remove the first doped layer 120, the tunneling oxide layer 110, and the inner expansion layer 121 in the non-metallized region.

[0081] Furthermore, the laser wavelength is 350-600nm, and the laser power is greater than 40W and less than 50W. In this way, while the laser process is used to modify the protective layer in the non-metallized area on the back, the first doped layer 120, tunneling oxide layer 110, and inner expansion layer 121 in the non-metallized area are effectively modified. This facilitates subsequent pre-cleaning and alkaline cleaning, effectively eluting the first doped layer 120, tunneling oxide layer 110, and inner expansion layer 121 in the non-metallized area, and ensuring an effective doping concentration difference between the substrate 100 corresponding to the non-metallized area and the inner expansion layer 121 in the metallized area.

[0082] It should be noted that the laser processing can be performed using nanosecond, picosecond, or femtosecond lasers.

[0083] Optionally, the width of the non-metallized region is 400-900μm, for example, 400μm, 500μm, 600μm, 700μm, 800μm, 900μm, etc. Optimizing the width of the non-metallized region ensures that photogenerated carriers can effectively diffuse into the metallized region, achieving a balance between light absorption and carrier recombination. This ensures sufficient light absorption while reducing recombination losses, significantly increasing open-circuit voltage and carrier collection efficiency. It also avoids excessively long carrier transmission paths caused by excessively wide non-metallized regions, thereby reducing series resistance and improving fill factor and conversion efficiency.

[0084] The inventors have found that if alkaline washing is performed directly after the laser treatment step, a longer alkaline washing time is required to effectively remove the polysilicon layer coated on the front and side surfaces, and the protective layer after laser treatment is thin. In order to slow down the rate at which the protective layer is washed off by alkaline washing, the related technology needs to add additives to the alkaline solution during alkaline washing to reduce the elution of the protective layer, so as to achieve the purpose of smoothly eluting the polysilicon layer coated on the front and side surfaces and protecting the polysilicon layer on the back surface; however, due to the use of additives, there is no obvious difference in the elution rate between the non-metallized area and the metallized area, and it is difficult to form a doping concentration difference between the substrate 100 corresponding to the non-metallized area and the inner expansion layer 121 of the metallized area after alkaline washing.

[0085] To improve the above-mentioned problem, the present disclosure uses a first alkaline solution for pre-cleaning, followed by alkaline washing with a second alkaline solution containing an additive. This allows the use of the first alkaline solution without the additive for pre-cleaning, thereby expanding the corrosion window of the laser-treated non-metallized area and the non-laser-treated metallized area. Specifically, during pre-cleaning, the laser-treated non-metallized area (including the PSG, the first doped layer 120, the tunneling oxide layer 110, and the inner expansion layer 121) reacts more easily with the first alkaline solution, resulting in a faster reaction rate. After pre-cleaning, the structure of the non-metallized area is significantly thinned, while the structure of the metallized area is not significantly thinned. Furthermore, a portion of the polysilicon plated on the front and side surfaces is also washed away. Subsequently, alkaline washing is performed using the second alkaline solution containing the additive. Even with the presence of the additive, the non-metallized area is washed away more quickly. Furthermore, the alkaline washing ensures the washing of the polysilicon on the front and side surfaces. While the non-metallized area is being washed away, the metallized area is not washed away due to the presence of the additive, thereby creating a difference in doping concentration between the substrate 100 corresponding to the non-metallized area and the inner expansion layer 121 of the metallized area.

[0086] Optionally, the first alkali liquor and the second alkali liquor comprise sodium hydroxide solution. Of course, in other embodiments, the first alkali liquor and the second alkali liquor may also comprise potassium hydroxide solution, etc., which is not specifically limited here.

[0087] Furthermore, the mass concentration of at least one of the first alkaline solution and the second alkaline solution is 2-3%, for example, 2%, 2.3%, 2.5%, 2.7%, 3%, etc., without specific limitation herein. Increasing the concentration of the alkaline solution used in the pre-cleaning and alkaline washing processes further increases the depth of the non-metallized region formed by the wet process, lengthens the narrow channel beneath the metallized region, increases the string resistance, causes current loss, and reduces the fill factor (FF). If the concentration is less than 2%, elution is difficult to achieve.

[0088] Optionally, the concentrations of the first alkali solution and the second alkali solution are the same. In this way, it is easier to control the elution rates of the non-metallized area and the metallized area during pre-cleaning and alkali washing, so as to ensure that an ideal doping concentration difference is achieved between the substrate 100 corresponding to the non-metallized area and the inner diffusion layer 121 of the metallized area.

[0089] Optionally, the additive includes a surfactant; the volume ratio of the additive to the second alkaline solution is 0.5-1.5%, for example, 0.5%, 0.7%, 1%, 1.3%, 1.5%, etc. Optimizing the dosage of the additive can protect the metallized area and slow down its elution, while also ensuring reliable elution of the non-metallized area and effective elution of the polysilicon wrapped around the front and side surfaces.

[0090] It should be noted that the types of additives are similar to those in the related art and are not specifically limited here. They can be anionic surfactants (for example, sodium dodecylbenzenesulfonate, sodium lauryl sulfate, etc.), non-ionic surfactants (for example, polyoxyethylene ethers, fatty alcohol polyoxyethylene ethers, etc.), or amphoteric surfactants (for example, cocamidopropyl betaine, alkyl dimethyl amine oxide, etc.), which are not listed one by one here.

[0091] Optionally, the temperature of the pre-cleaning is lower than the temperature of the alkali washing. Controlling the pre-cleaning temperature to be lower can further reduce the elution rate of the metallized area, or even prevent the metallized area from being eluted.

[0092] Furthermore, the pre-cleaning temperature is 60-70°C, for example, 60°C, 62°C, 65°C, 68°C, 70°C, etc.; the alkaline washing temperature is 75-85°C, for example, 75°C, 78°C, 80°C, 83°C, 85°C, etc. At the above pre-cleaning temperature, the elution rate of the metallized area can be reduced while ensuring efficient and reliable elution of the non-metallized area. During the alkaline washing, due to the addition of additives and the increase in the alkaline washing temperature, the non-metallized area can be reliably eluted, thereby ensuring a difference in doping concentration between the substrate 100 corresponding to the non-metallized area and the inner expansion layer 121 of the metallized area. If the alkaline washing temperature is further increased, the depth of the non-metallized area formed by the wet process will increase, the narrow channel under the metallized area will become longer, the string resistance will increase, the current will be lost, and the fill factor (FF) will be reduced.

[0093] Optionally, the pre-cleaning time is longer than the alkali cleaning time. In this way, it is possible to ensure that the laser-treated non-metallized areas are significantly washed away during the pre-cleaning.

[0094] Furthermore, the pre-cleaning time is not less than 97 seconds, and the alkali washing time is 90-95 seconds. If the pre-cleaning time is less than 97 seconds, it is easy to cause incomplete cleaning of the non-metallized area, making it difficult to form an ideal doping concentration difference between the substrate 100 corresponding to the non-metallized area and the inner expansion layer 121 of the metallized area. If the alkali washing time is too short, it is difficult to thoroughly clean the non-metallized area, making it difficult to form an ideal doping concentration difference between the substrate 100 corresponding to the non-metallized area and the inner expansion layer 121 of the metallized area. At the same time, if the alkali washing time is too long, it is easy to cause excessive alkali washing of the non-metallized area. Although it can form a doping concentration difference between the substrate 100 corresponding to the non-metallized area and the inner expansion layer 121 of the metallized area, the depth of the non-metallized area formed by the wet process increases, the narrow channel under the metallized area becomes longer, the string resistance becomes larger, the current will be lost, and the fill factor (FF) will be reduced.

[0095] Optionally, the pre-cleaning time is less than 110 seconds, so that a large amount of elution of the metallized area can be avoided.

[0096] The chain pickling cleaning machine disclosed in the present invention includes hydrofluoric acid and water. The method and principle of chain pickling are similar to those in the related art and will not be described in detail here.

[0097] The preparation processes not described in detail in the present disclosure, such as the boron diffusion process, the deposition process for forming the tunnel oxide layer 110 and the polysilicon layer, and the doping process, are similar to those in the related art and will not be described in detail here.

[0098] The technical solutions disclosed in the invention will be described in detail below with reference to specific embodiments.

[0099] Example 1

[0100] Example 1 provides a tunneling oxide layer passivation contact cell, which includes an n-type single crystal silicon substrate (doping concentration of 1.2×10 16 atom / cm 3 ), the substrate has a front side and a back side, a boron diffusion layer, an aluminum oxide layer, and a silicon nitride layer are formed in sequence on the front side, and a tunneling oxide layer, a phosphorus-doped polysilicon layer (thickness 90nm), an aluminum oxide layer, and a silicon nitride layer are formed in sequence on the back side, wherein an inner expansion layer is formed on the side of the tunneling oxide layer away from the phosphorus-doped polysilicon layer; the tunneling oxide layer passivation contact cell also includes a front electrode and a back electrode.

[0101] The doping concentration of the substrate corresponding to the non-metallized area on the back of the tunnel oxide passivation contact cell is 1.2×10 16 atom / cm 3 The doping concentration of the inner diffusion layer in the metallized area is 1.4×10 20 atom / cm 3 The ratio of the doping concentration of the substrate in the non-metallized area to the doping concentration of the inner diffusion layer in the metallized area is 8.57×10 -5 :1; the width of the non-metallized area is 400μm.

[0102] Example 2

[0103] The difference between the tunnel oxide passivation contact cell of Example 2 and Example 1 is that the doping concentration of the n-type single crystal silicon substrate is 5×10 16 atom / cm 3 The thickness of the phosphorus-doped polysilicon layer is 150 nm, wherein the doping concentration of the substrate corresponding to the non-metallized area on the back of the tunnel oxide layer passivating the contact cell is 5×10 16 atom / cm 3 The doping concentration of the inner diffusion layer in the metallized area is 1×10 21 atom / cm 3 The ratio of the doping concentration of the substrate in the non-metallized area to the doping concentration of the inner diffusion layer in the metallized area is 5×10 -5 :1; the width of the non-metallized area is 900 μm. Except for the above differences, please refer to Example 1 for the rest.

[0104] Example 3

[0105] The difference between the tunnel oxide passivation contact cell of Example 3 and Example 1 is that the doping concentration of the n-type single crystal silicon substrate is 5×10 15 atom / cm 3The thickness of the phosphorus-doped polysilicon layer is 120 nm, wherein the doping concentration of the substrate corresponding to the non-metallized area on the back of the tunnel oxide layer passivating the contact cell is 5×10 15 atom / cm 3 The doping concentration of the inner diffusion layer in the metallized area is 5×10 20 atom / cm 3 The ratio of the doping concentration of the substrate in the non-metallized area to the doping concentration of the inner diffusion layer in the metallized area is 1×10 -5 :1; the width of the non-metallized area is 700 μm. Except for the above differences, please refer to Example 1 for the rest.

[0106] Comparative Example 1

[0107] The difference between the tunnel oxide passivation contact cell of Comparative Example 1 and Example 1 is that the doping concentration of the substrate corresponding to the non-metallized area on the back is 1.2×10 16 atom / cm 3 The doping concentration of the inner diffusion layer in the metallized area is 1.2×10 21 atom / cm 3 The ratio of the doping concentration of the substrate in the non-metallized area to the doping concentration of the inner diffusion layer in the metallized area is 1×10 -5 :1. For the rest except the above differences, please refer to Example 1.

[0108] Comparative Example 2

[0109] The tunnel oxide passivation contact cell of Comparative Example 2 differs from that of Example 1 in that the thickness of the phosphorus-doped polysilicon layer is 80 nm. For all other aspects except the above differences, please refer to Example 1.

[0110] Comparative Example 3

[0111] The tunnel oxide passivation contact cell of Comparative Example 3 differs from that of Example 1 in that the thickness of the phosphorus-doped polysilicon layer is 160 nm. For all other aspects except the above differences, please refer to Example 1.

[0112] Example 4

[0113] The front surface of the n-type silicon substrate is subjected to texturing treatment to form a textured surface on the front surface.

[0114] Boron diffusion is performed on the front surface of the substrate after the texturing process to form a front boron diffusion layer.

[0115] The back side of the substrate is etched to remove the borosilicate glass (BSG) layer on the back side, and the back side of the substrate is alkali polished.

[0116] A tunneling oxide layer and a polysilicon layer are deposited on the back side of the substrate, and the polysilicon layer is doped to form a phosphorus-doped polysilicon layer and an inner diffusion layer located on the side of the tunneling oxide layer away from the phosphorus-doped polysilicon layer; wherein the thickness of the phosphorus-doped polysilicon layer is 90nm.

[0117] Laser treatment was used on the non-metallized area on the back side of the substrate to modify the protective layer on the doped surface of the polysilicon layer in the non-metallized area. The area not subjected to laser treatment was the metallized area. The laser had a wavelength of 400 nm, a spot size of 150 μm, a scanning speed of 45 m / s, a power of 41 W, and a frequency of 300 kHz. The width of the non-metallized area was 600 μm.

[0118] The protective layer (e.g., phosphosilicate glass layer, PSG) on the front and side surfaces is removed by chain pickling, and the polysilicon layer on the surface is exposed.

[0119] The non-metallized area and the metallized area were pre-cleaned; the cleaning agent for the pre-cleaning was a sodium hydroxide solution with a mass concentration of 2.3%, the cleaning temperature was 65° C., and the cleaning time was 97 s.

[0120] The non-metallized area and the metallized area are then alkaline washed to remove the first doped layer, tunnel oxide layer and inner diffusion layer in the non-metallized area, so that the phosphorus-doped polysilicon layer and tunnel oxide layer in the metallized area are retained; the alkaline washing cleaning agent includes sodium hydroxide with a mass concentration of 2.3% and an additive, and the volume ratio of the additive to the sodium hydroxide solution is 1%. The alkaline washing temperature is 80°C and the time is 95s.

[0121] Then, a second passivation layer, a first passivation layer, a second anti-reflection layer and a first anti-reflection layer are prepared in sequence, as well as a front electrode and a back electrode.

[0122] The doping concentration of the substrate corresponding to the non-metallized area on the back of the prepared tunnel oxide passivation contact cell is 1×10 15 atom / cm 3 The doping concentration of the inner diffusion layer in the metallized area is 1×10 20 atom / cm 3 The ratio of the doping concentration of the substrate in the non-metallized area to the doping concentration of the inner diffusion layer in the metallized area is 1×10 -5 :1.

[0123] Example 5

[0124] The difference between Example 5 and Example 4 lies in the processes of the laser step, the pre-cleaning step and the alkaline cleaning step.

[0125] The laser has a wavelength of 550 nm, a spot size of 400 μm, a scanning speed of 40 m / s, a power of 45 W, and a frequency of 400 kHz.

[0126] The cleaning agent for pre-cleaning is a sodium hydroxide solution with a mass concentration of 2%, the cleaning temperature is 70°C, and the cleaning time is 98s.

[0127] The cleaning agent for alkaline washing includes sodium hydroxide with a mass concentration of 2% and an additive, the volume ratio of the additive to the sodium hydroxide solution is 0.5%, the temperature of the alkaline washing is 85°C, and the time is 90s.

[0128] The doping concentration of the substrate corresponding to the non-metallized area on the back of the prepared tunnel oxide passivation contact cell is 1×10 15 atom / cm 3 The doping concentration of the inner diffusion layer in the metallized area is 1×10 20 atom / cm 3 The ratio of the doping concentration of the substrate in the non-metallized area to the doping concentration of the inner diffusion layer in the metallized area is 1×10 -5 :1.

[0129] For the rest of the differences except the above, please refer to Example 4.

[0130] Example 6

[0131] The difference between Example 6 and Example 4 lies in the processes of the laser step, the pre-cleaning step and the alkaline cleaning step.

[0132] The laser has a wavelength of 650 nm, a spot size of 420 μm, a scanning speed of 32 m / s, a power of 42 W, and a frequency of 300 kHz.

[0133] The cleaning agent for pre-cleaning is a sodium hydroxide solution with a mass concentration of 3%, the cleaning temperature is 60°C, and the cleaning time is 99s.

[0134] The cleaning agent for alkaline washing includes sodium hydroxide with a mass concentration of 3% and an additive, the volume ratio of the additive to the sodium hydroxide solution is 1.5%, the temperature of the alkaline washing is 75°C, and the time is 92s.

[0135] The doping concentration of the substrate corresponding to the non-metallized area on the back of the prepared tunnel oxide passivation contact cell is 1×10 15 atom / cm 3 The doping concentration of the inner diffusion layer in the metallized area is 1×10 20 atom / cm 3 The ratio of the doping concentration of the substrate in the non-metallized area to the doping concentration of the inner diffusion layer in the metallized area is 1×10 -5 :1.

[0136] For the rest of the differences except the above, please refer to Example 4.

[0137] Example 7

[0138] The difference between Example 7 and Example 4 lies in the processes of the laser step, the pre-cleaning step and the alkaline washing step.

[0139] The laser has a wavelength of 325 nm, a spot size of 130 μm, a scanning speed of 32 m / s, a power of 50 W, and a frequency of 300 kHz.

[0140] The cleaning agent for pre-cleaning is a sodium hydroxide solution with a mass concentration of 2.5%, the cleaning temperature is 62°C, and the cleaning time is 97s.

[0141] The cleaning agent for alkaline washing includes sodium hydroxide with a mass concentration of 2.5% and an additive, the volume ratio of the additive to the sodium hydroxide solution is 1.1%, the temperature of the alkaline washing is 73°C, and the time is 90s.

[0142] The doping concentration of the substrate corresponding to the non-metallized area on the back of the prepared tunnel oxide passivation contact cell is 1×10 15 atom / cm 3 The doping concentration of the inner diffusion layer in the metallized area is 1×10 20 atom / cm 3 The ratio of the doping concentration of the substrate in the non-metallized area to the doping concentration of the inner diffusion layer in the metallized area is 1×10 -5 :1.

[0143] For the rest of the differences except the above, please refer to Example 4.

[0144] Example 8

[0145] The difference between Example 8 and Example 4 is that the wavelength of the laser treatment is 300 nm and the laser power is 35 W; the doping concentration of the substrate corresponding to the non-metallized area on the back of the prepared tunnel oxide passivation contact cell is 1×10 15 atom / cm 3 The doping concentration of the inner diffusion layer in the metallized area is 1×10 20 atom / cm 3 The ratio of the doping concentration of the substrate in the non-metallized area to the doping concentration of the inner diffusion layer in the metallized area is 1×10 -5 :1.

[0146] For the rest of the differences except the above, please refer to Example 4.

[0147] Comparative Example 4

[0148] The difference between Comparative Example 4 and Example 4 is that the wavelength of the laser treatment is 750 nm and the laser power is 50 W; the doping concentration of the substrate corresponding to the non-metallized area on the back of the prepared tunneling oxide passivation contact cell is 6×10 18 atom / cm 3 The doping concentration of the inner diffusion layer in the metallized area is 1×10 20 atom / cm 3 The ratio of the doping concentration of the substrate in the non-metallized area to the doping concentration of the inner diffusion layer in the metallized area is 6×10 -2 :1.

[0149] For the rest of the differences except the above, please refer to Example 4.

[0150] Comparative Example 5

[0151] The difference between Comparative Example 5 and Example 4 is that no pre-cleaning is performed and alkali washing is performed directly. The concentration difference between the non-metallized area and the metallized area on the back of the prepared tunneling oxide layer passivation contact cell is not obvious. The doping concentration of the substrate corresponding to the non-metallized area is 1×10 20 atom / cm 3 The doping concentration of the inner diffusion layer in the metallized area is 1.4×10 20 atom / cm 3 The ratio of the doping concentration of the substrate corresponding to the non-metallized area to the doping concentration of the inner diffusion layer in the metallized area is 0.71:1.

[0152] For the rest of the differences except the above, please refer to Example 4.

[0153] Comparative Example 6

[0154] The difference between Comparative Example 6 and Example 4 is that the mass concentration of the pre-cleaning sodium hydroxide solution is 3.5%, and the pre-cleaning temperature is 80°C. The doping concentration of the substrate corresponding to the non-metallized area on the back of the prepared tunneling oxide passivation contact cell is 1×10 15 atom / cm 3 The doping concentration of the inner diffusion layer in the metallized area is 1×10 20 atom / cm 3 The ratio of the doping concentration of the substrate in the non-metallized area to the doping concentration of the inner diffusion layer in the metallized area is 1×10 -5 :1.

[0155] The depth of the non-metallized area of ​​Comparative Example 6 after alkali washing is 1.15 times the depth of the non-metallized area of ​​Example 4 after alkali washing.

[0156] For the rest of the differences except the above, please refer to Example 4.

[0157] Comparative Example 7

[0158] The difference between Comparative Example 7 and Example 4 is that the mass concentration of the sodium hydroxide solution for alkali washing is 3.5%, and the alkali washing temperature is 90°C. The doping concentration of the substrate corresponding to the non-metallized area on the back of the prepared tunneling oxide passivation contact cell is 1×10 15 atom / cm 3 The doping concentration of the inner diffusion layer in the metallized area is 1×10 20 atom / cm 3 The ratio of the doping concentration of the substrate in the non-metallized area to the doping concentration of the inner diffusion layer in the metallized area is 1×10 -5 :1.

[0159] The depth of the non-metallized area of ​​Comparative Example 7 after alkali washing is 1.3 times the depth of the non-metallized area of ​​Example 4 after alkali washing.

[0160] For the rest of the differences except the above, please refer to Example 4.

[0161] Comparative Example 8

[0162] The difference between Comparative Example 8 and Example 4 is that the pre-cleaning time is 90s, and the doping concentration of the substrate corresponding to the non-metallized area on the back of the prepared tunneling oxide passivation contact cell is 1×10 17 atom / cm 3 The doping concentration of the inner diffusion layer in the metallized area is 1×10 20 atom / cm 3 The ratio of the doping concentration of the substrate in the non-metallized area to the doping concentration of the inner diffusion layer in the metallized area is 1×10 -3 :1.

[0163] For the rest of the differences except the above, please refer to Example 4.

[0164] Comparative Example 9

[0165] The difference between Comparative Example 9 and Example 4 is that the pre-cleaning time is 120s, and the doping concentration of the substrate corresponding to the non-metallized area on the back of the prepared tunneling oxide passivation contact cell is 1×10 15 atom / cm 3 The doping concentration of the inner diffusion layer in the metallized area is 1×10 19 atom / cm 3 The ratio of the doping concentration of the substrate in the non-metallized area to the doping concentration of the inner diffusion layer in the metallized area is 1×10 -4 :1.

[0166] For the rest of the differences except the above, please refer to Example 4.

[0167] Comparative Example 10

[0168] The difference between Comparative Example 10 and Example 4 is that the alkali washing time is 85s, and the doping concentration of the substrate corresponding to the non-metallized area on the back of the prepared tunneling oxide passivation contact cell is 8×10 16 atom / cm 3 The doping concentration of the inner diffusion layer in the metallized area is 1×10 19 atom / cm 3 The ratio of the doping concentration of the substrate in the non-metallized area to the doping concentration of the inner diffusion layer in the metallized area is 8×10 -3 :1.

[0169] For the rest of the differences except the above, please refer to Example 4.

[0170] Comparative Example 11

[0171] The difference between Comparative Example 11 and Example 4 is that the alkali washing time is 100s, and the doping concentration of the substrate corresponding to the non-metallized area on the back of the prepared tunneling oxide passivation contact cell is 1×10 15 atom / cm 3 The doping concentration of the inner diffusion layer in the metallization area is 2×10 19 atom / cm 3 The ratio of the doping concentration of the substrate in the non-metallized area to the doping concentration of the inner diffusion layer in the metallized area is 5×10 -5 :1.

[0172] For the rest of the differences except the above, please refer to Example 4.

[0173] Comparative Example 12

[0174] The difference between Comparative Example 12 and Example 4 is that the scanning speed of the laser treatment is 31 m / s, the power is 100 W, and the frequency is 200 kHz; the doping concentration of the substrate corresponding to the non-metallized area on the back of the prepared tunneling oxide passivation contact cell is 1×10 15 atom / cm 3 The doping concentration of the inner diffusion layer in the metallized area is 1×10 20 atom / cm 3 The ratio of the doping concentration of the substrate in the non-metallized area to the doping concentration of the inner diffusion layer in the metallized area is 1×10 -5 :1.

[0175] The depth of the non-metallized area of ​​Comparative Example 12 after alkali washing is 1.10 times the depth of the non-metallized area of ​​Example 4 after alkali washing.

[0176] For the rest of the differences except the above, please refer to Example 4.

[0177] Experimental Example 1

[0178] For Example 1 (such as Figure 2 As shown) and Comparative Example 5 (as Figure 3 The tunnel oxide layer passivation contact cell was tested and characterized. The characterization results are shown in Figure 4 ;in, Figure 2 and Figure 3 The area 1 corresponds to the metallized area, Figure 2 Region 3 and Figure 3 Region 2 in FIG corresponds to a non-metallized area.

[0179] according to Figure 4 It can be seen that by optimizing the doping concentration difference between the expansion layer in the metallized area and the corresponding substrate in the non-metallized area, the performance of the battery can be effectively improved; wherein, region 2 is the inner expansion layer portion that is not washed out in Example 5, and has a higher doping concentration, resulting in the inability to form a large doping concentration difference between the metallized area and the non-metallized area in Example 5, and causing electrons and holes to recombine, electrons lose the ability to move freely, and cannot participate in current transmission or energy conversion, and the electrical performance of the battery cannot be improved; in Example 1, which eliminates the influence of region 2, a large doping concentration difference is formed between the metallized area and the non-metallized area, which can improve the problem of electron and hole recombination and improve battery performance.

[0180] Experimental Example 2

[0181] The electrical properties of the above embodiments and comparative examples were tested, and the test results are shown in the table below.

[0182]

[0183] According to the above table, by comparing Example 1 with Comparative Example 1, it can be seen that the ratio of the doping concentration of the substrate corresponding to the non-metallized area to the doping concentration of the inner diffusion layer in the metallized area satisfies: (1×10 -6 ~5×10 -4 ) :1, the doping concentration of the metallization area is too high, which is not conducive to the electrical performance of the tunnel oxide passivation contact cell, that is, its fill factor and open circuit voltage are reduced, and ultimately lead to a decrease in photoelectric conversion efficiency.

[0184] Comparing Examples 1-3 with Comparative Examples 2 and 3, it can be seen that optimizing the thickness of the phosphorus-doped polysilicon layer can improve the photoelectric conversion efficiency.

[0185] By comparing Example 4 and Comparative Example 4, it can be seen that optimizing the wavelength and power during laser treatment can effectively improve the fill factor and reduce the open circuit voltage, and ultimately lead to a decrease in the photoelectric conversion efficiency; among them, the increase in laser wavelength, on the contrary, leads to the subsequent pre-cleaning and alkaline washing, and it is impossible to achieve effective elution in the non-metallized area.

[0186] By comparing Example 4 and Comparative Example 5, it can be seen that without pre-cleaning, differential elution cannot be formed in the non-metallized area and the metallized area, and it is difficult to form a difference in doping concentration in the non-metallized area and the metallized area, which leads to a decrease in the fill factor and open circuit voltage, and ultimately leads to a decrease in the photoelectric conversion efficiency.

[0187] By comparing Example 4 and Comparative Example 6, it can be seen that by optimizing the pre-cleaning alkali solution concentration and the pre-cleaning temperature to avoid excessive alkali solution concentration and temperature, the elution amount of the non-metallized area can be controlled during alkali washing, the phenomenon of excessive elution in the non-metallized area can be improved, the problem of deterioration of battery performance can be improved, and the photoelectric conversion efficiency can be ensured.

[0188] By comparing Example 4 and Comparative Example 7, it can be seen that by optimizing the alkali solution concentration and alkali washing temperature of alkali washing to avoid excessive alkali solution concentration and temperature, the elution amount of the non-metallized area can be controlled during alkali washing, the phenomenon of excessive elution in the non-metallized area can be improved, the problem of deterioration of battery performance can be improved, and the photoelectric conversion efficiency can be ensured.

[0189] By comparing Example 4 with Comparative Examples 8 and 9, it can be seen that optimizing the pre-cleaning time can ensure the photoelectric conversion efficiency of the battery; among them, if the pre-cleaning time is too short, it is difficult for the non-metallized area to reach the expected elution amount, and if the pre-cleaning time is too long, it will lead to excessive elution of the metallized area. Whether the non-metallized area cannot reach the expected elution amount or the metallized area is excessively eluted, the photoelectric conversion efficiency of the battery will be reduced.

[0190] By comparing Example 4 with Comparative Examples 10 and 11, it can be seen that optimizing the alkali washing time can ensure the photoelectric conversion efficiency of the battery; among them, if the alkali washing time is too short, it is difficult to achieve the expected elution amount in the non-metallized area, and if the alkali washing time is too long, it will lead to excessive elution in the metallized area. Whether the non-metallized area cannot achieve the expected elution amount or the metallized area is excessively eluted, the photoelectric conversion efficiency of the battery will be reduced.

[0191] By comparing Example 4 and Comparative Example 12, it can be seen that optimizing the power and frequency of laser processing can ensure the photoelectric conversion efficiency of the battery; among them, when the laser frequency decreases, the spot energy increases, which will cause excessive corrosion of the non-metallized area under higher power conditions, and then in the subsequent pre-cleaning and alkaline washing processes, it will cause excessive elution of the non-metallized area, increase the depth of the non-metallized area, and reduce the photoelectric conversion efficiency of the battery.

[0192] In summary, a doping concentration difference is formed between the inner diffusion layer 121 of the metallized region and the substrate 100 corresponding to the non-metallized region of the tunneling oxide passivation contact battery 010 of the present invention, wherein the doping concentration of the substrate 100 corresponding to the non-metallized region is lower than the doping concentration of the inner diffusion layer 121 of the metallized region. The doping concentration of the inner diffusion layer 121 of the metallized region is high, which can ensure the transmission of electrons and ensure a higher fill factor (FF), while the doping concentration of the substrate 100 corresponding to the non-metallized region is low, which can effectively suppress the increase of Auger recombination, improve the problem of a large number of electrons being recombined, and reduce the open circuit voltage (Voc); in short, the battery prepared by the preparation method of the present invention forms a doping concentration difference between the non-metallized region and the metallized region, which ensures the electron transmission of the metallized region, improves the fill factor (FF), and avoids the reduction of the open circuit voltage of the non-metallized region, thereby improving the photoelectric conversion efficiency (Power Conversion Efficiency). The PCE) is positively correlated with both the fill factor (FF) and the open circuit voltage (Voc), which means that the photoelectric conversion efficiency of the tunnel oxide passivation contact cell 010 can be improved by increasing the concentration difference between the non-metallized area and the metallized area.

[0193] The above description is only a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by any technician familiar with this technical field within the technical scope disclosed in the present invention should be covered by the scope of protection of the present invention.

Claims

1. A tunneling oxide passivation contact cell, characterized in that: include: A substrate (100), the substrate (100) having a front side and a back side that are arranged in opposite directions, at least the back side having a metallized area and a non-metallized area; a tunneling oxide layer (110), the tunneling oxide layer (110) being formed on the back surface and located within the metallized region; A first doping layer (120), the first doping layer (120) is formed on a side of the tunneling oxide layer (110) facing away from the substrate (100); wherein, The tunneling oxide layer (110) forms an inner expansion layer (121) on a side facing away from the first doping layer (120); the ratio of the doping concentration of the substrate (100) corresponding to the non-metallized region to the doping concentration of the inner expansion layer (121) in the metallized region is (1×10 -6 ~5×10 -4 ):1; The doping concentration of the substrate (100) corresponding to the non-metallized area is 1×10 15 ~5×10 16 atom / cm 3 The doping concentration of the inner expansion layer (121) of the metallized region is 1×10 20 ~1×10 21 atom / cm 3 ; The preparation method of the tunneling oxide layer passivation contact cell comprises: forming a tunneling oxide layer (110) and a polysilicon layer on the back side of the substrate (100), and doping the polysilicon layer to form a first doping layer (120) and an inner diffusion layer (121) located on a side of the tunneling oxide layer (110) away from the first doping layer (120); The non-metallized area on the back side of the substrate (100) is processed using a laser, and the area not processed by the laser is the metallized area; Pre-cleaning the non-metallized area and the metallized area; Then, the non-metallized area and the metallized area are subjected to alkali washing to remove the first doping layer (120), the tunneling oxide layer (110), and the inner expansion layer (121) in the non-metallized area; The cleaning solution for the pre-cleaning is a first alkaline solution; the cleaning solution for the alkaline washing comprises a second alkaline solution and an additive, wherein the additive comprises a surfactant; The temperature of the pre-cleaning is 60-70° C.; the temperature of the alkali washing is 75-85° C.; and the volume ratio of the additive to the second alkali solution is 0.5-1.5%.

2. The tunneling oxide passivation contact cell according to claim 1, characterized in that: The first doped layer (120) is a phosphorus-doped polysilicon layer.

3. The tunneling oxide passivation contact cell according to claim 2, characterized in that: The thickness of the first doping layer (120) is 90-150 nm.

4. The tunneling oxide passivation contact cell according to claim 1, characterized in that: The tunneling oxide layer passivation contact cell further comprises a first passivation layer (141), wherein the first passivation layer (141) covers the outside of the inner expansion layer (121), the tunneling oxide layer (110) and the first doping layer (120) of the metallization region.

5. The tunneling oxide passivation contact cell according to claim 4, characterized in that: The first passivation layer (141) also covers the outside of the substrate (100) in the non-metallized area.

6. A method for preparing a tunnel oxide passivation contact cell, characterized in that: Used to prepare the tunneling oxide layer passivation contact cell according to any one of claims 1 to 5; The preparation method of the tunneling oxide layer passivation contact cell comprises: forming a tunneling oxide layer (110) and a polysilicon layer on the back side of the substrate (100), and doping the polysilicon layer to form a first doping layer (120) and an inner diffusion layer (121) located on a side of the tunneling oxide layer (110) away from the first doping layer (120); The non-metallized area on the back side of the substrate (100) is processed using a laser, and the area not processed by the laser is the metallized area; Pre-cleaning the non-metallized area and the metallized area; Then, the non-metallized area and the metallized area are subjected to alkali washing to remove the first doping layer (120), the tunneling oxide layer (110), and the inner expansion layer (121) in the non-metallized area; The cleaning solution for the pre-cleaning is a first alkaline solution; the cleaning solution for the alkaline washing comprises a second alkaline solution and an additive, wherein the additive comprises a surfactant; The temperature of the pre-cleaning is 60-70° C.; the temperature of the alkali washing is 75-85° C.; and the volume ratio of the additive to the second alkali solution is 0.5-1.5%.

7. The method for preparing a tunneling oxide layer passivation contact cell according to claim 6, characterized in that: The temperature of the pre-cleaning is lower than the temperature of the alkali washing.

8. The method for preparing a tunneling oxide passivation contact cell according to claim 6, characterized in that: The mass concentration of at least one of the first alkali solution and the second alkali solution is 2-3%.

9. The method for preparing a tunneling oxide layer passivation contact cell according to claim 6, characterized in that: The pre-cleaning time is longer than the alkali cleaning time.

10. The method for preparing a tunneling oxide layer passivation contact cell according to claim 9, characterized in that: The pre-cleaning time is not less than 97s, and the alkali cleaning time is 90-95s.

11. The method for preparing a tunneling oxide layer passivation contact cell according to claim 6, characterized in that: The laser has a wavelength of 300-650 nm, a spot size of 130-420 μm, a scanning speed greater than 30 m / s, a power greater than or equal to 35 W, and a frequency greater than or equal to 300 kHz.

12. The method for preparing a tunneling oxide layer passivation contact cell according to claim 11, characterized in that: The width of the non-metallized area is 400-900 μm.

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