Tunneling oxide layer passivation contact battery and preparation method thereof

Abstract

The invention relates to the technical field of solar cells, in particular to a tunneling oxide layer passivation contact cell and a preparation method thereof.The cell comprises a substrate, a tunneling oxide layer and a first doping layer, the substrate is provided with a front face and a back face which are distributed oppositely, and at least the back face is provided with a metallization area and a non-metallization area; the tunneling oxide layer and the first doping layer are sequentially formed on the back face, and an inner expansion layer is formed on the side, away from the first doping layer, of the tunneling oxide layer; and the ratio of the doping concentration of the substrate corresponding to the non-metallization region to the doping concentration of the inner expansion layer of the metallization region is (1 * 10 <-6 >-5 * 10 <-4 >): 1. According to the cell, the photoelectric conversion efficiency of the tunneling oxide layer passivation contact cell is improved by increasing the concentration difference between the non-metallization region and the metallization region.

Description

Technical Field

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

[0002] A tunneling oxide passivated contact cell (i.e., TOPCon cell, Thin Oxide Passivated Contact) is a passivated contact type cell. It reduces minority carrier recombination (i.e., the process in which minority carriers (electrons or holes) in a semiconductor recombine with majority carriers) by isolating the metal from the silicon substrate through a thin film. An ultrathin silicon oxide layer is prepared on the back of the cell, and then a doped polysilicon thin layer is deposited to jointly form a passivated contact structure. The ultrathin silicon oxide layer allows majority carrier electrons to tunnel into the polysilicon layer and can also block the recombination of minority carrier holes, enabling the lateral transport of electrons in the polysilicon layer to be collected by the metal, greatly reducing the metal contact recombination current, improving the open-circuit voltage and short-circuit current of the cell, and thus enhancing the cell conversion efficiency. In short, the passivation mechanism of the tunneling silicon oxide passivated contact structure mainly comes from the following aspects: one is the chemical passivation effect provided by the silicon oxide interface, the second is the field passivation effect of the doped polysilicon, and the third is that the valence band mismatch between the polysilicon and silicon blocks the transport of holes.

[0003] However, the tunneling oxide passivated contact cells provided by the related technologies are also restricted by the problems of increased Auger recombination and reduced open-circuit voltage, which restricts the improvement of the photoelectric conversion efficiency. Summary of the Invention

[0004] The objectives of the present invention include providing a tunneling oxide passivated contact cell and a preparation method thereof. This preparation method can form a doping concentration difference between the metallized area and the non-metallized area of the tunneling oxide passivated contact cell. Among them, the doping concentration of the substrate corresponding to the non-metallized area is lower than that of the inner diffusion layer in the metallized area. The high doping concentration of the inner diffusion layer in the metallized area can ensure the transmission of electrons and ensure a high fill factor (FF). The low doping concentration of the substrate corresponding to the non-metallized area can effectively suppress the increase in Auger recombination and improve the problem of a large number of electrons being recombined and reducing 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 not only ensures the electron transmission in the metallized area and improves the fill factor (FF), but also avoids the reduction of the open-circuit voltage in the non-metallized area. The photoelectric conversion efficiency (Power Conversion Efficiency, PCE) is positively correlated with both the fill factor (FF) and the open-circuit voltage (Voc). Therefore, by increasing the concentration difference between the non-metallized area and the metallized area, the photoelectric conversion efficiency of the tunneling oxide passivated contact cell can be improved.

[0005] Embodiments of the present invention can be implemented as follows: In a first aspect, the present invention provides a tunneling oxide passivated contact cell, comprising: A substrate having a front side and a back side distributed opposite to each other, and at least the back side having a metallized region and a non-metallized region; A tunneling oxide layer formed on the back side and located within the metallized region; A first doped layer formed on a side of the tunneling oxide layer facing away from the substrate; wherein, An inner diffusion layer is formed on a side of the tunneling oxide layer facing 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 diffusion layer of the metallized region is (1×10 -6 ~5×10 -4 ):1.

[0006] In an optional embodiment, the doping concentration of the substrate corresponding to the non-metallized region is 1×10 15 ~5×10 16 atom / cm 3 ; the doping concentration of the inner diffusion layer of the metallized region is 1×10 20 ~1×10 21 atom / cm 3 .

[0007] In an optional embodiment, the first doped layer is a phosphorus-doped polysilicon layer.

[0008] In an optional embodiment, the thickness of the first doped layer is 90 - 150 nm.

[0009] In an optional embodiment, the tunneling oxide passivated contact cell further comprises a first passivation layer covering the outside of the inner diffusion layer of the metallized region, the tunneling oxide layer, and the first doped layer.

[0010] In an optional embodiment, the first passivation layer further covers the outside of the substrate of the non-metallized region.

[0011] In a second aspect, the present invention provides a method for manufacturing a tunneling oxide passivated contact cell for manufacturing the tunneling oxide passivated contact cell according to any one of the foregoing embodiments; the method for manufacturing the tunneling oxide passivated contact cell comprises: Forming a tunneling 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 tunneling oxide layer facing away from the first doped layer; Processing the non-metallized region on the back side of the substrate with a laser, and the unprocessed region is the metallized region; Performing pre-cleaning on the non-metallized region and the metallized region; Then, the non-metallized region and the metallized region are subjected to alkali cleaning to remove the first doping layer, the tunneling oxide layer, and the inner diffusion layer in the non-metallized region.

[0012] In an optional embodiment, the cleaning solution for pre-cleaning is a first alkali solution; the cleaning solution for alkali cleaning includes a second alkali solution and an additive.

[0013] In an optional embodiment, the temperature of the pre-cleaning is lower than that of the alkali cleaning.

[0014] In an optional embodiment, the temperature of the pre-cleaning is 60 - 70 °C; the temperature of the alkali cleaning is 75 - 85 °C.

[0015] In an optional embodiment, the additive includes a surfactant; the volume ratio of the additive to the second alkali solution is 0.5 - 1.5%.

[0016] In an optional embodiment, the mass concentration of at least one of the first alkali solution and the second alkali solution is 2 - 3%.

[0017] In an optional embodiment, the time of the pre-cleaning is longer than that of the alkali cleaning.

[0018] In an optional embodiment, the time of the pre-cleaning is not less than 97 s, and the time of the alkali cleaning is 90 - 95 s.

[0019] 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.

[0020] In an optional embodiment, the width of the non-metallized region is 400 - 900 μm.

[0021] The beneficial effects of the tunneling oxide passivated contact cell according to the embodiments of the present invention include: A doping concentration difference is formed between the metallized area and the non-metallized area of the tunneling oxide passivated contact cell provided by the embodiments of the present invention. Among them, the doping concentration of the substrate corresponding to the non-metallized area is lower than the doping concentration of the inner diffusion layer in the metallized area. The high doping concentration of the inner diffusion layer in the metallized area can ensure the transmission of electrons and ensure a relatively high fill factor (FF). The low doping concentration of the substrate corresponding to the non-metallized area can effectively suppress the increase in Auger recombination, improve the problem that a large number of electrons are recombined and the open-circuit voltage (Voc) is reduced. In short, a doping concentration difference is formed between the non-metallized area and the metallized area of the tunneling oxide passivated contact cell of the present invention, which not only ensures the electron transmission in the metallized area and improves the fill factor (FF), but also avoids the reduction of the open-circuit voltage in the non-metallized area. The photoelectric conversion efficiency (Power Conversion Efficiency, PCE) is positively correlated with both the fill factor (FF) and the open-circuit voltage (Voc). Therefore, the photoelectric conversion efficiency of the tunneling oxide passivated contact cell can be improved by increasing the concentration difference between the non-metallized area and the metallized area.

[0022] Moreover, the lower doping concentration of the substrate corresponding to the non-metallized area relative to the doping concentration of the inner diffusion layer in the metallized area can also reduce the parasitic absorption of light and increase the ISC (short-circuit current).

[0023] The beneficial effects of the preparation method of the tunneling oxide passivated contact cell according to the embodiments of the present invention include: In the preparation method provided by the embodiments of the present invention, after forming a tunneling oxide layer and a first doped layer on the back of the substrate, the non-metallized area of the substrate is first subjected to laser treatment, and then the non-metallized area and the metallized area that have not been subjected to laser treatment are sequentially subjected to pre-cleaning and alkali washing, so as to form a concentration difference between the non-metallized area and the metallized area after alkali washing. Among them, the doping concentration of the substrate corresponding to the non-metallized area is lower than the doping concentration of the inner diffusion layer in the metallized area. The high doping concentration of the inner diffusion layer in the metallized area can ensure the transmission of electrons and ensure a relatively high fill factor (FF). The low doping concentration of the substrate corresponding to the non-metallized area can effectively suppress the increase in Auger recombination, improve the problem that a large number of electrons are recombined and the open-circuit voltage (Voc) is reduced. In short, the preparation method of the present invention forms a doping concentration difference between the non-metallized area and the metallized area, which not only ensures the electron transmission in the metallized area and improves the fill factor (FF), but also avoids the reduction of the open-circuit voltage in the non-metallized area. The photoelectric conversion efficiency (Power Conversion Efficiency, PCE) is positively correlated with both the fill factor (FF) and the open-circuit voltage (Voc). Therefore, the photoelectric conversion efficiency of the tunneling oxide passivated contact cell can be improved by increasing the concentration difference between the non-metallized area and the metallized area. Brief Description of the Drawings

[0024] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as limiting the scope. For those of ordinary skill in the art, without creative efforts, other related drawings can also be obtained based on these drawings.

[0025] Figure 1 It is a flowchart for preparing a tunneling oxide passivated contact cell in the present disclosure; Figure 2 It is a schematic structural diagram of the tunneling oxide passivated contact cell of Embodiment 1 of the present invention; Figure 3 It is a schematic structural diagram of the tunneling oxide passivated contact cell of Comparative Example 5 of the present invention; Figure 4 It is a detection result diagram of Experimental Example 1 of the present invention.

[0026] Icons: 010 - tunneling oxide passivated 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 antireflection layer; 152 - second antireflection layer; 161 - back metal electrode; 162 - front metal electrode. Detailed Description of the Embodiments

[0027] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. Usually, the components of the embodiments of the present invention described and illustrated in the drawings here can be arranged and designed in various different configurations.

[0028] Therefore, the following detailed description of the embodiments of the present invention provided in the drawings is not intended to limit the scope of the claimed present invention, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the scope of protection of the present invention.

[0029] It should be noted that similar reference numerals and letters indicate similar items in the following drawings. Therefore, once an item is defined in one drawing, it does not need to be further defined and explained in subsequent drawings.

[0030] In the description of the present invention, it should be noted that if terms such as "upper", "lower", "inner", "outer", etc. are used to indicate the orientation or positional relationship, it is based on the orientation or positional relationship shown in the drawings, or the orientation or positional relationship in which the product of the invention is usually placed. This is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying 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 construed as a limitation to the present invention.

[0031] In addition, if terms such as "first", "second", etc. are only used for distinguishing descriptions, they cannot be understood as indicating or implying relative importance.

[0032] It should be noted that, without conflict, the features in the embodiments of the present invention can be combined with each other.

[0033] The tunneling oxide passivated contact cell (i.e., TOPCon cell, Thin Oxide Passivated Contact) provided by the related technology can reduce minority carrier recombination (i.e., the process in which minority carriers (electrons or holes) in a semiconductor recombine with majority carriers) by isolating the metal from the silicon substrate through a thin film; a tunneling oxide passivated contact cell prepares a layer of ultra-thin silicon oxide on the back of a silicon substrate (usually an n-type monocrystalline silicon substrate), and then deposits a doped polysilicon thin layer to jointly form a passivated contact structure; the ultra-thin silicon oxide layer allows majority carrier electrons to tunnel into the polysilicon layer, and can also block the recombination of minority carrier holes, enabling the lateral transport of electrons in the polysilicon layer to be collected by the metal, greatly reducing the metal contact recombination current, improving the open-circuit voltage and short-circuit current of the cell, and thus improving the cell conversion efficiency. In short, the passivation mechanism of the tunneling silicon oxide passivated contact structure mainly comes from the following aspects: one is the chemical passivation effect provided by the silicon oxide interface, the second is the field passivation effect of the doped polysilicon, and the third is the valence band mismatch between the polysilicon and the silicon that blocks the transport of holes.

[0034] The inventors have found through research that, as one of the important component layers of the passivated contact structure, the thickness of the doped polysilicon film layer has an obvious impact on the parasitic absorption of long wavelengths, etc.; if the doped polysilicon film layer is too thick, it will cause serious parasitic absorption of long-wavelength light, resulting in a series of problems such as poor long-wavelength response and low bifaciality of the crystalline silicon solar cell, thus restricting the improvement of the photoelectric conversion efficiency; if the thickness of the doped polysilicon film layer is too thin, after the sintering process, it will affect the performance of the back polysilicon layer and the tunneling oxide layer, resulting in a decline in the passivation performance of the cell. Therefore, when improving the photoelectric conversion efficiency of the tunneling oxide passivated contact cell, it is difficult to achieve it by optimizing the thickness (thickening or thinning) of the doped polysilicon film.

[0035] Correspondingly, in order to improve the photoelectric conversion efficiency of the tunneling oxide passivated contact cell on the premise of ensuring the passivation and contact of the tunneling oxide passivated contact cell (that is, on the premise of ensuring that the doped polysilicon film has an optimal thickness), the inventor realizes it by suppressing the increase of Auger recombination in the tunneling oxide passivated contact cell and increasing the open circuit voltage.

[0036] Hereinafter, the tunneling oxide passivated contact cell and its manufacturing method of the present disclosure will be described in detail.

[0037] Please refer to Figure 1 , the tunneling oxide passivated contact cell 010 of the present disclosure includes a substrate 100 (for example: n-type monocrystalline silicon wafer), a tunneling oxide layer 110 and a first doped layer 120; the substrate 100 has a front side and a back side distributed opposite to each other, and at least the back side has a metallized area and a non-metallized area; the tunneling oxide layer 110 is formed on the back side and is located within the metallized area; the first doped layer 120 is formed on the side of the tunneling oxide layer 110 facing away from the substrate 100; wherein, an inner diffusion layer 121 is formed on the side of the tunneling oxide layer 110 facing away from the first doped layer 120; the ratio of the doping concentration of the non-metallized area corresponding to the substrate 100 to the doping concentration of the inner diffusion layer 121 in the metallized area is (1×10 -6 ~5×10 -4 ):1.

[0038] It can be seen that the doping concentration of the substrate 100 corresponding to the non-metallized area of the tunneling oxide passivated contact cell 010 of the present disclosure is lower than the doping concentration of the inner diffusion layer 121 in the metallized area; among them, the high doping concentration of the inner diffusion layer 121 in the metallized area can ensure the transmission of electrons and ensure a high fill factor (FF), while the low doping concentration of the substrate 100 corresponding to the non-metallized area can effectively suppress the increase of Auger recombination and improve the problem that a large number of electrons are recombined and the open circuit voltage (Voc) is reduced; in short, the battery of the present disclosure 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 and improves the fill factor (FF), and also avoids the reduction of the open circuit voltage in the non-metallized area. According to the calculation formula of the photoelectric conversion efficiency (Power 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 known 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 passivated contact cell 010 can be improved by increasing the concentration difference between the non-metallized area and the metallized area.

[0039] Moreover, the doping concentration of the substrate 100 corresponding to the non-metallized region is lower than that of the inner diffusion layer 121 of the metallized region, which can also reduce the parasitic absorption of light and improve the ISC (short-circuit current).

[0040] It should be noted that the doping concentration of the substrate 100 corresponding to the non-metallized region may refer to the highest concentration of the substrate 100 in the corresponding region; correspondingly, the doping concentration of the inner diffusion layer 121 of the metallized region may also refer to the highest concentration of the inner diffusion layer 121.

[0041] Of course, in other embodiments, the doping concentration of the substrate 100 corresponding to the non-metallized region may also refer to the median value of the doping concentration of the substrate 100 in the corresponding region; correspondingly, the doping concentration of the inner diffusion layer 121 of the metallized region may also refer to the median value of the doping concentration of the inner diffusion layer 121.

[0042] Optionally, the doping concentration of the substrate 100 corresponding to the non-metallized region 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 diffusion layer 121 of the metallized region 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 etc. By optimizing the doping concentrations of the metallized region and the non - metallized region, on the one hand, the non - metallized region can effectively reduce carrier recombination, improve the minority carrier lifetime and open - circuit voltage, thereby enhancing the overall efficiency of the battery, that is, directly improving the energy conversion efficiency of the battery. On the other hand, the metallized region can optimize the charge carrier transport, ensure good ohmic contact, reduce the contact resistance, improve the collection efficiency of charge carriers, increase the 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 region and the non - metallized region, optimize the carrier transport path, reduce energy loss, and further enhance the performance and stability of the battery.

[0043] Meanwhile, optimizing the doping concentrations of the metallized region and the non - metallized region can also reduce the series resistance and reduce non - radiative recombination centers to increase the fill factor (FF), and further ensure the improvement of the photoelectric conversion efficiency. Moreover, it can also improve the stability and reliability of the tunnel oxide passivated contact cell 010, that is, it is not only beneficial to improve the initial efficiency of the tunnel oxide passivated contact cell 010, but also enhance its long - term stability and reliability, enabling it to maintain a high energy output under different working environments.

[0044] The inventor further studied and found that if the doping concentration of the inner diffusion layer 121 in the metallized region is further increased (i.e., greater than 1×10 21 atom / cm 3Instead, it will have a negative impact on the various performances of the tunnel oxide passivated contact cell 010. For example, too high doping concentration will significantly increase Auger recombination, resulting in more carriers recombining in the metallization region, reducing the minority carrier lifetime, thus affecting the open circuit voltage of the cell and leading to a decrease in the photoelectric conversion efficiency; too high doping concentration is likely to introduce more crystal defects and stress, damaging the crystal quality of the material, such as causing deformation of the crystal structure or generating defects such as dislocations, increasing non-radiative recombination centers, further reducing the cell performance and stability; although high doping can reduce the contact resistance, after exceeding a certain concentration, the improvement of the resistance will tend to saturate, and may even increase the resistance due to the impurity scattering effect, and is even likely to cause damage to the substrate 100, and there will even be problems of decreased contact quality in the metallization process; too high doping may also lead to distortion of the energy band structure, resulting in the formation of excessive deep-level defects or non-radiative recombination centers, and becoming traps for carriers, increasing the recombination probability of electrons and holes, affecting the transport characteristics of carriers, and reducing the open circuit voltage, short circuit current density, fill factor and conversion efficiency of the cell.

[0045] Moreover, if the doping concentration is too high, more complex processes are required, the cost is difficult to control, and the manufacturing difficulty is greater.

[0046] Optionally, the first doping layer 120 is a phosphorus-doped polysilicon layer. The phosphorus-doped polysilicon layer plays a crucial role in surface passivation, carrier selectivity, tunneling effect, optical performance optimization, etc.; among them, the phosphorus-doped polysilicon layer combines with the tunnel oxide layer 110 to provide excellent surface passivation effect, significantly reducing the carrier recombination rate on the back surface, thus improving the minority carrier lifetime and open circuit voltage; phosphorus doping makes the polysilicon layer an electron-selective contact layer, allowing electrons to pass through efficiently and blocking holes, reducing recombination losses, and at the same time, the high doping concentration reduces the contact resistance and improves the carrier collection efficiency; in addition, the phosphorus-doped polysilicon layer and the tunnel oxide layer 110 work together to achieve efficient electron transport using the quantum tunneling effect, avoiding the recombination problem of traditional metal-semiconductor contacts; the phosphorus-doped polysilicon layer also optimizes the optical characteristics of the back surface of the cell, enhances the reflection of long-wavelength light, and further improves the light absorption efficiency of the cell.

[0047] 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, it can improve the parasitic absorption problem caused by the too thick thickness of the first doping layer 120. If the thickness is greater than 150 nm, it will cause serious parasitic absorption to long-wavelength light, increase the absorption loss of incident light, resulting in poor long-wavelength response and low bifaciality of the tunnel oxide passivated contact cell 010. That is, optimizing the thickness of the first doping layer 120 can reduce the absorption loss of 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 the degradation of the passivation performance of the tunnel oxide passivated contact cell 010 caused by the too thin thickness of the first doping layer 120. 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. At the same time, it can also form a high-quality electron-selective contact layer, allowing electrons to tunnel through and pass efficiently, while blocking holes, reducing recombination losses, and reducing the contact resistance, improving the carrier collection efficiency.

[0048] The tunnel oxide passivated contact cell 010 of the present disclosure further includes a first passivation layer 141, and the first passivation layer 141 covers the inner diffusion layer 121, the tunnel oxide layer 110, and the outside of the first doping layer 120 in the metallization region. In this way, the performance and reliability of the tunnel oxide passivated contact cell 010 can be significantly improved; among them, the first passivation layer 141 effectively reduces the carrier recombination rate at the interface between the metallization region and the semiconductor, reduces the recombination loss caused by surface states, thereby improving 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 doping layer 120, can act as a physical barrier to reduce the influence of impurity diffusion and the external environment on the device, and enhances the interface stability, preventing the oxide layer from being damaged in subsequent processes, ensuring the high efficiency of the tunneling effect, as well as long-term stability and durability; at the same time, the first passivation layer 141 also optimizes the contact performance of the metallization region, reduces the contact resistance, and improves the carrier collection efficiency.

[0049] Further, the first passivation layer 141 also covers the outside of the substrate 100 in the non-metallized region. In this way, not only can the carrier recombination rate on the surface of the non-metallized region be effectively reduced, and the recombination loss caused by surface states be reduced, thereby improving the minority carrier lifetime and open-circuit voltage, but also the first passivation layer 141 covering the outside of the substrate 100 in the non-metallized region helps to improve the transport characteristics of carriers in the substrate 100, reduces the leakage current, and further improves 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 region, reduces surface reflection, improves the light absorption efficiency, and provides additional protection for the substrate 100 to prevent the erosion of the material by the external environment (such as moisture, impurities), enhancing the long-term reliability of the device.

[0050] The tunneling oxide passivation contact battery 010 of the present disclosure further includes a second doping layer 130; the second doping layer 130 is formed on the front surface of the substrate 100, and it can be a boron diffusion layer as a p+ emitter. The second doping layer 130 (p+ emitter) not only helps to improve the separation efficiency of photo-generated carriers, but also can reduce the surface recombination rate, thereby increasing the open-circuit voltage (Voc) and short-circuit current density (Jsc), and ultimately improving the overall conversion efficiency of the battery.

[0051] Further, the tunneling oxide passivation contact battery 010 further includes a second passivation layer 142, and the second passivation layer 142 is formed on the side of the second doping layer 130 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 the influence of subsequent process steps.

[0052] Optionally, the first passivation layer 141 and the second passivation layer 142 can be Al2O3. In other embodiments, the second passivation layer 142 can also be silicon oxide, silicon nitride, etc., which are not specifically limited herein.

[0053] Still further, the tunneling oxide passivation contact battery 010 further includes a first antireflection layer 151 and a second antireflection layer 152; wherein, the first antireflection layer 151 is formed on the side of the first passivation layer 141 away from the substrate 100, and the second antireflection layer 152 is formed on the side of the second passivation layer 142 away from the substrate 100.

[0054] The present disclosure also provides a method for manufacturing a tunneling oxide passivation contact battery 010 for manufacturing the above-mentioned tunneling oxide passivation contact battery 010; the manufacturing method includes: Texturing the front surface of the substrate 100 (for example: n-type silicon substrate 100) to form a textured surface on the front surface of the substrate 100; Performing boron diffusion on the front surface of the substrate 100 after the texturing process is completed to form a front boron diffusion layer (i.e., the second doping layer 130); Etching is performed on the back side of the substrate 100 to remove the borosilicate glass layer (BSG) on the back side, and alkali polishing is performed on the back side of the substrate 100; A tunneling 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 doping layer 120 and an inner extension 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 by 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 processed by laser is the metallized area; 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. Pre-cleaning of non-metallized and metallized areas; Then, the non-metallized area and the metallized area are alkali washed to remove the first doped layer 120, the tunneling oxide layer 110 and the inner expansion 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; 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 are prepared, and the electrodes are made to form good contact through sintering, light injection and laser-assisted sintering.

[0055] After forming the tunneling oxide layer 110 and the first doped layer 120 on the back surface of the substrate 100, the non-metallized area of the substrate 100 is first subjected to laser treatment to ensure that the protective layer corresponding to the non-metallized area is modified. Then, the non-metallized area and the metallized area that has not been laser-treated are sequentially subjected to pre-cleaning and alkali cleaning, so that after alkali cleaning, a concentration difference is formed between the non-metallized area and the metallized area. Among them, 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 of the metallized area. The high doping concentration of the inner diffusion layer 121 in the metallized area can ensure the transmission of electrons and ensure a high fill factor (FF). The low doping concentration of the substrate 100 corresponding to the non-metallized area can effectively suppress the increase in Auger recombination, improve the problem that a large number of electrons are recombined and the open-circuit voltage (Voc) is reduced. In short, the preparation method of the present invention forms a doping concentration difference between the non-metallized area and the metallized area, which not only ensures the electron transmission in the metallized area and improves the fill factor (FF), but also avoids the reduction of the open-circuit voltage in the non-metallized area. 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 layer passivated contact cell 010 can be improved by increasing the concentration difference between the non-metallized area and the metallized area.

[0056] It should be noted that the inner diffusion layer 121 formed on the side of the tunneling oxide layer 110 facing away from the first doped layer 120 is formed by doping atoms of phosphorus diffusing into the silicon substrate 100 through the polysilicon layer when the first doped layer 120 is prepared by the phosphorus diffusion process. The retention of the inner diffusion layer 121 in the metallized area ensures the high doping concentration of the inner diffusion layer 121 in the metallized area, and the inner diffusion layer 121 is distributed on the side of the tunneling oxide layer 110 facing away from the first doped layer 120, that is, the inner diffusion layer 121 has a certain depth, that is, the doping has a certain depth. The high doping concentration and depth are beneficial to the transmission of electrons, thereby ensuring a high fill factor (FF).

[0057] It should also be noted that after pre-cleaning and alkali cleaning, the polysilicon wrap-around plating on the front and side surfaces will also be removed.

[0058] 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 the back metal electrode 161, all of the first doped layer 120, the tunneling oxide layer 110, and the inner diffusion layer 121 corresponding to the back metal electrode 161. It can even be understood as including the first passivation layer 141 and the first antireflection layer 151 wrapped outside the above structure.

[0059] Optionally, the wavelength of the laser is 300 - 650 nm (e.g., 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.), the spot size is 130 - 420 μm (e.g., 130 μm, 150 μm, 180 μm, 200 μm, 240 μm, 280 μm, 300 μm, 320 μm, 350 μm, 380 μm, 400 μm, 420 μm, etc.), the scanning speed is greater than 30 m / s (e.g., 31 m / s, 32 m / s, 35 m / s, 38 m / s, 40 m / s, etc.), the power is greater than or equal to 35 W (e.g., 35 W, 38 W, 41 W, 42 W, 45 W, 47 W, 50 W, etc.), and the frequency is greater than or equal to 300 kHz (e.g., 300 kHz, 400 kHz, etc.). Under the above laser processing parameter conditions, on the one hand, it can ensure that the protective layer formed in the non-metallized area is reliably modified into a structure that can react with subsequent pre-cleaning and alkali cleaning, so as to efficiently and reliably remove the protective layer in the pre-cleaning and alkali cleaning processes; on the other hand, it can also make at least part of the first doping layer 120, tunneling oxide layer 110, and inner diffusion layer 121 in the non-metallized area be laser-modified into a structure that is more easily eluted (corroded) by subsequent pre-cleaning and alkali cleaning steps (e.g., causing the first doping layer 120 to undergo a phase change and oxidation, reducing its chemical stability and making it easier to be eluted; for another example, changing the interface between the inner diffusion layer 121 and the substrate 100 to reduce the adhesion strength of the inner diffusion layer 121 on the substrate 100; for still another example, making the crystal structure of the tunneling oxide layer 110 unstable), thereby ensuring that the subsequent pre-cleaning and alkali cleaning steps can efficiently and reliably remove the first doping layer 120, tunneling oxide layer 110, and inner diffusion layer 121 in the non-metallized area.

[0060] Furthermore, the wavelength of the laser is 350 - 600 nm; the power of the laser is greater than 40 W and less than 50 W. In this way, while using the laser process to modify the protective layer in the non-metallized area on the back side, it can effectively cause obvious modifications to the first doping layer 120, tunneling oxide layer 110, and inner diffusion layer 121 in the non-metallized area, facilitating subsequent pre-cleaning and alkali cleaning, and can effectively elute the first doping layer 120, tunneling oxide layer 110, and inner diffusion layer 121 in the non-metallized area, ensuring an effective doping concentration difference is formed between the substrate 100 corresponding to the non-metallized area and the inner diffusion layer 121 in the metallized area.

[0061] It should be noted that the laser treatment can be carried out using nanosecond, picosecond, and femtosecond lasers.

[0062] Optionally, the width of the non-metallized region is 400-900 μm, for example: 400 μm, 500 μm, 600 μm, 700 μm, 800 μm, 900 μm, etc. Optimizing the width of the non-metallized region ensures that photo-generated carriers can effectively diffuse into the metallized region, achieving a balance between light absorption and carrier recombination, ensuring sufficient light absorption while reducing recombination losses, significantly increasing the open-circuit voltage, and improving the carrier collection efficiency; it can also avoid the excessively long carrier transmission path caused by the overly wide non-metallized region, thereby reducing the series resistance, enhancing the fill factor, and improving the conversion efficiency.

[0063] The inventors' research found that if, after the laser treatment step, the alkali cleaning is directly carried out, in order to effectively remove the polycrystalline silicon layers plated around the front and side surfaces, a relatively long alkali cleaning time is required. Since the protective layer after laser treatment is relatively thin, in order to delay the rate of the protective layer being washed off by the alkali, in the related art, additives need to be added to the alkali solution to reduce the elution of the protective layer, so as to achieve the purpose of smoothly eluting the polycrystalline silicon layers plated around the front and side surfaces while protecting the polycrystalline silicon 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 region and the metallized region, and thus it is difficult to form a doping concentration difference between the substrate 100 corresponding to the non-metallized region and the inner diffusion layer 121 of the metallized region after alkali cleaning.

[0064] To improve the above problems, in the present disclosure, a first alkali solution is used for pre-cleaning; then an alkali cleaning is carried out using a second alkali solution containing additives. In this way, the corrosion window of the non-metallized region treated by laser and the metallized region of the non-laser-treated region can be enlarged by pre-cleaning with the first alkali solution without additives, that is, during pre-cleaning, the non-metallized region treated by laser (including PSG, the first doping layer 120, the tunneling oxide layer 110, and the inner diffusion layer 121) is more likely to react with the first alkali solution, that is, the reaction rate is faster. After pre-cleaning, the structure of the non-metallized region is significantly thinned, while the structure of the metallized region is not significantly thinned. At the same time, part of the polycrystalline silicon plated around the front and side surfaces is also eluted; then an alkali cleaning is carried out using the second alkali solution containing additives. Even in the presence of additives, the non-metallized region can be eluted faster, and the alkali cleaning can also ensure the elution of the polycrystalline silicon on the front and side surfaces. When the non-metallized region is eluted, due to the presence of additives, the metallized region will not be eluted, thereby causing a difference in the doping concentration between the substrate 100 corresponding to the non-metallized region and the inner diffusion layer 121 of the metallized region.

[0065] Optionally, the first alkali solution and the second alkali solution include sodium hydroxide solution. Of course, in other embodiments, the first alkali solution and the second alkali solution may also include potassium hydroxide solution, etc., which are not specifically limited herein.

[0066] Furthermore, the mass concentration of at least one of the first lye and the second lye is 2-3%, for example: 2%, 2.3%, 2.5%, 2.7%, 3%, etc., and no specific limitation is made here. If the concentration of the lye for pre-cleaning and alkali cleaning is further increased, the depth of the non-metallized area formed by wet method will increase, the narrow channel under the metallized area will become longer, the series resistance will become larger, there will be current loss, and the fill factor (FF) will instead decrease; if the concentration is less than 2%, it is difficult to cause elution.

[0067] Optionally, the concentrations of the first lye and the second lye 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 cleaning, so as to ensure an ideal doping concentration difference between the substrate 100 corresponding to the non-metallized area and the inner diffusion layer 121 of the metallized area.

[0068] Optionally, the additive includes a surfactant; the volume ratio of the additive to the second lye is 0.5-1.5%, for example: 0.5%, 0.7%, 1%, 1.3%, 1.5%, etc. Optimizing the dosage of the additive can, while protecting the metallized area and slowing down its elution, also ensure the reliable elution of the non-metallized area and guarantee the effective elution of the polysilicon plated around the front and side.

[0069] It should be noted that the types of additives are similar to those in the related art and are not specifically limited here. It can be an anionic surfactant (for example: sodium dodecylbenzenesulfonate, sodium dodecyl sulfate, etc.), a non-ionic surfactant (for example: polyoxyethylene ethers, fatty alcohol polyoxyethylene ethers, etc.), or an amphoteric surfactant (for example: cocamidopropyl betaine, alkyl dimethylamine oxide, etc.), and no further listing is made here.

[0070] Optionally, the temperature of pre-cleaning is lower than that of alkali cleaning. Controlling the temperature of pre-cleaning at a lower level can further reduce the elution rate of the metallized area and even prevent the metallized area from being eluted.

[0071] Further, the temperature of the pre - cleaning is 60 - 70°C, for example: 60°C, 62°C, 65°C, 68°C, 70°C, etc.; the temperature of the alkali - cleaning is 75 - 85°C, for example: 75°C, 78°C, 80°C, 83°C, 85°C, etc. At the above - mentioned pre - cleaning temperature, while ensuring a reduction in the elution rate of the metallized area, it can ensure efficient and reliable elution of the non - metallized area; during alkali - cleaning, due to the addition of additives and an increase in the alkali - cleaning temperature, reliable elution of the non - metallized area can be ensured, thereby ensuring a difference in the doping concentration between the substrate 100 corresponding to the non - metallized area and the inner diffusion layer 121 of the metallized area; if the temperature of the alkali - cleaning further increases, it is easy to cause an increase in the depth of the non - metallized area formed by wet - process, the lengthening of the narrow channel under the metallized area, an increase in the series resistance, current loss, and a decrease in the fill factor (FF).

[0072] Optionally, the time of the pre - cleaning is longer than that of the alkali - cleaning. In this way, during the pre - cleaning, obvious elution of the non - metallized area treated by laser can be ensured.

[0073] Further, the time of the pre - cleaning is not less than 97 s, and the time of the alkali - cleaning is 90 - 95 s. If the time of the pre - cleaning is less than 97 s, it is easy to cause incomplete cleaning of the non - metallized area, and it is difficult to form an ideal doping concentration difference between the substrate 100 corresponding to the non - metallized area and the inner diffusion layer 121 of the metallized area; if the time of the alkali - cleaning is too short, it is not easy to clean the non - metallized area thoroughly, and it is difficult to form an ideal doping concentration difference between the substrate 100 corresponding to the non - metallized area and the inner diffusion layer 121 of the metallized area. At the same time, if the time of the alkali - cleaning is too long, it is easy to cause over - alkali - cleaning 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 diffusion layer 121 of the metallized area, however, the depth of the non - metallized area formed by wet - process increases, the narrow channel under the metallized area becomes longer, the series resistance increases, current loss occurs, and the fill factor (FF) decreases instead.

[0074] Optionally, the time of the pre - cleaning is less than 110 s. In this way, a large amount of elution of the metallized area can be avoided.

[0075] The chain - type pickling cleaning machine in the present disclosure includes hydrofluoric acid and water. The method and principle of the chain - type pickling are similar to those in the related art and will not be elaborated here.

[0076] The preparation processes not detailed in the present disclosure, such as the boron diffusion process, the process of depositing and forming the tunneling oxide layer 110 and the polysilicon layer, the doping process, etc., are similar to those in the related art and will not be elaborated here.

[0077] Hereinafter, the technical solutions disclosed in the invention will be described in detail with specific embodiments.

[0078] Embodiment 1 Example 1 provides a tunneling oxide passivated contact cell, which includes an n-type single-crystalline silicon substrate (doping concentration is 1.2×10 16 atom / cm 3 ). The substrate has a front side and a back side. A boron diffusion layer, an alumina layer, and a silicon nitride layer are sequentially formed on the front side. A tunneling oxide layer, a phosphorus-doped polysilicon layer (thickness 90 nm), an alumina layer, and a silicon nitride layer are sequentially formed on the back side. An inner diffusion layer is formed on a side of the tunneling oxide layer facing away from the phosphorus-doped polysilicon layer. The tunneling oxide passivated contact cell further includes a front electrode and a back electrode.

[0079] The doping concentration of the substrate corresponding to the non-metallized area on the back side of the tunneling oxide passivated 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 , and 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 8.57×10 -5 :1; the width of the non-metallized area is 400 μm.

[0080] Example 2 The difference between the tunneling oxide passivated contact cell of Example 2 and that of Example 1 is that the doping concentration of the n-type single-crystalline silicon substrate is 5×10 16 atom / cm 3 , the thickness of the phosphorus-doped polysilicon layer is 150 nm. Among them, the doping concentration of the substrate corresponding to the non-metallized area on the back side of the tunneling oxide passivated 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 , and 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 5×10 -5 :1; the width of the non-metallized area is 900 μm. For the rest other than the above differences, please refer to Example 1.

[0081] Example 3 The difference between the tunneling oxide passivated contact cell of Example 3 and that of Example 1 is that the doping concentration of the n-type single-crystalline silicon substrate is 5×10 15 atom / cm 3 , the thickness of the phosphorus-doped polysilicon layer is 120 nm. Among them, the doping concentration of the substrate corresponding to the non-metallized area on the back side of the tunneling oxide passivated contact cell is 5×10 15 atom / cm3 ; The doping concentration of the inner diffusion layer of the metallized region is 5×10 20 atom / cm 3 , and the ratio of the doping concentration of the substrate corresponding to the non-metallized region to the doping concentration of the inner diffusion layer of the metallized region is 1×10 -5 :1; The width of the non-metallized region is 700 μm. For the rest except the above differences, please refer to Example 1.

[0082] Comparative Example 1 The difference between the tunneling oxide passivated contact cell of Comparative Example 1 and Example 1 is that the doping concentration of the substrate corresponding to the non-metallized region on the back is 1.2×10 16 atom / cm 3 ; The doping concentration of the inner diffusion layer of the metallized region is 1.2×10 21 atom / cm 3 , and the ratio of the doping concentration of the substrate corresponding to the non-metallized region to the doping concentration of the inner diffusion layer of the metallized region is 1×10 -5 :1. For the rest except the above differences, please refer to Example 1.

[0083] Comparative Example 2 The difference between the tunneling oxide passivated contact cell of Comparative Example 2 and Example 1 is that the thickness of the phosphorus-doped polysilicon layer is 80 nm. For the rest except the above differences, please refer to Example 1.

[0084] Comparative Example 3 The difference between the tunneling oxide passivated contact cell of Comparative Example 3 and Example 1 is that the thickness of the phosphorus-doped polysilicon layer is 160 nm. For the rest except the above differences, please refer to Example 1.

[0085] Example 4 Texturing treatment is performed on the front surface of the n-type silicon substrate to form a textured surface on the front surface.

[0086] Boron diffusion is performed on the front surface of the substrate after the texturing treatment is completed to form a front boron diffusion layer.

[0087] Etching is performed on the back surface of the substrate to remove the borosilicate glass layer (BSG) on the back surface, and alkaline polishing is performed on the back surface of the substrate.

[0088] A tunneling oxide layer and a polysilicon layer are deposited on the back surface 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 90 nm.

[0089] The non-metallized area on the back of the substrate is processed by laser 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 is the metallized area; wherein, the wavelength of the laser is 400 nm, the spot size is 150 μm, the scanning speed is 45 m / s, the power is 41 W, and the frequency is 300 kHz; the width of the non-metallized area is 600 μm.

[0090] The protective layer (e.g., phosphosilicate glass layer, PSG) plated around the front and side is removed by chain pickling, and the polysilicon layer with wrap-around is exposed.

[0091] The non-metallized area and the metallized area are pre-cleaned; the cleaning agent for pre-cleaning is a sodium hydroxide solution with a mass concentration of 2.3%, the cleaning temperature is 65 °C, and the time is 97 s.

[0092] Then, the non-metallized area and the metallized area are alkali-cleaned to remove the first doped layer, the tunneling oxide layer, and the inner diffusion layer in the non-metallized area, so that the phosphorus-doped polysilicon layer and the tunneling oxide layer in the metallized area are retained; the cleaning agent for alkali-cleaning includes sodium hydroxide with a mass concentration of 2.3% and an additive, the volume ratio of the additive to the sodium hydroxide solution is 1%, the temperature for alkali-cleaning is 80 °C, and the time is 95 s.

[0093] Then, a second passivation layer, a first passivation layer, a second antireflection layer, and a first antireflection layer are prepared in sequence, and a front electrode and a back electrode are prepared.

[0094] The doping concentration of the substrate corresponding to the non-metallized area on the back of the fabricated tunneling oxide passivated 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 corresponding to the non-metallized area to the doping concentration of the inner diffusion layer in the metallized area is 1×10 -5 :1.

[0095] Example 5 The difference between Example 5 and Example 4 lies in the processes of the laser step, the pre-cleaning step, and the alkali-cleaning step.

[0096] The wavelength of the laser is 550 nm, the spot size is 400 μm, the scanning speed is 40 m / s, the power is 45 W, and the frequency is 400 kHz.

[0097] 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 time is 98 s.

[0098] The cleaning agent for alkaline cleaning 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 alkaline cleaning is 85 °C, and the time is 90 s.

[0099] The doping concentration of the substrate corresponding to the non-metallized area on the back of the obtained tunneling oxide passivated 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 , and 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 1×10 -5 :1.

[0100] For the rest other than the above differences, please refer to Example 4.

[0101] Example 6 The differences between Example 6 and Example 4 lie in the processes of the laser step, the pre-cleaning step, and the alkaline cleaning step.

[0102] The wavelength of the laser is 650 nm, the spot size is 420 μm, the scanning speed is 32 m / s, the power is 42 W, and the frequency is 300 kHz.

[0103] 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 time is 99 s.

[0104] The cleaning agent for alkaline cleaning 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 alkaline cleaning is 75 °C, and the time is 92 s.

[0105] The doping concentration of the substrate corresponding to the non-metallized area on the back of the obtained tunneling oxide passivated 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 , and 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 1×10 -5 :1.

[0106] For the rest other than the above differences, please refer to Example 4.

[0107] Example 7 The differences between Example 7 and Example 4 lie in the processes of the laser step, the pre-cleaning step, and the alkaline cleaning step.

[0108] The wavelength of the laser is 325 nm, the spot size is 130 μm, the scanning speed is 32 m / s, the power is 50 W, and the frequency is 300 kHz.

[0109] 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 time is 97 s.

[0110] The cleaning agent for alkali cleaning 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 for alkali cleaning is 73 °C, and the time is 90 s.

[0111] The doping concentration of the substrate corresponding to the non - metallized area on the back of the fabricated tunneling oxide passivated 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 , and 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 1×10 -5 :1.

[0112] For the rest except the above - mentioned differences, please refer to Example 4.

[0113] Example 8 The difference between Example 8 and Example 4 is that during laser treatment, the wavelength 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 fabricated tunneling oxide passivated 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 , and 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 1×10 -5 :1.

[0114] For the rest except the above - mentioned differences, please refer to Example 4.

[0115] Comparative Example 4 The difference between Comparative Example 4 and Example 4 is that during laser treatment, the wavelength 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 fabricated tunneling oxide passivated 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 corresponding to the non-metallized region to the doping concentration of the inner diffusion layer of the metallized region is 6×10 -2 :1.

[0116] For the rest other than the above differences, please refer to Example 4.

[0117] Comparative Example 5 The difference between Comparative Example 5 and Example 4 is that pre-cleaning is not performed, and alkali cleaning is directly carried out. The concentration difference between the non-metallized region and the metallized region on the back of the tunneling oxide passivated contact cell prepared is not obvious. The doping concentration of the substrate corresponding to the non-metallized region is 1×10 20 atom / cm 3 ; the doping concentration of the inner diffusion layer of the metallized region is 1.4×10 20 atom / cm 3 , and the ratio of the doping concentration of the substrate corresponding to the non-metallized region to the doping concentration of the inner diffusion layer of the metallized region is 0.71:1.

[0118] For the rest other than the above differences, please refer to Example 4.

[0119] Comparative Example 6 The difference between Comparative Example 6 and Example 4 is that the mass concentration of the sodium hydroxide solution for pre-cleaning is 3.5%, and the temperature for pre-cleaning is 80°C. The doping concentration of the substrate corresponding to the non-metallized region on the back of the tunneling oxide passivated contact cell prepared is 1×10 15 atom / cm 3 ; the doping concentration of the inner diffusion layer of the metallized region is 1×10 20 atom / cm 3 , and the ratio of the doping concentration of the substrate corresponding to the non-metallized region to the doping concentration of the inner diffusion layer of the metallized region is 1×10 -5 :1.

[0120] The depth of the non-metallized region after alkali cleaning in Comparative Example 6 is 1.15 times the depth of the non-metallized region after alkali cleaning in Example 4.

[0121] For the rest other than the above differences, please refer to Example 4.

[0122] Comparative Example 7 The difference between Comparative Example 7 and Example 4 is that the mass concentration of the sodium hydroxide solution for alkali cleaning is 3.5%, and the temperature for alkali cleaning is 90°C. The doping concentration of the substrate corresponding to the non-metallized region on the back of the tunneling oxide passivated contact cell prepared is 1×10 15 atom / cm 3 ; the doping concentration of the inner diffusion layer of the metallized region is 1×10 20 atom / cm3 , the ratio of the doping concentration of the substrate corresponding to the non-metallized region to the doping concentration of the inner diffusion layer of the metallized region is 1×10 -5 :1.

[0123] The depth of the non-metallized region of Comparative Example 7 after alkali washing is 1.3 times that of the non-metallized region of Example 4 after alkali washing.

[0124] For the rest other than the above differences, please refer to Example 4.

[0125] Comparative Example 8 The difference between Comparative Example 8 and Example 4 is that the pre-cleaning time is 90 s, and the doping concentration of the substrate corresponding to the non-metallized region on the back of the tunneling oxide passivated contact cell prepared is 1×10 17 atom / cm 3 ; the doping concentration of the inner diffusion layer of the metallized region is 1×10 20 atom / cm 3 , the ratio of the doping concentration of the substrate corresponding to the non-metallized region to the doping concentration of the inner diffusion layer of the metallized region is 1×10 -3 :1.

[0126] For the rest other than the above differences, please refer to Example 4.

[0127] Comparative Example 9 The difference between Comparative Example 9 and Example 4 is that the pre-cleaning time is 120 s, and the doping concentration of the substrate corresponding to the non-metallized region on the back of the tunneling oxide passivated contact cell prepared is 1×10 15 atom / cm 3 ; the doping concentration of the inner diffusion layer of the metallized region is 1×10 19 atom / cm 3 , the ratio of the doping concentration of the substrate corresponding to the non-metallized region to the doping concentration of the inner diffusion layer of the metallized region is 1×10 -4 :1.

[0128] For the rest other than the above differences, please refer to Example 4.

[0129] Comparative Example 10 The difference between Comparative Example 10 and Example 4 is that the alkali washing time is 85 s, and the doping concentration of the substrate corresponding to the non-metallized region on the back of the tunneling oxide passivated contact cell prepared is 8×10 16 atom / cm 3 ; the doping concentration of the inner diffusion layer of the metallized region is 1×10 19 atom / cm 3, the ratio of the doping concentration of the substrate corresponding to the non-metallized region to the doping concentration of the inner diffusion layer of the metallized region is 8×10 -3 :1.

[0130] For the rest other than the above differences, please refer to Example 4.

[0131] Comparative Example 11 The difference between Comparative Example 11 and Example 4 is that the alkali washing time is 100 s, and the doping concentration of the substrate corresponding to the non-metallized region on the back of the tunneling oxide passivated contact cell prepared is 1×10 15 atom / cm 3 ; the doping concentration of the inner diffusion layer of the metallized region is 2×10 19 atom / cm 3 , and the ratio of the doping concentration of the substrate corresponding to the non-metallized region to the doping concentration of the inner diffusion layer of the metallized region is 5×10 -5 :1.

[0132] For the rest other than the above differences, please refer to Example 4.

[0133] Comparative Example 12 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 region on the back of the tunneling oxide passivated contact cell prepared is 1×10 15 atom / cm 3 ; the doping concentration of the inner diffusion layer of the metallized region is 1×10 20 atom / cm 3 , and the ratio of the doping concentration of the substrate corresponding to the non-metallized region to the doping concentration of the inner diffusion layer of the metallized region is 1×10 -5 :1.

[0134] The depth of the non-metallized region after alkali washing in Comparative Example 12 is 1.10 times that of the non-metallized region after alkali washing in Example 4.

[0135] For the rest other than the above differences, please refer to Example 4.

[0136] Experimental Example 1 The tunneling oxide passivated contact cells of Example 1 (as Figure 2 shown) and Comparative Example 5 (as Figure 3 shown) were tested and characterized, and the characterization results are shown in Figure 4 ; among them, Figure 2 and Figure 3 Region 1 of both correspond to the metallized region, Figure 2 Region 3 in Figure 3The regions 2 therein all correspond to non-metallized regions.

[0137] According to Figure 4 it can be seen that by optimizing the doping concentration difference between the inner diffusion layer in the metallized region and the corresponding substrate in the non-metallized region, the performance of the battery can be effectively improved; among them, region 2 is the part of the inner diffusion layer that was not eluted in Comparative Example 5, which has a high doping concentration, resulting in no large doping concentration difference between the metallized region and the non-metallized region in Comparative Example 5, and will cause electrons and holes to recombine, and the electrons lose the ability to move freely and cannot participate in the current transmission or energy conversion, and the electrical performance of the battery cannot be improved; in Example 1 where the influence of region 2 is eliminated, a large doping concentration difference is formed between the metallized region and the non-metallized region, then the problem of electron-hole recombination can be improved, and the performance of the battery can be improved.

[0138] Experimental Example 2 The electrical properties of each of the above examples and comparative examples were detected, and the detection results are shown in the following table.

[0139]

[0140] According to the above table, by comparing Example 1 and Comparative Example 1, it can be seen that when the ratio of the doping concentration of the substrate corresponding to the non-metallized region to the doping concentration of the inner diffusion layer of the metallized region satisfies: (1×10 -6 ~5×10 -4 ) : 1, the doping concentration of the metallized region is too high, which is not conducive to the electrical performance of the prepared tunneling oxide layer passivated contact battery, that is, its fill factor and open circuit voltage decrease, and ultimately lead to a decrease in the photoelectric conversion efficiency.

[0141] By comparing Examples 1-3 and 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.

[0142] By comparing Example 4 and Comparative Example 4, it can be seen that optimizing the wavelength and power during laser treatment can effectively increase the fill factor and open circuit voltage, and ultimately lead to a decrease in the photoelectric conversion efficiency; among them, the increase in the laser wavelength instead causes subsequent pre-cleaning and alkali cleaning to be unable to achieve effective elution in the non-metallized region.

[0143] By comparing Example 4 and Comparative Example 5, it can be seen that without pre-cleaning, it is impossible to form a differential elution between the non-metallized region and the metallized region, and thus it is difficult to form a doping concentration difference between the non-metallized region and the metallized region, which ultimately leads to a decrease in the fill factor and open circuit voltage and a decrease in the photoelectric conversion efficiency.

[0144] Comparing Example 4 with Comparative Example 6, it can be seen that by optimizing the concentration of the pre-cleaning alkaline solution and the pre-cleaning temperature, and avoiding too high concentrations and temperatures of the alkaline solution, the elution amount in the non-metallized area can be controlled during alkaline cleaning, 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.

[0145] Comparing Example 4 with Comparative Example 7, it can be seen that by optimizing the concentration of the alkaline solution and the temperature during alkaline cleaning, and avoiding too high concentrations and temperatures of the alkaline solution, the elution amount in the non-metallized area can be controlled during alkaline cleaning, 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.

[0146] 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 to achieve the expected elution amount in the non-metallized area, and if the pre-cleaning time is too long, it will lead to excessive elution in the metallized area. Whether the non-metallized area fails to reach the expected elution amount or the metallized area is over-eluted, it will cause a decrease in the photoelectric conversion efficiency of the battery.

[0147] Comparing Example 4 with Comparative Examples 10 and 11, it can be seen that optimizing the alkaline cleaning time can ensure the photoelectric conversion efficiency of the battery; among them, if the alkaline cleaning time is too short, it is difficult to achieve the expected elution amount in the non-metallized area, and if the alkaline cleaning time is too long, it will lead to excessive elution in the metallized area. Whether the non-metallized area fails to reach the expected elution amount or the metallized area is over-eluted, it will cause a decrease in the photoelectric conversion efficiency of the battery.

[0148] Comparing Example 4 with Comparative Example 12, it can be seen that optimizing the power and frequency of laser treatment can ensure the photoelectric conversion efficiency of the battery; among them, when the laser frequency decreases, the spot energy increases, and under a relatively large power condition, it will cause excessive corrosion in the non-metallized area. Subsequently, during the subsequent pre-cleaning and alkaline cleaning processes, it will lead to excessive elution in the non-metallized area, increasing the depth of the non-metallized area and causing a decrease in the photoelectric conversion efficiency of the battery.

[0149] In summary, a doping concentration difference is formed between the inner diffusion layer 121 in the metallization region of the tunneling oxide passivated contact cell 010 of the present invention and the substrate 100 corresponding to the non-metallization region. Among them, the doping concentration of the substrate 100 corresponding to the non-metallization region is lower than that of the inner diffusion layer 121 in the metallization region. The high doping concentration of the inner diffusion layer 121 in the metallization region can ensure the transmission of electrons and ensure a high fill factor (FF). The low doping concentration of the substrate 100 corresponding to the non-metallization region can effectively inhibit the increase in Auger recombination, improve the problem that a large number of electrons are recombined and the open circuit voltage (Voc) is reduced; in short, the battery prepared by the preparation method of the present invention forms a doping concentration difference between the non-metallization region and the metallization region, which not only ensures the electron transmission in the metallization region and improves the fill factor (FF), but also avoids the reduction of the open circuit voltage in the non-metallization 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 passivated contact cell 010 can be improved by increasing the concentration difference between the non-metallization region and the metallization region.

[0150] As described above, the above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention should be covered by the protection scope of the present invention.

Claims

1. A tunneling oxide passivated contact cell, characterized in that, include: A substrate (100), the substrate (100) having a front side and a back side arranged opposite to each other, 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 side and located in the metallization area; A first doping layer (120), wherein the first doping layer (120) is formed on a side of the tunneling oxide layer (110) facing away from the substrate (100); wherein: An inner diffusion layer (121) is formed on a side of the tunneling oxide layer (110) facing away from the first doped layer (120); a ratio of a doping concentration of the substrate (100) corresponding to the non-metallization region to a doping concentration of the inner diffusion layer (121) in the metallization region is (1×10 -6 ~5×10 -4 ):

1.

2. The tunneling oxide passivated contact cell according to claim 1, wherein The doping concentration of the substrate (100) corresponding to the non-metallized region is 1×10 15 ~5×10 16 atom / cm 3 ; the doping concentration of the inner diffusion layer (121) in the metallized region is 1×10 20 ~1×10 21 atom / cm 3 .

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

4. The tunneling oxide passivated contact cell according to claim 3, wherein The thickness of the first doping layer (120) is 90-150 nm.

5. The tunneling oxide passivated 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 inner diffusion layer (121), the tunneling oxide layer (110) and the outside of the first doping layer (120) in the metallization region.

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

7. A preparation method of a tunneling oxide passivated contact battery, characterized in that, Used to prepare the tunneling oxide layer passivation contact cell according to any one of claims 1 to 6; 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 by laser, and the area not processed by laser is the metallized area; Pre-cleaning the non-metallized area and the metallized area; The non-metallized area and the metallized area are then subjected to alkali washing to remove the first doping layer (120), the tunneling oxide layer (110) and the inner diffusion layer (121) in the non-metallized area.

8. The manufacturing method of the tunneling oxide passivated contact battery according to claim 7, characterized in that, The cleaning solution for the pre-cleaning is a first alkaline solution; the cleaning solution for the alkaline washing includes a second alkaline solution and an additive.

9. The preparation method of the tunneling oxide passivated contact battery according to claim 8, characterized in that, The temperature of the pre-cleaning is lower than the temperature of the alkali washing.

10. The manufacturing method of the tunneling oxide passivated contact cell according to claim 9, characterized in that, The temperature of the pre-cleaning is 60-70°C; the temperature of the alkali washing is 75-85°C.

11. The manufacturing method of the tunneling oxide passivated contact cell according to claim 8, characterized in that, The additive includes a surfactant; the volume ratio of the additive to the second alkali solution is 0.5-1.5%.

12. The preparation method of the tunneling oxide passivated contact battery according to claim 8, wherein, The mass concentration of at least one of the first alkali solution and the second alkali solution is 2-3%.

13. The preparation method of the tunneling oxide passivated contact battery according to claim 8, wherein, The pre-cleaning time is longer than the alkali cleaning time.

14. The preparation method of the tunneling oxide passivated contact cell according to claim 13, wherein The pre-cleaning time is not less than 97 seconds, and the alkali cleaning time is 90-95 seconds.

15. The manufacturing method of the tunneling oxide passivated contact cell according to claim 7, characterized in that, The wavelength of the laser is 300-650nm, the spot size is 130-420μm, the scanning speed is greater than 30m / s, the power is greater than or equal to 35W, and the frequency is greater than or equal to 300kHz.

16. The preparation method of the tunneling oxide passivated contact cell according to claim 15, wherein, The width of the non-metallized area is 400-900 μm.

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