Passivated contact battery

Abstract

The utility model discloses a passivation contact cell, and relates to the technical field of solar cells. The passivation contact cell includes: a silicon substrate; the metal contact areas and the non-metal contact areas are alternately arranged on the textured structure of the first main surface of the silicon substrate; the first hybrid modification layer, the first tunneling oxide layer and the first doping layer are stacked in the metal contact area from inside to outside, and the first hybrid modification layer is used for providing a growth core for the first tunneling oxide layer and reducing the binding energy difference of different crystal faces on the surface of the silicon substrate; the emitter layer and the passivation anti-reflection layer are stacked in the non-metal contact area from inside to outside. According to the embodiment, the hybrid modification layer formed by the organic-inorganic mixture is arranged in the metal contact area of the first main surface of the silicon substrate, so that the growth uniformity of the tunneling oxide layer is improved, and the performance of the passivation contact cell is improved.

Description

Technical Field

[0001] The utility model relates to the technical field of solar cells, in particular to a passivated contact cell. Background Art

[0002] A tunnel oxide and passivated contact (TOPCon) solar cell is a solar cell that uses an ultra-thin tunnel oxide layer and a doped polysilicon layer as a passivation layer. In order to produce a light trapping effect, its front surface is usually set as a textured structure. Research shows that the quality of the tunnel oxide layer grown on the textured structure is much lower than that grown on the flat surface. For example, the open-circuit voltage (iVoc) of the flat structure of a p-type TOPCon solar cell can reach up to 734 mV at most, while the iVoc of the textured structure is only 700 mV at most.

[0003] The larger surface area of the textured structure results in stronger surface recombination, and the (100), (110), and (111) crystal planes of silicon in the textured structure are all exposed. Since different crystal planes have different surface energies and there are significant differences in their reaction activities, the growth uniformity of the tunnel oxide layer is poor, resulting in poor passivation performance of the passivated contact cell. Therefore, there is an urgent need for a passivated contact cell with a uniform tunnel oxide layer on the textured structure. Summary of the Utility Model

[0004] In view of this, the embodiments of the utility model provide a passivated contact cell and a preparation method thereof. By setting a first hybrid modification layer in the metal contact area on the surface of the silicon substrate, the difference in the binding energy between different crystal planes on the surface of the silicon substrate is adjusted, so that the growth of the tunnel oxide layer is more uniform, and the passivation performance of the passivated contact cell is improved.

[0005] To achieve the above object, in a first aspect, the embodiments of the utility model provide a passivated contact cell, including:

[0006] A silicon substrate;

[0007] Alternately arranged metal contact areas and non-metal contact areas provided on the textured structure on the first main surface of the silicon substrate;

[0008] A first hybrid modification layer, a first tunnel oxide layer, and a first doping layer stacked from the inside to the outside in the metal contact area, where the first hybrid modification layer is used to provide a growth nucleus for the first tunnel oxide layer and reduce the difference in the binding energy between different crystal planes on the surface of the silicon substrate;

[0009] An emitter layer and a passivation and antireflection layer stacked from the inside to the outside in the non-metal contact area.

[0010] Optionally, the first hybrid modification layer is formed at least by an organic-inorganic mixture,

[0011] wherein the organic-inorganic mixture includes a hydrogen-rich inorganic silicon oxide precursor and an organic compound for reducing the binding energy difference between different crystal planes of the silicon substrate;

[0012] the organic compound is an organic compound containing a pyrrole-based methylene ring structure; and / or

[0013] the organic compound includes porphyrin and / or polypeptide; and / or

[0014] the inorganic silicon oxide precursor includes an alkaline solution of tetraethyl orthosilicate or an acidic solution of tetraethyl orthosilicate.

[0015] Optionally, the thickness of the first hybrid modification layer is 0.01 - 1 nm.

[0016] Optionally, the thickness of the silicon substrate 10 is 80 - 300 μm; and / or

[0017] the width of the metal contact area is 20 - 500 μm; and / or

[0018] the proportion of the projected area of the metal contact area in the projected area of the first main surface is 1% - 20%.

[0019] Optionally, the doping concentration of the emitter layer is 1E 18 -5E 18 atoms / cm 3 ; and / or

[0020] the junction depth of the emitter layer is 0.1 - 1.5 μm; and / or

[0021] the doping concentration of the first doping layer is 1E 19 -5E 20 atoms / cm 3 ; and / or

[0022] the thickness of the first tunneling oxide layer is 1 - 2 nm; and / or

[0023] the thickness of the first doping layer is 50 - 300 nm.

[0024] Optionally, it further includes:

[0025] a second tunneling oxide layer, a second doping layer, and an antireflection layer sequentially arranged from inside to outside on the second main surface of the silicon substrate;

[0026] a second metal electrode electrically connected to the second doping layer.

[0027] Optionally, the thickness of the second tunneling oxide layer is 0.2 - 2 nm.

[0028] Optionally, the thickness of the second doping layer is 20 - 200 nm.

[0029] Optionally, a second hybrid modification layer is provided between the second tunneling oxide layer and the silicon substrate.

[0030] Optionally, the passivated contact cell further includes: a first metal electrode electrically connected to the first doping layer.

[0031] In a second aspect, a method for manufacturing a passivated contact cell is provided, including:

[0032] Step 1: Sequentially form a first hybrid modification layer, a first tunneling oxide layer, and a polysilicon layer from the inside to the outside on the textured structure of the first main surface of the silicon substrate. The first hybrid modification layer is used to provide growth nuclei for the first tunneling oxide layer and reduce the binding energy gap between different crystal planes on the surface of the silicon substrate.

[0033] Step 2: Form a mask layer on the surface of the polysilicon layer facing away from the silicon substrate. The first main surface of the silicon substrate includes a metal contact region and a non-metal contact region. Remove the mask layer in the non-metal contact region and retain the mask layer in the metal contact region.

[0034] Step 3: Remove the polysilicon layer, the first tunneling oxide layer, and the first hybrid modification layer in the non-metal contact region, as well as the mask layer.

[0035] Step 4: Perform diffusion of a first doping element on the metal contact region and the non-metal contact region to form an emitter layer in the non-metal contact region and a first doping layer on the polysilicon layer in the metal contact region.

[0036] Step 5: Perform passivation and antireflection treatment on the first doping layer and the emitter layer.

[0037] One embodiment of the above utility model has the following advantages or beneficial effects:

[0038] By providing a first hybrid modification layer in the metal contact region of the first main surface of the silicon substrate, the surface binding energy of the exposed (100) and (110) crystal planes in the textured surface is reduced, so that the binding energy gap between the exposed (100), (110), and (111) crystal planes on the textured surface is reduced, improving the growth uniformity of the first tunneling oxide layer and the performance of the passivated contact cell. In addition, the first hybrid modification layer can provide nuclei for the growth of the first tunneling oxide layer, making the growth of the first tunneling oxide layer faster and reducing the process duration for growing the first tunneling oxide layer.

[0039] Furthermore, a first hybrid modification layer formed of an organic-inorganic mixture is provided in the metal contact region on the first main surface of the silicon substrate. Among them, the organic matter in the organic-inorganic mixture can adjust the binding energy gap between different crystal planes on the surface of the silicon substrate, reduce the surface binding energy of the exposed (100) crystal plane and (110) crystal plane in the textured surface, so that the binding energy gap of the exposed (100) crystal plane, (110) crystal plane and (111) crystal plane on the textured surface is reduced, improving the growth uniformity of the tunneling oxide layer and enhancing the performance of the passivated contact cell.

[0040] In addition, the hydrogen-rich inorganic silica precursor in the organic-inorganic mixture can provide nuclei for the growth of the tunneling oxide layer, making the growth of the tunneling oxide layer faster, reducing the process duration for growing the tunneling oxide layer. At the same time, the high content of hydrogen in the hydrogen-rich inorganic silica precursor can diffuse into the silicon substrate at high temperature to enhance the passivation performance of the passivated contact cell.

[0041] The further effects of the above non-conventional optional methods will be described in conjunction with specific embodiments below. Description of the Drawings

[0042] The drawings are used to better understand the present utility model and do not constitute an improper limitation to the present utility model. Among them:

[0043] Figure 1 is a schematic structural diagram of a passivated contact cell according to an embodiment of the present utility model;

[0044] Figure 2 is a schematic structural diagram of the metal contact region according to an embodiment of the present utility model;

[0045] Figure 3 is a schematic structural diagram of the non-metal contact region according to an embodiment of the present utility model;

[0046] Figure 4 is a schematic structural diagram of a passivated contact cell including a second hybrid modification layer according to another embodiment of the present utility model.

[0047] The reference numerals are as follows:

[0048] 10 - silicon substrate; 20 - metal contact region; 21 - first hybrid modification layer; 22 - first tunneling oxide layer; 23 - first doping layer; 30 - non-metal contact region; 31 - emitter layer; 32 - passivation and antireflection layer; 40 - first metal electrode; 50 - second tunneling oxide layer; 60 - second doping layer; 70 - antireflection layer; 80 - second metal electrode; 90 - second hybrid modification layer. Detailed Embodiments

[0049] In existing passivated contact cells, due to the uneven growth of the tunneling oxide layer on the textured structure, there are certain holes and gaps. During the metallization process (i.e., the process of fabricating electrodes), the tunneling oxide layer is easily burned through, resulting in the contact between the metal paste and the silicon substrate, forming an ohmic contact and generating a large amount of metal recombination loss, thus affecting the passivation performance and cell efficiency. To solve these problems existing in the prior art, the embodiments of the present utility model provide a passivated contact cell with a novel structure and a preparation method thereof.

[0050] The following provides a description of exemplary embodiments of the passivated contact cell and its preparation method provided by the present utility model in conjunction with the accompanying drawings. Various details of the embodiments of the present utility model are included to facilitate understanding, and they should be considered merely exemplary. Therefore, those of ordinary skill in the art should recognize that various changes and modifications can be made to the embodiments described herein without departing from the scope and spirit of the present utility model. Similarly, for the sake of clarity and conciseness, descriptions of well-known functions and structures are omitted in the following description.

[0051] In the embodiments of the present utility model, the inside-to-outside direction refers to the direction extending from the silicon substrate to the surface of the passivated contact cell in sequence.

[0052] In the embodiments of the present utility model, the "first", "second", etc. involved are used to distinguish different structures or components or the same structures in different positions, and do not limit the quantity, order, etc. of the structures or components. For example, the first main surface of the silicon substrate is the main surface of the silicon substrate facing the sunlight, and the second main surface of the silicon substrate is the main surface of the silicon substrate facing away from the sunlight, etc.

[0053] Specifically, as Figure 1 , Figure 2 and Figure 3 shown, the passivated contact cell of the embodiments of the present utility model mainly includes: a silicon substrate 10; alternately arranged metal contact regions 20 and non-metal contact regions 30 provided on the textured structure of the first main surface of the silicon substrate 10, and a first hybrid modification layer 21, a first tunneling oxide layer 22, and a first doping layer 23 stacked from the inside to the outside in the metal contact region 20; wherein, the first hybrid modification layer 21 is used to provide a growth nucleus for the first tunneling oxide layer 22 and reduce the binding energy difference of different crystal planes on the surface of the silicon substrate 10; an emitter layer 31 and a passivation and antireflection layer 32 are stacked from the inside to the outside in the non-metal contact region 30.

[0054] The first main surface of the silicon substrate 10 has a textured structure, in which there are a metal contact region 20 and a non-metal contact region 30. When screen printing, it is necessary to print a metal paste to form the surface region of the first metal electrode 40, and the region between this surface region and the silicon substrate 10 is used as the metal contact region 20; the region between the surface region where the metal paste does not need to be printed during screen printing (i.e., the surface region other than the metal contact region 20) and the silicon substrate 10 is used as the non-metal contact region 30.

[0055] The first hybrid modification layer 21 is formed at least by an organic-inorganic mixture. Among them, the organic-inorganic mixture contains a hydrogen-rich inorganic silica precursor and an organic substance for reducing the binding energy gap between different crystal planes on the surface of the above-mentioned silicon substrate 10. Specifically, by coating the organic-inorganic mixture on the surface of the silicon substrate 10, after the solvent volatilizes, the organic-inorganic mixture adheres to the surface of the silicon substrate 10. The hydrogen-rich inorganic silica precursor therein provides a growth nucleus for the first tunneling oxide layer 22, so that under thermal oxidation conditions, the first tunneling oxide layer 22 can grow rapidly to form, saving the preparation time of the first tunneling oxide layer 22. The organic substance in the organic-inorganic mixture for reducing the binding energy gap between different crystal planes on the surface of the silicon substrate 10 adjusts the crystal plane activity of different crystal planes exposed on the surface of the silicon substrate 10, narrowing the binding energy gap between each crystal plane, making the growth of the first tunneling oxide layer 22 tend to be uniform and grow more evenly on the surface of the silicon substrate 10, and improving the growth uniformity of the first tunneling oxide layer 22. Specifically, the growth uniformity refers to the thickness uniformity of the first tunneling oxide layer 22 when growing on the surface of the silicon substrate 10. When the thickness uniformity of the first tunneling oxide layer 22 is better, its growth uniformity is higher.

[0056] Among them, the hydrogen-rich inorganic silica precursor can adopt an alkaline or acidic solution of tetraethyl orthosilicate. When in a high-temperature environment, such as the temperature for forming the first tunneling oxide layer 22, the hydrogen-containing part will split out free hydrogen; the tetraethyl orthosilicate deposited on the silicon substrate 10 polymerizes into mesoporous silica, providing a growth nucleus for the growth of the first tunneling oxide layer 22.

[0057] In addition, the organic substance is an organic substance containing a pyrrole-based methylene cyclic structure. The pyrrole-based methylene cyclic structure has high conjugation, making the organic substance containing this structure more likely to adsorb on the (100) crystal plane and (110) crystal plane with higher surface binding energy. Due to the large steric hindrance of the pyrrole-based methylene cyclic structure, the surface binding energy of the (100) crystal plane and (110) crystal plane is reduced, thereby narrowing the gap in surface binding energy between the (100) crystal plane, (110) crystal plane, and (111) crystal plane, so that the subsequent growth of the first tunneling oxide layer 22 is more uniform. As an example, the organic substance used to reduce the gap in binding energy of different crystal planes on the surface of the above-mentioned silicon substrate 10 may include organic small molecules such as porphyrin and / or polymers such as polypeptides.

[0058] Furthermore, since the molecular weight of the organic substance affects its steric hindrance, in order for the organic substance to reduce the surface binding energy of the (100) crystal plane and (110) crystal plane and minimize the gap in surface binding energy between the (100) crystal plane, (110) crystal plane, and (111) crystal plane, therefore, the molecular weight of the organic substance is 100 - 10000000 Da. The mass ratio of the hydrogen-rich inorganic silicon oxide precursor to the organic substance in the organic-inorganic mixture is 1:1000 to 1000:1. The thickness of the first hybrid modification layer 21 formed by the organic-inorganic mixture is 0.01 - 1 nm. As an example, the molecular weight of the organic substance can be 100 Da, 10000 Da, or 10000000 Da; the mass ratio of the hydrogen-rich inorganic silicon oxide precursor to the organic substance in the organic-inorganic mixture can be 1:1000, 1:100, 1:1, 100:1, or 1000:1; the thickness of the first hybrid modification layer 21 can be 0.01 nm, 0.1 nm, or 1 nm. Through the above settings, the first hybrid modification layer 21 formed by the organic-inorganic mixture can have a better effect of reducing the gap in binding energy of different crystal planes on the surface of the above-mentioned silicon substrate 10. By the interfacial modification effect of the organic-inorganic mixture, the pore size and pore area ratio of the first tunneling oxide layer 22 can be adjusted, making the subsequent growth of the first tunneling oxide layer 22 more uniform.

[0059] The thickness of the first tunneling oxide layer 22 in the metal contact region 20 is 1 - 2 nm. The first tunneling oxide layer 22 can include one or more of silicon oxide, silicon nitride, silicon oxynitride, but is not limited thereto. The thickness of the first doping layer 23 is 50 - 300 nm, and the doping concentration is 1E 19 -5E 20 atoms / cm 3, where the doping type of the first doping layer 23 can be a boron doping type or a phosphorus doping type. As an example, the thickness of the first tunneling oxide layer 22 can be 1 nm, 1.5 nm, or 2 nm; the thickness of the first doping layer 23 can be 50 nm, 150 nm, 200 nm, or 300 nm; the doping concentration of the first doping layer 23 can be 1E 19 atoms / cm 3 , 2E 20 atoms / cm 3 or 5E 20 atoms / cm 3 . By setting the thicknesses of the first tunneling oxide layer 22 and the first doping layer 23, each functional layer in the metal contact region 20 has an appropriate thickness, and there is an optimal thickness ratio between the functional layers, which can effectively improve the cell efficiency of the passivated contact cell and enhance the performance of the passivated contact cell; meanwhile, by setting the doping concentration of the first doping layer 23, the selective effect and passivation performance of the first tunneling oxide layer 22 can be effectively improved, thereby enhancing the cell performance.

[0060] In the first main surface of the silicon substrate 10, the width of the metal contact region 20 is 20 - 500 μm, and the ratio of the projected area of the metal contact region 20 to the projected area of the first main surface is 1% - 20%. As an example, the width of the metal contact region 20 can be 20 μm, 200 μm, or 500 μm; the ratio of the projected area of the metal contact region 20 to the projected area of the first main surface is 1%, 10%, or 20%.

[0061] In the non - metal contact region 30, an emitter layer 31 is formed on the surface of the silicon substrate 10, and a passivation and antireflection layer 32 is covered on the emitter layer 31. Among them, the doping type of the emitter layer 31 is the same as that of the first doping layer 23, which can be a boron doping type or a phosphorus doping type, and the doping concentration of the emitter layer 31 is 1E 18 - 5E 18 atoms / cm 3 , and the junction depth is 0.1 - 1.5 μm. As an example, the doping concentration of the emitter layer 31 can be 1E 18 atoms / cm 3 , 3E 18 atoms / cm 3 or 5E 18 atoms / cm 3 , and the junction depth can be 0.1 μm, 0.8 μm, or 1.5 μm. By setting the doping concentration and junction depth of the emitter layer 31 within an appropriate range, the cell efficiency of the passivated contact cell can be effectively improved.

[0062] The passivation and antireflection layer 32 may include a metal oxide layer and a silicon nitride layer. The thickness of the metal oxide layer may be 5 - 20 nm, and the thickness of the silicon nitride layer may be 20 - 100 nm. Among them, the metal oxide layer can bring a passivation effect, prevent premature recombination of electrons and electron holes in the silicon substrate 10, and reduce the losses existing in the internal energy conversion process of the battery. The metal oxide can be alumina. As an example, the thickness of the metal oxide layer may be 5 nm, 10 nm, or 20 nm; the thickness of the silicon nitride layer may be 20 nm, 50 nm, 70 nm, or 100 nm.

[0063] The above-mentioned passivated contact battery may further include: a second tunneling oxide layer 50, a second doped layer 60, and an antireflection layer 70 sequentially arranged from the inside to the outside on the second main surface of the silicon substrate 10. Further, as Figure 4 shown, a second hybrid modification layer 90 may also be provided between the silicon substrate 10 and the second tunneling oxide layer 50 to promote the uniform growth of the second tunneling oxide layer 50 on the second main surface of the silicon substrate 10 and improve the growth uniformity of the second tunneling oxide layer 50.

[0064] The thickness of the second tunneling oxide layer 50 on the second main surface of the silicon substrate 10 is 0.2 - 2 nm. The second tunneling oxide layer 50 may include one or more of silicon oxide, silicon nitride, and silicon oxynitride, but is not limited thereto. The thickness of the second doped layer 60 is 20 - 200 nm, and the doping concentration may be 1E 20 -9E 20 atoms / cm 3 ³, and the doping type may be boron doping type or phosphorus doping type. As an example, the thickness of the second tunneling oxide layer 50 may be 0.2 nm, 0.8 nm, 1.5 nm, or 2 nm; the thickness of the second doped layer 60 may be 20 nm, 50 nm, 150 nm, or 200 nm; the doping concentration of the second doped layer 60 may be 1E 20 atoms / cm 3 ³, 5E 20 atoms / cm 3 ³, or 9E 20 atoms / cm 3 ³. Further, the doping type of the second doped layer 60 is opposite to that of the first doped layer 23. When the doping type of the first doped layer 23 is boron doping type, the doping type of the second doped layer 60 is phosphorus doping type; when the doping type of the first doped layer 23 is phosphorus doping type, the doping type of the second doped layer 60 is boron doping type.

[0065] The passivated contact cell further includes: a first metal electrode 40 electrically connected to the first doped layer 23, and / or, a second metal electrode 80 electrically connected to the second doped layer 60. Wherein, the width of the first metal electrode 40 can be 15-50 μm, the width of the second metal electrode 80 can be 15-50 μm, and the widths of the first metal electrode 40 and the second metal electrode 80 can be the same or different. As an example, the width of the first metal electrode 40 can be 15 μm, 30 μm or 50 μm, and the width of the second metal electrode 80 can be 15 μm, 25 μm, 40 μm or 50 μm. The first metal electrode 40 and the second metal electrode 80 can be electrodes of the same material, including but not limited to silver electrodes, aluminum electrodes, nickel electrodes, copper electrodes, alloy electrodes, and metal composite electrodes.

[0066] The silicon substrate 10 can be a single-crystalline silicon wafer doped with phosphorus atoms, i.e., an N-type silicon wafer, or a single-crystalline silicon wafer doped with boron atoms, i.e., a P-type silicon wafer. The resistivity of the silicon substrate 10 can be 0.1-5 Ω·cm, and the thickness can be 80-300 μm. The width of the base of the pyramid-shaped structure of the textured surface on the first main surface of the silicon substrate 10 can be 1-5 μm; the second main surface of the silicon substrate 10 is flatter than the first main surface, and the width of the base therein can be 8-10 μm. As an example, the resistivity of the silicon substrate 10 can be 0.1 Ω·cm, 1 Ω·cm, 3 Ω·cm or 5 Ω·cm; the thickness of the silicon substrate 10 can be 80 μm, 150 μm or 300 μm; the width of the base of the pyramid-shaped structure of the textured surface on the first main surface of the silicon substrate 10 can be 1 μm, 3 μm or 5 μm; the width of the base of the second main surface of the silicon substrate 10 can be 8 μm, 9 μm or 10 μm.

[0067] In the passivated contact cell provided by the embodiment of the present invention, a first hybrid modification layer formed by an organic-inorganic mixture is provided in the metal contact area on the first main surface of the silicon substrate. Among them, the hydrogen-rich inorganic silicon oxide precursor in the organic-inorganic mixture can provide nuclei for the growth of the tunneling oxide layer, so that the growth of the tunneling oxide layer is faster, reducing the process duration of growing the tunneling oxide layer. At the same time, free hydrogen is cracked out from the hydrogen-rich inorganic silicon oxide precursor at high temperature and can diffuse into the silicon substrate to enhance the passivation performance of the passivated contact cell; the organic matter in the organic-inorganic mixture can adjust the binding energy difference between different crystal planes on the surface of the silicon substrate, reducing the surface binding energy of the exposed (100) and (110) crystal planes in the textured surface, so that the difference in the surface binding energy of the exposed (100), (110) and (111) crystal planes on the textured surface is reduced, improving the growth uniformity of the tunneling oxide layer and enhancing the performance of the passivated contact cell.

[0068] Furthermore, the organic compound has a pyrrole-based methylene cyclic structure. Due to the high conjugation of this structure, the organic compound with this structure is more likely to adsorb on the (100) crystal plane and (110) crystal plane on the surface of the silicon substrate. Since the pyrrole-based methylene cyclic structure has a large steric hindrance, the surface binding energy of the (100) crystal plane and (110) crystal plane is reduced, and the binding energy gap between the three crystal planes on the surface of the silicon substrate is narrowed, making the growth of the subsequent first tunneling oxide layer more uniform.

[0069] The present utility model also provides a method for preparing a passivated contact battery, including the following steps 1 to 5:

[0070] Step 1: Sequentially form a first hybrid modification layer, a first tunneling oxide layer, and a polysilicon layer from the inside to the outside on the textured structure of the first main surface of the silicon substrate. The above-mentioned first hybrid modification layer is used to provide a growth nucleus for the above-mentioned first tunneling oxide layer and reduce the binding energy gap between different crystal planes on the surface of the above-mentioned silicon substrate;

[0071] Step 2: Form a mask layer on the surface of the above-mentioned polysilicon layer facing away from the above-mentioned silicon substrate. The first main surface of the above-mentioned silicon substrate includes a metal contact area and a non-metal contact area. Remove the mask layer in the above-mentioned non-metal contact area and retain the mask layer in the above-mentioned metal contact area;

[0072] Step 3: Remove the polysilicon layer, the first tunneling oxide layer, and the first hybrid modification layer in the above-mentioned non-metal contact area, as well as the above-mentioned mask layer;

[0073] Step 4: Perform diffusion of a first doping element on the above-mentioned metal contact area and the above-mentioned non-metal contact area to form an emitter layer in the above-mentioned non-metal contact area and form a first doped layer on the polysilicon layer in the above-mentioned metal contact area;

[0074] Step 5: Perform passivation and antireflection treatment on the above-mentioned first doped layer and the above-mentioned emitter layer.

[0075] Furthermore, forming the first hybrid modification layer on the textured structure of the first main surface of the silicon substrate includes: forming the above-mentioned first hybrid modification layer by coating an organic-inorganic mixture on the textured structure of the first main surface of the above-mentioned silicon substrate; wherein, the above-mentioned organic-inorganic mixture includes a hydrogen-rich inorganic silicon oxide precursor and an organic compound for reducing the binding energy gap between different crystal planes on the surface of the above-mentioned silicon substrate.

[0076] In a thermal oxidation environment, the organic compound adsorbed on the first main surface of the above-mentioned silicon substrate and the unreacted hydrogen-rich inorganic silicon oxide precursor form the above-mentioned first hybrid modification layer.

[0077] The methods of coating the organic-inorganic mixture include spraying, knife coating, spin coating, or evaporation coating. Specifically, after double-sided texturing of the silicon substrate, the organic-inorganic mixture is coated on the textured structure of the first main surface by spraying, knife coating, spin coating, or other coating methods, or the organic-inorganic mixture is modified on the textured structure of the first main surface by evaporation coating or other methods.

[0078] Among them, the solvents in the organic-inorganic mixture include ethanol or chloroform. Specifically, the organic-inorganic mixture is prepared by dissolving an organic substance and a hydrogen-rich silicon dioxide precursor in solvents such as ethanol and chloroform. The mass concentration of the solute is 0.0001%-20%wt, and the mass ratio of the organic substance to the hydrogen-rich silicon dioxide precursor in the organic-inorganic mixture is 1:1000 to 1000:1. As an example, the mass concentration of the organic-inorganic mixture can be 0.001%wt, 0.01%wt, 1%wt, 20%wt, etc.; the mass ratio of the hydrogen-rich inorganic silicon dioxide precursor to the organic substance in the organic-inorganic mixture can be 1:1000, 1:500, 1:1, 500:1, or 1000:1.

[0079] The hydrogen-rich silicon dioxide precursor in the organic-inorganic mixture includes an acidic solution or a basic solution of tetraethyl orthosilicate. Since the neutral solution of tetraethyl orthosilicate will affect the growth rate of the subsequent first tunneling oxide layer, it is adjusted to an acidic solution or a basic solution to increase the growth rate of the first tunneling oxide layer. The acidic solution or basic solution of tetraethyl orthosilicate is obtained by adjusting the solution of tetraethyl orthosilicate to acidic or basic with a weak acid or a weak base. The weak acid can be acetic acid, etc., and the weak base can be ammonia water, etc., but not limited thereto.

[0080] The organic substance in the organic-inorganic mixture for reducing the binding energy gap between different crystal planes on the surface of the above silicon substrate is an organic substance containing a pyrrole-based methylene cyclic structure, and the molecular weight of the organic substance can be 100-10000000 Da. The pyrrole-based methylene cyclic structure has high conjugation, making the organic substance containing this structure more likely to adsorb on the (100) crystal plane and (110) crystal plane with higher surface binding energy. Due to the large steric hindrance of the pyrrole-based methylene cyclic structure, the surface binding energy of the (100) crystal plane and (110) crystal plane adsorbed with the substance containing the pyrrole-based methylene cyclic structure is reduced, thereby narrowing the binding energy gap between the (100) crystal plane, (110) crystal plane, and (111) crystal plane, so that the holes are smaller and the hole area ratio is reduced during the growth process of the subsequent first tunneling oxide layer, and the first tunneling oxide layer has better growth uniformity. As an example, the molecular weight of the organic substance can be 100 Da, 100000 Da, or 10000000 Da; the organic substance can include organic small molecules such as porphyrin and / or polymers such as polypeptides.

[0081] After coating the organic-inorganic mixture on the textured structure of the first main surface of the silicon substrate, the temperature is raised to a temperature higher than the boiling point of the solvent in the organic-inorganic mixture to volatilize the solvent, and then the silicon substrate is placed in a thermal oxidation environment. In the thermal oxidation environment, hydrogen in the hydrogen-rich silica precursor diffuses into the silicon substrate for hydrogenation to improve the passivation performance; a small amount of silica can be generated from part of the silica precursor to provide nuclei for the growth of the subsequent first tunneling oxide layer, thereby reducing the growth time of the first tunneling oxide layer. Part of the organic matter volatilizes in the thermal oxidation environment. Therefore, the remaining organic matter or the decomposition products of the organic matter together with the remaining silica precursor form the first hybrid modification layer. Or, only the remaining silica forms the first hybrid modification layer. Among them, the temperature of the thermal oxidation environment can be 550°C - 650°C. As an example, the temperature of the thermal oxidation environment can be 550°C, 600°C or 650°C.

[0082] In the thermal oxidation environment, based on the growth nuclei formed from the silica precursor, a uniform first tunneling oxide layer is grown on the first main surface of the silicon substrate, and the thickness can be 1 - 2 nm. Subsequently, a polysilicon layer is deposited on the first tunneling oxide layer, and the thickness can be 50 - 300 nm. As an example, the thickness of the first tunneling oxide layer can be 1 nm, 1.5 nm or 2 nm; the thickness of the polysilicon layer can be 50 nm, 200 nm or 300 nm.

[0083] A mask layer is formed on the surface of the polysilicon layer facing away from the silicon substrate. The mask layer in the non-metal contact area is removed by laser, and the mask layer in the metal contact area is retained. Among them, the metal contact area represents the area where metal paste needs to be printed, and the non-metal area represents the area where no metal paste needs to be printed, that is, other areas on the first main surface of the silicon substrate except the metal contact area.

[0084] Then, the polysilicon layer in the non-metal contact area is removed. At this time, the metal contact area includes the first hybrid modification layer, the first tunneling oxide layer, the polysilicon layer and the mask layer; the non-metal contact area includes the first hybrid modification layer and the first tunneling oxide layer. Among them, the thickness of the mask layer can be 1 - 20 nm. As an example, the thickness of the mask layer can be 1 nm, 5 nm, 10 nm or 20 nm.

[0085] The mask layer in the metal contact area, and the first tunneling oxide layer and the first hybrid modification layer in the non-metal contact area are removed. At this time, the metal contact area includes the first hybrid modification layer, the first tunneling oxide layer and the polysilicon layer; there is no functional layer in the non-metal contact area, and only the textured structure of the first main surface of the silicon substrate is exposed.

[0086] Diffuse a first doping element into the silicon substrate, where the first doping element can be boron or phosphorus. In the non-metal contact region, the first doping element diffuses into the first main surface of the silicon substrate to form an emitter layer in the silicon substrate, and the doping concentration of the emitter layer can be 1E 18 -5E 18 atoms / cm 3 , and the junction depth can be 0.1 - 1.5 μm. In the metal contact region, the first doping element diffuses into the polysilicon layer to convert the polysilicon layer into a first doped layer, and the doping concentration of the first doped layer can be 1E 19 -5E 20 atoms / cm 3 . As an example, the doping concentration of the emitter layer can be 1E 18 atoms / cm 3 , 3E 18 atoms / cm 3 or 5E 18 atoms / cm 3 ; the junction depth of the emitter layer can be 0.1 μm, 1 μm or 1.5 μm; the doping concentration of the first doped layer can be 1E 19 atoms / cm 3 , 1E 20 atoms / cm 3 or 5E 20 atoms / cm 3 . At this time, the metal contact region includes a first hybrid modification layer, a first tunneling oxide layer and a first doped layer; the non-metal contact region includes an emitter layer.

[0087] Remove the plating parts formed on the side and the second main surface of the silicon substrate due to the diffusion of the first doping element. Polish the second main surface of the silicon substrate, and grow a second tunneling oxide layer and a polysilicon layer on the polished second main surface in sequence from the inside to the outside.

[0088] Furthermore, an organic-inorganic mixture can also be coated on the polished second main surface to form a second hybrid modification layer, and then, a second tunneling oxide layer and a polysilicon layer are grown, so as to promote the uniform growth of the second tunneling oxide layer on the second main surface of the silicon substrate through the setting of the second hybrid modification layer and improve the growth uniformity of the second tunneling oxide layer.

[0089] Diffuse a second doping element into the silicon substrate to convert the polysilicon layer on the second main surface into a second doped layer. Among them, the second doping element can be boron or phosphorus, and the first doping element and the second doping element are different. When the first doping element is boron, the second doping element is phosphorus; when the first doping element is phosphorus, the second doping element is boron. Remove the plating parts formed on the first main surface and the side due to the diffusion of the second doping element.

[0090] The first doped layer and the emitter layer on the first main surface are passivated and antireflection-treated to form a passivation and antireflection layer on the first doped layer and the emitter layer, and the second doped layer on the second main surface is antireflection-treated to cover an antireflection layer on the second doped layer on the second main surface. After metal printing and high-temperature sintering, the metal paste burns through the passivation and antireflection layer covering the first doped layer and contacts the first doped layer, so that there is no passivation and antireflection layer in the metal contact area, and finally a passivated contact cell is obtained.

[0091] In the method for preparing a passivated contact cell according to an embodiment of the present invention, an organic-inorganic mixture is coated on the textured structure of the first main surface of the silicon substrate to form a first hybrid modification layer. The hydrogen-rich inorganic silicon oxide precursor in the organic-inorganic mixture can provide nuclei for the growth of the tunneling oxide layer, so that the growth of the tunneling oxide layer is faster, reducing the process time for growing the tunneling oxide layer. At the same time, the high content of hydrogen in the hydrogen-rich inorganic silicon oxide precursor can diffuse into the silicon substrate at high temperature to enhance the passivation performance of the passivated contact cell; the organic matter in the organic-inorganic mixture can reduce the binding energy difference between different crystal planes on the surface of the silicon substrate, reduce the surface binding energy of the exposed (100) crystal plane and (110) crystal plane in the textured surface, so that the difference in the surface binding energy of the exposed (100) crystal plane, (110) crystal plane and (111) crystal plane on the textured surface is reduced, reducing the interface recombination loss, improving the growth uniformity of the tunneling oxide layer, and improving the performance of the passivated contact cell.

[0092] The method for preparing a passivated contact cell will be described in detail below through a specific embodiment.

[0093] An N-type silicon wafer with a resistivity of 1 Ω·cm and a thickness of 150 μm is used as the silicon substrate, and the silicon substrate is textured on both sides by means of alkaline etching. Among them, the alkaline solution is a potassium hydroxide solution with a volume concentration of 5%, and the etching time of the alkaline solution is 200 s.

[0094] After the silicon substrate is dried, an organic-inorganic mixture is spin-coated on the first main surface of the silicon substrate. The organic-inorganic mixture is an ethanol solution containing porphyrin with a total mass concentration of 0.1%wt and tetraethyl orthosilicate. The silicon substrate is placed in an environment with a temperature higher than the boiling point temperature of ethanol to promote the volatilization of ethanol. After the ethanol volatilizes, the porphyrin and tetraethyl orthosilicate adhere to the suede structure on the surface of the silicon substrate. The silicon substrate after ethanol volatilization is placed in a low-pressure chemical vapor deposition (LPCVD) quartz boat, and oxygen with a flow rate of 2000 sccm is introduced. The temperature is gradually increased to 600 °C under low pressure. On three crystal planes of the first main surface of the silicon substrate, mesoporous silica is formed by tetraethyl orthosilicate, which can provide growth nuclei for the first tunneling oxide layer, and a first tunneling oxide layer with a thickness of about 1.5 nm is grown. Then, silane is introduced, and a polysilicon layer with a thickness of 200 nm is grown on the first tunneling oxide layer.

[0095] A 5-nm mask layer is formed on the surface of the polysilicon layer by laser oxidation. Specifically, a UV nanosecond laser is used to irradiate the surface of the polysilicon to form the mask layer. After the mask layer is formed on the surface of the polysilicon layer, the mask layer in the non-metal contact area is removed by laser, and the polysilicon layer in the non-metal contact area is removed by alkali etching. The mask layer in the metal contact area, the first tunneling oxide layer and the first hybrid modification layer in the non-metal contact area are removed by acid etching using an acid etching solution with a mass concentration of 1%. Among them, the alkali etching solution can be potassium hydroxide solution or sodium hydroxide solution, and the acid etching solution can be hydrofluoric acid solution, but is not limited thereto.

[0096] The silicon substrate is dried and placed in an LPCVD quartz boat. The temperature is raised to 950 °C, and boron tribromide with a flow rate of 200 sccm and oxygen with a flow rate of 880 sccm are introduced for boron diffusion. In the non-metal contact area, boron diffuses into the silicon substrate to form a P+ emitter layer, and the doping concentration of the P+ emitter layer is 3E 18 atoms / cm 3 , and the junction depth is 1.2 μm; in the metal contact area, boron diffuses into the polysilicon layer to form a boron-doped polysilicon layer, and the doping concentration of the boron-doped polysilicon layer is 1E 20 atoms / cm 3 . After boron diffusion, a layer of borosilicate glass (BSG) is formed on the surface of the boron-doped polysilicon layer. The plating-around parts formed by boron diffusion on the side and the second main surface of the silicon substrate are removed by cleaning, including BSG and boron-doped polysilicon, and the BSG on the first main surface is retained as a protective layer.

[0097] The second main surface of the silicon substrate is polished. The polished silicon substrate is placed in an LPCVD quartz boat, and under thermal oxidation conditions, a second tunneling oxide layer with a thickness of 1.5 nm is grown on the second main surface. Silane is introduced, and a polysilicon layer with a thickness of 150 nm is grown on the second tunneling oxide layer. The temperature is raised to 890 °C, and phosphorus oxychloride with a flow rate of 650 sccm and oxygen with a flow rate of 1500 sccm are introduced for phosphorus diffusion. On the second main surface, phosphorus diffuses into the polysilicon layer to form a phosphorus-doped polysilicon layer, and the doping concentration of the phosphorus-doped polysilicon layer is 6E 20 atoms / cm 3 . A layer of phosphosilicate glass (PSG) is formed on the surface of the phosphorus-doped polysilicon layer. The wet chemical method is used to sequentially clean and remove the overplated parts (including PSG and phosphorus-doped polysilicon) formed on the first main surface and the side surfaces due to phosphorus diffusion, the BSG on the first main surface, and the PSG on the second main surface.

[0098] In a plate-type atomic layer deposition equipment, an aluminum oxide (Al 2 O 3 ) layer with a thickness of 5 nm is deposited on the first main surface of the silicon substrate. After the deposition of the aluminum oxide layer is completed, in a plasma-enhanced chemical vapor deposition equipment, silane and ammonia are introduced to complete the deposition of the silicon nitride layer on the first main surface and the second main surface, and the thickness of the silicon nitride layer is 75 nm.

[0099] The silver paste is printed on the first main surface and the second main surface by screen printing to form a first metal electrode and a second metal electrode. After high-temperature sintering and light injection treatment, an N-type passivated contact cell is obtained.

[0100] The above specific embodiments do not constitute a limitation to the protection scope of the present utility model. Those skilled in the art should understand that various modifications, combinations, sub-combinations, and substitutions can occur depending on design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principle of the present utility model shall be included within the protection scope of the present utility model.

Claims

1. A passivated contact battery, characterized in that: include: Silicon substrate (10); Alternatingly arranged metal contact areas (20) and non-metal contact areas (30) are arranged on the velvet structure of the first main surface of the silicon substrate (10); A first hybrid modified layer (21), a first tunnel oxide layer (22), and a first doped layer (23) are stacked from inside to outside in the metal contact region (20), wherein the first hybrid modified layer (21) is used to provide a growth nucleus for the first tunnel oxide layer (22) and reduce the bonding energy difference between different crystal planes on the surface of the silicon substrate (10); An emitter layer (31) and a passivation anti-reflection layer (32) are stacked from inside to outside in the non-metal contact area (30); The thickness of the first tunneling oxide layer (22) is 1-2 nm; The thickness of the first doping layer (23) is 50-300 nm.

2. The passivated contact cell according to claim 1, characterized in that: The thickness of the first hybrid modified layer (21) is 0.01-1 nm.

3. The passivated contact cell according to claim 1, characterized in that: The thickness of the silicon substrate (10) is 80-300 μm; and / or The width of the metal contact area (20) is 20-500 μm; and / or The proportion of the projection area of ​​the metal contact region (20) to the projection area of ​​the first main surface is 1%-20%.

4. The passivated contact cell according to claim 1, characterized in that: The doping concentration of the emitter layer (31) is 1E 18 -5E 18 atoms / cm 3 ; and / or The junction depth of the emitter layer (31) is 0.1-1.5 μm; and / or The doping concentration of the first doping layer (23) is 1E 19 -5E 20 atoms / cm 3 .

5. The passivated contact cell according to claim 1, characterized in that: Also includes: A second tunneling oxide layer (50), a second doping layer (60) and an anti-reflection layer (70) are sequentially arranged from inside to outside on the second main surface of the silicon substrate (10); A second metal electrode (80) electrically connected to the second doped layer (60).

6. The passivated contact cell according to claim 5, characterized in that: The thickness of the second tunneling oxide layer (50) is 0.2-2 nm.

7. The passivated contact cell according to claim 5, characterized in that: The thickness of the second doping layer (60) is 20-200 nm.

8. The passivated contact cell according to claim 5, characterized in that: A second hybrid modification layer (90) is provided between the second tunneling oxide layer (50) and the silicon substrate (10).

9. The passivated contact cell according to claim 1, characterized in that: The passivation contact cell further comprises: a first metal electrode (40) electrically connected to the first doping layer (23).

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