Preparation method of solar cell contact structure, contact structure and solar cell

Abstract

The present application discloses a method for preparing a solar cell contact structure, a contact structure and a solar cell, wherein the solar cell contact structure comprises: providing a semiconductor substrate; performing ozone pretreatment on the surface of the semiconductor substrate using gaseous ozone to generate a first oxide layer on the surface of the semiconductor substrate; using the first oxide layer as a seed layer to assist in growing a second oxide layer, wherein the first oxide layer and the second oxide layer constitute a tunneling oxide layer; and forming a doping layer on the side of the tunneling oxide layer away from the semiconductor substrate. By performing ozone pretreatment on the semiconductor substrate, an extremely thin and dense oxide layer will be generated on the surface of the substrate due to the strong oxidizing property of ozone, thereby eliminating the unevenness of the tunneling oxide layer in the conventional high-temperature oxidation process, so that the tunneling oxide layer at different positions of the high-temperature furnace tube has consistent quality, and the photoelectric conversion efficiency of the overall cell is improved. This solves the problem of high temperature and uneven thickness of the tunneling oxide layer in the high-temperature oxidation process in the related art.

Description

Technical Field

[0001] The present application relates to the field of solar cells, and in particular to a method for preparing a solar cell contact structure, a solar cell contact structure and a solar cell. Background Art

[0002] The high-temperature diffusion process of crystalline silicon cells is a key link in the production process of solar crystalline silicon cells. The main purpose is to form a PN junction on the silicon wafer, which is the basis for achieving photoelectric conversion. The tunneling oxide layer (also called tunneling oxide passivation contact) in the crystalline silicon cell plays a vital role in the cell structure. The tunneling oxide layer is mainly composed of an ultra-thin layer of silicon oxide, which can significantly improve the surface passivation effect on the back of the silicon wafer. It can effectively reduce the surface state and defect state density, reduce the surface recombination rate, and thus increase the open circuit voltage of the crystalline silicon cell. Good surface passivation can reduce the recombination loss of photogenerated carriers on the surface of the silicon wafer and improve the photoelectric conversion efficiency of the cell.

[0003] The tunneling oxide layer usually forms a passivation contact structure with a layer of heavily doped polysilicon. The ultra-thin oxide layer allows majority electrons to tunnel into the polysilicon layer while blocking the recombination of minority holes. This structure allows electrons to be transmitted laterally in the polysilicon layer and collected by the metal, greatly reducing the metal contact recombination current and further improving the open circuit voltage and short circuit current of the battery. The tunneling oxide layer comprehensively improves the conversion efficiency of crystalline silicon cells through multiple functions such as surface passivation, selective carrier collection, and transparent conductive anti-reflection.

[0004] In summary, the tunnel oxide layer plays a vital role in crystalline silicon cells and is one of the key factors in improving cell efficiency and performance. The quality of the tunnel oxide layer growth is particularly important.

[0005] In conventional high-temperature oxidation processes, the quality of the tunnel oxide layer is improved by increasing the growth temperature and time of the tunnel oxide layer to improve the efficiency of the cell. The growth temperature and source concentration at different positions in the high-temperature furnace tube are inevitably different, resulting in uneven growth of the tunnel oxide layer at different positions. In addition, the conventional high-temperature oxidation process has a high growth temperature and a long time, which is not friendly to the energy environment. Summary of the invention

[0006] The present application provides a method for preparing a solar cell contact structure, a solar cell contact structure and a solar cell, so as to solve the problems of high temperature oxidation process and uneven thickness of tunneling oxide layer in the related art.

[0007] According to one aspect of the present application, a method for preparing a solar cell contact structure is provided, comprising: providing a semiconductor substrate; performing ozone pretreatment on the surface of the semiconductor substrate using gaseous ozone to generate a first oxide layer on the surface of the semiconductor substrate; and using the first oxide layer as a seed layer to assist in growing a tunneling oxide layer.

[0008] Optionally, the ozone pretreatment is performed in an ozone atmosphere, and the ozone atmosphere includes flowing the gaseous ozone over the surface of the semiconductor substrate.

[0009] Optionally, the concentration of the gaseous ozone subjected to the ozone pretreatment is 0.01 ppm to 50 ppm.

[0010] Optionally, the reaction temperature for the ozone pretreatment is 15° C. to 95° C., and the reaction time is 10 s to 1000 s.

[0011] Optionally, the process of forming the tunnel oxide layer includes a high temperature oxidation process, and the reaction temperature of the high temperature oxidation process is 500° C. to 650° C.

[0012] Optionally, the total thickness of the tunnel oxide layer is 1 nm to 2 nm.

[0013] Optionally, the thickness of the first oxide layer is smaller than the thickness of the tunnel oxide layer.

[0014] Optionally, the first oxide layer has a higher density than the tunnel oxide layer.

[0015] According to another aspect of the present application, a contact structure of a solar cell is provided, which is prepared by any one of the preparation methods described above.

[0016] According to another aspect of the present application, a solar cell is provided, comprising a solar cell contact structure prepared by any one of the preparation methods described above.

[0017] Through the technical solution of the present application, a method for preparing a solar cell contact structure is provided. By pre-treating the semiconductor substrate with ozone, the substrate is placed in an ozone environment. Due to the strong oxidizing property of ozone, an extremely thin and dense oxide layer will be generated on the surface of the substrate, eliminating the growth temperature at different positions in the high-temperature furnace tube in the conventional high-temperature oxidation process. The tunneling layer quality differences caused by the differences in source concentrations are eliminated, so that the tunneling oxide layers at different positions in the high-temperature furnace tube have consistent quality, and the photoelectric conversion efficiency of the overall cell is improved. The present invention can also reduce the temperature and time of the high-temperature oxidation process, save energy, and be environmentally friendly, thereby solving the problems of high temperature oxidation process temperature and uneven thickness of the tunneling oxide layer in the related art. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The drawings constituting a part of the present application are used to provide a further understanding of the present application. The illustrative embodiments and descriptions of the present application are used to explain the present application and do not constitute an improper limitation on the present application. In the drawings:

[0019] Figure 1 A schematic diagram of a solar cell contact structure in the prior art is shown;

[0020] Figure 2 A schematic diagram showing another solar cell contact structure in the prior art is shown;

[0021] Figure 3 A flow chart showing a method for preparing a solar cell contact structure according to an embodiment of the present application is shown;

[0022] Figure 4 is a schematic cross-sectional structure diagram of a solar cell contact structure according to an embodiment of the present application;

[0023] Figure 5 It is a schematic diagram of the cross-sectional structure of a solar cell according to an embodiment of the present application.

[0024] The above drawings include the following reference numerals:

[0025] 10′, semiconductor substrate; 20′, tunneling oxide layer; 30′, doping layer; 10, semiconductor substrate; 20, tunneling oxide layer; 21, first oxide layer; 22, second oxide layer; 30, doping layer; 40, anti-reflection film layer; 50, emitter film layer; 60, passivation film layer; 71, first electrode; 72, second electrode; 80, contact structure. DETAILED DESCRIPTION

[0026] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present application will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0027] In order to enable those skilled in the art to better understand the solution of the present application, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present application.

[0028] It should be noted that the terms "first", "second", etc. in the specification and claims of the present application and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequential order. It should be understood that the data used in this way can be interchanged where appropriate, so that the embodiments of the present application described here. In addition, the terms "including" and "having" and any of their variations are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device comprising a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0029] As introduced in the background technology, in the prior art, the tunnel oxide layer is grown using a high-temperature oxidation process. For example, improving the quality of the tunnel oxide layer often increases the growth temperature and time, resulting in an increase in cost. In addition, when the tunnel oxide layer is grown on a substrate, the substrate is in a high-temperature furnace, and the thickness of the tunnel oxide layer grown at different positions is uneven due to problems such as growth temperature and reaction source concentration. In order to solve the above technical problems, the present application provides a method for preparing a solar cell contact structure, a solar cell contact structure, and a solar cell.

[0030] Specifically, the tunnel oxide layer is grown on the semiconductor substrate using the current high temperature oxidation process. Due to the growth temperature and reaction source concentration of the semiconductor substrate at different positions in the high temperature furnace tube, the tunnel oxide layer grown at different positions of the semiconductor substrate is inevitably uneven. Figure 1 to Figure 2 As shown, a tunnel oxide layer 20' is formed on a semiconductor substrate 10' by a high temperature oxidation process, and a doping layer 30' is formed on the tunnel oxide layer 20' by a high temperature diffusion process, wherein the tunnel oxide layer 20' has film non-uniformity due to the growth temperature and reaction source concentration at different positions in the high temperature furnace tube. Figure 1 As shown, the thickness of the tunnel oxide layer 20' is uneven, with some areas being thicker and some areas being thinner. Figure 2 As shown, during the preparation of the contact structure, the tunnel oxide layer 20' does not form a complete film layer, but a film layer is disconnected. The above-mentioned uneven tunnel oxide layer 20' will lead to poor photoelectric conversion efficiency of the overall cell.

[0031] According to one aspect of the present application, a method for preparing a solar cell contact structure is provided, such as Figure 3 As shown, the preparation method comprises the following steps:

[0032] Step S101, providing a semiconductor substrate;

[0033] Step S102, using gaseous ozone to perform ozone pretreatment on the surface of the semiconductor substrate to form a first oxide layer on the surface of the semiconductor substrate;

[0034] Step S103, using the first oxide layer as a seed layer to assist in growing a second oxide layer, the first oxide layer and the second oxide layer forming a tunneling oxide layer;

[0035] Step S104: forming a doping layer on a side of the tunneling oxide layer facing away from the semiconductor substrate.

[0036] By using the above-mentioned preparation method of the contact structure of the solar cell of the present application, the semiconductor substrate is pretreated with ozone, so that the substrate is placed in an ozone environment. Due to the strong oxidizing property of ozone, an extremely thin and dense oxide layer will be generated on the surface of the substrate, eliminating the growth temperature at different positions in the high-temperature furnace tube in the conventional high-temperature oxidation process. The tunneling oxide layer at different positions of the high-temperature furnace tube has consistent quality, and the photoelectric conversion efficiency of the overall battery cell is improved. The present invention can also reduce the temperature and time of the high-temperature oxidation process. It saves energy and is environmentally friendly. It solves the problems of high temperature oxidation process temperature and uneven thickness of the tunneling oxide layer in the related art.

[0037] The exemplary embodiments of the method for preparing the solar cell contact structure provided by the present application will be described in more detail below. However, these exemplary embodiments can be implemented in a variety of different forms and should not be interpreted as being limited to the embodiments described herein. It should be understood that these embodiments are provided to make the disclosure of the present application thorough and complete, and to fully convey the concepts of these exemplary embodiments to those of ordinary skill in the art.

[0038] First, step S101 is performed to provide a semiconductor substrate.

[0039] Specifically, the semiconductor substrate material includes a combination of at least one or more materials selected from silicon (doped or undoped), germanium, silicon carbide, gallium arsenide, gallium phosphide, gallium nitride, indium phosphide, indium arsenide and / or indium antimonide, SiGe, GaAsP, AlInAs, AlGaAs, GaInAs, GaInP and GaInAsP, and may also include a multilayer substrate or a gradient substrate.

[0040] In some optional embodiments, the semiconductor substrate is first polished, cleaned and dried to improve the flatness and uniformity of the substrate surface, reduce defects, particles and impurities on the substrate surface, ensure the purity and reliability of the substrate surface, facilitate the growth of the subsequent oxide layer, and improve the quality and yield of the device.

[0041] Then, step S102 is performed to perform ozone pretreatment on the surface of the semiconductor substrate using gaseous ozone to form a first oxide layer on the surface of the semiconductor substrate.

[0042] Specifically, ozone is composed of an oxygen molecule carrying an oxygen atom. The molecule is unstable and has strong oxidizing ability. Ozone gas reacts with the surface atoms of the semiconductor substrate to form an extremely thin and dense oxide layer on the surface of the substrate. The tunnel oxide layer grows on the dense oxide layer, which is beneficial to improving the lattice quality of the tunnel oxide layer. Moreover, using the oxide layer as the seed layer for high-temperature growth of the tunnel oxide layer, a tunnel oxide layer with high density and uniformity can be grown without increasing the temperature and adding time. In addition, since ozone only contains oxygen, oxygen can be decomposed into oxygen at room temperature, and no harmful substances will be produced when it is oxidized with the substrate, and it has no toxic side effects on the environment, that is, it is an environmentally friendly pretreatment process step.

[0043] Among other things, since ozone generally decays much more slowly in the gas phase, gas phase treatments require less actual ozone use than treatments using ozone mixed with high purity water. Ozone gas processes can also be significantly simpler, easier, and less costly than retrofitting existing equipment.

[0044] In addition, due to the strong oxidizing property of ozone, the substrate is pre-treated with gaseous ozone, wherein ozone reacts with organic impurities remaining on the substrate surface to remove impurities on the substrate surface and achieve a cleaning effect on the substrate, wherein the impurities include organic residues. The removal reaction formula for a part of the organic residual impurities is as follows:

[0045] O3(g) + organic residue → O2(g) + oxidized organic matter (g).

[0046] In some alternative embodiments, the ozone pre-treatment is under an ozone atmosphere, which includes flowing gaseous ozone over the surface of the semiconductor substrate.

[0047] Specifically, when the semiconductor substrate is subjected to ozone pretreatment, the semiconductor substrate needs to be placed in a ventilation container filled with ozone, wherein the ventilation container has a gas inlet and a gas outlet. When the ozone pretreatment is performed, gaseous ozone is continuously input into the gas inlet, and the gas generated by the reaction and the unreacted ozone gas are discharged from the gas outlet to maintain a constant ozone concentration in the ventilation container. The ozone pretreatment is performed in a flowing ozone atmosphere, so that the gaseous ozone around the semiconductor substrate is uniform and sufficient, the difference in the concentration of the reaction source is reduced, the generation of an uneven oxide layer is avoided, and an oxide layer with uniform thickness and quality is generated on the surface of the semiconductor.

[0048] In some optional embodiments, the concentration of gaseous ozone for ozone pretreatment is 0.01ppm to 50ppm. By maintaining the concentration of gaseous ozone, the reaction rate of ozone oxidation is stabilized, the thickness of the oxide layer is better controlled, and the thickness of the oxide layer is ensured to be uniform.

[0049] In some optional embodiments, the reaction temperature for ozone pretreatment is 15°C to 95°C, and the reaction time is 10s to 1000s. Relative to cost and ozone treatment, a longer exposure duration can provide effective treatment and ensure that the growth of the oxide layer has good uniformity, while a shorter exposure duration can avoid a reduction in the benefits of the treatment. Ozone molecules will decompose into oxygen under certain conditions, reducing the ozone concentration of the ozone atmosphere. The ozone decomposition temperature refers to the minimum temperature required for ozone molecules to decompose into oxygen molecules, which is usually 150°C to 200°C. Therefore, in order to maintain the ozone concentration of the ozone atmosphere and reduce energy consumption, the reaction temperature of ozone pretreatment is 15°C to 95°C.

[0050] Then, after the semiconductor substrate is pre-treated with ozone, step S103 is performed to use the first oxide layer as a seed layer to assist in growing a second oxide layer, and the first oxide layer and the second oxide layer constitute a tunneling oxide layer.

[0051] Among them, the tunneling oxide layer is a thin oxide layer that can significantly improve the surface passivation effect on the back of the silicon wafer, effectively reduce the surface state and defect state density, reduce the surface recombination rate, and thus increase the open circuit voltage of the crystalline silicon cell. Good surface passivation can reduce the recombination loss of photogenerated carriers on the surface of the silicon wafer and improve the photoelectric conversion efficiency of the cell. The surface of the semiconductor substrate pretreated with ozone will form an extremely thin and dense oxide layer on the surface of the substrate due to the strong oxidizing property of ozone, which can serve as the seed layer of the subsequent tunneling oxide layer, guiding the growth of the tunneling oxide layer and improving the quality and stability of the tunneling oxide layer.

[0052] Specifically, the first oxide layer as a seed layer can provide a suitable lattice structure for the tunnel oxide layer. The first oxide layer can guide the growth of the subsequent tunnel oxide layer, help the tunnel oxide layer to form a better lattice match, and reduce the defects and stress caused by lattice mismatch. Therefore, using a dense first oxide layer as the growth starting point of the tunnel oxide layer can help the tunnel oxide layer form an ordered crystal structure, improve the quality and performance of the film layer, form the first oxide layer between the substrate and the tunnel oxide layer, enhance the bonding strength between the tunnel oxide layer and the semiconductor substrate, and improve the adhesion and stability of the tunnel oxide layer.

[0053] In some optional embodiments, the process of forming the tunnel oxide layer includes a high temperature oxidation process, and the reaction temperature of the high temperature oxidation process is 500°C to 650°C.

[0054] Specifically, a high-temperature oxidation process is usually used to prepare the tunnel oxide layer. In order to improve the quality of the tunnel oxide layer and improve the efficiency of the cell, a higher growth temperature and time are usually used to grow the tunnel oxide layer, generally at a temperature of 700°C to 1000°C, resulting in energy loss. The relatively dense first oxide layer grown by ozone pretreatment is used as a seed layer, which guides the growth of a high-quality and stable tunnel oxide layer. A tunnel oxide layer with high density and uniformity can still be grown at a lower temperature and time. The growth temperature of the high-temperature oxidation process is 500°C to 650°C, reducing energy loss.

[0055] Then, step S104 is performed to form a doping layer on a side of the tunneling oxide layer away from the semiconductor substrate.

[0056] Specifically, the tunnel oxide layer and a layer of heavily doped polysilicon together form a passivation contact structure, which can effectively reduce the resistance of the electron and hole injection contact interface in the solar cell, improve the carrier injection efficiency of electrons and holes, and thus improve the photoelectric conversion efficiency of the solar cell. In addition, through the design of the passivation contact structure, the recombination rate of electrons and holes in the solar cell can be reduced, the life of the carriers can be extended, and the stability and long-term performance of the solar cell can be improved.

[0057] Among them, polysilicon can be doped to form a doped layer, which can help form a better energy band structure, reduce the recombination of electrons and holes, and improve the pumping efficiency of photogenerated carriers, thereby improving the photoelectric conversion efficiency. The doped layer can also reduce the surface reflectivity of the battery, improve the light absorption rate, and increase the amount of photogenerated carriers generated. Among them, the doped layer includes p-type doping and n-type doping, p-type doping includes but is not limited to doping with boron or aluminum elements, and n-type doping includes but is not limited to doping with nitrogen or phosphorus elements.

[0058] In some optional implementations, the process of forming the doping layer includes but is not limited to a high-temperature diffusion process and an ion diffusion process, wherein the high-temperature diffusion process is relatively simple, the equipment cost is low, the doping distribution is isotropic, and the introduced lattice damage is low; the ion implantation process is relatively complex and the equipment is relatively expensive, but the temperature of the ion implantation process is lower and a more flexible and accurate doping distribution can be formed. Those skilled in the art can select according to product requirements, and this application does not make any specific limitations.

[0059] In some optional embodiments, the thickness of the tunnel oxide layer is 1 nm to 2 nm.

[0060] Specifically, the tunneling oxide layer is an extremely thin transparent film layer. On the one hand, it can reduce the interface recombination between the semiconductor substrate and the doped layer. On the other hand, the tunneling oxide layer can also play a good tunneling role, so that the majority carriers are transported through the tunneling principle, while the minority carriers are difficult to tunnel through the tunneling oxide layer into the doped layer due to the higher potential barrier and be recombined. The thickness of the tunneling oxide layer needs to be selected by technical personnel in this field according to the performance and efficiency of the product. Under normal circumstances, a tunneling oxide layer with a smaller thickness can improve the light transmittance and light absorption capacity of the battery, thereby improving the efficiency of the battery. However, an oxide layer with too thin a thickness may affect the stability and durability of the battery. Therefore, when designing the thickness of the tunneling oxide layer, it is necessary to balance performance and efficiency to achieve optimal performance and efficiency.

[0061] Exemplarily, the thickness of the tunnel oxide layer is 1 nm, 1.5 nm, 2.5 nm or 2 nm.

[0062] In some optional embodiments, the thickness of the first oxide layer is less than the thickness of the second oxide layer.

[0063] Specifically, an ozone generator is required to generate ozone gas. An ozone generator is a device that uses the principle of electrical discharge to generate ozone gas. Its working principle is to decompose oxygen molecules (O2) into oxygen atoms (O) through electric current and recombine them into ozone molecules (O3). The ozone generator usually applies a high-voltage electric field to cause oxygen molecules to undergo electrolysis near the electrode to produce ozone gas. The production cost of ozone gas is high, and the oxidation reaction of gaseous ozone on semiconductor substrates is slow. Therefore, the first oxide layer generated by gaseous ozone is only used as a seed layer to guide the growth of the second oxide layer. In order to improve production efficiency and reduce costs, the thickness of the first oxide layer is less than the thickness of the second oxide layer.

[0064] Specifically, the thickness of the first oxide layer is 0.1nm~0.3nm, and the thickness of the second oxide layer is 0.7nm~1.9nm. For example, the thickness of the first oxide layer is 0.3nm, and the thickness of the second oxide layer is 0.7nm; or the thickness of the first oxide layer is 0.1nm, and the thickness of the second oxide layer is 1.9nm; or the thickness of the first oxide layer is 0.1nm, and the thickness of the second oxide layer is 1.5nm; or the thickness of the first oxide layer is 0.3nm, and the thickness of the second oxide layer is 1.5nm, etc.

[0065] In some optional embodiments, the density of the first oxide layer is higher than the density of the tunnel oxide layer.

[0066] Specifically, the first oxide layer generated by the strong oxidizing property of ozone has a higher density, and the second oxide layer generated by the high temperature oxidation process has a lower density than the first oxide layer.

[0067] According to another aspect of the present application, a solar cell contact structure prepared by using any one of the above-mentioned methods for preparing a solar cell contact structure is provided, such as Figure 4 As shown, the contact structure includes a semiconductor substrate 10 , a tunneling oxide layer 20 and a doping layer 30 which are stacked together. The tunneling oxide layer 20 includes a first oxide layer 21 and a second oxide layer 22 .

[0068] Specifically, the first oxide layer 21 is formed on the surface of the semiconductor substrate by ozone pretreatment, and the second oxide layer 22 is formed on the surface of the first oxide layer 21 by using the first oxide layer as a seed layer and a high temperature oxidation process. The first oxide layer 21 is used as a seed layer of the second oxide layer 22, so that the tunneling oxide layers at different positions have consistent quality and thickness, and the uniformity of the tunneling oxide layer 20 is improved while also improving the lattice structure of the tunneling oxide layer 20, so that the tunneling oxide layers 20 at different positions on the semiconductor substrate 10 have consistent quality. The tunneling oxide layer with uniform quality can better allow majority electrons to tunnel into the polysilicon layer while blocking the recombination of minority holes. This allows electrons to be transmitted laterally in the polysilicon layer and collected by the metal, improving the passivation effect of the contact structure.

[0069] According to another aspect of the present application, a solar cell is provided. The solar cell includes a contact structure prepared by any one of the above-mentioned methods for preparing a solar cell contact structure.

[0070] For example, Figure 5 A solar cell including the above contact structure, such as Figure 5 As shown, it includes an anti-reflection film layer 40, a contact structure 80, an emitter film layer 50, and a passivation film layer 60 which are stacked in sequence, wherein the contact structure 80 is prepared by any one of the above-mentioned contact structure preparation methods, and the contact structure 80 includes a semiconductor substrate 10, a tunneling oxide layer 20 and a doping layer 30, the tunneling oxide layer 20 includes a first oxide layer 21 and a second oxide layer 22, the doping layer 30 in the contact structure is in contact with the anti-reflection film layer 40, and the semiconductor substrate 10 is in contact with the emitter film layer 50; the solar cell also includes a first electrode 71 and a second electrode 72, wherein the first electrode 71 is located on the side of the anti-reflection film layer 40 away from the contact structure 80, and the second electrode 72 is located on the side of the passivation film layer 60 away from the contact structure 80.

[0071] Specifically, the above-mentioned contact structure has a good passivation effect, and the tunneling oxide layer therein is uniform, so that electrons can be transmitted laterally in the polysilicon layer and collected by the metal, which greatly reduces the metal contact recombination current, so that the solar cell has a smaller open circuit voltage and short circuit current. In addition, the contact structure in the above-mentioned solar cell enables the battery to perform multiple functions such as selective carrier collection and transparent conductive anti-reflection when working, thereby improving the conversion efficiency of the solar cell.

[0072] The method for preparing the solar cell in the present application will be further described below in combination with specific embodiments and comparative examples.

[0073] Example 1

[0074] The method for preparing a solar cell provided in this embodiment comprises the following steps:

[0075] Step S111: providing a silicon wafer, wherein the silicon wafer has a first surface and a second surface;

[0076] Step S112: cleaning and texturing the first surface of the silicon wafer;

[0077] Step S113: forming a boron-diffused emitter film layer on the surface of the substrate textured by using a boron diffusion process;

[0078] Step S114: polishing, cleaning and drying the second surface of the silicon wafer, so that the surface is in a dry and hydrophobic state;

[0079] Step S115: placing the dry hydrophobic silicon wafer in a ventilation container filled with gaseous ozone for ozone pretreatment, continuously introducing gaseous ozone into the ventilation container, maintaining a constant gaseous ozone concentration of 10 ppm, a temperature in the container of 50° C., and a time of 800 seconds to form a first oxide layer;

[0080] Step S116: forming a second oxide layer on the first oxide layer using a high temperature oxidation process, wherein the temperature of the high temperature oxidation process is 550° C.;

[0081] Step S117: forming a phosphorus-doped n-type doping layer by a high temperature diffusion process;

[0082] Step S118: forming an aluminum oxide / silicon nitride film layer on the emitter film layer by a deposition process to form a passivation film layer.

[0083] Step S119: forming a silicon nitride film layer on the n-type doped layer by a deposition process to form an anti-reflection film layer;

[0084] Step S1110: using a deposition process to form Ag layers on the surface of the anti-reflection film layer and the surface of the passivation film layer, respectively serving as the first conductive layer and the second conductive layer.

[0085] Example 2

[0086] The passivation process verification experiment provided in this embodiment includes the following steps:

[0087] Step S211: providing a silicon wafer, wherein the silicon wafer has a first surface and a second surface;

[0088] Step S212: cleaning and polishing the first surface and the second surface of the silicon wafer;

[0089] Step S213: placing the polished silicon wafer in a ventilation container filled with gaseous ozone for double-sided ozone pretreatment, continuously introducing gaseous ozone into the ventilation container, maintaining a constant gaseous ozone concentration of 10 ppm, a temperature in the container of 50° C., and a time of 800 s, to form a first oxide layer on both the first surface and the second surface of the silicon wafer;

[0090] Step S214: forming a second oxide layer on the first oxide layer by a high temperature oxidation process, wherein the temperature of the high temperature oxidation process is 550° C., so that tunnel oxide layers are formed on both the first surface and the second surface of the silicon wafer;

[0091] Step S215: forming a boron-doped p-type doped layer on both sides of the tunnel oxide layer by using a high temperature diffusion process.

[0092] Example 3

[0093] The difference between this embodiment and embodiment 2 is that:

[0094] Step S215: forming a phosphorus-doped n-type doping layer on both sides of the tunnel oxide layer by using a high temperature diffusion process.

[0095] Example 4

[0096] The difference between this embodiment and embodiment 1 is that:

[0097] Step S115: placing the dry hydrophobic silicon wafer in a ventilation container filled with gaseous ozone for ozone pretreatment, continuously introducing gaseous ozone into the ventilation container, maintaining a constant gaseous ozone concentration of 0.01 ppm, a temperature in the container of 15° C., and a time of 10 seconds to form a first oxide layer;

[0098] Step S116: forming a second oxide layer on the first oxide layer by a high temperature oxidation process, wherein the temperature of the high temperature oxidation process is 500° C.;

[0099] Example 5

[0100] The difference between this embodiment and embodiment 1 is that:

[0101] Step S115: placing the dry hydrophobic silicon wafer in a ventilation container filled with gaseous ozone for ozone pretreatment, continuously introducing gaseous ozone into the ventilation container, maintaining a constant gaseous ozone concentration of 50 ppm, a temperature in the container of 95° C., and a time of 1000 s to form a first oxide layer;

[0102] Step S116: forming a second oxide layer on the first oxide layer using a high temperature oxidation process, wherein the temperature of the high temperature oxidation process is 650° C.;

[0103] Example 6

[0104] The difference between this embodiment and embodiment 1 is that:

[0105] Step S115: placing the dry hydrophobic silicon wafer in a ventilation container filled with gaseous ozone for ozone pretreatment, continuously introducing gaseous ozone into the ventilation container, maintaining a constant gaseous ozone concentration of 10 ppm, a temperature in the container of 110° C., and a time of 1300 seconds to form a first oxide layer;

[0106] Step S116: forming a second oxide layer on the first oxide layer using a high temperature oxidation process, wherein the temperature of the high temperature oxidation process is 550° C.;

[0107] Example 7

[0108] The difference between this embodiment and embodiment 1 is that:

[0109] Step S115: placing the dry hydrophobic silicon wafer in a ventilation container filled with gaseous ozone for ozone pretreatment, continuously introducing gaseous ozone into the ventilation container, maintaining a constant gaseous ozone concentration of 80 ppm, a temperature in the container of 50° C., and a time of 800 seconds to form a first oxide layer;

[0110] Step S116: forming a second oxide layer on the first oxide layer using a high temperature oxidation process, wherein the temperature of the high temperature oxidation process is 550° C.;

[0111] Example 8

[0112] The difference between this embodiment and embodiment 1 is that:

[0113] Step S115: placing the dry hydrophobic silicon wafer in a ventilation container filled with gaseous ozone for ozone pretreatment, continuously introducing gaseous ozone into the ventilation container, maintaining a constant gaseous ozone concentration of 10 ppm, a temperature in the container of 50° C., and a time of 800 seconds to form a first oxide layer;

[0114] Step S116: forming a second oxide layer on the first oxide layer by a high temperature oxidation process, wherein the temperature of the high temperature oxidation process is 700° C.;

[0115] Example 9

[0116] The difference between this embodiment and embodiment 1 is that:

[0117] Step S115: placing the dry hydrophobic silicon wafer in a ventilation container filled with gaseous ozone for ozone pretreatment, continuously introducing gaseous ozone into the ventilation container, maintaining a constant gaseous ozone concentration of 80 ppm, a temperature in the container of 110° C., and a time of 1300 seconds to form a first oxide layer;

[0118] Step S116: forming a second oxide layer on the first oxide layer by a high temperature oxidation process, wherein the temperature of the high temperature oxidation process is 700° C.;

[0119] Comparative Example 1

[0120] The difference between this comparative example and Example 1 is that the above-mentioned step S115 is not performed, that is, step S116 is directly performed after step S114, wherein the temperature of the high-temperature oxidation process in step S116 is 850°C.

[0121] Comparative Example 2

[0122] The difference between this comparative example and Example 2 is that the above-mentioned step S213 is not performed, that is, step S214 is directly performed after step S212, wherein the temperature of the high-temperature oxidation process in step S214 is 850°C.

[0123] Comparative Example 3

[0124] The difference between this comparative example and Example 3 is that the above-mentioned step S213 is not performed, that is, step S214 is directly performed after step S212, wherein the temperature of the high-temperature oxidation process in step S214 is 850°C.

[0125] According to the steps of the above-mentioned embodiments 1, 4-9 and comparative example 1, 500 solar cells were prepared respectively, and according to the steps of the above-mentioned embodiments 2-3 and comparative examples 2-3, 500 substrate structures were prepared respectively. The solar cells obtained in the above-mentioned embodiments 1, 4-9 and comparative example 1 were tested by an IV tester (Halm) to obtain the photoelectric conversion efficiency of each solar cell, and the obtained results were statistically analyzed to obtain the average photoelectric conversion efficiency; the solar cells and substrate structures obtained in embodiments 1-9 and comparative examples 1-3 were tested by a minority carrier lifetime tester (WCT-120), and the test results were fitted with a specific model to obtain the reverse dark saturation current J0 (in faram FA). At the same time, the reverse dark saturation current J0 results obtained by the substrate structures of embodiments 2-3 and comparative examples 2-3 were fitted to obtain the ideal photoelectric conversion efficiency of the substrate structure. The test results are shown in Table 1:

[0126] Table 1

[0127]

[0128]

[0129] The results show that, in the preparation process of solar cells, the average photoelectric conversion efficiency of solar cells obtained by ozone pretreatment is 0.3% higher than that of solar cells obtained by the existing process, and the reverse dark saturation current J0 is reduced by 5FA; in the passivation process experiment, the substrate structure obtained by ozone pretreatment has a fitted photoelectric conversion efficiency improved by 0.5% to 1.1% compared with the substrate structure without ozone pretreatment, and the reverse dark saturation current J0 is significantly reduced, indicating that ozone pretreatment of the substrate can significantly improve the photoelectric conversion of solar cells and substrate structures, and the reverse dark saturation current J0 is significantly reduced, which can suppress the drift motion of minority carriers in solar cells, thereby reducing the leakage current of solar cells.

[0130] It should also be noted that the terms "include", "comprises" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, commodity or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, commodity or device. In the absence of more restrictions, the elements defined by the sentence "comprises a ..." do not exclude the existence of other identical elements in the process, method, commodity or device including the elements.

[0131] The above are only embodiments of the present application and are not intended to limit the present application. For those skilled in the art, the present application may have various changes and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application should be included within the scope of the claims of the present application.

Claims

1. A method for preparing a solar cell contact structure, characterized in that: include: providing a semiconductor substrate; Using gaseous ozone to perform ozone pretreatment on the surface of the semiconductor substrate so as to form a first oxide layer on the surface of the semiconductor substrate; Using the first oxide layer as a seed layer to assist in growing a second oxide layer, the first oxide layer and the second oxide layer forming a tunneling oxide layer; A doping layer is formed on a side of the tunnel oxide layer facing away from the semiconductor substrate.

2. The preparation method according to claim 1, characterized in that: The ozone pretreatment is under an ozone atmosphere, and the ozone atmosphere includes flowing the gaseous ozone over the surface of the semiconductor substrate.

3. The preparation method according to claim 2, characterized in that: The concentration of the gaseous ozone subjected to the ozone pretreatment is 0.01 ppm to 50 ppm.

4. The preparation method according to claim 2, characterized in that: The reaction temperature for the ozone pretreatment is 15° C. to 95° C., and the reaction time is 10s to 1000s.

5. The preparation method according to claim 1, characterized in that: The process of forming the second oxide layer includes a high temperature oxidation process, and the reaction temperature of the high temperature oxidation process is 500° C. to 650° C.

6. The preparation method according to claim 1, characterized in that: The thickness of the tunnel oxide layer is 1 nm to 2 nm.

7. The preparation method according to claim 1, characterized in that: The thickness of the first oxide layer is smaller than the thickness of the second oxide layer.

8. The preparation method according to claim 1, characterized in that: The density of the first oxide layer is higher than that of the second oxide layer.

9. A solar cell contact structure, characterized in that: Prepared by the preparation method according to any one of claims 1 to 8.

10. A solar cell, characterized in that: It comprises a solar cell contact structure prepared by the preparation method according to any one of claims 1 to 8.

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