Solar cell and method for manufacturing the same

Abstract

The present application relates to a solar cell and a method for preparing the same. The method utilizes atomic layer deposition (ALD) technology to form a first transparent conductive oxide layer on the surface of a substrate, and then forms a second transparent conductive oxide layer on the side of the first transparent conductive oxide layer away from the substrate. The ALD process eliminates the need for plasma bombardment of a target material, resulting in near-innocuous formation of the first transparent conductive oxide layer. The formed first transparent conductive oxide layer, in addition to its original basic functions, also possesses a protective function, isolating the second transparent conductive oxide layer from any potential impact on the substrate during the preparation process. The risk of damage caused by ion bombardment can be significantly reduced, which is beneficial for improving cell efficiency. Furthermore, the method allows for flexible selection of preparation methods for the second transparent conductive oxide layer, improving preparation selectivity. ALD possesses excellent step coverage, making it easier for each first transparent conductive oxide layer to match the more complex surface structure of the front end, further improving cell efficiency.

Description

Technical Field

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

[0002] With the rapid development of photovoltaic technology, the conversion efficiency of crystalline silicon solar cells has increased year by year. In particular, heterojunction (HJT) solar cells have achieved a peak conversion efficiency of 26.81%, attracting significant attention. The transparent conductive oxide (TCO) layer is crucial for improving the photoelectric conversion efficiency of solar cells.

[0003] However, in the related art, the TCO layer of the solar cell is usually prone to damage the cell substrate during the preparation process, which is detrimental to the cell efficiency. Summary of the Invention

[0004] The embodiments of the present application provide a solar cell and a method for manufacturing the same, which can reduce the risk of damage to the cell substrate caused by the TCO layer during the manufacturing process.

[0005] In a first aspect, the present application provides a method for preparing a solar cell, comprising:

[0006] providing a substrate;

[0007] forming a first transparent conductive oxide layer on the surface of the substrate using atomic layer deposition technology, wherein the surface includes a light-receiving surface and a backlight surface opposite to each other;

[0008] A second transparent conductive oxide layer is formed on a side of the first transparent conductive oxide layer away from the substrate.

[0009] In one embodiment, forming a first transparent conductive oxide layer on the surface of the substrate using atomic layer deposition technology includes:

[0010] introducing a metal source precursor and an oxidizing gas into the first reaction chamber in a pulsed alternating manner to form the first transparent conductive oxide layer on the surface of the substrate;

[0011] Wherein, in one cycle, the metal source precursor includes one of a main source precursor and a doping source precursor.

[0012] In one embodiment, the backlight surface is a P surface, and the light-receiving surface is an N surface; the doping concentration ratio of the doping source precursor of the first transparent conductive oxide layer formed on the backlight surface is less than the doping concentration of the doping source precursor of the first transparent conductive oxide layer formed on the light-receiving surface.

[0013] In one embodiment, in the multiple periods of the first transparent conductive oxide layer formed on the backlight surface, the period interval of the doping source precursor is gradually reduced; in the multiple periods of the first transparent conductive oxide layer formed on the light-receiving surface, the period interval of the doping source precursor is gradually reduced.

[0014] In one embodiment, on the backlight side, the doping ratio of the first transparent conductive oxide layer is less than the doping ratio of the second transparent conductive oxide layer; on the light-receiving side, the doping ratio of the first transparent conductive oxide layer is greater than the doping ratio of the second transparent conductive oxide layer.

[0015] In one embodiment, the main source precursor includes an indium source precursor, and the dopant source precursor includes a transition metal source precursor.

[0016] In one embodiment, a wall of the first reaction chamber opposite to the surface of the substrate is provided with a first group of inlet holes, a second group of inlet holes, and a third group of inlet holes alternately arranged along a first direction;

[0017] Among them, the first inlet hole group includes a plurality of first inlet holes arranged at intervals along the second direction for introducing the main source precursor, the second inlet hole group includes a plurality of second inlet holes arranged at intervals along the second direction for introducing the oxidizing gas, and the third inlet hole group includes a plurality of third inlet holes arranged at intervals along the second direction for introducing the doping source precursor, and the second direction intersects with the first direction.

[0018] In one embodiment, the thickness of the first transparent conductive oxide layer is smaller than the thickness of the second transparent conductive oxide layer.

[0019] In one embodiment, the thickness of the first transparent conductive oxide layer is 5 nm-15 nm; the thickness of the second transparent conductive oxide layer is 85 nm-95 nm.

[0020] In one embodiment, the second transparent conductive oxide layer is formed by using physical vapor deposition technology.

[0021] In one embodiment, the first transparent conductive oxide layer is formed in a first reaction chamber, and the second transparent conductive oxide layer is formed in a second reaction chamber; the first reaction chamber and the second reaction chamber are isolated from each other.

[0022] In one embodiment, the method for preparing a solar cell further includes:

[0023] forming a first doped layer on the backlight surface of the substrate, wherein the first doped layer has a first conductivity type, and the first transparent conductive oxide layer on the backlight surface is located on a side of the first doped layer away from the substrate;

[0024] A second doped layer is formed on the light-receiving surface of the substrate. The second doped layer has a second conductivity type that is opposite to the first conductivity type. The first transparent conductive oxide layer of the light-receiving surface is located on a side of the first doped layer away from the substrate.

[0025] In one embodiment, the method for preparing a solar cell further includes:

[0026] An electrode material is deposited on a side of each of the second transparent conductive oxide layers away from the substrate to form a backlight surface electrode and a light-receiving surface electrode respectively.

[0027] A second aspect of the present application provides a solar cell, comprising:

[0028] substrate;

[0029] a first transparent conductive oxide layer, located on a surface of the substrate, the surface including a backlight surface and a light-receiving surface, the first transparent conductive oxide layer being formed based on atomic layer deposition technology;

[0030] The second transparent conductive oxide layer is located on a side of each of the first transparent conductive oxide layers away from the substrate.

[0031] The solar cell and its preparation method use atomic layer deposition technology to form a first transparent conductive oxide layer on the surface of a substrate, and then form a second transparent conductive oxide layer on the side of the first transparent conductive oxide layer away from the substrate. On the one hand, the atomic layer deposition process does not require plasma bombardment of the target material, and the substrate is almost damage-free during the formation of the first transparent conductive oxide layer. The formed first transparent conductive oxide layer not only has its original basic function, but also has a protective function, which can isolate the second transparent conductive oxide layer from the possible impact on the substrate during the preparation process. The risk of damage caused by ion bombardment can be greatly reduced, which is beneficial to improving battery efficiency. At the same time, the second transparent conductive oxide layer can be flexibly prepared in a variety of ways, improving the selectivity of the preparation. The atomic layer deposition process does not require the use of a target material, which is beneficial to reducing costs and large-scale mass production. On the other hand, during the atomic layer deposition process, only one atomic layer is deposited in each reaction. The chemical reaction of the new atomic layer is directly related to the previous layer, which has the characteristics of self-limiting growth. It can effectively control the growth of each first transparent conductive oxide layer and is beneficial to carrier collection. At the same time, atomic layer deposition has excellent step coverage, which can make each first transparent conductive oxide layer have good shape retention, making it easier to match the more complex surface structure of the front end, further improving battery efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0033] Figure 1 This is a flow chart of a method for preparing a solar cell according to an embodiment;

[0034] Figure 2 This is a schematic structural diagram of a solar cell according to an embodiment;

[0035] Figure 3 Schematic diagram of the access hole group of the first reaction chamber wall according to one embodiment;

[0036] Figure 4 This is a second flow chart of a method for preparing a solar cell according to an embodiment;

[0037] Figure 5 This is a second structural diagram of a solar cell according to an embodiment;

[0038] Figure 6 This is a third structural diagram of a solar cell according to an embodiment;

[0039] Figure 7 FIG1 is a schematic diagram of the structure of a solar cell and the corresponding doping ratio according to an embodiment;

[0040] Figure 8 A second schematic diagram of the structure and corresponding doping ratio of a solar cell according to an embodiment;

[0041] Figure 9 The third schematic diagram of the structure of a solar cell and the corresponding doping ratio according to an embodiment;

[0042] Figure 10 Schematic diagram of the preparation process and equipment structure in one embodiment. DETAILED DESCRIPTION

[0043] In order to make the purpose, technical solutions and advantages of this application more clearly understood, the present application is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain this application and are not intended to limit this application.

[0044] It is understood that the terms "first", "second", etc. used in this application can be used to describe various elements in this article, but these elements are not limited by these terms. These terms are only used to distinguish the first element from another element, and cannot be understood as indicating or suggesting relative importance or implicitly indicating the number of technical features indicated. Thus, the features defined as "first" and "second" can explicitly or implicitly include at least one of the features. In the description of this application, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly defined. It should be noted that when an element is referred to as "formed on" another element, it can be directly on the other element or there can be a central element.

[0045] Figure 1 This is a flow chart of a method for preparing a solar cell according to an embodiment of the present invention. Figure 1 In this embodiment, the method for preparing a solar cell includes: steps 102 to 106.

[0046] Step 102: providing a substrate.

[0047] Please refer to Figure 2 ( Figure 2 110 is a substrate), the substrate is used to receive incident light and generate photogenerated carriers. The surface of the substrate includes a backlight surface and a light-receiving surface opposite to each other. The light-receiving surface can be understood as the surface facing the sunlight, also called the front side; the backlight surface can be understood as the surface facing away from the sunlight, also called the back side. In this embodiment, the backlight surface and the light-receiving surface of the substrate can have certain morphological changes based on the morphology of features such as the battery film layer. For example, the light-receiving surface can be a velvet structure; part of the backlight surface can be a planar structure, and another part of the backlight surface can also be a velvet structure. Optionally, the backlight surface can be a P-surface, and the light-receiving surface can be an N-surface. In other embodiments, the backlight surface can also be an N-surface, and the light-receiving surface can also be a P-surface. The P-surface can be understood as one end that collects holes, and the N-surface can be understood as one end that collects electrons.

[0048] The substrate includes, but is not limited to, a doped semiconductor substrate made of silicon or germanium, or a doped compound semiconductor substrate made of silicon carbide, silicon germanium, gallium arsenide, indium phosphide, zinc oxide, or gallium oxide. For example, in an embodiment of the present application, the substrate material can be a doped single-crystal silicon material. Furthermore, the doping element type of the substrate can be N-type, where the N-type element can be, for example, any one of phosphorus, arsenic, or antimony; the doping element type of the substrate can also be P-type, where the P-type element can be, for example, boron and gallium. Furthermore, the substrate can be an N-type single-crystal silicon wafer, and the thickness of the substrate can be in the range of 60-180 μm.

[0049] Step 104 : forming a first transparent conductive oxide layer on the surface of the substrate using atomic layer deposition technology, the surface including the backlight surface and the light-receiving surface.

[0050] Please refer to Figure 2 ( Figure 2 120 is a first transparent conductive oxide layer). In this embodiment, two first transparent conductive oxide layers are formed correspondingly on the backlight side and the light-receiving side of the substrate. The two first transparent conductive oxide layers can be understood as the TCO contact layer corresponding to the backlight side and the TCO contact layer corresponding to the light-receiving side, respectively.

[0051] In the process of forming the first transparent conductive oxide layer using atomic layer deposition (ALD) technology, on the one hand, the ALD process does not require plasma bombardment of the target material, and the process of forming the first transparent conductive oxide layer is nearly damageless to the substrate. The first transparent conductive oxide layer acts as a protective layer, which can isolate the impact of other TCO stack layers on the substrate during the preparation process. The risk of damage caused by ion bombardment can be greatly reduced, which is beneficial to improving battery efficiency. At the same time, the ALD process does not require the use of a target material, which is beneficial to reducing costs. On the other hand, during the ALD process, only one atomic layer is deposited in each reaction. The chemical reaction of the new atomic layer is directly related to the previous layer. The self-limiting growth characteristic can effectively control the growth of each first transparent conductive oxide layer and facilitate carrier collection. At the same time, ALD has excellent step coverage, which can make each first transparent conductive oxide layer have good shape conformality, making it easier to match more complex surface structures such as small suede on the front end.

[0052] It should be noted that there is no limitation on the order of step 1 of forming the first transparent conductive oxide layer on the backlight surface of the substrate and step 2 of forming the first transparent conductive oxide layer on the light-receiving surface of the substrate. Step 1 may be performed before step 2, or step 2 may be performed before step 1, or step 2 and step 1 may be performed simultaneously.

[0053] Step 106 : forming a second transparent conductive oxide layer on a side of the first transparent conductive oxide layer away from the substrate.

[0054] Please refer to Figure 2 ( Figure 2In the figure, 130 is a second transparent conductive oxide layer), the second transparent conductive oxide layer is formed on the side of the first transparent conductive oxide layer away from the substrate. Taking the backlight side as the P side and the light-receiving side as the N side as an example, the second transparent conductive oxide layer can form an adjacent stacked structure with the first transparent conductive oxide layer, so that the second transparent conductive oxide layer on the light-receiving side is combined with the first transparent conductive oxide layer on the light-receiving side to ensure optical transmittance and longitudinal transmission, and collect electrons; and the second transparent conductive oxide layer on the backlight side is combined with the first transparent conductive oxide layer on the backlight side to ensure the collection of holes. It can be understood that in other embodiments, without affecting the overall battery function and battery efficiency, other auxiliary layers can be provided between the second transparent conductive oxide layer and the first transparent conductive oxide layer according to actual needs, and this embodiment does not limit this. Optionally, the second transparent conductive oxide layer can be a layer ( Figure 2 Taking one layer as an example), it can also be a stack of multiple layers, which is not limited in this embodiment.

[0055] The second transparent conductive oxide layer is formed after the first transparent conductive oxide layer. The preparation process for the second transparent conductive oxide layer is not limited and can utilize the same atomic layer deposition technology or techniques other than atomic layer deposition, such as physical vapor deposition (PVD) or reactive plasma deposition (RPD). Because the second transparent conductive oxide layer is formed on the side of the first transparent conductive oxide layer, which serves as a protective layer and is away from the substrate, the risk of damage to the substrate during the formation of the second transparent conductive oxide layer is greatly reduced, regardless of the deposition method used, thereby improving battery efficiency.

[0056] Generally, TCO layers are deposited using two methods in this field: PVD and RPD. PVD uses accelerated high-energy particles to bombard a target, causing atoms on the target's surface to escape from the crystal lattice and deposit on the substrate, where they react and form a thin film. RPD uses a plasma gun to generate an argon plasma. After entering a growth chamber, the argon plasma bombards the target under the influence of a magnetic field, causing the target to sublime and form vapor, achieving thin film deposition. However, the high ion voltage during PVD deposition can easily damage the battery substrate. While RPD deposition causes less damage to the substrate than PVD deposition, the resulting TCO has poor uniformity and is more expensive, resulting in low target utilization and equipment utilization, making it unsuitable for large-scale mass production.

[0057] In this embodiment, during the preparation of the TCO, the TCO is prepared in layers, using atomic layer deposition technology to form a first transparent conductive oxide layer on the surface of the substrate, and then a second transparent conductive oxide layer is formed on the side of the first transparent conductive oxide layer away from the substrate. On the one hand, the atomic layer deposition process does not require plasma bombardment of the target material, and the substrate is almost damage-free during the formation of the first transparent conductive oxide layer. The formed first transparent conductive oxide layer not only has its original basic function, but also has a protective function, which can isolate the second transparent conductive oxide layer from the possible impact on the substrate during the preparation process. The risk of damage caused by ion bombardment can be greatly reduced, which is beneficial to improving battery efficiency. At the same time, the second transparent conductive oxide layer can be flexibly prepared in a variety of ways, improving the selectivity of the preparation. The atomic layer deposition process does not require the use of a target material, which is beneficial to reducing costs and large-scale mass production. On the other hand, during the atomic layer deposition process, only one atomic layer is deposited in each reaction. The chemical reaction of the new atomic layer is directly related to the previous layer, which has the characteristics of self-limiting growth. It can effectively control the growth of each first transparent conductive oxide layer and is beneficial to carrier collection. At the same time, atomic layer deposition has excellent step coverage, which can make each first transparent conductive oxide layer have good shape retention, making it easier to match the more complex surface structure of the front end, further improving battery efficiency.

[0058] In one embodiment, a first transparent conductive oxide layer is formed on a surface of a substrate using atomic layer deposition technology, including: alternately introducing a metal source precursor and an oxidizing gas into a first reaction chamber in pulses to form the first transparent conductive oxide layer on the surface of the substrate.

[0059] Among them, one pulse alternating process corresponds to one cycle, which can also be simply understood as one circle. One pulse alternating process includes a first pulse process and a second pulse process. The first pulse process: a metal source precursor is introduced into the first reaction chamber to allow the metal source precursor to fully adsorb and react on the substrate to grow an atomic layer. After the adsorption reaction is completed, an inert gas can be introduced to purge the excess metal source precursor and remove residual gas. The second pulse process: an oxidizing gas is introduced into the first reaction chamber to allow the oxidizing gas to adsorb and react with the metal source precursor to grow an atomic layer. After the reaction is completed, an inert gas or an oxidizing gas can be introduced to purge the generated waste gas. After completing one pulse alternating process, the aforementioned pulse alternating process is repeated, and finally the first transparent conductive oxide layer is efficiently, stably and uniformly formed on the substrate.

[0060] In one cycle, the metal source precursor includes one of a main source precursor and a dopant source precursor. That is, the main source precursor and the dopant source precursor are introduced alternately in different cycles to form the TCO contact layer. For example, the main source precursor is introduced in the first cycle and cycles 3-10, and the dopant source precursor is introduced in the second cycle.

[0061] The step of alternately introducing a metal source precursor and an oxidizing gas into the first reaction chamber in pulses to form a first transparent conductive oxide layer on the surface of the substrate comprises: alternately introducing a metal source precursor and an oxidizing gas into the first reaction chamber in pulses to form the first transparent conductive oxide layer on the backlight surface of the substrate; and alternately introducing a metal source precursor and an oxidizing gas into the first reaction chamber in pulses to form the first transparent conductive oxide layer on the light-receiving surface of the substrate. Optionally, the first reaction chambers in the two steps can be the same chamber or different chambers. In the case of the same chamber, the two steps can be performed simultaneously or in different time periods. For example, the first transparent conductive layer on the backlight surface of the substrate can be deposited first, and then the semi-finished product can be flipped over to deposit the first transparent conductive layer on the light-receiving surface of the substrate.

[0062] In related technologies, PVD deposition methods generally use a target material with a fixed doping ratio for deposition, and the process window can only adjust the gas ratio and power, so ultimately only the doping ratio of the TCO can be fixed.

[0063] In this embodiment, the alternating introduction of different main source precursors and dopant source precursors at different intervals results in different doping ratios in the first transparent conductive oxide layer, effectively adjusting the doping ratio of the TCO contact layer and, in turn, achieving bandgap adjustability. The number of cycles of the dopant source precursors can control different doping levels, enabling the doping level to be regulated by selecting the appropriate number of cycles. Furthermore, the total number of cycles of alternating the introduction of different metal source precursors and oxidizing gases can result in different thicknesses in the first transparent conductive oxide layer, effectively adjusting the thickness of the TCO contact layer. Thus, this embodiment effectively controls the first transparent conductive oxide layer by adjusting the interval and number of cycles.

[0064] In one embodiment, the backlight side is the P-side, and the light-receiving side is the N-side. The doping concentration ratio of the doping source precursor of the first transparent conductive oxide layer formed on the backlight side is lower than the doping concentration of the doping source precursor of the first transparent conductive oxide layer formed on the light-receiving side. As a result, the first transparent conductive oxide layer formed on the N-side has a low doping concentration and a low work function, which can further ensure its longitudinal transmission performance and optical transmittance, and better collect electrons. The first transparent conductive oxide layer formed on the P-side has a low doping concentration and a high work function, which can better collect holes.

[0065] It can be understood that in other embodiments, if the light-receiving surface is the P surface and the backlight surface is the N surface, the doping concentration ratio of the doping source precursor of the first transparent conductive oxide layer formed on the backlight surface is adjusted accordingly to be greater than the doping concentration of the doping source precursor of the first transparent conductive oxide layer formed on the light-receiving surface.

[0066] In one embodiment, in multiple cycles of the first transparent conductive oxide layer formed on the backlight surface, the period interval of the introduction of the doping source precursor gradually decreases, the atomic layer formed in the early cycle is close to the backlight surface of the substrate, and the atomic layer formed in the later cycle is away from the backlight surface of the substrate. As a result, the doping amount of the first transparent conductive oxide layer gradually increases from the part close to the substrate to the part away from the substrate, which is beneficial to the collection of holes, and at the same time is beneficial to balancing the conductivity and optical properties of TCO, thereby improving the battery conversion efficiency.

[0067] In one embodiment, in multiple periods of the first transparent conductive oxide layer formed on the light-receiving surface, the period interval of introducing the doping source precursor gradually increases, the atomic layer formed in the early period is close to the light-receiving surface of the substrate, and the atomic layer formed in the later period is far away from the light-receiving surface of the substrate. As a result, the doping amount of the first transparent conductive oxide layer gradually decreases from the part close to the substrate to the part far away from the substrate, which is beneficial to the collection of electrons, and at the same time is beneficial to balancing the conductivity and optical properties of TCO, thereby improving the battery conversion efficiency.

[0068] Optionally, the above-mentioned gradual decrease, gradual increase, etc. can further correspond to a gradient decrease, a gradient increase, so that the corresponding doping amount corresponds to a gradient increase, a gradient decrease.

[0069] It can be understood that in other embodiments, the periodic interval of the doping source precursors in the two first transparent conductive oxide layers on the backlight surface and the light-receiving surface during the formation process can also be fixed, so that the doping sources in the first transparent conductive oxide layer are evenly distributed from the part close to the substrate to the part far away from the substrate.

[0070] In one embodiment, on the backlight side, the doping ratio of the first transparent conductive oxide layer formed is less than the doping ratio of the second transparent conductive oxide layer formed, so that the work function of the first transparent conductive oxide layer on the backlight side is higher than the work function of the second transparent conductive oxide layer, which is conducive to the migration of holes from high work function to low work function, thereby effectively collecting carriers.

[0071] In one embodiment, on the light-receiving surface, the doping ratio of the first transparent conductive oxide layer formed is greater than the doping ratio of the second transparent conductive oxide layer formed. As a result, the work function of the first transparent conductive oxide layer on the light-receiving surface is smaller than the work function of the second transparent conductive oxide layer, which is conducive to the migration of electrons from low work function to high work function, thereby effectively collecting carriers.

[0072] In one embodiment, the main source precursor may include an indium (In) source precursor, and the doping source precursor may include a transition metal source precursor, thereby forming a doped indium oxide thin film (ITO).

[0073] The In source precursor may be, for example, TMln; the transition metal source precursor may be, for example, a Sn source precursor, a Ti source precursor, a Zr source precursor, or a Ta source precursor; and the Sn source precursor may be, for example, TDMASn. The oxidizing gas may be, for example, O2. The alternating pulses of an In source precursor and an oxidizing gas may form In2O3. The alternating pulses of a transition metal source precursor and an oxidizing gas may form a dopant MOx, such as TiO2, ZrO2, Ta2O5, or SnO2.

[0074] The first transparent conductive oxide layer in any of the above embodiments can be prepared by alternately introducing an indium source precursor / a dopant source precursor and an oxidizing gas pulse into the channel.

[0075] In one embodiment, a first through hole group, a second through hole group, and a third through hole group arranged alternately along a first direction are provided on a cavity wall of the first reaction chamber opposite to the surface of the substrate; wherein the first through hole group includes a plurality of first through holes arranged at intervals along a second direction for introducing a main source precursor, the second through hole group includes a plurality of second through holes arranged at intervals along the second direction for introducing an oxidizing gas, and the third through hole group includes a plurality of third through holes arranged at intervals along the second direction for introducing a doping source precursor, and the second direction intersects with the first direction.

[0076] Take the second direction being perpendicular to the first direction, the oxidizing gas being O2, and the doping source precursor being the Sn source precursor as an example, Figure 3 As shown, the cavity wall can be provided with a group of Sn source access holes (310 in the figure), an O2 access hole group (320 in the figure), and an In source access hole group (330 in the figure), arranged alternately in the row direction. Each access hole group includes multiple access holes spaced apart in the column direction. Corresponding materials are alternately introduced through these access holes in corresponding pulses, thereby forming a first transparent conductive oxide layer. By controlling the amount, time, and cycle of each access hole, the first transparent conductive oxide layer can be effectively controlled.

[0077] Optionally, taking the example of the TCO of the backlight surface and the light-receiving surface being deposited in the same first reaction chamber, the gas can be first introduced alternately in pulses facing the backlight surface through the inlet holes of the chamber wall to form the first transparent conductive oxide layer on the backlight surface by a lower coating method; and then the substrate is flipped so that the gas can be introduced alternately in pulses facing the light-receiving surface through the inlet holes of the chamber wall to form the first transparent conductive oxide layer on the light-receiving surface by an upper coating method.

[0078] In one embodiment, the thickness of the first transparent conductive oxide layer is less than the thickness of the second transparent conductive oxide layer. It is understood that when the first transparent conductive oxide layer covers the substrate to a certain thickness, it can achieve a protective function to reduce damage to the substrate during deposition of other layers. By setting the thickness of the first transparent conductive oxide layer to be less than the thickness of the second transparent conductive oxide layer, the deposition time of the first transparent conductive oxide layer can be reduced, thereby balancing the time required for atomic layer deposition. Optionally, the thickness of the first transparent conductive oxide layer is 5 nm-15 nm; the thickness of the second transparent conductive oxide layer is 85 nm-95 nm. Within this range, the first and second transparent conductive oxide layers can reduce the risk of damage while better balancing the overall TCO preparation time.

[0079] In one embodiment, the second transparent conductive oxide layer is formed using physical vapor deposition (PVD). Due to the protective effect of the first transparent conductive oxide layer, the PVD deposition process can significantly reduce damage to the substrate. Furthermore, due to its faster deposition speed, the overall TCO production time can be reduced. Furthermore, PVD deposition is relatively less expensive than RPD deposition, which helps reduce both the overall TCO production time and cost.

[0080] It is understood that in other embodiments, the second transparent conductive oxide layer may be formed by atomic layer deposition technology or RPD deposition technology. The formation process may refer to the above embodiment and will not be described in detail.

[0081] In one embodiment, a first transparent conductive oxide layer is formed in a first reaction chamber, and a second transparent conductive oxide layer is formed in a second reaction chamber; the first reaction chamber and the second reaction chamber are isolated from each other. By isolating different chambers, it is beneficial to avoid reducing the mutual interference problem during the deposition process of the first reaction chamber and the second reaction chamber, thereby improving the controllability and reliability of the preparation.

[0082] In one embodiment, Figure 4 As shown, the method for preparing a solar cell further includes steps 402-404.

[0083] Step 402: forming a first doped layer on the backlight side of the substrate, wherein the first transparent conductive oxide layer on the backlight side is located on a side of the first doped layer away from the substrate. The first doped layer has a first conductivity type.

[0084] Step 404: forming a second doped layer on the light-receiving surface of the substrate, wherein the first transparent conductive oxide layer of the light-receiving surface is located on a side of the first doped layer away from the substrate. The second doped layer has a second conductivity type opposite to the first conductivity type.

[0085] Please refer to Figure 5 ( Figure 5 ( 140 is a first doped layer) The first doped layer is located between the backlight side of the substrate and the first transparent conductive oxide layer, and can serve as a contact layer between the backlight side of the substrate and the first transparent conductive layer. The first transparent conductive oxide layer is formed after the first doped layer. Because the first transparent conductive oxide layer is deposited by atomic layer deposition, it can serve as a protective layer for the first doped layer during the deposition of the second transparent conductive oxide layer, thereby greatly reducing the risk of damage to the first doped layer. Optionally, the material of the first doped layer may include at least one of doped amorphous silicon and doped microcrystalline silicon. The thickness of the first doped layer may be in the range of 5nm-30nm.

[0086] Please refer to Figure 5 ( Figure 5 ( 150 is a second doped layer) The second doped layer is located between the light-receiving surface of the substrate and the first transparent conductive oxide layer, and can serve as a contact layer between the light-receiving surface of the substrate and the first transparent conductive layer. The first transparent conductive oxide layer is formed after the second doped layer. Because the first transparent conductive oxide layer is deposited by atomic layer deposition, the first transparent conductive oxide layer can serve as a protective layer for the second doped layer during the deposition of the second transparent conductive oxide layer, thereby greatly reducing the risk of damage to the second doped layer. Optionally, the material of the second doped layer may include at least one of doped amorphous silicon and doped microcrystalline silicon, and the thickness of the second doped layer may be in the range of 5nm-30nm.

[0087] In one of the examples, please continue to refer to Figure 4 ,like Figure 4 As shown, the method for preparing a solar cell further includes: step 406.

[0088] In step 406 , electrode materials are deposited on the side of each second transparent conductive oxide layer away from the substrate to form a backlight electrode and a light-receiving electrode, respectively.

[0089] Please refer to Figure 6 ( Figure 5 ( 160 is a backlight electrode). The backlight electrode can be a metal electrode formed by screen printing, laser transfer, or electroplating. Furthermore, it can be formed by screen printing or laser transfer of low-temperature silver paste / low-temperature copper paste / silver-coated copper paste. It can also be a patterned electrode formed by electroplating one or more alloys of Al / Ti / Ni / Co / Ag / Cu / Sn. In this embodiment, the backlight electrode can be understood as a metal grid line, and the width and thickness of the metal grid line are not limited.

[0090] Please refer to Figure 6 ( Figure 6170 is the light-receiving surface electrode), the light-receiving surface electrode can be a metal electrode formed by screen printing, laser transfer or electroplating, and further, it can be realized by screen printing, laser transfer of low-temperature silver paste / low-temperature copper paste / silver-coated copper paste, or it can be a patterned electrode formed by electroplating one or more alloys of Al / Ti / Ni / Co / Ag / Cu / Sn, etc.

[0091] The following is an example in which the light-receiving surface of the substrate is the N surface and the backlight surface is the P surface, and detailed description is given in combination with specific embodiments.

[0092] Example 1 (as Figure 7 shown)

[0093] 1) ITO was deposited on the P side using ALD with a doping ratio of ln2O3:MOx = 99:1. Specifically, the number of turns (i.e., the number of cycles) of TMln and TDMASn introduced was 99:1. The doping Sn source was introduced at the 46th turn (i.e., the 46th cycle) during deposition (refer to this definition later and will not be repeated here). The deposition thickness was 10 nm.

[0094] 2) Continue to use PVD to deposit 90nm of ITO on the P side, with a doping ratio of ln2O3:SnO2=90:10.

[0095] 3) The silicon wafer is flipped over, and an ITO film is deposited on the N-side using ALD. The doping ratio is ln2O3:SnO2=90%:10%. Specifically, the number of turns of TMln and TDMASn introduced is 99:10, and the deposition thickness is 10nm.

[0096] 4) On the N side, a 90nm ITO film layer is deposited using PVD, with a doping ratio of ln2O3:MOx=99:1.

[0097] Example 2 (as Figure 8 shown)

[0098] 1) ITO was deposited on the P side using ALD with a doping ratio of ln2O3:SnO2=97:3. Specifically, the number of cycles of TMln and TDMASn was 97:3. The doping Sn source was introduced at the 2nd, 35th, and 68th cycles during deposition, and the deposition thickness was 10nm.

[0099] 2) On the P side, a 90nm ITO film layer is deposited using PVD, with a doping ratio of ln2O3:SnO2=90:10.

[0100] 3) The silicon wafer was flipped over, and an ITO film was deposited on the N-side using ALD. The doping ratio was ln2O3:SnO2 = 97:3. Specifically, the number of cycles of TMln and TDMASn was 97:3. The doping Sn source was introduced at the 2nd, 35th, and 68th cycles during deposition, and the deposition thickness was 10 nm.

[0101] 4) On the N side, a 90nm ITO film layer is deposited using PVD with a doping ratio of ln2O3:MOx = 99:1.

[0102] Example 3 (as Figure 9 shown)

[0103] 1) ITO was deposited on the P-side using ALD. The doping ratio was gradually increased. The number of cycles of TMln and TDMASn was 97:3. The doping Sn source was introduced at the 2nd, 68th, and 84th cycles during deposition. The deposition thickness was 10 nm.

[0104] 2) On the P side, a 90nm ITO film layer is deposited using PVD, with a doping ratio of ln2O3:SnO2=90:10.

[0105] 3) The silicon wafer was flipped over, and an ITO film was deposited on the N-side using ALD. The doping ratio was controlled to gradually decrease, and the number of cycles of TMln and TDMASn was 97:3. The doping Sn source was introduced at the 2nd, 18th, and 51st cycles during deposition, and the deposition thickness was 10 nm.

[0106] 4) On the N side, a 90nm ITO film layer is deposited using PVD with a doping ratio of ln2O3:MOx = 99:1.

[0107] Based on the implementation of the above embodiment, the loss of the substrate can be reduced while improving the battery conversion efficiency by 0.05-0.1.

[0108] Optionally, the specific process and device structure of the above embodiment can be as follows: Figure 10 As shown, the ALD deposition chamber can be isolated from the PVD deposition chamber by an isolation chamber, thereby avoiding interference between the two different deposition methods and improving the controllability and reliability of the preparation.

[0109] It is understandable that, in addition to the relevant steps of the solar cell manufacturing method involved in the above embodiment, other existing manufacturing steps may be included according to actual needs to obtain corresponding process effects, which will not be further limited here.

[0110] It should be understood that, although the steps in the flowcharts of the above embodiments are shown in sequence as indicated by the arrows, these steps are not necessarily performed in the order indicated by the arrows. Unless otherwise specified herein, there is no strict order restriction on the execution of these steps, and these steps can be performed in other orders. Moreover, at least a portion of the steps in the flowcharts of the above embodiments may include multiple steps or multiple stages, and these steps or stages are not necessarily performed at the same time, but can be performed at different times. The execution order of these steps or stages is not necessarily to be performed in sequence, but can be performed in turn or alternately with other steps or at least a portion of steps or stages in other steps.

[0111] An embodiment of the present application further provides a solar cell, which can be prepared by the preparation method in the above embodiment. The structure, function, working principle, etc. of the solar cell have been described in detail in the above embodiment and will not be repeated here.

[0112] In one embodiment, a solar cell includes a substrate, a first transparent conductive oxide layer, and a second transparent conductive oxide layer.

[0113] The first transparent conductive oxide layer is located on the surface of the substrate, including a backlight surface and a light-receiving surface, and is formed based on atomic layer deposition technology; the second transparent conductive oxide layer is located on the side of each first transparent conductive oxide layer away from the substrate.

[0114] For the description of the substrate, the first transparent conductive oxide layer and the second transparent conductive oxide layer, please refer to the above embodiments and will not be repeated here.

[0115] In the solar cell of this embodiment, the first transparent conductive oxide layer is formed using atomic layer deposition technology. On the one hand, the atomic layer deposition process does not require plasma bombardment of the target material, and the substrate is almost damage-free during the formation of the first transparent conductive oxide layer. In addition to its original basic function, the first transparent conductive oxide layer also has a protective function, which can isolate the second transparent conductive oxide layer from possible effects on the substrate during the preparation process. The risk of damage caused by ion bombardment can be greatly reduced, which is beneficial to improving cell efficiency. At the same time, the second transparent conductive oxide layer can be flexibly prepared in a variety of ways, improving preparation selectivity. The atomic layer deposition process does not require the use of a target material, which is beneficial to reducing costs and scalable mass production. On the other hand, during the atomic layer deposition process, only one atomic layer is deposited in each reaction. The chemical reaction of the new atomic layer is directly related to the previous layer, which has the characteristics of self-limiting growth. It can effectively control the growth of each first transparent conductive oxide layer, which is beneficial to carrier collection. At the same time, atomic layer deposition has excellent step coverage, which can make each first transparent conductive oxide layer have good shape retention, making it easier to adapt to more complex surface structures on the front end, further improving cell efficiency.

[0116] In one embodiment, the solar cell further includes a first doping layer and a second doping layer.

[0117] The first doped layer is located on the backlight side of the substrate and has a first conductivity type. The first transparent conductive oxide layer on the backlight side is located on the side of the first doped layer away from the substrate. The second doped layer is located on the light-receiving side of the substrate and has a second conductivity type that is opposite to the first conductivity type. The first transparent conductive oxide layer on the light-receiving side is located on the side of the first doped layer away from the substrate. The description of the first doped layer and the second doped layer is referred to the above embodiment and is not repeated here.

[0118] In one embodiment, the solar cell further comprises: a backlight electrode and a light-receiving electrode, each located on a side of each second transparent conductive oxide layer away from the substrate. The description of the backlight electrode and the light-receiving electrode is similar to the above embodiment and is not repeated here.

[0119] The technical features of the above embodiments can be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0120] The above embodiments merely illustrate several implementation methods of the present application. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that a person skilled in the art could make various modifications and improvements without departing from the spirit of the present invention, all of which fall within the scope of protection of the present invention. Therefore, the scope of protection of the present invention shall be determined by the appended claims.

Claims

1. A method for preparing a solar cell, characterized in that: include: providing a substrate; forming a first transparent conductive oxide layer on the surface of the substrate using atomic layer deposition technology, wherein the surface includes a light-receiving surface and a backlight surface opposite to each other; forming a second transparent conductive oxide layer on a side of the first transparent conductive oxide layer away from the substrate; Among them, on the backlight side, in the multiple periods of the first transparent conductive oxide layer formed, the periodic interval of the doping source precursor is gradually reduced, and the doping amount of the first transparent conductive oxide layer from the part close to the substrate to the part far away from the substrate is gradually increased; in the multiple periods of the first transparent conductive oxide layer formed on the light-receiving side, the periodic interval of the doping source precursor is gradually increased, and the doping amount of the first transparent conductive oxide layer from the part close to the substrate to the part far away from the substrate is gradually reduced.

2. The method for preparing a solar cell according to claim 1, wherein: Forming a first transparent conductive oxide layer on the surface of the substrate using atomic layer deposition technology, comprising: introducing a metal source precursor and an oxidizing gas into the first reaction chamber in a pulsed alternating manner to form the first transparent conductive oxide layer on the surface of the substrate; Wherein, in one cycle, the metal source precursor includes one of a main source precursor and a doping source precursor.

3. The method for preparing a solar cell according to claim 2, wherein: The backlight surface is a P surface, and the light-receiving surface is an N surface; the doping concentration ratio of the doping source precursor of the first transparent conductive oxide layer formed on the backlight surface is lower than the doping concentration of the doping source precursor of the first transparent conductive oxide layer formed on the light-receiving surface.

4. The method for preparing a solar cell according to claim 3, wherein: On the backlight side, the doping ratio of the first transparent conductive oxide layer is smaller than the doping ratio of the second transparent conductive oxide layer; on the light-receiving side, the doping ratio of the first transparent conductive oxide layer is larger than the doping ratio of the second transparent conductive oxide layer.

5. The method for preparing a solar cell according to claim 2, wherein: The main source precursor includes an indium source precursor, and the doping source precursor includes a transition metal source precursor.

6. The method for preparing a solar cell according to claim 2, wherein: A first through hole group, a second through hole group, and a third through hole group are formed on a wall of the first reaction chamber opposite to the surface of the substrate, and are alternately arranged along a first direction; Among them, the first inlet hole group includes a plurality of first inlet holes arranged at intervals along the second direction for introducing the main source precursor, the second inlet hole group includes a plurality of second inlet holes arranged at intervals along the second direction for introducing the oxidizing gas, and the third inlet hole group includes a plurality of third inlet holes arranged at intervals along the second direction for introducing the doping source precursor, and the second direction intersects with the first direction.

7. The method for preparing a solar cell according to claim 1, wherein: The thickness of the first transparent conductive oxide layer is smaller than the thickness of the second transparent conductive oxide layer.

8. The method for preparing a solar cell according to claim 7, wherein: The thickness of the first transparent conductive oxide layer is 5 nm-15 nm; the thickness of the second transparent conductive oxide layer is 85 nm-95 nm.

9. The method for preparing a solar cell according to claim 1, wherein: The second transparent conductive oxide layer is formed by using a physical vapor deposition technique.

10. The method for preparing a solar cell according to claim 9, wherein: The first transparent conductive oxide layer is formed in the first reaction cavity, and the second transparent conductive oxide layer is formed in the second reaction cavity; the first reaction cavity and the second reaction cavity are isolated from each other.

11. The method for preparing a solar cell according to any one of claims 1 to 10, characterized in that: The method for preparing the solar cell further includes: forming a first doped layer on the backlight surface of the substrate, wherein the first doped layer has a first conductivity type, and the first transparent conductive oxide layer on the backlight surface is located on a side of the first doped layer away from the substrate; A second doped layer is formed on the light-receiving surface of the substrate. The second doped layer has a second conductivity type that is opposite to the first conductivity type. The first transparent conductive oxide layer of the light-receiving surface is located on a side of the first doped layer away from the substrate.

12. The method for preparing a solar cell according to any one of claims 1 to 10, characterized in that: The method for preparing the solar cell further includes: An electrode material is deposited on a side of each of the second transparent conductive oxide layers away from the substrate to form a backlight surface electrode and a light-receiving surface electrode respectively.

13. A solar cell, characterized in that: include: substrate; a first transparent conductive oxide layer, located on a surface of the substrate, the surface including a backlight surface and a light-receiving surface, the first transparent conductive oxide layer being formed based on atomic layer deposition technology; a second transparent conductive oxide layer, located on a side of each of the first transparent conductive oxide layers away from the substrate; Among them, on the backlight side, in the multiple periods of the first transparent conductive oxide layer formed, the periodic interval of the doping source precursor is gradually reduced, and the doping amount of the first transparent conductive oxide layer from the part close to the substrate to the part far away from the substrate is gradually increased; in the multiple periods of the first transparent conductive oxide layer formed on the light-receiving side, the periodic interval of the doping source precursor is gradually increased, and the doping amount of the first transparent conductive oxide layer from the part close to the substrate to the part far away from the substrate is gradually reduced.

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