Solar cell and preparation method thereof

Abstract

The invention provides a solar cell and a preparation method thereof, and belongs to the technical field of semiconductors. The solar cell comprises a semiconductor substrate having a first surface and a second surface opposite to each other; the first passivation contact layer is located on the first surface of the semiconductor substrate; the first protection layer is located on the surface, away from the semiconductor substrate, of the first passivation contact layer, and the first protection layer is provided with an open groove penetrating in the thickness direction and a protection layer reserved part distributed in the open groove; the first electrode is located on the surface, away from the semiconductor substrate, of the first protection layer, and at least part of the first electrode is located in the open groove. According to the solar cell and the preparation method, the passivation effect and the electrode contact performance can be improved at the same time.

Description

Technical Field

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

[0002] With the development of solar cell technology, solar cells are divided into many types based on different cell structures. These different types of solar cells generally need to be metallized after passivation coating to make electrodes on the passivation contact layer. The mainstream metallization routes include screen printing, electroplating, evaporation, etc.

[0003] However, there are many problems that are difficult to overcome in these routes. For example, the accuracy and quality of screen printing are difficult to guarantee, and the cost of using printing or photolithography to achieve patterning when electroplating or evaporating electrodes is relatively high. Using laser film opening to achieve electroplating patterning can easily cause damage to the battery surface, and the electrode has poor bonding to the battery surface. Summary of the invention

[0004] In view of this, in order to at least partially solve at least one of the above-mentioned technical problems, the present application provides a solar cell.

[0005] In order to achieve the above purpose, the technical solution of this application is as follows:

[0006] According to an embodiment of one aspect of the present application, a solar cell is provided, comprising: a semiconductor substrate having a first surface and a second surface relative to each other; a first passivation contact layer located on the first surface of the semiconductor substrate; a first protective layer located on a surface of the first passivation contact layer away from the semiconductor substrate, the first protective layer being provided with a groove penetrating in a thickness direction, and a protective layer reserved portion distributed in the groove; and a first electrode located on a surface of the first protective layer away from the semiconductor substrate, at least a portion of the first electrode being located in the groove.

[0007] According to an embodiment of another aspect of the present application, a method for preparing a solar cell is provided, comprising: sequentially forming a first passivation contact layer and a first protective layer on a first surface of a semiconductor substrate; laser irradiating a grooved area of ​​the first protective layer so that a groove is formed in the first protective layer located in the laser irradiated area and a protective layer reserved portion distributed in the groove; and depositing a first electrode in the groove of the first protective layer.

[0008] According to the embodiments of the present application, the present application adopts the method of laser irradiation of the protective layer, and can locally groove the protective layer with high precision, so that there is a reserved portion of the protective layer at the groove position. On the one hand, it can ensure that the passivation contact layer under the protective layer is not damaged by the laser to achieve a good passivation effect. On the other hand, the reserved portion of the protective layer is used as the electrode growth point to improve the adhesion of the electrode to the battery surface. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] The above and other objects, features and advantages of the present application will become more apparent through the following description of the embodiments of the present application with reference to the accompanying drawings, in which:

[0010] Figure 1 A schematic diagram of a partial structure of a solar cell according to an embodiment of the present application;

[0011] Figure 2 It is a schematic diagram of the state of the reserved portion of the protective layer located at the groove position of the first protective layer on the velvet area according to an embodiment of the present application;

[0012] Figure 3A A scanning electron microscope (SEM) top view of a reserved portion of the protective layer at a grooved position of the first protective layer in an embodiment of the present application;

[0013] Figure 3B This is a SEM cross-sectional view of a reserved portion of the protective layer at a grooved position of the first protective layer according to an embodiment of the present application;

[0014] Figure 3C This is a SEM top view of the reserved portion of the protective layer at the first protective layer groove position of the comparative example of the present application;

[0015] Figure 4 A schematic diagram of a state of a reserved portion of the protective layer located at a groove position of the first protective layer on a polishing area according to another embodiment of the present application;

[0016] Figure 5A A SEM top view of a reserved portion of the protective layer at a grooved position of the first protective layer according to another embodiment of the present application;

[0017] Figure 5B A SEM top view of a first reserved portion at a groove position of the first protective layer according to another embodiment of the present application;

[0018] Fig. 6A This is a schematic diagram of the first electrode structure at the groove position of the first protective layer according to an embodiment of the present application;

[0019] Figure 6B This is a schematic diagram of the first electrode structure at the groove position of the first protective layer according to another embodiment of the present application;

[0020] Figure 7A schematic structural diagram of a solar cell according to another embodiment of the present application;

[0021] Fig. 8A This is a schematic diagram of a local groove structure on a first area of ​​a solar cell according to another embodiment of the present application;

[0022] Figure 8B This is a schematic diagram of a local groove structure on a first area of ​​a solar cell according to another embodiment of the present application;

[0023] Fig. 9 A SEM image of a solar cell on the first region according to another embodiment of the present application;

[0024] Fig.10 This is a schematic diagram of a local groove structure on a first area of ​​a solar cell according to another embodiment of the present application;

[0025] Fig.11 A schematic diagram of a process for preparing a solar cell according to an embodiment of the present application;

[0026] Fig.12 A schematic diagram of the preparation process of a solar cell according to an embodiment of the present application;

[0027] Fig.13 The SEM images of the electrode deposited by electroplating at different electroplating times according to the embodiment of the present application are shown. DETAILED DESCRIPTION

[0028] In order to make the objectives, technical solutions and advantages of the present application more clearly understood, the present application is further described in detail below in combination with specific embodiments and with reference to the accompanying drawings.

[0029] In the detailed description below, for ease of explanation, many specific details are set forth to provide a comprehensive understanding of the embodiments of the present application. However, it is apparent that one or more embodiments may be implemented without these specific details. In addition, in the following description, the description of known structures and technologies is omitted to avoid unnecessary confusion of the concepts of the present application.

[0030] The terms used herein are only for describing specific embodiments and are not intended to limit the present application. The term "comprising" used herein indicates the existence of features, steps, operations, but does not exclude the existence or addition of one or more other features.

[0031] In the case of using expressions such as "at least one of A, B, and C, etc.", it should generally be interpreted in accordance with the meaning of the expression generally understood by those skilled in the art (for example, "a system having at least one of A, B, and C" should include but is not limited to a system having A alone, B alone, C alone, A and B, A and C, B and C, and / or A, B, C, etc.). In the case of using expressions such as "at least one of A, B, or C, etc.", it should generally be interpreted in accordance with the meaning of the expression generally understood by those skilled in the art (for example, "a system having at least one of A, B, or C" should include but is not limited to a system having A alone, B alone, C alone, A and B, A and C, B and C, and / or A, B, C, etc.).

[0032] The relative position between two components (such as film layers or regions) mentioned in this application, such as "above", "upper" or "above", may refer to the direct contact between the two components, or may refer to the indirect contact between the two components. Similarly, the relative position between two components mentioned in this application, such as "below", "lower" or "below", may refer to the direct contact between the two components, or may refer to the indirect contact between the two components. For example, when one of the components (such as film layers or regions) is referred to as "on another component", it can be directly on the other component, or there may be other components between the two. On the other hand, when a component is referred to as "directly on another component", there is no component between the two. In addition, when one of the components is referred to as "on another component", the two have an up-and-down relationship in the top-view direction, and this component can be above or below the other component, so this up-and-down relationship depends on the orientation of the device.

[0033] Compared with screen printing technology, it is easier to deposit electrodes with better morphology and quality on the passivation contact layer by electroplating or evaporation. However, the protective layer needs to be patterned before depositing the electrode. The commonly used patterning method of printing or photolithography has the disadvantage of complex process, and the subsequently deposited electrodes also have the problem of poor adhesion, which is easy to fall off and cause poor electrode contact, affecting the use of the battery.

[0034] In the process of realizing the concept of this application, it was found that when laser grooving is used and then electroplating or evaporating electrodes, the protective layer can be structured by reasonably controlling the laser energy, and the protective layer can be locally grooved more accurately so that there is a reserved portion of the protective layer at the groove position. The reserved portion of the protective layer can protect the passivation contact layer from being damaged by the laser, so that the passivation contact layer maintains a good morphology and passivation effect, and at the same time is beneficial to increase the adhesion of the electrode and improve the electrode contact.

[0035] Specifically, according to an embodiment of one aspect of the present application, a solar cell is provided. Figure 1 is a schematic diagram of a partial structure of a solar cell according to an embodiment of the present application, such as Figure 1 As shown, the solar cell comprises a semiconductor substrate 1, a first passivation contact layer 2, a first protective layer 3 and a first electrode 4, wherein: the semiconductor substrate 1 has a first surface 1a and a second surface 1b opposite to each other; the first passivation contact layer 2 is located on the first surface 1a of the semiconductor substrate 1; the first protective layer 3 is located on the surface of the first passivation contact layer 2 away from the semiconductor substrate 1, and the first protective layer 3 is provided with a groove 31 penetrating in the thickness direction, and a protective layer reserved portion (not shown in the figure) distributed in the groove 31; and the first electrode 4 is located on the surface of the first protective layer 3 away from the semiconductor substrate 1, and at least part of the first electrode 4 is located in the groove 31. It should be noted that, unless otherwise specified, the "thickness direction" generally refers to the direction extending perpendicular to the surface of the semiconductor substrate.

[0036] According to an embodiment of the present application, the material of the semiconductor substrate 1 may be an N-type or P-type crystalline silicon substrate, for example, it may be a semiconductor material selected from monocrystalline silicon, polycrystalline silicon, and microcrystalline silicon, preferably an N-type or P-type monocrystalline silicon substrate, and the conversion efficiency of the battery based on the monocrystalline silicon substrate is higher than that of other types such as polycrystalline silicon batteries. By introducing donor impurities such as VA group elements such as phosphorus (P), arsenic (As) or antimony (Sb) into these semiconductor materials, an N-type crystalline silicon substrate is obtained, or by introducing acceptor impurities such as IIIA group elements such as boron (B), aluminum (Al) or gallium (Ga) into these semiconductor materials, a P-type crystalline silicon substrate is obtained.

[0037] According to the embodiment of the present application, the first surface 1a of the semiconductor substrate 1 can be the front or back of the battery, without limitation. Generally speaking, the front of the battery is used as the light-receiving surface, and the back is used as the backlight surface, or it can also be double-sided, in which case both the front and back are used as light-receiving surfaces. The first surface 1a of the semiconductor substrate 1 can be a polished area having a pyramid base structure, or a velvet area having a pyramid structure, without special limitation.

[0038] According to the embodiments of the present application, the first passivation contact layer 2 of the present application can adopt a variety of passivation contact structures, such as a tunneling oxide passivation structure, a heterojunction structure, etc. Therefore, the solar cell type applicable to the present application can be a bifacial cell, such as a bifacial heterojunction (Heterojunction with Intrinsic Thin-layer, referred to as HJT) cell, a tunneling oxide passivated contact (Tunnel Oxide Passivated Cell, referred to as TOPCon) cell, etc., or a back contact cell, such as a back contact heterojunction (Heterojunction Back Contac, referred to as HBC) cell, a hybrid HBC cell such as a hybrid cell combined with TBC (TopCon-BackContact)-HJT, etc., as long as the battery type needs to improve the electrode contact performance, it should be applicable.

[0039] According to the embodiments of the present application, the first protective layer 3 of the present application can be a single layer or a stacked layer structure, and its material can be selected from at least one of aluminum oxide, silicon oxide, silicon nitride, silicon oxynitride, silicon carbide, etc., which can provide protection for the battery structure under the first protective layer 3 and also have the effect of passivation and anti-reflection.

[0040] According to the embodiments of the present application, the applicant has discovered through experiments that when the electrode is manufactured by electroplating or evaporation after laser grooving, the first protective layer can be partially grooved by reasonably controlling the laser energy, and some protective layers can be left distributed at the grooved position of the first protective layer, that is, the reserved portion of the protective layer. This can ensure that the first passivation contact layer under the first protective layer is not damaged by the laser, so as to ensure a good passivation effect. At the same time, the reserved portion of the protective layer is used as the electrode growth point to improve the adhesion of the electrode to the battery surface, so as to improve the electrode contact stability. After the local grooving of the first protective layer by laser irradiation, an additional wet etching step can be added to clean the grooved position. Of course, under suitable laser energy conditions, the wet etching step can be omitted, and a better grooving morphology can be achieved. For example, under picosecond laser conditions, the laser energy density is adjusted to 2.6 J / cm 2 .

[0041] In order to facilitate the description of the structure of the reserved portion of the protective layer, Figure 2 Schematic diagram of the state of the reserved portion of the protective layer at the groove position of the first protective layer on the velvet area of ​​the embodiment of the present application; Figure 1 and 2As shown, taking the first surface 1a having a velvet area with multiple pyramid structures as an example, a protective layer reserved portion 32 is distributed in the groove 31. This distribution state allows the first electrode 4 located in the groove 31 to maintain good contact with the first passivation contact layer 2, and can ensure the contact between the first electrode 4 and the protective layer reserved portion 32, so as to improve the adhesion of the first electrode.

[0042] According to an embodiment of the present application, optionally, as Figure 2 As shown, the protective layer reserved portion 32 may include a plurality of first reserved portions 321, at least part of the first reserved portions 321 may have a porous structure, and / or the first reserved portion is a sheet structure, which can further increase the contact area between the first electrode 4 and the protective layer reserved portion 32, so as to improve the adhesion of the first electrode. At the same time, part of the first reserved portion 321 can form a spacing space with the first passivation contact layer 2, that is, the edge of the first reserved portion 321 is tilted away from the first passivation contact layer 2 to form the spacing space, and when the first electrode 4 is subsequently formed, its seed layer or first electrode layer can be filled into the spacing space.

[0043] Further optionally, at least one pore 321a included in the porous structure may be a through hole penetrating the first reserved portion 321, so that the first electrode may pass through the through hole and contact the first passivation contact layer 2. In this way, while improving the adhesion of the first electrode, good electrical contact between the first electrode 4 and the first passivation contact layer 2 can be taken into account at the same time.

[0044] According to the embodiment of the present application, similarly, taking the first surface 1a having a velvet area containing multiple pyramid structures as an example, along the direction away from the first surface 1a, the pyramid structure includes a tower bottom 12 and a tower top 11; the distribution density of the first reserved portion 321 located on the tower bottom 12 is greater than the distribution density of the first reserved portion 321 located on the tower top 11. The "distribution density" here can be the number of first reserved portions 321 located on the tower top 11 or the tower bottom 12 per unit cross-sectional area or per unit top-view area, or the area ratio of the first reserved portion 321 located on the tower top 11 or the tower bottom 12 per unit cross-sectional area or per unit top-view area.

[0045] In this way, more first reserved portions 321 are reserved on the tower bottom 12, so that the first passivation contact layer on the tower bottom 12 can maintain a good passivation effect and is not easily damaged, while relatively fewer first reserved portions 321 are reserved on the tower top 11, which is conducive to edge contact and reduces contact resistance, thereby achieving a balance between good contact and passivation effect.

[0046] This application does not impose any restrictions on the measurement of distribution density. Those skilled in the art can measure it by conventional methods in the art. For example, the number of the first reserved parts can be measured by a scanning electron microscope (SEM); because the first reserved part has obvious differences from other structures in the SEM test results of the cross-sectional view or the top view, the first reserved part can be found directly on the SEM test picture. The cross-sectional view can be a SEM test picture obtained by cutting the battery cell in a direction that forms a certain angle with the groove extension direction, such as 90°, or the top view can be a SEM test picture obtained by measuring the surface of the battery cell after local grooves or after the first electrode is peeled off. Take at least one area of ​​the same size above the top of the tower or the bottom of the tower, and then count and average the first reserved parts observed in each area, which is the number of the first reserved parts.

[0047] For another example, the area ratio of the first reserved portion can be obtained by SEM measurement, and the first reserved portion can be found in the SEM test image of the cross-sectional view or the top view. At least one area is taken above the top of the tower or the bottom of the tower, and then the total area of ​​the first reserved portion observed in each area is calculated using image processing software, and the area ratio of the total area of ​​the first reserved portion in the value area is calculated and averaged, which is the area ratio of the first reserved portion.

[0048] According to an embodiment of the present application, optionally, Figure 2 As shown, the protective layer reserved portion 32 may also include a plurality of second reserved portions 322, which are protruding particles protruding from the surface of the first passivation contact layer 2 in a direction away from the first surface 101a. It can be understood that the plurality of second reserved portions 322 are different from the first reserved portions 321 because they do not have obvious pores. Based on the setting of the second reserved portions 322, on the one hand, the first passivation contact layer can be protected from being damaged by the laser, and on the other hand, the adhesion of the first electrode can be improved to maintain good contact of the first electrode.

[0049] Further optionally, the particle size of the protruding particles is 50-300 nm, for example, 50 nm, 100 nm, 130 nm, 150 nm, 180 nm, 200 nm, 220 nm, 250 nm, 280 nm, 300 nm, etc. Protruding particles of appropriate size are beneficial for increasing the adhesion of the first electrode without affecting the passivation effect of the first passivation contact layer 2.

[0050] According to an embodiment of the present application, the second reserved portion 322 is a protruding particle formed by the agglomeration of the surface layer of the first passivation contact layer 2 and the first protective layer 3 during laser irradiation. In other words, the protruding particle includes a mixture of the first protective layer material and the first passivation contact layer material. Since the first passivation contact layer 2 and the first protective layer 3 have good contact, the formation of the second reserved portion 322 is jointly regulated by the first protective layer 3 and the first passivation contact layer 2, so that the second reserved portion 322 is randomly distributed on the surface of the first passivation contact layer 2.

[0051] For example, taking the case where the first passivation contact layer 2 is a tunneling oxide passivation structure and the first protective layer is silicon nitride, the morphology of the reserved portion of the protective layer after the first protective layer is partially grooved on the first passivation contact layer 2 is characterized. Figure 1 As shown, along the direction away from the first surface 101, the first passivation contact layer 2 includes a first tunneling layer 21 and a first semiconductor layer 22. The first tunneling layer 21 is silicon oxide (SiOx) in this example, but is not limited thereto, and may also be aluminum oxide, titanium oxide, etc. The first semiconductor layer 22 is preferably a polycrystalline silicon layer in this example, but is not limited thereto, and may also be a microcrystalline silicon layer, etc. The conductivity type of the first semiconductor layer 22 may be N-type or P-type, specifically, by doping at least one element of the VA group elements to form an N-type first semiconductor layer 22, or by doping at least one element of the IIIA group elements to form a P-type first semiconductor layer 22. The first protective layer 3 located on the first passivation contact layer 2 is laser irradiated and wet-etched, and a SEM top view of the reserved portion of the protective layer located in the groove is collected.

[0052] Figure 3A This is a scanning electron microscope (SEM) top view of the reserved portion of the protective layer at the first protective layer groove position of the embodiment of the present application. Figure 3A As shown, after laser irradiation and wet etching of the first protective layer, the pyramid structure in the groove is intact and the protective layer is partially left. Specifically, a plurality of first reserved portions 321 and a plurality of second reserved portions 322 are respectively distributed on the first semiconductor layer 22 .

[0053] from Figure 3A It can be seen that part of the first reserved portion 321 has a porous structure, and there are through holes penetrating the first reserved portion 321 in the plurality of pores 321a of the porous structure, so that the first electrode can pass through the through holes to contact the first semiconductor layer 22 of the first passivation contact layer 2. It can also be observed that the first reserved portion 321 is a sheet-like structure, and a space is formed between the first semiconductor layer 22. Further, it can be seen from Figure 3A It is observed that the first reserved portions 321 are mainly distributed on the bottom of the tower, that is, the distribution density of the first reserved portions 321 located on the bottom of the tower is greater than the distribution density of the first reserved portions 321 located on the top of the tower.

[0054] Figure 3B This is a SEM cross-sectional view of the reserved portion of the protective layer at the groove position of the first protective layer of the embodiment of the present application, showing the cross-sectional morphology after the first electrode 4 is formed at the groove. Figure 3B As shown, the distribution morphology of the plurality of first reserved portions 321 can be clearly observed, and a separation space is formed between part of the first reserved portions 321 and the first semiconductor layer 22 , and the first electrode 4 is filled in the separation space.

[0055] And then Figure 3A As shown, these second reserved portions 322 are mainly randomly distributed on the first semiconductor layer 22 at the bottom and top of the tower. The light-colored protruding particles can be easily observed through the SEM test image, which are the second reserved portions. The particle size of the second reserved portion 322 is between 50 and 100 nm. Through the detection of the scanning electron microscope (or scanning electron microscope, Scanning ElectronMicroscope) and the energy dispersive spectrometer (Energy Dispersive Spectrometer), these protruding particles have the components of the first protective layer and the polysilicon layer, and are particles formed by the agglomeration of the protective layer and the polysilicon layer after laser irradiation.

[0056] Further, by adjusting the laser conditions, the energy density of the laser is adjusted to be larger (for example, greater than 4 J / cm 2 ), and observe the morphology at the slotting position. Figure 3C This is a SEM top view of the reserved portion of the protective layer at the first protective layer groove position of the comparative embodiment of the present application, as shown in FIG. Figure 3C As shown, when the granular second reserved portion is not observed, or even when a smaller reserved portion of the protective layer is distributed, the pyramid structure is also destroyed, and the first semiconductor layer 22 mainly forms a microstructure with an uneven surface. At this time, the field passivation effect of the first semiconductor layer 22 is damaged, resulting in a decrease in battery efficiency. This comparative embodiment is a suboptimal solution, which damages the passivation of the first passivation contact layer 2. Further, by increasing the energy density of the laser, the reserved portion of the protective layer will tend to disappear, the passivation of the entire groove 31 area will be too damaged, and the efficiency of the entire battery will be greatly reduced.

[0057] For ease of explanation and illustration, in this example, the first reserved portion 321 and the second reserved portion 322 exist and are distributed in the groove 31 at the same time, but it can be understood that if it is for the purpose of improving the adhesion of the first electrode on the surface, either of the two can also exist and be distributed in the groove 31, which can be achieved by adjusting the appropriate laser energy and wet etching conditions.

[0058] According to an embodiment of the present application, in other embodiments, at least part of the first surface 1a may also be a polishing area with a tower base structure, and in this case, a protective layer reserved portion 32 is also distributed in the groove 31. Different from the above-mentioned local groove of the protective layer on the velvet area, the protective layer reserved portion 32 is randomly distributed in the groove 31. Since the polishing area has a lower roughness than the velvet area, the problem of poor electrode adhesion is more significant. By setting the protective layer reserved portion 32, while protecting the first passivation contact layer, it is more conducive to increasing the adhesion of the electrode and improving the electrode contact in the polishing area.

[0059] Figure 4 Schematic diagram of the state of the reserved portion of the protective layer at the first protective layer groove position on the polishing area according to another embodiment of the present application; Figure 4 As shown, a protection layer reserved portion 32 is distributed in the groove 31 located on the polishing area, and the protection layer reserved portion 32 may include a plurality of first reserved portions 321 and / or a plurality of second reserved portions 322 .

[0060] The first reserved portion 321 is a sheet structure, and optionally, at least part of the first reserved portion 321 has a porous structure. In this way, the contact area between the first electrode 4 and the protective layer reserved portion 32 is further provided. Further optionally, at least one pore 321a included in the porous structure can be a through hole that penetrates the first residual portion 321. The first electrode 4 can pass through the through hole and contact the first passivation contact layer 2. The second residual portion 322 is also a protruding particle protruding from the surface of the first passivation contact layer 2 in a direction away from the first surface 101a.

[0061] Further optionally, in the direction away from the first surface 101a, the thickness of the first reserved portion 321 located on the polishing area can be less than the thickness of the first protective layer 3 except the groove 31, and similarly, the height of the second reserved portion 322 located on the polishing area can also be less than the thickness of the first protective layer 3 except the groove 31. The first reserved portion 321 and the second reserved portion 322 of appropriate size are conducive to protecting the first passivation contact layer while maintaining a good passivation effect and reducing the contact resistance.

[0062] By way of example, also taking the case where the first passivation contact layer 2 is a tunneling oxide passivation structure and the first protective layer is silicon nitride, the morphology of the protective layer reserved portion after the first protective layer 3 located on the polishing area is partially grooved is characterized. Specifically, the first passivation contact layer in this example includes a first tunneling layer 21 and a first semiconductor layer 22, and the first semiconductor layer is preferably a polysilicon layer. The first protective layer 3 is laser irradiated, and a SEM top view is collected of the protective layer reserved portion located in the groove.

[0063] Figure 5AA SEM top view of a reserved portion of the protective layer at a grooved position of the first protective layer according to another embodiment of the present application; Figure 5B This is a SEM top view of the first reserved portion at the groove position of the first protective layer according to another embodiment of the present application. Figure 5A and Figure 5B As shown, the protective layer reserved portion 32 is relatively randomly distributed on the first semiconductor layer 22 in the groove 31. It can be observed that the protective layer reserved portion 32 includes a first reserved portion 321 of a sheet structure and a second reserved portion 322 of dot-shaped protruding particles. There are also pores 321a in the first reserved portion 321 of the sheet structure, thereby forming a porous structure.

[0064] According to the embodiments of the present application, Figure 1 As shown, the first electrode 4 on the first protective layer 3 can be prepared by electroplating or evaporation. The first electrode 4 can be a single-layer structure formed by one or more metals such as gold, silver, copper, nickel, tin, chromium, etc., but is not limited thereto.

[0065] In order to further improve the contact performance between the first electrode 4 and the first passivation contact layer 2 in the groove 31, the structure of the first electrode 4 can be optimized so that the first electrode 4 forms a stacked structure. Specifically, Fig. 6A Schematic diagram of the electrode structure at the grooved position of the protective layer in the embodiment of the present application. Fig. 6A As shown, in an optional embodiment, along the direction away from the first surface 101, the first electrode 4 includes a first electrode layer 41 and a second electrode layer 42, and the reserved portion 32 of the protective layer is wrapped in the first electrode layer 41. Through the stacking arrangement, the first electrode layer 41 acts as a seed layer, which is suitable for direct contact with the first passivation contact layer 2 to play a linking role, and can also act as a barrier layer to block the material of the second electrode layer 42 from reaching the first passivation contact layer 2. In addition, the first electrode layer 41 is easy to deposit and prepare, and it is easy to wrap the reserved portion 32 of the protective layer. As a conductive body, the second electrode layer 42 can take into account both cost and conductive performance, and can be made of base metal materials such as copper by printing and other low-cost methods.

[0066] Exemplarily, optionally, the first electrode layer 41 can be made of materials such as nickel and / or silver, which have a low diffusion rate and are not easily doped into the substrate, and can form a chemical bond with silicon, thereby reducing contact resistance. The second electrode layer 42 can be made of materials such as copper, tin and / or chromium, which have good conductivity and low cost.

[0067] According to an embodiment of the present application, the thickness of the first electrode 41 is greater than the thickness of the first protective layer 3 , and while coating the first protective layer 3 to improve mechanical stability, suitable resistance can also be obtained, balancing current collection and stability.

[0068] According to an embodiment of the present application, the thickness of the first electrode layer 41 may be 0.1 μm to 5 μm, for example, 0.1 μm, 0.5 μm, 1.0 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm, 4.5 μm, 5 μm, etc. The thickness of the second electrode layer 42 may be 1 μm to 100 μm, for example, 1 μm, 5 μm, 10 μm, 15 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, 50 μm, 55 μm, 60 μm, 65 μm, 70 μm, 75 μm, 80 μm, 85 μm, 90 μm, 95 μm, 100 μm, etc.

[0069] By setting each layer of the first electrode within the above thickness range, it is possible to facilitate the first electrode layer to wrap and cover the reserved portion of the protective layer, and the first electrode layer is easy to be well bonded to the first passivation contact layer and the reserved portion of the protective layer, thereby ensuring the binding force of the first electrode as a whole on the battery surface. As a conductive body, the optimization of the thickness of the second electrode layer is conducive to the regulation of resistance and mechanical stability, and takes into account the balance between current collection and stability.

[0070] Figure 6B Schematic diagram of the electrode structure at the grooved position of the protective layer in the embodiment of the present application. Figure 6B As shown, in another optional embodiment, along the direction away from the first surface 101, the first electrode 4 may include a third electrode layer 43 in addition to the first electrode layer 41 and the second electrode layer 42. In particular, when the second electrode layer 42 is an electroplated layer deposited by electroplating, it is preferred to have a third electrode layer 43. The third electrode layer can be used as an electrode protection layer to protect the second electrode layer 42. Exemplarily, the third electrode layer 43 can be made of materials such as nickel and / or silver, which have good oxidation resistance.

[0071] According to an embodiment of the present application, further optionally, the thickness of the third electrode layer 43 may be 0.005 μm to 5 μm, for example, 0.005 μm, 0.01 μm, 0.05 μm, 0.1 μm, 0.5 μm, 1 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm, 4.5 μm, 5 μm, etc. Optimizing the thickness of the third electrode layer 43 is beneficial to balancing the cost and the protection of the second electrode layer.

[0072] According to an embodiment of the present application, further optionally, as Figure 1 , Fig. 6A or Figure 6B As shown, on a section perpendicular to the extension direction of the first electrode 4, the width of the first electrode 4 is greater than the width of the groove 31. Such a configuration is conducive to reducing resistance and achieving good contact between the first electrode and the first passivation contact layer 2.

[0073] According to the embodiment of the present application, similarly, taking the first passivation contact layer 2 as a tunneling oxide passivation structure as an example, the first passivation contact layer 2 can be as follows: Figure 1 As shown, the entire surface is covered on the first surface 1a, so that the first protective layer 3 located on the first passivation contact layer 2 is partially grooved. In this case, a good passivation effect can be achieved. In other embodiments, the first passivation contact layer 2 can be disposed in a partial area of ​​the first surface 1a, so that while ensuring the passivation effect, the optical parasitic absorption of the first semiconductor layer 22 can be reduced, taking into account the balance between the passivation effect and the carrier transport effect.

[0074] Specifically, Figure 7 This is a schematic diagram of the structure of a solar cell according to another embodiment of the present application. Figure 7 As shown, the first passivation contact layer 2 is located on the first region A of the first surface 1a; and, along the direction away from the first surface 1a, the first passivation contact layer 2 includes a first tunneling layer 21 and a first semiconductor layer 22, the first semiconductor layer 22 is preferably a polysilicon layer, and the extension direction of the groove 31 located on the first passivation contact layer 2 is the same as the extension direction of the first region A. Thus, the first passivation contact layer 2 forms a Poly-Finger structure.

[0075] According to an embodiment of the present application, in an optional implementation, in order to better balance the passivation effect and the carrier transport effect, and to adapt to the electrode structure of the collector electrode arranged to improve the shading effect, the first passivation contact layer 2 and the groove 31 can be patterned to form a parallel and spaced strip pattern.

[0076] Specifically, Fig. 8A FIG. 1 is a schematic diagram of a local groove structure on a first region of a solar cell according to another embodiment of the present application. Fig. 8A As shown, the first area A includes a plurality of first strip areas A1 extending along the second direction S2 and arranged at intervals along the first direction S1, wherein the first direction S1 and the second direction S2 intersect;

[0077] The width W1 of the first passivation contact layer 2 located on the first strip-shaped area A1 in the first direction S1 is 5-100 μm (for example, it can be 5 μm, 20 μm, 50 μm, 80 μm, 100 μm, etc.), and the width W2 of the groove 31 located on the first strip-shaped area A1 in the first direction S1 is 5-80 μm (for example, it can be 5 μm, 20 μm, 30 μm, 50 μm, 60 μm, 80 μm, etc.).

[0078] Furthermore, the first electrode 4 located on the first strip area A1 may be a collector electrode 4a. In this case, since no bus electrode intersecting with the collector electrode 4a is provided, the battery cells are interconnected through other bus structures such as welding strips, thereby saving the amount of electrode material.

[0079] In another optional embodiment, the first electrode 4 may include a bus electrode in addition to a collector electrode, so that in order to adapt to the setting of the bus electrode, the first passivation contact layer 2 and the groove 31 may be patterned to form a "cross" pattern.

[0080] Specifically, Figure 8B FIG. 1 is a schematic diagram of a local groove structure on a first region of a solar cell according to another embodiment of the present application. Figure 8B As shown, the first area A also includes a second strip area A2 extending along the first direction S1, and the width W3 of the first passivation contact layer 2 located on the second strip area A2 in the second direction S2 is 5~300μm (for example, it can be 5μm, 20μm, 50μm, 80μm, 100μm, 120μm, 150μm, 180μm, 200μm, 230μm, 250μm, 280μm, 300μm, etc.), and the width W4 of the groove 31 located on the second strip area A2 in the second direction S2 is 5~250μm (for example, it can be 5μm, 20μm, 50μm, 80μm, 100μm, 120μm, 150μm, 180μm, 200μm, 230μm, 250μm, etc.).

[0081] Further, the first electrode located on the first strip region A1 may be a collector electrode 4a, and the first electrode 4 located on the second strip region A2 may be a bus electrode 4b. The widths of the bus electrode 4b and the collector electrode 4a may be the same or different.

[0082] For example, Fig. 9 This is a SEM image of a solar cell in the first region according to another embodiment of the present application, as shown in FIG. Fig. 9 As shown, the middle "cross-shaped" area represents the Poly-Finger structure formed by the first passivation contact layer 2, and the light-colored "cross-shaped" structure located in the middle "cross-shaped" area is the first electrode, which is the collector electrode 4a in the horizontal direction and the bus electrode 4b in the vertical direction. The slot 31 located on the first area is not represented in the SEM image.

[0083] It should be noted that although Fig. 8A , 8B and Fig. 9The slot 31 shown is continuous. In some other embodiments, the slot 31 may be discontinuous. For example, a plurality of opening areas may be arranged at intervals along the extension direction of the first strip area A1 to form a discontinuous slot 31 .

[0084] To facilitate understanding of the specific structure of the discontinuous slot 31, illustratively, Fig.10 FIG. 1 is a schematic diagram of a local groove structure on a first region of a solar cell according to another embodiment of the present application. Fig.10 As shown, the groove 31 includes a plurality of openings arranged at intervals along the extension direction S2 of the first strip area A1, and the shape of these openings is schematically circular, but is not limited thereto, and may also be polygonal or other shapes. And further optionally, the discontinuous groove 31 may be located on the velvet area or the polished area of ​​the semiconductor substrate 1, without special limitation.

[0085] By providing a discontinuous groove 31, on the one hand, the protective layer reserved portion 32 in the groove 31 can be used to improve the adhesion of the first electrode 4. On the other hand, the portion of the first protective layer 3 other than the groove 31 is not irradiated by laser, so as not to destroy the passivation effect of the first contact passivation layer, which is beneficial to balance the current collection and passivation effect.

[0086] According to the embodiments of the present application, the above is an example of a solar cell having a tunneling oxidation passivation structure, but is not limited thereto. Figure 1 As shown, the tunneling oxide passivation structure of the first passivation contact layer 2 may also be replaced by other passivation contact structures, so as to cover the entire surface of the first surface 1 a or be located in a partial area of ​​the first surface 1 a .

[0087] Exemplarily, the first passivation contact layer 2 may adopt a heterojunction structure, in which case, along the direction away from the first surface, the first tunneling layer 21 and the first semiconductor layer 22 may be replaced as a whole by a second semiconductor layer. Further optionally, the second semiconductor layer may include an intrinsic semiconductor layer and a doped semiconductor layer, the intrinsic semiconductor layer may be, for example, an intrinsic amorphous silicon layer, and the doped semiconductor layer may be, for example, a doped amorphous silicon layer or a doped microcrystalline silicon layer.

[0088] According to the embodiments of the present application, Figure 7 As shown, the solar cell further includes a second passivation contact layer 5, a second protective layer 7, and a second electrode 8, wherein the second passivation contact layer 5 is located on the second surface 1b of the semiconductor substrate 1, and the second passivation contact layer 5 has a conductivity type different from that of the first passivation contact layer 2. The second protective layer 7 is located on the surface of the second passivation contact layer 5 away from the semiconductor substrate 1. The second electrode 8 is located on the surface of the second protective layer 7 away from the semiconductor substrate 1, and the second electrode 8 contacts the second passivation contact layer 5 through the second protective layer 7.

[0089] According to the embodiment of the present application, the second surface 1b of the semiconductor substrate may also have a polished area with a pyramid base structure, or may have a velvet area with a pyramid structure, without any particular limitation.

[0090] Further optionally, the second passivation contact layer 5 may also adopt a variety of passivation contact structures, such as a tunneling oxide passivation structure, a heterojunction structure, etc. Exemplarily, taking the tunneling oxide passivation structure as an example, along the direction away from the second surface 1b, the second passivation contact layer 5 may include a second tunneling layer 51 and a third semiconductor layer 52. The second tunneling layer 51 is similar to the first tunneling layer 21, and the third semiconductor layer 52 is similar to the first semiconductor layer 22, which will not be described one by one here.

[0091] Further optionally, the second passivation contact layer 5 may cover the entire surface of the second surface 1b, or be located in a partial area of ​​the second surface 1b, for example, a Poly-Finger structure may be formed. It is foreseeable that the second protective layer 7 located on the second passivation contact layer 5 may be partially grooved similar to the first protective layer 3, so as to obtain a protective layer reserved portion with a similar structure as that located on the first surface 101 on the second protective layer 7, which will not be described in detail here.

[0092] In addition, it can be understood that the solar cell provided in the embodiment of the present application is not limited to Figure 7 The bifacial cell shown can also be a back-contact cell. Unlike the above-mentioned solar cell, the first passivation contact layer 2 and the second passivation contact layer 5 are located on the same surface of the solar cell, that is, the first surface 1a. In this case, the first surface 1a includes a first region A and a second region B alternately arranged. The first passivation contact layer 2 can be located in the first region A of the first surface 1a, and the second passivation contact layer 5 can be located in the second region B of the first surface 1a. In this case, the first protective layer 3 located on the first region A and the second protective layer 7 located on the second region B can be partially grooved, respectively, so as to obtain protective layer reserved portions with similar structures on the first protective layer 3 and the second protective layer 7, which will not be described one by one here.

[0093] According to another embodiment of the present application, a method for preparing a solar cell is provided. Fig.11 is a schematic diagram of a process for preparing a solar cell according to an embodiment of the present application, Fig.12 Schematic diagram of the preparation process of the solar cell according to the embodiment of the present application, such as Fig.11 and Fig.12 As shown, the preparation method of the embodiment of the present application includes operations S1 to S3:

[0094] In operation S1, a first passivation contact layer 2 and a first protection layer 3 are sequentially formed on a first surface 1a of a semiconductor substrate 1;

[0095] In operation S2, laser irradiation is performed on the grooved region of the first protective layer 3, so that the first protective layer 3 located in the laser irradiated region forms a groove 31 and a protective layer reserved portion 32 distributed in the groove 31;

[0096] In operation S3 , the first electrode 4 is deposited in the groove 31 of the first protection layer 3 .

[0097] According to the embodiments of the present application, the present application adopts laser irradiation to locally groove the first protective layer, and distributes the protective layer reserved portion 32 in the formed groove 31. On the one hand, there is no need to adopt complex processes such as printing or photolithography when patterning the first protective layer, which has the advantage of simple patterning; on the other hand, compared with traditional laser film opening conditions, it is not easy to cause damage to the battery surface, thereby maintaining a good passivation effect; on the other hand, the protective layer reserved portion 32 can be distributed in the groove 31, which is beneficial to improve the bonding force of the electrode on the battery surface.

[0098] According to an embodiment of the present application, in operation S1, the first passivation contact layer 2 can be prepared by a common deposition method. Taking the first passivation contact layer 2 as a tunneling oxide passivation structure as an example, the first passivation contact layer 2 can be prepared by plasma chemical vapor deposition (PECVD). Specifically, a first tunneling layer 21 and a doped polysilicon layer as a first semiconductor layer 22 can be sequentially formed on the first surface 1a of the semiconductor substrate 1, such as Fig.12 The deposition conditions of the tunnel layer and the doped polysilicon layer can be selected according to actual needs, which is not the key to this application and will not be described in detail.

[0099] Further optionally, the thickness of the tunneling layer can be 2~10nm, for example, 2nm, 3nm, 5nm, 8nm, 10nm, etc., and the thickness of the doped polysilicon layer can be 80~250nm, 80nm, 100nm, 120nm, 150nm, 180nm, 200nm, 220nm, 250nm, etc.

[0100] According to an embodiment of the present application, the first protective layer 3 may be prepared by a common deposition method, such as a PECVD method or a physical vapor deposition (PVD) method.

[0101] According to the embodiment of the present application, in operation S2, there is no specific restriction on the conditions of laser irradiation, and it can be flexibly adjusted according to actual needs. Specifically, the laser energy density can be adjusted within a relatively wide range of wavelength conditions. For example, for the same film layer, lasers with different wavelengths, different energy densities and different overlap rates can be used. Through gradient tests, a variety of matching laser parameters can be obtained, and it is only necessary to form a reserved portion for the protective layer. For example, the laser energy density can be 2.5~3.1 J / cm 2 , for example, 2.5 J / cm 2 , 2.6 J / cm 2 , 2.7 J / cm 2 , 2.8 J / cm 2 , 2.9 J / cm 2 、3.0J / cm 2 , 3.1 J / cm 2 wait.

[0102] According to an embodiment of the present application, further optionally, in operation S2, after laser irradiation of the first protective layer 3, wet etching may be additionally performed to clean the slotted position. There is no special restriction on the wet etching method of the first protective layer 3, for example, acid etching may be used. Acid etching may, for example, be performed by soaking in an HF solution of a suitable concentration (for example, a concentration of 0.5%, 1%, 2%) for a certain period of time (for example, 10s, 20s, 30s, 1min, etc.). Based on the difference in looseness of the first protective layer 3 in the laser irradiation area compared to the first protective layer 3 in other areas, it is easy to realize local slotting in combination with wet etching, and distribute the reserved portion of the protective layer in the slot, such as Fig.12 As shown in Figure (b). Of course, it is not limited to this, and pure water cleaning can also be used instead of wet etching to clean the groove position.

[0103] According to an embodiment of the present application, in order to take into account both good electrical contact and cost of the electrode, in an optional implementation, operation S3 may specifically include: depositing a first electrode layer 41 of the first electrode 4 on the first passivation contact layer 2 in the groove 31 until the first electrode layer 41 covers the reserved portion 32 of the protective layer; sequentially depositing a second electrode layer 42 and a third electrode layer 43 of the first electrode 4 on the first electrode layer 41 to obtain the first electrode 4, such as Fig.12 As shown in Figure (c).

[0104] In another optional embodiment, in order to further reduce the electrode manufacturing cost, operation S3 specifically includes: depositing a first electrode layer 41 on the first passivation contact layer 2 in the groove 31, until the first electrode layer 41 covers the reserved portion of the protective layer; printing a second electrode layer 42 on the first electrode layer 41 to obtain a first electrode 4.

[0105] At this time, the printing method of the second electrode layer 42 in the first electrode 4 includes but is not limited to screen printing, inkjet printing, etc. The printed electrode slurry may contain antioxidant components, or additional antioxidants may be applied to passivate the surface of the second electrode layer 42. Therefore, there is no need to set the third electrode layer 43, thereby simplifying the electrode manufacturing process and reducing the electrode manufacturing cost.

[0106] Further optionally, the deposition method of the first electrode 4 includes but is not limited to electroplating, evaporation, etc. Taking the electroplating method for depositing the first electrode layer of nickel as an example, Fig.13 The SEM images of the electrode deposited by electroplating at different electroplating times in the embodiment of the present application are as follows: Fig.13 As shown, 5s-10s after the start of electroplating, the electroplated nickel particles are generated at the position not covered by the first protective layer 3 (including the pores of the protective layer reserved portion 32), and then plated to the top and sides of the protective layer reserved portion 32 in the subsequent 10-30s, until finally 60s after which the protective layer reserved portion 32 is completely covered and the pores inside the protective layer reserved portion 32 are filled, thereby finally forming the first electrode layer of nickel.

[0107] The specific embodiments described above further illustrate the purpose, technical solutions and beneficial effects of the present application. It should be understood that the above description is only a specific embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present application should be included in the scope of protection of the present application.

Claims

1. A solar cell comprising: A semiconductor substrate having a first surface and a second surface opposite to each other; A first passivation contact layer, located on the first surface of the semiconductor substrate; A first protective layer, located on a surface of the first passivation contact layer away from the semiconductor substrate, the first protective layer being provided with a groove penetrating in a thickness direction and a protective layer reserved portion distributed in the groove; as well as The first electrode is located on a surface of the first protection layer away from the semiconductor substrate, and at least a portion of the first electrode is located in the groove.

2. The solar cell according to claim 1, wherein: The protective layer reserved portion includes a plurality of first reserved portions, at least part of the first reserved portions has a porous structure, and / or the first reserved portions are a sheet-like structure.

3. The solar cell according to claim 2, wherein: At least one pore included in the porous structure is a through hole penetrating the first reserved portion; The first electrode passes through the through hole and contacts the first passivation contact layer.

4. The solar cell according to claim 2 or 3, wherein: The first surface has a velvet area containing a plurality of pyramid structures, and along a direction away from the first surface, the pyramid structures include a tower bottom and a tower top; The distribution density of the first reserved portions located on the bottom of the tower is greater than the distribution density of the first reserved portions located on the top of the tower.

5. The solar cell according to claim 1, wherein: The protection layer reserved portion includes a plurality of second reserved portions, and the second reserved portions are protruding particles protruding from the surface of the first passivation contact layer in a direction away from the first surface.

6. The solar cell according to claim 5, wherein: The particle size of the protruding particles is 50-300 nm, and / or the protruding particles include a mixture of the first protection layer material and the first passivation contact layer material.

7. The solar cell according to claim 5 or 6, wherein: The second reserved portions are randomly distributed on the surface of the first passivation contact layer.

8. The solar cell according to claim 1, wherein: Along a direction away from the first surface, the first electrode includes a first electrode layer and a second electrode layer in sequence, and the reserved portion of the protection layer is wrapped in the first electrode layer.

9. The solar cell according to claim 8, wherein: The thickness of the first electrode is greater than the thickness of the first protective layer.

10. The solar cell according to claim 8 or 9, wherein: The thickness of the first electrode layer is 0.1 μm to 5 μm, and the thickness of the second electrode layer is 1 μm to 100 μm.

11. The solar cell according to claim 1 or 8, wherein: On a section perpendicular to the extending direction of the first electrode, the width of the first electrode is greater than the width of the groove.

12. The solar cell according to claim 1, wherein: The first passivation contact layer is located on a first region of the first surface; Furthermore, along a direction away from the first surface, the first passivation contact layer includes a first tunneling layer and a polysilicon layer; Wherein, an extension direction of the groove located on the first passivation contact layer is the same as an extension direction of the first region.

13. The solar cell according to claim 12, wherein: The first area includes a plurality of first strip areas extending along a second direction and arranged at intervals along the first direction, and the first direction intersects with the second direction; The width of the first passivation contact layer located on the first strip-shaped region in the first direction is 5-100 μm, and the width of the groove located on the first strip-shaped region in the first direction is 5-80 μm.

14. A method for preparing a solar cell, comprising: forming a first passivation contact layer and a first protective layer in sequence on a first surface of the semiconductor substrate; Performing laser irradiation on the grooved area of ​​the first protective layer, so that the first protective layer located in the laser irradiated area forms a groove and a protective layer reserved portion distributed in the groove; A first electrode is formed in the groove of the first protection layer.

15. The preparation method according to claim 14, wherein: The depositing of the first electrode in the groove of the first protective layer comprises: Depositing a first electrode layer on the first passivation contact layer in the groove until the first electrode layer covers the reserved portion of the protection layer; The second electrode layer is printed on the first electrode layer to obtain the first electrode.

16. The preparation method according to claim 14, wherein: The depositing of the first electrode in the groove of the first protective layer comprises: Depositing a first electrode layer on the first passivation contact layer in the groove until the first electrode layer covers the reserved portion of the protection layer; A second electrode layer and a third electrode layer are sequentially deposited on the first electrode layer to obtain the first electrode.

Images