阅读说明：本技术 钝化接触结构、其制备方法以及其应用的太阳能电池 (Passivated contact structure, preparation method thereof and solar cell using passivated contact structure ) 是由 皮亚同·P·阿特玛特 陈艺琦 高纪凡 陈奕峰 于 2021-08-05 设计创作，主要内容包括：本发明提供了一种用于太阳能电池的钝化接触结构、其制备方法以及其应用的太阳能电池。钝化接触结构包括隧穿层；透明导电膜,位于所述隧穿层上且与所述隧穿层接触；覆盖层,位于所述透明导电膜上；以及金属电极,穿过所述覆盖层而接触所述透明导电膜,所述电极金属电极的端面位于所述透明导电膜中。本发明的用于太阳能电池的钝化接触结构、其制备方法以及其应用的太阳能电池既能够导电又能够起到钝化作用,还具有减少吸光损失的效果。(The invention provides a passivation contact structure for a solar cell, a preparation method thereof and a solar cell using the same. The passivation contact structure includes a tunneling layer; the transparent conducting film is positioned on the tunneling layer and is in contact with the tunneling layer; a cover layer on the transparent conductive film; and a metal electrode that contacts the transparent conductive film through the cover layer, an end surface of the electrode metal electrode being located in the transparent conductive film. The passivation contact structure for the solar cell, the preparation method thereof and the solar cell applied by the passivation contact structure can conduct electricity, play a passivation role and have the effect of reducing light absorption loss.)

1. A passivated contact structure for a solar cell, comprising:

a tunneling layer;

the transparent conducting film is positioned on the tunneling layer and is in contact with the tunneling layer;

a cover layer on the transparent conductive film; and

and a metal electrode that contacts the transparent conductive film through the cover layer, an end surface of the metal electrode being located in the transparent conductive film.

2. The passivated contact structure of claim 1, wherein the transparent conductive film is a first doping type transparent conductive film.

3. The passivated contact structure of claim 1, further comprising:

a substrate;

a first semiconductor layer of a first doping type located on the substrate, wherein the tunneling layer is located on the first semiconductor layer.

4. The passivated contact structure of claim 2 or 3, wherein the first doping type is N-type.

5. The passivated contact structure of claim 1, wherein the tunneling layer is between 0.5 nm and 3nm thick.

6. The passivated contact structure of claim 1, wherein the transparent conductive film has a thickness between 10-300 nm.

7. The passivation contact structure of claim 1, wherein the transparent conductive film is made of one of zinc oxide, tin oxide, and titanium oxide.

8. A solar cell comprising a passivated contact structure according to any one of claims 1-7.

9. A method of making a passivated contact structure for a solar cell, comprising the steps of:

forming a tunneling layer;

forming a transparent conductive film on the tunneling layer;

forming a cover layer on the transparent conductive film; and

forming a metal electrode contacting the transparent conductive film through the cover layer, an end face of the metal electrode staying in the transparent conductive film.

10. The method of claim 9, further comprising:

a semiconductor layer of a first doping type is formed on a substrate, wherein the tunneling layer is formed on the semiconductor layer.

Technical Field

The present invention relates generally to solar cells, and more particularly to a passivation contact structure, a method for fabricating the same, and a solar cell using the same.

Background

In conventional silicon-based solar cells, metal grid lines are in direct contact with the silicon for the purpose of collecting carriers. But direct metal to silicon contact causes a large amount of additional carrier recombination and thus loss. In order to reduce the recombination loss in the metal contact on the silicon-based solar cell, the concept of "passivation contact" is proposed, and the principle is that one type of carriers are blocked by a tunneling layer at the front end of the metal contact, so that no relevant recombination occurs at the metal contact interface. Meanwhile, the tunneling layer is passivated, which means that the tunneling layer does not cause a large amount of carriers to be recombined, thereby realizing the effect of only a small amount of recombination loss when the metal is contacted.

However, the conventional passivation contact structure generally has amorphous silicon, and most of the polycrystalline layer adopting silicon material has serious light absorption, so that the parasitic light absorption loss is generated on the basis of reducing the recombination loss caused by direct contact of the metal grid line and the silicon in the conventional passivation contact structure. Therefore, in a whole, the conventional passivation contact structure placed on the front surface does not have a good effect on improving the energy conversion performance of the solar cell.

Disclosure of Invention

The technical problem to be solved by the invention is to provide a passivation contact structure, a preparation method thereof and a solar cell using the passivation contact structure, wherein the passivation contact structure can conduct electricity and play a passivation role, and has the effect of reducing light absorption loss.

To solve the above technical problem, the present invention provides a passivation contact structure for a solar cell, comprising: a tunneling layer; the transparent conducting film is positioned on the tunneling layer and is in contact with the tunneling layer; a cover layer on the transparent conductive film; and a metal electrode that contacts the transparent conductive film through the cover layer, an end surface of the metal electrode being located in the transparent conductive film.

In an embodiment of the invention, the transparent conductive film is a transparent conductive film of a first doping type.

In an embodiment of the present invention, the passivation contact structure further includes a substrate; a first semiconductor layer of a first doping type located on the substrate, wherein the tunneling layer is located on the first semiconductor layer.

In an embodiment of the invention, the first doping type is N-type.

In an embodiment of the invention, a thickness of the tunneling layer is between 0.5 nm and 3 nm.

In an embodiment of the invention, the thickness of the transparent conductive film is between 10 nm and 300 nm.

In an embodiment of the invention, the material of the transparent conductive film is zinc oxide.

In another aspect, the invention also provides a solar cell comprising the passivation contact structure.

In another aspect of the present invention, a method for preparing a passivation contact structure for a solar cell is further provided, including the steps of: forming a tunneling layer; forming a transparent conductive film on the tunneling layer; forming a cover layer on the transparent conductive film; and forming a metal electrode that contacts the transparent conductive film through the cover layer, an end surface of the metal electrode staying in the transparent conductive film.

In an embodiment of the present invention, the preparation method further includes: a semiconductor layer of a first doping type is formed on a substrate, wherein the tunneling layer is formed on the semiconductor layer.

Compared with the prior art, the invention has the following advantages:

according to the passivation contact structure for the solar cell, the solar cell with the passivation contact structure and the preparation method of the passivation contact structure, the transparent conductive film and the tunneling layer are combined for use, so that the passivation contact structure can conduct electricity and can play a role in passivation contact of a metal-nonmetal area, and the recombination loss of carriers on the silicon-based solar cell can be effectively reduced. Meanwhile, the transparent conductive film has the effect of reducing the light absorption loss of incident light by utilizing the high light transmittance of the transparent conductive film, and the energy conversion efficiency of the solar cell is improved on the whole.

Drawings

The accompanying drawings, which are included to provide a further understanding of the application and are incorporated in and constitute a part of this application, illustrate embodiment(s) of the application and together with the description serve to explain the principle of the invention. In the drawings:

fig. 1 is a schematic structural diagram of a passivation contact structure of a solar cell according to an embodiment of the invention;

FIG. 2 is a schematic structural diagram of a P-type substrate solar cell employing the passivated contact structure of the invention according to one embodiment of the invention;

FIG. 3 is a schematic structural diagram of an N-type substrate solar cell employing the passivated contact structure of the invention according to one embodiment of the invention; and

fig. 4 is a schematic flow chart of a method for manufacturing a passivation contact structure for a solar cell according to an embodiment of the invention.

Detailed Description

In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings used in the description of the embodiments will be briefly introduced below. It is obvious that the drawings in the following description are only examples or embodiments of the application, from which the application can also be applied to other similar scenarios without inventive effort for a person skilled in the art. Unless otherwise apparent from the context, or otherwise indicated, like reference numbers in the figures refer to the same structure or operation.

As used in this application and the appended claims, the terms "a," "an," "the," and/or "the" are not intended to be inclusive in the singular, but rather are intended to be inclusive in the plural unless the context clearly dictates otherwise. In general, the terms "comprises" and "comprising" merely indicate that steps and elements are included which are explicitly identified, that the steps and elements do not form an exclusive list, and that a method or apparatus may include other steps or elements.

The relative arrangement of the components and steps, the numerical expressions, and numerical values set forth in these embodiments do not limit the scope of the present application unless specifically stated otherwise. Meanwhile, it should be understood that the sizes of the respective portions shown in the drawings are not drawn in an actual proportional relationship for the convenience of description. Techniques, methods, and apparatus known to those of ordinary skill in the relevant art may not be discussed in detail but are intended to be part of the specification where appropriate. In all examples shown and discussed herein, any particular value should be construed as merely illustrative, and not limiting. Thus, other examples of the exemplary embodiments may have different values. It should be noted that: like reference numbers and letters refer to like items in the following figures, and thus, once an item is defined in one figure, further discussion thereof is not required in subsequent figures.

In the description of the present application, it is to be understood that the orientation or positional relationship indicated by the directional terms such as "front, rear, upper, lower, left, right", "lateral, vertical, horizontal" and "top, bottom", etc., are generally based on the orientation or positional relationship shown in the drawings, and are used for convenience of description and simplicity of description only, and in the case of not making a reverse description, these directional terms do not indicate and imply that the device or element being referred to must have a particular orientation or be constructed and operated in a particular orientation, and therefore, should not be considered as limiting the scope of the present application; the terms "inner and outer" refer to the inner and outer relative to the profile of the respective component itself.

Spatially relative terms, such as "above … …," "above … …," "above … …," "above," and the like, may be used herein for ease of description to describe one device or feature's spatial relationship to another device or feature as illustrated in the figures. It will be understood that the spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if a device in the figures is turned over, devices described as "above" or "on" other devices or configurations would then be oriented "below" or "under" the other devices or configurations. Thus, the exemplary term "above … …" can include both an orientation of "above … …" and "below … …". The device may be otherwise variously oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein interpreted accordingly.

It should be noted that the terms "first", "second", and the like are used to define the components, and are only used for convenience of distinguishing the corresponding components, and the terms have no special meanings unless otherwise stated, and therefore, the scope of protection of the present application is not to be construed as being limited. Further, although the terms used in the present application are selected from publicly known and used terms, some of the terms mentioned in the specification of the present application may be selected by the applicant at his or her discretion, the detailed meanings of which are described in relevant parts of the description herein. Further, it is required that the present application is understood not only by the actual terms used but also by the meaning of each term lying within.

It will be understood that when an element is referred to as being "on," "connected to," "coupled to" or "contacting" another element, it can be directly on, connected or coupled to, or contacting the other element or intervening elements may be present. In contrast, when an element is referred to as being "directly on," "directly connected to," "directly coupled to" or "directly contacting" another element, there are no intervening elements present. Similarly, when a first component is said to be "in electrical contact with" or "electrically coupled to" a second component, there is an electrical path between the first component and the second component that allows current to flow. The electrical path may include capacitors, coupled inductors, and/or other components that allow current to flow even without direct contact between the conductive components.

An embodiment of the present invention provides a passivation contact structure for a solar cell, in which a transparent conductive film is used in combination with a tunneling layer, so that the passivation contact structure can conduct electricity and perform a passivation function, and has an effect of reducing light absorption loss.

Fig. 1 is a schematic structural diagram of a passivation contact structure 10 of a solar cell according to an embodiment of the present invention, where the passivation contact structure 10 can be used on the front side or the back side of the solar cell. According to fig. 1, the passivation contact structure 10 includes a tunneling layer 11, a transparent conductive film 12, a capping layer 13, and a metal electrode 14 in sequence.

Specifically, the tunneling layer 11 can block holes from entering the transparent conductive film 12. From the material perspective, the tunneling layer may be silicon oxide, but the material of the tunneling layer is not limited thereto, and in other embodiments of the present invention, the tunneling layer may be made of other materials. And from a dimensional perspective, in some embodiments of the present invention, the tunneling layer 11 has a thickness between 0.5-3 nm.

Further, the transparent conductive film 12 is located on the tunneling layer 11 and directly contacts the tunneling layer 11, and there is no other battery layer structure between the two. Preferably, the material of the transparent conductive film 12 is zinc oxide. However, the transparent conductive film 12 may be made of other materials such as silicon oxide and aluminum oxide. Illustratively, in some embodiments of the present invention, the transparent conductive film 12 has a thickness of between 10-300 nm.

Further, the covering layer 13 is located on the transparent conductive film 12, and the covering layer 13 may protect the transparent conductive film 12, and is generally made of a material such as silicon nitride or aluminum oxide. For example, the cover layer 13 may protect the transparent conductive film 12 from moisture, pid (potential Induced degradation) ions, physical friction, loss of hydrogen source during sintering, and metal peeling.

Finally, the metal electrode 14 contacts the transparent conductive film 12 through the cover layer 13, and the end face 14a of the metal electrode 14 is located in the transparent conductive film 12. The material of the metal electrode 14 may be silver, aluminum, or copper, and the invention is not limited to the material of the metal electrode. In the actual process of manufacturing the solar cell, especially in the metal sintering process, the following metal corrosion degree is ensured: the metallic metal electrode 14 passes through the uppermost cover layer 13 and comes into contact with the transparent conductive film 12, but does not reach the tunneling layer 11 any further and even damages it.

In some embodiments of the present invention, transparent conductive film 12 as shown in fig. 1 is a transparent conductive film of a first doping type. Specifically, the first doping type may be N-type, and the transparent conductive film 12 is an N-type doped transparent conductive film. Illustratively, when the material of the transparent conductive film 12 is zinc oxide, an appropriate amount of aluminum may be added in the paste when preparing the passivation contact structure 10. This may enhance the N-type doping of the zinc oxide and metal contact areas, facilitating easier electron transport from the transparent conductive film 12 into the metal electrode 14.

In general, the transparent conductive film 12 is not required to be highly doped, and is only required to function to provide longitudinal transport of electrons. In the preparation process, the transparent conductive film 12 receives the end face 14a of the metal electrode 14, the bottom tunneling layer 11 can be effectively protected from being damaged, high-efficiency collection and transmission of electrons in the battery can be guaranteed after the battery is prepared, and in the actual use process of the battery, the incidence rate of sunlight is increased by utilizing the high light transmittance of the transparent conductive film (because the transparent conductive film does not need very high doping), and the influence caused by light absorption of amorphous silicon and polycrystalline silicon in the traditional passivation structure can be effectively solved.

On the basis of the above structure, in the embodiment shown in fig. 1, the passivation contact structure 10 further includes a substrate 15 and a first semiconductor layer 16 adopting the above-mentioned first doping type, and the first semiconductor layer 16 is located on the substrate 15, and the tunneling layer 11 is located on the first semiconductor layer 16. Illustratively, the material of the substrate 15 is silicon. In some embodiments of the present invention, the first semiconductor layer 16 is an N-type doped semiconductor layer. The N-type doping is chosen to increase lateral conduction in the substrate 15 (i.e., the silicon body) and to make better contact with the transparent conductive film 12. Illustratively, the N-type doped first semiconductor layer 16 may be implemented by doping phosphorus or gallium, etc., and the present invention is not limited thereto. In embodiments of the present invention, the substrate 15 itself may be either P-type doped or N-type doped. P-type doping may be achieved by doping with boron or gallium and N-type doping may be achieved by doping with phosphorus or arsenic.

It is understood that, depending on the manufacturing process, the first semiconductor layer 16 may be independently manufactured on the substrate 15 or doped in the substrate 15, and the present invention is not limited to the manufacturing process, and after the manufacturing process, the first semiconductor layer 16 with N-type doping attached to the substrate 15 as shown in fig. 1 is formed.

The invention adopts a structure that the transparent conductive film (such as zinc oxide) is directly contacted with the tunneling layer so as to be combined for use, and the passivation effect is achieved together. In the process of actually preparing the solar cell, particularly in the metal sintering process, the transparent conductive film can effectively protect the tunneling layer in direct contact with the transparent conductive film from being damaged, and after the cell is prepared, the efficient collection and transmission of electrons can be ensured.

In addition, the structure of the transparent conducting film and the tunneling layer is combined, the adverse effect of serious light absorption of the polycrystalline silicon layer in the conventional passivation structure is avoided, and the passivation contact structure can effectively reduce light absorption loss while providing a passivation contact effect by utilizing the high light transmittance of the transparent conducting film. For example, when an ellipsometer is used to compare aluminum-doped ZnO (i.e., a transparent conductive film in a passivation contact structure for a solar cell according to an embodiment of the present invention) with polysilicon, which is a material providing a passivation contact for a conventional solar cell, the extinction coefficient of the aluminum-doped ZnO is about 0.017 at 632nm at the same wavelength, and the extinction coefficient of the polysilicon is 0.252. Therefore, the passivation contact structure can obviously reduce light absorption loss, improve the energy conversion efficiency of the solar cell and optimize the performance of the solar cell.

On the basis of the passivation contact structure of the solar cell, an embodiment of the invention further provides a solar cell including the passivation contact structure. Compared with the solar cell with the traditional passivation contact structure, the solar cell with the passivation contact structure avoids the adverse effect of light absorption of the polycrystalline silicon layer, and has better energy conversion effect.

Fig. 2 is a structural diagram of a toporc (back side structure of passivated emitter and back side cell (PERC) combined with front side structure of topocon cell) solar cell 20 using the passivated contact structure of the present invention according to an embodiment of the present invention. The solar cell 20 of this embodiment is a P-type substrate cell, but the present invention is not limited to this structure type. As can be seen in fig. 2, the upper half (i.e. the positive part) of the solar cell 20 adopts the passivation contact structure shown in fig. 1, and specifically includes the tunneling layer 21, the transparent conductive film 22, the capping layer 23, the front metal electrode 241, the P-type substrate 25, and the N-type doped first semiconductor layer 26. For example, in an embodiment of the invention, the P-type substrate 25 is a P-type silicon substrate, the first semiconductor layer 26 is N-type doped (e.g., phosphorus doped), the tunneling layer 21 is silicon oxide, the transparent conductive film 22 is aluminum-doped zinc oxide, and the capping layer 23 is silicon nitride, but the solar cell of the invention is not limited to such a material.

On the basis of this, on the back side of the solar cell 20, there are also a passivation layer 27 and a passivated antireflection film 28 below the P-type substrate 25, and a metal electrode 242 on the back side. The material of passivation layer 27 is, for example, aluminum oxide, and the material of passivation anti-reflective film 28 is, for example, silicon nitride. The metal electrode 242 on the rear side also has an aluminum back field 29 on its end face in the P-type substrate 25. These structures are conventional PERC cell structures and are not developed herein as they are not the focus of the present invention.

Similarly, as shown in fig. 3, it is a schematic structural diagram of an N-type solar cell adopting the passivation contact structure of the present invention according to an embodiment of the present invention. The back side of the solar cell 30 has the above-described passivated contact structure. Specifically, the solar cell 30 has a tunneling layer 31, a transparent conductive film 32, a capping layer 33, a back metal electrode 341, an N-type substrate 35, and an N-type doped first semiconductor layer 36. On the basis, the front surface of the solar cell 30 also has a metal electrode 342, a passivated antireflection film 39, a passivation layer 38 and an emitter 37 on the front surface. Illustratively, antireflective film 39 is passivated, such as with silicon nitride, the passivation layer is, for example, aluminum oxide, and emitter 37 is, for example, a boron diffused emitter. Illustratively, in an embodiment of the invention, the N-type substrate 35 is an N-type silicon substrate, the first semiconductor layer 36 is N-type doped (e.g., phosphorus doped), the tunneling layer 31 is silicon oxide, the transparent conductive film 32 is aluminum-doped zinc oxide, and the capping layer 33 is silicon nitride. Similarly, the solar cell of the present invention is not limited to such a material.

The solar cell is provided with the passivation contact structure on the front side or the back side, wherein the transparent conductive film has high light transmittance and is combined with the tunneling layer, so that on the basis of providing a passivation contact effect, the passivation contact structure also has the effect of reducing light absorption loss compared with the traditional solar cell using polycrystalline silicon as a passivation layer. However, the present invention is not limited to the embodiments shown in fig. 2 and fig. 3, for example, in some embodiments of the present invention, the front surface and the back surface of the solar cell may both adopt the passivation contact structure described above, so as to effectively reduce the light absorption loss while better providing the passivation contact effect in different application scenarios.

Another embodiment of the present invention also provides a method for manufacturing the passivation contact structure for a solar cell. As shown in fig. 4, the preparation method 40 includes the following steps.

Step 41 is to form a tunneling layer. For example, the tunneling layer may be deposited by a thermal oxygen reaction. In one embodiment of the present invention, the deposition temperature is 750 ℃, and the thickness of the finally formed tunneling layer is 1.5 nm.

Step 42 is to form a transparent conductive film on the tunneling layer. In an embodiment of the present invention, the transparent conductive film is formed by depositing a transparent conductive film ZnO on one side of the tunneling layer by using an ALD method (atomic layer deposition method), wherein the deposition temperature is 200 ℃, and the thickness of the finally formed transparent conductive film is 60 nm.

Step 43 is to form a capping layer on the transparent conductive film. Specifically, in some embodiments of the present invention, the step of forming the capping layer in step 43 may use a tubular PECVD (plasma enhanced chemical vapor deposition) method to form SiNx as the capping layer.

Step 44 is to form a metal electrode that contacts the transparent conductive film through the cover layer, with an end face of the metal electrode residing in the transparent conductive film.

Based on the above steps, in some embodiments of the present invention, the method for manufacturing a passivation contact structure for a solar cell further includes forming a semiconductor layer of a first doping type on the substrate, and the tunneling layer formed in step 41 is to be formed on the semiconductor layer, where the first doping type may be N-type. For further details and technical effects of the method for manufacturing a passivation contact structure for a solar cell according to the present invention, reference may be made to the above description of the passivation contact structure and the solar cell having the passivation contact structure according to the present invention, and further description thereof is omitted here.

Fig. 4 uses a flowchart in this application to illustrate the operations performed by a system according to embodiments of the present application. It should be understood that the preceding or following operations are not necessarily performed in the exact order in which they are performed. Rather, various steps may be processed in reverse order or simultaneously. Meanwhile, other operations are added to or removed from these processes.

Referring to fig. 2 in combination, in one embodiment, a method of fabricating a TOPerc solar cell (taking a P-type substrate cell as an example) having the above-described passivation contact structure is as follows:

(1) a P-type silicon substrate 25 is selected and the surface is subjected to texturing.

(2) And (2) cleaning the silicon wafer treated in the step (1), putting the silicon wafer into a diffusion furnace, and performing phosphorus diffusion on the silicon wafer to form an N-type doped first semiconductor layer 26 and simultaneously form a P-N junction and phosphosilicate glass (PSG).

(3) And cleaning one surface of the silicon wafer after hydrofluoric acid is carried out, and removing the PSG on the back surface by using a single-surface etching cleaning machine.

(4) And (3) polishing the back surface of the silicon wafer, wherein the front surface has PSG protection and is not influenced, and then cleaning the silicon wafer by concentrated sulfuric acid, hydrofluoric acid, ammonia water, hydrofluoric acid, hydrochloric acid and hydrofluoric acid in sequence, and cleaning the silicon wafer and removing the front surface PSG film.

(5) And putting the silicon wafer into a tube furnace for thermal oxidation reaction, and depositing silicon oxide as a tunneling layer 21 at the deposition temperature of 750 ℃ to obtain a film with the thickness of about 1.5 nm.

(6) And (atomic layer deposition) ALD method is used for depositing an undoped ZnO or ZnO-Al layer as the transparent oxide film 22 on one side of the tunneling layer 21 of the silicon wafer, the deposition temperature is 200 ℃, and the thickness is 60 nm.

(7) And performing back passivation film deposition, and sequentially performing aluminum oxide/silicon nitride layer deposition on the back of the silicon wafer by using a tubular PECVD method to form a passivation layer 27 and a passivation antireflection film 28. The front side is then subjected to a blanket layer 23 deposition, i.e. a tubular PECVD process is used to sequentially prepare the silicon nitride layers.

(8) The backside passivation layer 27 and the passivated antireflection film 28 are opened using a laser.

(9) The front and back metal electrodes 241 and 242 and the fine gate lines are printed and sintered.

Referring collectively to fig. 3, in one embodiment, a method of fabricating, for example, an N-type substrate cell having the above-described passivated contact structure is as follows:

(1) an N-type silicon substrate 35 is selected and the surface is subjected to texturing.

(2) And (2) cleaning the silicon substrate 35 treated in the step (1), putting the silicon substrate into a diffusion furnace, and performing boron diffusion on the silicon wafer to form a P + type doped emitter 37 and borosilicate glass (BSG).

(3) And (3) carrying out HF acid cleaning on one surface of the silicon wafer, wherein the surface is used as a back surface, removing BSG (BSG) on the back surface by using a single-surface etching cleaning machine, and cleaning the silicon wafer.

(4) And polishing the back surface of the silicon wafer, and performing secondary texturing, wherein the BSG protection exists on the front surface, so that the silicon wafer is not influenced and is cleaned.

(5) The cleaned silicon wafer is placed in a tubular diffusion furnace, and phosphorus diffusion is performed on the back surface to form an n + + doped layer 36. And then, cleaning the silicon wafer by HF acid to remove the PSG on the back side and the PSG and BSG on the front side.

(5) And putting the silicon wafer into a tube furnace for thermal oxidation reaction, and depositing silicon oxide as the tunneling layer 31 at the deposition temperature of 750 ℃ to obtain a film with the thickness of about 1.5 nm.

(6) An undoped ZnO or doped ZnO-Al layer is deposited as the transparent oxide film 32 on the tunneling layer 31 using an ALD method or a PECVD method at a deposition temperature of 200 c for ALD or 350 c for PECVD and a thickness of 100 nm.

(7) A back side cap layer 33 is deposited, i.e., a silicon nitride layer is deposited on the back side of the silicon wafer using a tubular PECVD process. Then, the front surface is deposited with the passivation layer 38 and the passivated antireflection layer 39, and AlOx can be deposited by using ALD method even though the tubular PECVD method is used for preparing the aluminum oxide/silicon nitride layers in sequence.

(8) The front and back metal electrodes 341 and 342 and the fine grid are printed and sintered.

Having thus described the basic concept, it will be apparent to those skilled in the art that the foregoing disclosure is by way of example only, and is not intended to limit the present application. Various modifications, improvements and adaptations to the present application may occur to those skilled in the art, although not explicitly described herein. Such modifications, improvements and adaptations are proposed in the present application and thus fall within the spirit and scope of the exemplary embodiments of the present application.

Also, this application uses specific language to describe embodiments of the application. Reference throughout this specification to "one embodiment," "an embodiment," and/or "some embodiments" means that a particular feature, structure, or characteristic described in connection with at least one embodiment of the present application is included in at least one embodiment of the present application. Therefore, it is emphasized and should be appreciated that two or more references to "an embodiment" or "one embodiment" or "an alternative embodiment" in various places throughout this specification are not necessarily all referring to the same embodiment. Furthermore, some features, structures, or characteristics of one or more embodiments of the present application may be combined as appropriate.

Similarly, it should be noted that in the preceding description of embodiments of the application, various features are sometimes grouped together in a single embodiment, figure, or description thereof for the purpose of streamlining the disclosure aiding in the understanding of one or more of the embodiments. This method of disclosure, however, is not intended to require more features than are expressly recited in the claims. Indeed, the embodiments may be characterized as having less than all of the features of a single embodiment disclosed above.

Numerals describing the number of components, attributes, etc. are used in some embodiments, it being understood that such numerals used in the description of the embodiments are modified in some instances by the use of the modifier "about", "approximately" or "substantially". Unless otherwise indicated, "about", "approximately" or "substantially" indicates that the number allows a variation of ± 20%. Accordingly, in some embodiments, the numerical parameters used in the specification and claims are approximations that may vary depending upon the desired properties of the individual embodiments. In some embodiments, the numerical parameter should take into account the specified significant digits and employ a general digit preserving approach. Notwithstanding that the numerical ranges and parameters setting forth the broad scope of the range are approximations, in the specific examples, such numerical values are set forth as precisely as possible within the scope of the application.

Although the present application has been described with reference to the present specific embodiments, it will be recognized by those skilled in the art that the foregoing embodiments are merely illustrative of the present application and that various changes and substitutions of equivalents may be made without departing from the spirit of the application, and therefore, it is intended that all changes and modifications to the above-described embodiments that come within the spirit of the application fall within the scope of the claims of the application.