CN116314396B - Back contact solar cell and preparation method thereof - Google Patents

Abstract

The present application provides a back-contact solar cell and a preparation method. The back-contact solar cell includes: a silicon substrate having a relative front and back side and being of a first doping type; and a first emitter and a second emitter, wherein the first emitter and the second emitter are adjacently arranged on the back side of the silicon substrate along a first direction, the first emitter is of the second doping type, the second emitter is of the first doping type, and the doping concentration of the first emitter is 1×10 ¹³ ‑1×10 ¹⁸ cm ^‑3 , wherein the first direction intersects with the thickness direction of the silicon substrate. The back-contact solar cell of the present application achieves the technical effect of isolating the first emitter and the second emitter by controlling the doping concentration of the first emitter and adjusting the doping concentration of the first emitter adjacent to the second emitter through a second passivation layer and/or a tunneling oxide layer; and at the same time, it has the technical effect of having better mechanical load capacity and fewer process steps.

Description

Back contact solar cell and method for preparing the same

Technical Field

The present application mainly relates to the field of photovoltaic technology, and specifically to a back-contact solar cell and a method for preparing a back-contact solar cell.

Background Art

The positive electrode and negative electrode of the back contact battery (IBC) are located on the back of the battery, and there is no electrode blocking the front of the battery, which increases the light-receiving area of the battery and improves the aesthetics of the battery.

In conventional technology, when preparing back-contact batteries, alkaline solutions are often used to prepare pyramid velvet morphology on the front and back of the battery. The P region on the back of the battery is inevitably etched by the alkaline solution. On the one hand, this will lead to the formation of grooves with a certain depth in the P region, which will reduce the mechanical load capacity of the battery; on the other hand, the pyramid velvet morphology on the back of the battery will reduce the reflectivity of the back of the battery to light. For this problem, although the tunneling oxide layer on the back of the battery can be used as a barrier layer for etching the pyramid velvet morphology with an alkaline solution, this will result in the diffusion junction not being effectively removed, resulting in battery short circuit and leakage.

Therefore, how to simultaneously take into account the mechanical load capacity of the back contact battery and reduce battery leakage is an urgent problem to be solved.

Summary of the invention

The technical problem to be solved by the present application is to provide a back-contact solar cell and a method for preparing a back-contact solar cell, wherein the back-contact solar cell can reduce the leakage of the battery while ensuring that the mechanical load capacity meets the requirements.

The technical solution adopted by the present application to solve the above technical problems is a back-contact solar cell, comprising: a silicon substrate having a front side and a back side opposite to each other and being of a first doping type; and a first emitter and a second emitter, wherein the first emitter and the second emitter are adjacently arranged on the back side of the silicon substrate along a first direction, the first emitter is of the second doping type, the second emitter is of the first doping type, and the doping concentration of the first emitter is 1×10 ¹³ -1×10 ¹⁸ cm ^-3 , wherein the first direction intersects with the thickness direction of the silicon substrate.

In an embodiment of the present application, the first emitter includes a diffusion layer, the diffusion layer is disposed on the back side of the silicon substrate, the diffusion layer is of the second doping type, and the diffusion layer is connected to the second emitter.

In an embodiment of the present application, the first emitter further includes a tunneling oxide layer and a polysilicon layer, and the tunneling oxide layer and the polysilicon layer are sequentially arranged on a side of the diffusion layer away from the silicon substrate.

In one embodiment of the present application, it also includes: a second passivation layer, a first portion of the second passivation layer is arranged on a side of the polysilicon layer away from the silicon substrate, and a second portion of the second passivation layer is arranged on a side of the tunneling oxide layer away from the silicon substrate, wherein the second passivation layer is of the first doping type.

In one embodiment of the present application, it also includes: a third passivation layer, which is arranged on a side of the second passivation layer away from the silicon substrate.

In one embodiment of the present application, it also includes: a first electrode and a second electrode, one end of the first electrode passes through the second passivation layer to contact the first emitter, and one end of the second electrode passes through the second passivation layer to contact the second emitter.

In one embodiment of the present application, it also includes: a first passivation layer and an anti-reflection layer, wherein the first passivation layer and the anti-reflection layer are sequentially arranged on the front side of the silicon substrate.

In one embodiment of the present application, the first passivation layer includes a chemical passivation layer and a field passivation layer, wherein the chemical passivation layer is disposed on the front side of the silicon substrate, and the field passivation layer is disposed on a side of the chemical passivation layer away from the silicon substrate.

On the other hand, the present application also proposes a method for preparing a back-contact solar cell, comprising the following steps: providing a silicon substrate having a front side and a back side opposite to each other and being of a first doping type; and forming a first emitter and a second emitter adjacent to each other along a first direction on the back side of the silicon substrate, wherein the first emitter is of the second doping type and the second emitter is of the first doping type, and the doping concentration of the first emitter is 1×10 ¹³ -1×10 ¹⁸ cm ^-3 , wherein the first direction intersects with a thickness direction of the silicon substrate.

In an embodiment of the present application, the first emitter includes a diffusion layer, the diffusion layer is disposed on the back side of the silicon substrate, the diffusion layer is of the second doping type, and the diffusion layer is connected to the second emitter.

In an embodiment of the present application, the first emitter further includes a tunneling oxide layer and a polysilicon layer, and the tunneling oxide layer and the polysilicon layer are sequentially arranged on a side of the diffusion layer away from the silicon substrate.

In one embodiment of the present application, the method for forming the diffusion layer includes: forming a transition diffusion layer on the back side of the silicon substrate, the transition diffusion layer being of the first doping type; and performing a doping treatment on the transition diffusion layer, the dopant of the doping treatment being a dopant for forming the second doping type, and after the doping treatment, the transition diffusion layer is inverted into the diffusion layer.

In an embodiment of the present application, the doping concentration of the first emitter is controlled by controlling the doping concentration of the transition diffusion layer.

In one embodiment of the present application, a second passivation layer is formed on a side of the polysilicon layer away from the silicon substrate along the thickness direction, wherein the second passivation layer is of the first doping type.

In one embodiment of the present application, a third passivation layer is formed on a side of the second passivation layer away from the silicon substrate along the thickness direction.

In one embodiment of the present application, a first passivation layer and an anti-reflection layer are sequentially formed on the front surface of the silicon substrate.

In one embodiment of the present application, the first passivation layer includes a chemical passivation layer and a field passivation layer, wherein the chemical passivation layer is disposed on the front side of the silicon substrate, and the field passivation layer is disposed on a side of the chemical passivation layer away from the silicon substrate.

The back-contact solar cell of the present application achieves the technical effect of isolating the first emitter and the second emitter by controlling the doping concentration of the first emitter and adjusting the doping concentration of the first emitter adjacent to the second emitter through the second passivation layer and/or the tunneling oxide layer; at the same time, it has the technical effect of better mechanical load capacity and fewer process steps.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to make the above-mentioned objects, features and advantages of the present application more obvious and easy to understand, the specific implementation methods of the present application are described in detail below with reference to the accompanying drawings, wherein:

FIG1 is a schematic cross-sectional view of a back-contact solar cell;

FIG2 is a schematic cross-sectional view of another back-contact solar cell;

FIG3 is a cross-sectional schematic diagram of a back-contact solar cell according to an embodiment of the present application;

FIG4 is an exemplary flow chart of a method for preparing a back-contact solar cell according to an embodiment of the present application;

5 to 7 are schematic cross-sectional views of a solar cell at various intermediate steps in a preparation method according to an embodiment of the present application.

Reference numerals

Back contact solar cell 100 Second emitter 130 First electrode 191

Silicon substrate 110, 310 Groove 140 Second electrode 192

Front surface 111, 311 First passivation layer 150 Transition diffusion layer 320

Back surface 112, 312 Anti-reflection layer 160 Transition doping layer 330 after inversion

First emitter 120 Second passivation layer 170, 380 Diffusion region 340

Diffusion layer 121 First portion 171 Diffusion layer 350

Tunneling oxide layer 122, 360 Second portion 172 Tunneling oxide layer 360

Polysilicon layer 123, 370 Third passivation layer 180, 390

DETAILED DESCRIPTION

In order to make the above-mentioned objects, features and advantages of the present application more obvious and easy to understand, the specific implementation methods of the present application are described in detail below with reference to the accompanying drawings.

In the following description, many specific details are set forth to facilitate a full understanding of the present application, but the present application may also be implemented in other ways different from those described herein, and therefore the present application is not limited to the specific embodiments disclosed below.

As shown in this application and claims, unless the context clearly indicates an exception, the words "a", "an", "an" and/or "the" do not refer to the singular and may also include the plural. Generally speaking, the terms "comprises" and "includes" only indicate the inclusion of the steps and elements that have been clearly identified, and these steps and elements do not constitute an exclusive list. The method or device may also include other steps or elements.

In addition, it should be noted that the use of words such as "first" and "second" to define components is only for the convenience of distinguishing the corresponding components. If not otherwise stated, the above words have no special meaning and cannot be understood as limiting the scope of protection of this application. In addition, although the terms used in this application are selected from well-known and commonly used terms, some terms mentioned in the specification of this application may be selected by the applicant at his or her discretion, and their detailed meanings are explained in the relevant parts of the description of this article. In addition, it is required to understand this application not only by the actual terms used, but also by the meaning implied by each term.

Flowcharts are used in the present application to illustrate the operations performed by the system according to the embodiments of the present application. It should be understood that the preceding or following operations are not necessarily performed accurately in order. On the contrary, various steps may be processed in reverse order or simultaneously. At the same time, other operations may be added to these processes, or one or more operations may be removed from these processes.

FIG1 is a cross-sectional schematic diagram of a back-contact solar cell. The back-contact solar cell 10 in FIG1 has the following problems: due to the production process steps and other reasons, when an alkaline solution is used to construct a pyramid velvet morphology on the front of the silicon substrate 11, the P region on the back of the silicon substrate 11 is also etched at the same time, which results in the formation of a groove 12 with a certain depth in the P region, and the formation of a pyramid velvet morphology 13 in the P region. The groove 12 in the P region will cause the mechanical load capacity of the solar cell 10 to decrease; at the same time, the pyramid velvet morphology 13 in the P region will reduce the reflectivity of the solar cell 10 to light, thereby causing a decrease in current.

FIG2 is a cross-sectional schematic diagram of another back-contact solar cell. Compared with the back-contact solar cell 10 in FIG1 , the depth of the groove 22 at the P region of the back-contact solar cell 20 in FIG2 is shallower; and the P region does not have a pyramid velvet morphology; in addition, an isolation region 25 is provided between the emitter 23 and the emitter 24 in FIG2 by etching or the like, which is beneficial to reduce the leakage of the battery. Although the back-contact solar cell 20 in FIG2 can solve the problems faced by the back-contact solar cell 10 in FIG1 and reduce the leakage of the battery. However, the realization of the structure in FIG2 requires additional process steps, which leads to an increase in production costs. In addition, the increase in process steps will increase the number of heat treatments on the silicon substrate 21, which will shorten the service life of the silicon substrate 21.

In view of the shortcomings of the back-contact solar cells in Figures 1 and 2, the back-contact solar cell of the present application can take into account both the mechanical load capacity of the cell and the number of process steps, while also being able to reduce the leakage of the back-contact cell.

Next, the back contact solar cell of the present application is described through specific embodiments.

FIG3 is a schematic cross-sectional view of a back-contact solar cell according to an embodiment of the present application. Referring to FIG3 , the back-contact solar cell 100 includes a silicon substrate 110 , a first emitter 120 , and a second emitter 130 .

Specifically, the silicon substrate 110 has a front side 111 and a back side 112 relative to each other along the thickness direction D2. The "front side" refers to the side of the silicon substrate 110 that receives light when the solar cell is working. The silicon substrate 110 of the present application is of a first doping type, and the first doping type can be P-type, that is, the silicon substrate 110 is a P-type silicon substrate; or it can be N-type, that is, the silicon substrate 110 is an N-type silicon substrate. The present application does not limit the specific doping elements that form the P-type silicon substrate and the N-type silicon substrate.

As shown in FIG3 , the first emitter 120 and the second emitter 130 are adjacently disposed on the back side 112 of the silicon substrate 110 along the first direction D1. The first emitter 120 is of the second doping type, and the second emitter 130 is of the first doping type. The doping concentration of the first emitter 120 is 1×10 ¹³ -1×10 ¹⁸ cm ^-3 . The second doping type has an opposite polarity to the first doping type, that is, when the first doping type is P-type, the second doping type is N-type; when the first doping type is N-type, the second doping type is P-type.

In FIG3 , the first emitter 120 includes a diffusion layer 121, a tunneling oxide layer 122, and a polysilicon layer 123. The diffusion layer 121 is disposed on the back side of the silicon substrate 110, and one end 121a of the diffusion layer 121 is connected to the second emitter 130. The tunneling oxide layer 122 and the polysilicon layer 123 are sequentially disposed on a side of the diffusion layer 121 away from the silicon substrate 110, and one end 122a of the tunneling oxide layer 122 is connected to the second emitter 130. Among them, the diffusion layer 121 and the polysilicon layer 123 are of the second doping type, and the tunneling oxide layer 122 is of the first doping type.

In one embodiment, the thickness of the tunnel oxide layer 122 is 1-20 nm, and the thickness of the polysilicon layer 123 is 20-1000 nm. The tunnel oxide layer 122 can be implemented as silicon dioxide. The tunnel oxide layer 122 and the polysilicon layer 123 can realize the selective collection of carriers, that is, the majority carriers can easily pass through the tunnel oxide layer 122, while the minority carriers are difficult to pass through the tunnel oxide layer 122. In some embodiments, the first emitter 120 may only have a diffusion layer 121. It should be understood that, as shown in FIG. 3, the polysilicon layer 123 does not extend into the P region along the first direction D1.

In order to make the description clearer, "the first emitter 120 is of the second doping type" and "the doping concentration of the first emitter 120 is 1×10 ¹³ -1×10 ¹⁸ cm ^-3 " are explained here. In FIG3 , the first emitter 120 includes a diffusion layer 121, a tunneling oxide layer 122 and a polysilicon layer 123. The diffusion layer 121 and the polysilicon layer 123 are of the second doping type, and the doping type of the tunneling oxide layer 122 is opposite to that of the diffusion layer 121 and the polysilicon layer 123, that is, the tunneling oxide layer 122 is of the first doping type. "The first emitter 120 is of the second doping type" means that the diffusion layer 121 is of the second doping type, and does not include the tunneling oxide layer 122 and the polysilicon layer 123. “The doping concentration of the first emitter 120 is 1×10 ¹³ -1×10 ¹⁸ cm ⁻³ ” means that the doping concentration of the dopant forming the second doping type in the diffusion layer 121 is 1×10 ¹³ -1×10 ¹⁸ cm ⁻³ .

As shown in FIG3 , although one end 121a of the diffusion layer 121 in the first emitter 120 is connected to the second emitter 130, the doping concentration of the first emitter 120 is set to 1×10 ¹³ -1×10 ¹⁸ cm ^-3 in the present application. Thus, compared with the back contact solar cell 20 in FIG2 , the present application does not need to set an isolation region between the first emitter 120 and the second emitter 130 by etching or the like, that is, as shown in FIG3 , one end 121a of the diffusion layer 121 in the first emitter 120 is connected to the second emitter 130, thereby reducing the process steps and the production cost. At the same time, since the doping concentration of the first emitter 120 is set to 1×10 ¹³ -1×10 ¹⁸ cm ^-3 in the present application, even if one end 121a of the diffusion layer 121 is connected to the second emitter 130, the leakage of the solar cell 100 can still be ensured to be small.

In Fig. 3, one side 121b of the diffusion layer 121 adjacent to the silicon substrate 110 is flat, which can be obtained by chemical mechanical polishing (CMP). Thus, compared with the back contact solar cell 10 in Fig. 1, the depth of the groove 140 at the P region of the back contact solar cell 100 is smaller, thereby ensuring the mechanical load capacity of the back contact solar cell 100.

In one embodiment, as shown in FIG3 , the back contact solar cell 100 further includes a first passivation layer 150 and an anti-reflection layer 160. The first passivation layer 150 is disposed on the front side of the silicon substrate 110 along the thickness direction D1, and the anti-reflection layer 160 is disposed on the side of the first passivation layer 150 away from the silicon substrate 110 along the thickness direction D1. The first passivation layer 150 can reduce the recombination of carriers on the front side of the silicon substrate 110, thereby improving the efficiency of the cell. The anti-reflection layer 160 can reduce the reflection of incident light, thereby improving the absorption of incident light by the solar cell. In some embodiments, the first passivation layer 150 includes one or more of aluminum oxide, silicon oxide, and silicon oxynitride, and the anti-reflection layer 160 includes silicon nitride.

In one embodiment, the first passivation layer 150 includes a chemical passivation layer (not shown) and a field passivation layer (not shown). The chemical passivation layer is disposed on the front side of the silicon substrate 110, and the field passivation layer is disposed on the side of the chemical passivation layer away from the silicon substrate 110. Correspondingly, the anti-reflection layer 160 is disposed on the side of the field passivation layer away from the silicon substrate 110. The chemical passivation layer can saturate the defects at the front side of the silicon substrate 110 and reduce the defect concentration, thereby reducing the recombination centers in the bandgap, thereby improving the efficiency of the solar cell. The field passivation layer can form an electrostatic field at the interface through charge accumulation, thereby reducing the minority carrier concentration, thereby improving the efficiency of the solar cell.

As shown in Fig. 3, in some embodiments, the front side 111 of the silicon substrate 110 and the first passivation layer 150 and the anti-reflection layer 160 located on the front side 111 have a pyramid suede morphology. When the solar cell is working, sunlight is incident on the silicon substrate 110 from the front side 111 of the silicon substrate 110, and the pyramid suede morphology can trap light and reduce surface reflection, which is beneficial to improve the utilization rate of light by the solar cell.

In order to reduce the battery leakage caused by the contact between the diffusion layer 121 in the first emitter 120 and the second emitter 130 , the present application also makes the following design.

Referring to FIG3 , in one embodiment, the back contact solar cell 100 further includes a second passivation layer 170 and a third passivation layer 180. As shown in FIG3 , a first portion of the second passivation layer 170 is disposed on a side of the polysilicon layer 123 away from the silicon substrate 110, and the first portion is marked as 171 in FIG3 ; a second portion of the second passivation layer 170 is disposed on a side of the tunneling oxide layer 122 away from the silicon substrate 110, and the second portion is marked as 172 in FIG3 , wherein the second passivation layer 170 is of the first doping type. In FIG3 , in order to clearly indicate the first portion 171 and the second portion 172, a dotted line A is used in FIG3 to indicate the boundary between the first portion 171 and the second portion 172. The above design has the following technical effects: in FIG3 , the diffusion layer 121 is of the second doping type, and the second passivation layer 170 is of the first doping type, wherein the second portion 172 of the second passivation layer 170 is located in the P region and adjacent to the diffusion layer 121 in the P region, so that the diffusion layer 121 in the P region can be inverted by the second portion 172, and the doping concentration of the diffusion layer 121 in the P region will be reduced after the inversion; in other words, after the inversion, the doping concentration of the diffusion layer 121 in the P region is lower than the doping concentration of the diffusion layer 121 outside the P region. In this way, the effect of electrically isolating the first emitter 120 and the second emitter 130 is achieved.

In addition, referring to FIG. 3 , it is described in the foregoing that “the tunneling oxide layer 122 is of the first doping type”, and the tunneling oxide layer 122 located in the P region has the same inversion effect as the second passivation layer 170 located in the P region. Specifically, the tunneling oxide layer 122 located in the P region is in contact with the diffusion layer 121 located in the P region, and the doping type of the tunneling oxide layer 122 is opposite to the doping type of the diffusion layer 121. In this way, the tunneling oxide layer 122 located in the P region can invert the diffusion layer 121 located in the P region, thereby further reducing the doping concentration of the diffusion layer 121 in the P region, and further achieving the effect of electrically isolating the first emitter 120 and the second emitter 130.

Here, the inversion effect of the tunneling oxide layer 122 and the second passivation layer 170 in FIG. 3 is briefly described. The doping type of the tunneling oxide layer 122 and the second passivation layer 170 is opposite to that of the diffusion layer 121, so that the tunneling oxide layer 122 and the second passivation layer 170 adjacent to the diffusion layer 121 in the P region can invert the diffusion layer 121 in the P region. In other words, the tunneling oxide layer 122 and the second passivation layer 170 adjacent to the diffusion layer 121 in the P region can reduce the doping concentration of the portion of the diffusion layer 121 (i.e., the second portion 172) adjacent to the second emitter 130, thereby achieving the technical effect of isolating the first emitter 120 and the second emitter 130.

Continuing to refer to FIG. 3 , in some embodiments, the third passivation layer 180 is disposed on a side of the second passivation layer 170 away from the silicon substrate 110. The third passivation layer 180 can play a passivation role, thereby improving the efficiency of the solar cell. In some embodiments, the back contact solar cell 100 further includes a first electrode 191 and a second electrode 192. One end of the first electrode 191 passes through the second passivation layer 170 and the third passivation layer 180 to contact the first emitter 120, and one end of the second electrode 192 passes through the second passivation layer 170 and the third passivation layer 180 to contact the second emitter 130.

The back-contact solar cell in the above-mentioned embodiments of the present application achieves the technical effect of isolating the first emitter and the second emitter by controlling the doping concentration of the first emitter and adjusting the doping concentration of the first emitter adjacent to the second emitter through the second passivation layer and/or the tunneling oxide layer; at the same time, it has the technical effect of better mechanical load capacity and fewer process steps.

On the other hand, the present application also proposes a method for preparing a back-contact solar cell, which is described below through specific examples.

FIG4 is an exemplary flow chart of a method for preparing a back-contact solar cell according to an embodiment of the present application. Referring to FIG4 , the preparation method of this embodiment includes the following steps:

Step S210: providing a silicon substrate having a front side and a back side opposite to each other and being of a first doping type;

Step S220: forming a first emitter and a second emitter adjacent to each other along a first direction on the back side of the silicon substrate, the first emitter being of the second doping type, the second emitter being of the first doping type, and the doping concentration of the first emitter being 1×10 ¹³ -1×10 ¹⁸ cm ^-3 , wherein the first direction intersects with the thickness direction of the silicon substrate.

The above steps S210 and S220 are described in detail below with reference to the cross-sectional schematic diagrams of the solar cell at various intermediate steps in the preparation method of one embodiment shown in FIG. 5 to FIG. 7 .

5 , in step S210 , a silicon substrate 310 is provided. The silicon substrate 310 has a front side 311 and a back side 312 opposite to each other along a thickness direction D2 . The silicon substrate 310 is of a first doping type.

In step S220, a first emitter and a second emitter adjacent to each other along the first direction D1 are formed on the back side of the silicon substrate 310. The first emitter is of the second doping type, the second emitter is of the first doping type, and the doping concentration of the first emitter is 1×10 ¹³ -1×10 ¹⁸ cm ^-3 .

Referring to FIG. 3 , in one embodiment, the first emitter 120 includes a diffusion layer 121, the diffusion layer 121 is disposed on the back side 112 of the silicon substrate 110, and one end 121a of the diffusion layer 121 is connected to the second emitter 130, and the diffusion layer 121 is of the second doping type. In some embodiments, the first emitter 120 further includes a tunneling oxide layer 122 and a polysilicon layer 123, and the tunneling oxide layer 122 and the polysilicon layer 123 are sequentially disposed on a side of the diffusion layer 121 away from the silicon substrate 110. When the first emitter 120 includes the diffusion layer 121, the doping concentration of the first emitter 120 refers to the doping concentration of the diffusion layer 121, for example, the doping concentration of the first emitter is 1×10 ¹³ -1×10 ¹⁸ cm ^-3, which means that the doping concentration of the diffusion layer 121 is 1×10 ¹³ -1×10 ¹⁸ cm ^-3 .

In one embodiment, a method of forming the first emitter is as follows.

Referring to FIG5 , a transition diffusion layer 320 is formed on the back side 312 of the silicon substrate 310, and the transition diffusion layer 320 is of the first doping type. The transition diffusion layer 320 is doped, and the dopant used in the doping is a dopant that forms the second doping type, and the doping method includes high-temperature diffusion. In conjunction with FIG6 , after the transition diffusion layer 320 is doped, the transition diffusion layer 320 is inverted to the second doping type, and the portion is marked as 330 in FIG6 . For the convenience of description, 330 is referred to as the inverted transition doping layer. When the doping treatment is performed, the dopant diffuses into the silicon substrate 310 adjacent to the transition diffusion layer 320, thereby forming a diffusion region 340 having a certain size along the thickness direction D2 on the back side 312 of the silicon substrate 310, and the diffusion region 340 and the inverted transition doping layer 330 together constitute a diffusion layer 350, as shown in FIG6 .

In the above embodiment, the doping concentration of the diffusion layer 350 is related to the transition diffusion layer 320. Specifically, since the doping type of the transition diffusion layer 320 is opposite to the doping type of the diffusion layer 350, the doping concentration in the diffusion layer 350 can be adjusted by changing the doping concentration of the transition diffusion layer 320. In this way, by first forming a transition doping layer on the back side of the silicon substrate and then performing a doping treatment on the transition doping layer, the effect of adjusting the doping concentration of the diffusion layer through the transition doping layer can be achieved.

Further, referring to FIG5 , in one embodiment, a tunneling oxide layer 360 is formed on one side of the transition diffusion layer 320 away from the silicon substrate 310 along the thickness direction D2, and a polysilicon layer 370 is formed on one side of the tunneling oxide layer 360 away from the silicon substrate 310 along the thickness direction D2. The tunneling oxide layer 360 is of the first doping type, and the polysilicon layer 370 is of intrinsic polysilicon or the second doping type. The tunneling oxide layer 360 has the same technical effect as the transition diffusion layer 320, that is, the effect of adjusting the doping concentration of the diffusion layer. Referring to FIG6 , if the polysilicon layer 370 in FIG5 is of intrinsic polysilicon, the polysilicon layer 370 will be transformed into a polysilicon layer of the second doping type through doping treatment in the subsequent process steps.

The above embodiment provides a method for forming a first emitter. It should be understood that the method for forming a first emitter is not limited to the above embodiment.

Referring to FIG. 7 , in one embodiment, a second passivation layer 380 is formed on a side of the polysilicon layer 370 away from the silicon substrate 310 along the thickness direction D2, and a third passivation layer 390 is formed on a side of the second passivation layer 380 away from the silicon substrate 310 along the thickness direction D2, wherein the second passivation layer 380 is of the first doping type. As described above, the second passivation layer 380 can achieve the technical effect of isolating the first emitter and the second emitter. The third passivation layer 390 can play a passivation role, thereby improving the efficiency of the solar cell.

In one embodiment, a first passivation layer and an anti-reflection layer are sequentially formed on the front surface of the silicon substrate. The first passivation layer includes a chemical passivation layer and a field passivation layer, wherein the chemical passivation layer is disposed on the front surface of the silicon substrate, and the field passivation layer is disposed on a side of the chemical passivation layer away from the silicon substrate.

For other details about the preparation method of the back-contact solar cell of the present application, please refer to the relevant description above, which will not be repeated here. The preparation method in the above embodiment achieves the technical effect of isolating the first emitter and the second emitter by controlling the doping concentration of the first emitter to adjust the doping concentration of the first emitter adjacent to the second emitter; at the same time, it has the technical effect of better mechanical load capacity and fewer process steps.

The basic concepts have been described above. Obviously, for those skilled in the art, the above application disclosure is only an example and does not constitute a limitation of the present application. Although not explicitly stated herein, those skilled in the art may make various modifications, improvements and amendments to the present application. Such modifications, improvements and amendments are suggested in the present application, so such modifications, improvements and amendments still belong to the spirit and scope of the exemplary embodiments of the present application.

At the same time, the present application uses specific words to describe the embodiments of the present application. For example, "one embodiment", "an embodiment", and/or "some embodiments" refer to a certain feature, structure or characteristic related to at least one embodiment of the present application. Therefore, it should be emphasized and noted that "one embodiment" or "an embodiment" or "an alternative embodiment" mentioned twice or more in different positions in this specification does not necessarily refer to the same embodiment. In addition, some features, structures or characteristics in one or more embodiments of the present application can be appropriately combined.

In some embodiments, numbers describing the number of components and attributes are used. It should be understood that such numbers used in the description of the embodiments are modified by the modifiers "about", "approximately" or "substantially" in some examples. Unless otherwise specified, "about", "approximately" or "substantially" indicate that the numbers are allowed to vary by ±20%. Accordingly, in some embodiments, the numerical parameters used in the specification and claims are approximate values, which may change according to the required features of individual embodiments. In some embodiments, the numerical parameters should take into account the specified significant digits and adopt the general method of retaining digits. Although the numerical domains and parameters used to confirm the breadth of their range in some embodiments of the present application are approximate values, in specific embodiments, the setting of such numerical values is as accurate as possible within the feasible range.

Claims (11)

1. A back contact solar cell, comprising: A silicon substrate having opposite front and back surfaces and being of a first doping type; a first emitter and a second emitter, wherein the first emitter and the second emitter are adjacently arranged on the back side of the silicon substrate along a first direction, the first emitter is of a second doping type, the second emitter is of a first doping type, the doping concentration of the first emitter is 1×10 ¹³ -1×10 ¹⁸ cm ^-3 , the first emitter comprises a diffusion layer, a tunneling oxide layer and a polysilicon layer, the diffusion layer, the tunneling oxide layer and the polysilicon layer are arranged on the back side of the silicon substrate, the diffusion layer is of the second doping type, and the diffusion layer is connected to the second emitter, wherein the first direction intersects with a thickness direction of the silicon substrate; and The second passivation layer includes a first portion of the second passivation layer and a second portion of the second passivation layer adjacent to each other in the first direction, the first portion of the second passivation layer is arranged on a side of the polysilicon layer away from the silicon substrate, the second portion of the second passivation layer is arranged on a side of the tunneling oxide layer away from the silicon substrate, the second passivation layer is of the first doping type, and the first doping type is opposite to the second doping type. 2 . The solar cell according to claim 1 , further comprising: a third passivation layer, disposed on a side of the second passivation layer away from the silicon substrate. 3. The solar cell according to claim 2, further comprising: a first electrode and a second electrode, wherein one end of the first electrode passes through the second passivation layer to contact the first emitter, and one end of the second electrode passes through the second passivation layer to contact the second emitter. 4 . The solar cell according to claim 1 , further comprising: a first passivation layer and an anti-reflection layer, wherein the first passivation layer and the anti-reflection layer are sequentially arranged on the front side of the silicon substrate. 5. The solar cell according to claim 4, characterized in that the first passivation layer comprises a chemical passivation layer and a field passivation layer, wherein the chemical passivation layer is arranged on the front side of the silicon substrate, and the field passivation layer is arranged on a side of the chemical passivation layer away from the silicon substrate. 6. A method for preparing a back contact solar cell, characterized in that it comprises the following steps: Providing a silicon substrate having opposite front and back surfaces and being of a first doping type; forming a first emitter and a second emitter adjacent to each other along a first direction on the back side of the silicon substrate, wherein the first emitter is of the second doping type, the second emitter is of the first doping type, the doping concentration of the first emitter is 1×10 ¹³ -1×10 ¹⁸ cm ^-3 , the first emitter comprises a diffusion layer, a tunneling oxide layer and a polysilicon layer, the diffusion layer, the tunneling oxide layer and the polysilicon layer are arranged on the back side of the silicon substrate, the diffusion layer is of the second doping type, and the diffusion layer is connected to the second emitter, wherein the first direction intersects with a thickness direction of the silicon substrate; and A second passivation layer is formed, wherein the second passivation layer includes a first portion of the second passivation layer and a second portion of the second passivation layer adjacent to each other in the first direction, wherein the first portion of the second passivation layer is disposed on a side of the polysilicon layer away from the silicon substrate, and the second portion of the second passivation layer is disposed on a side of the tunneling oxide layer away from the silicon substrate, and the second passivation layer is of the first doping type, which is opposite to the second doping type. 7. The preparation method according to claim 6, characterized in that the method of forming the diffusion layer comprises: forming a transition diffusion layer on the back side of the silicon substrate, wherein the transition diffusion layer is of the first doping type; and The transition diffusion layer is subjected to a doping treatment, wherein the dopant used in the doping treatment is a dopant that forms the second doping type. After the doping treatment, the transition diffusion layer is inverted into the diffusion layer. 8 . The preparation method according to claim 7 , wherein the doping concentration of the first emitter is controlled by controlling the doping concentration of the transition diffusion layer. 9 . The preparation method according to claim 6 , wherein a third passivation layer is formed on a side of the second passivation layer away from the silicon substrate along the thickness direction. 10. The preparation method according to claim 6, characterized in that a first passivation layer and an anti-reflection layer are sequentially formed on the front surface of the silicon substrate. 11. The preparation method according to claim 10, characterized in that the first passivation layer comprises a chemical passivation layer and a field passivation layer, wherein the chemical passivation layer is arranged on the front side of the silicon substrate, and the field passivation layer is arranged on a side of the chemical passivation layer away from the silicon substrate.