CN218498078U

CN218498078U - Solar cell lamination passivation structure

Info

Publication number: CN218498078U
Application number: CN202220128952.1U
Authority: CN
Inventors: 张学玲; 柳伟; 陈红; 简磊; 陈奕峰
Original assignee: Trina Solar Co Ltd
Current assignee: Trina Solar Co Ltd
Priority date: 2021-01-19
Filing date: 2022-01-18
Publication date: 2023-02-17
Anticipated expiration: 2032-01-18
Also published as: CN214753783U; CN218351477U

Abstract

The utility model provides a solar cell stromatolite passivation structure. The solar cell laminated passivation structure comprises a P-type silicon substrate, and a first dielectric layer, a second dielectric layer, a third dielectric layer and a fourth dielectric layer which are sequentially arranged on the back surface of the P-type silicon substrate from inside to outside; the fourth dielectric layer is a combination of at least two of a silicon oxide layer, a silicon oxynitride layer, a silicon nitride layer and a silicon carbide layer. The utility model provides a solar cell back stromatolite passivation structure has very good chemical passivation and field passivation effect.

Description

Solar cell lamination passivation structure

Technical Field

The utility model belongs to the technical field of solar energy, a solar cell stromatolite passivation structure is related to.

Background

Among the effective utilization of solar energy, solar photovoltaic utilization is one of the most spotlighted projects in the fastest-growing and most active research fields in recent years. The single crystal silicon solar cell has the highest conversion efficiency and the most mature technology. For a traditional P-type all-aluminum back surface field solar cell, the composition of back surface metal and a silicon contact region, namely the all-aluminum back surface field formed by back surface all-aluminum doping, is a key factor for limiting the further improvement of the efficiency, and meanwhile, the long-wave reflectivity of the all-aluminum back surface field is low, and the optical loss is high. In order to solve the problem, various large research institutions at home and abroad focus on passivation treatment and structure improvement of the surface of a high-efficiency cell, and through introducing a back passivation film and a local aluminum back field technology, the recombination of a metal and silicon contact interface is reduced, the back long-wave reflection is improved, the open-circuit voltage and the short-circuit current of the cell are greatly improved, and the photoelectric conversion efficiency of the solar cell is improved by more than 1%, namely the P-type PERC cell. The process path is relatively simple and compatible with existing battery production lines. Therefore, the battery is rapidly popularized and applied in a large area, and the market share of the current PERC battery reaches over 90 percent. At present, the conversion efficiency of mass production PERC batteries reaches about 23%. In order to further improve the conversion efficiency of a PERC cell, the cell surface must be well passivated to reduce surface defect recombination and thereby increase the open circuit voltage of the cell.

Currently, the most common passivation technique for commercial PERC cells is front side silicon nitride passivation film, with the back side being stack-passivated with layers of aluminum oxide and silicon nitride.

CN111987191A discloses a method for repairing PERC cell laser film opening damage, which comprises texturing the front and back of a P-type monocrystalline silicon wafer and performing phosphorus diffusion on the front and/or back to form a phosphorus doped surface; carrying out local doping on the front surface of the P-type monocrystalline silicon wafer by using a laser to manufacture a selective emitter; after back etching and thermal oxidation, depositing an aluminum oxide and silicon nitride lamination or a silicon nitride and silicon oxynitride lamination on the back and depositing a passivated antireflection layer on the front, laser film opening and damage repair are carried out, solid phase epitaxial growth of a damaged area is realized, and crystalline silicon recrystallization is recovered to be orderly arranged.

CN211929505U discloses a crystalline silicon solar cell, wherein the passivation layer is a lamination of an aluminum oxide layer and a silicon nitride layer, the thickness of the passivation layer is 110nm-140nm, and the silicon nitride layer is disposed on the bottom surface of the aluminum oxide layer.

The current industrialized PERC battery is based on a laminated passivation result of back side aluminum oxide and silicon nitride, the positive charge quantity of a silicon nitride film is higher, the field passivation effect of an aluminum oxide film with negative charge can be influenced, and meanwhile, the deposition power of the silicon nitride film is higher than that of the aluminum oxide film, and the passivation effect of the aluminum oxide film can be damaged in the deposition process. In addition, the refractive index of the aluminum oxide film is about 1.6, the refractive index of the silicon nitride film is about 2.0, the difference between the two is large, and the back light reflection effect is poor. Therefore, the chemical passivation effect, the field passivation effect and the back light reflection capability of the scheme are all required to be further improved.

SUMMERY OF THE UTILITY MODEL

To the above-mentioned not enough that exist among the prior art, the utility model aims at providing a solar cell stromatolite passivation structure. The utility model provides a solar cell stromatolite passivation structure has good passivation effect.

To achieve the purpose, the utility model adopts the following technical proposal:

the utility model provides a solar cell lamination passivation structure, which comprises a P-type silicon substrate, a first dielectric layer, a second dielectric layer, a third dielectric layer and a fourth dielectric layer, wherein the first dielectric layer, the second dielectric layer, the third dielectric layer and the fourth dielectric layer are sequentially arranged on the back surface of the P-type silicon substrate from inside to outside;

the fourth dielectric layer is a combination of at least two of a silicon oxide layer, a silicon oxynitride layer, a silicon nitride layer and a silicon carbide layer.

In the laminated passivation structure of the solar cell provided by the utility model, the first dielectric layer has the function that the film can reduce the density of the dangling bond, can well control the interface trap and plays a role in chemical passivation; the second dielectric layer has the function that a large amount of hydrogen exists in the film deposition process, and chemical passivation can be formed on the surface of the silicon wafer. In addition, the contact surface of the film and the silicon has high fixed negative charge density, and can show good field passivation property by shielding minority carriers on the surface of the p-type silicon; the third dielectric layer and the fourth dielectric layer have similar functions, but the refractive index of the third dielectric layer is between that of the second dielectric layer and that of the fourth dielectric layer, so that the film design can better increase the light reflection on the back surface and improve the current; in addition, the third dielectric layer has a lower positive charge density than the fourth dielectric layer, which can reduce the effect on the negative charge of the second dielectric layer, i.e., the field passivation effect. The third dielectric layer and the fourth dielectric layer are provided with a large amount of free hydrogen atoms and hydrogen ions which can diffuse to a silicon-silicon oxide interface and combine with a silicon dangling bond at the interface to reduce the interface state density of the surface so as to achieve the effect of reducing the surface recombination rate, the surface of the battery is passivated, and simultaneously, hydrogen can also diffuse into the silicon wafer body to passivate defects and impurities in the silicon wafer body.

The utility model provides an among the back stromatolite passivation structure, contain a large amount of hydrogen ions or atom in the stromatolite membrane at the P type silicon substrate back, can pour into silicon chip surface and inside in follow-up annealing process or sintering process into, passivate compound center. The laminated passivation film has strong field passivation effect. Therefore, the utility model discloses a solar cell passivation structure has good passivation effect.

Following conduct the utility model discloses preferred technical scheme, nevertheless do not regard as right the utility model provides a technical scheme's restriction, through following preferred technical scheme, can be better reach and realize the utility model discloses a technical purpose and beneficial effect.

Preferably, the first dielectric layer is a silicon oxide layer and/or a silicon oxynitride layer.

Preferably, the thickness of the first dielectric layer is 1-10nm, such as 1nm, 2nm, 3nm, 4nm, 5nm, 6nm, 7nm, 8nm, 9nm, or 10nm, etc.

In the utility model, if the thickness of the first dielectric layer is too thin, the chemical passivation effect is unstable; if the thickness of the first dielectric layer is too thick, the negative charge of the second dielectric layer is shielded, resulting in a reduced field passivation effect.

Preferably, the second dielectric layer is an aluminum oxide layer.

Preferably, the thickness of the second dielectric layer is 1-60nm, such as 1nm, 5nm, 10nm, 20nm, 30nm, 40nm, 50nm, 60nm, or the like.

In the utility model, if the thickness of the second dielectric layer is too thin, the field passivation effect is weakened or unstable; if the thickness of the second dielectric layer is too thick, the back reflection effect of the laminated film is reduced, and the production cost is increased.

Preferably, the third dielectric layer is any one of a silicon oxide layer, a silicon oxynitride layer, a silicon nitride layer, or a silicon carbide layer, or a combination of at least two of them.

Preferably, the thickness of the third dielectric layer is 1-80nm, such as 1nm, 10nm, 20nm, 30nm, 40nm, 50nm, 60nm, 70nm, or 80nm, etc.

In the utility model, if the thickness of the third dielectric layer is too thick, the back laser grooving can be opened only by high-energy laser, and the high energy of the laser leads to the reduction of the service life of the silicon wafer body and the reduction of the battery conversion efficiency; the thickness of the third dielectric layer is too thick or too thin, which also results in a reduced back reflection effect.

Preferably, the refractive index of the third dielectric layer is 1.5-2.4, such as 1.5, 1.6, 1.7, 1.8, 1.9, 2.0, 2.1, 2.2, 2.3, 2.4, etc.

Preferably, the third dielectric layer is a stacked film structure having different refractive indexes.

Preferably, the third dielectric layer is a stacked film structure of silicon oxynitride having a refractive index in the range of 1.6 to 2.2 and silicon oxynitride having a refractive index in the range of 1.7 to 2.4.

Preferably, the third dielectric layer is a laminated film structure of a silicon oxynitride layer having a refractive index ranging from 1.5 to 2.35 and a silicon carbide layer having a refractive index ranging from 1.6 to 2.4.

Preferably, in the stacked film structure of the third dielectric layer, the refractive index of each film of the stacked film increases sequentially in a direction away from the P-type silicon substrate.

The utility model discloses in, adopt the stromatolite membrane that the refracting index was arranged like this in the third dielectric layer, can promote short-circuit current, this is because the stromatolite membrane structure that high low refracting index was arranged can strengthen the reflection of back light, guarantees the absorption utilization of long wave band light.

Illustratively, the stacked film structure of the third dielectric layer may be a 3-layer film structure, and a third dielectric layer first film, a third dielectric layer second film and a third dielectric layer third film are respectively arranged along a direction away from the P-type silicon substrate, the refractive index of the third dielectric layer first film is 1.5-2.2, the refractive index of the third dielectric layer second film is 1.6-2.3, and the refractive index of the third dielectric layer third film is 1.7-2.4.

Preferably, the thickness of the fourth dielectric layer is 1-200nm, such as 1nm, 20nm, 50nm, 70nm, 80nm, 90nm, 100nm, 120nm, 150nm, 180nm, or 200nm, etc.

The utility model discloses in, if fourth dielectric layer thickness is too thin, can lead to the film to weaken the effect of blockking of the corrosivity of back aluminium thick liquid or silver thick liquid, influence the passivation effect of stromatolite membrane. If the thickness of the fourth dielectric layer is too thick, the back laser grooving needs to be carried out by high-energy laser, the silicon wafer body can be opened by the high-energy laser, the service life of the silicon wafer body is shortened by the high energy of the laser, and the conversion efficiency of the battery is reduced. Too thick or too thin a film also results in a reduced back reflection effect.

Preferably, the refractive index of the fourth dielectric layer is 1.5-2.4, such as 1.5, 1.6, 1.7, 1.8, 1.9, 2.0, 2.1, 2.2, 2.3, 2.4, etc.

Preferably, the fourth dielectric layer is a stacked film structure having different refractive indexes.

Preferably, the fourth dielectric layer is a stacked film structure of a silicon oxynitride layer having a refractive index ranging from 1.6 to 2.2 and a silicon nitride layer having a refractive index ranging from 1.9 to 2.4.

Preferably, in the stacked film structure of the fourth dielectric layer, the refractive index of each film of the stacked film is sequentially increased in a direction away from the P-type silicon substrate.

The utility model discloses in, adopt the stromatolite membrane that the refracting index was arranged like this in the fourth dielectric layer, can promote short-circuit current, this is because the stromatolite membrane structure that high low refracting index was arranged can strengthen the reflection of back light, guarantees the absorption utilization of long wave band light.

Illustratively, the stacked film structure of the fourth dielectric layer may be a 3-layer film structure, and a fourth dielectric layer first film, a fourth dielectric layer second film and a fourth dielectric layer third film are respectively arranged along a direction away from the P-type silicon substrate, the refractive index of the fourth dielectric layer first film is 1.5-2.2, the refractive index of the fourth dielectric layer second film is 1.6-2.3, and the refractive index of the fourth dielectric layer third film is 1.7-2.4.

Preferably, the refractive index of the third dielectric layer is smaller than the refractive index of the fourth dielectric layer.

As the preferred technical proposal of the utility model, the solar cell laminated passivation structure also comprises N which is arranged on the front surface of the P-type silicon substrate from inside to outside in sequence ⁺⁺ Heavy diffusion region and N ⁺ A light diffusion region, a fifth dielectric layer, and a sixth dielectric layer.

In the utility model, N ⁺ The light diffusion region refers to a region formed by phosphorus doping, N being a region having a relatively low phosphorus concentration ⁺⁺ The heavily diffused region is a region having a relatively high phosphorus doping concentration formed by laser doping or high-temperature diffusion in order to obtain a relatively high metal contact resistance and a relatively low recombination current of the metal region.

Preferably, the fifth dielectric layer is a silicon oxide layer.

Preferably, the thickness of the fifth dielectric layer is 1-10nm, such as 1nm, 2nm, 5nm, 8nm, 10nm, or the like.

Preferably, the sixth dielectric layer is any one of a silicon oxide layer, a silicon oxynitride layer, a silicon nitride layer, or a silicon carbide layer, or a combination of at least two of them.

Preferably, the thickness of the sixth dielectric layer is 50-150nm, such as 50nm, 100nm, 150nm, or the like.

Preferably, the solar cell stack passivation structure further comprises a sixth dielectric layer, a fifth dielectric layer and N ⁺⁺ A front Ag electrode in contact with the heavy diffusion region.

Preferably, the solar cell stack passivation structure further includes an aluminum back surface field sequentially passing through the fourth dielectric layer, the third dielectric layer, the second dielectric layer and the first dielectric layer and then connecting to the P-type silicon substrate.

The utility model provides a solar cell stromatolite passivation structure can prepare according to following method, the method includes following step:

and oxidizing the back surface of the P-type silicon substrate to generate a first dielectric layer, and then sequentially depositing a second dielectric layer, a third dielectric layer and a fourth dielectric layer on the first dielectric layer.

The utility model provides a method easy operation, the flow is short, and low cost easily carries out extensive industrial production, can make the utility model provides a solar cell stromatolite passivation structure has good industrialization prospect.

The growth method of the first dielectric layer comprises any one of a thermal oxidation method, a solution method or a Plasma Enhanced Chemical Vapor Deposition (PECVD) method or a combination of at least two of the methods.

The first dielectric layer is silicon oxide film, and its growth method can be thermal oxidation method, solution method or plasma enhanced chemical vapor deposition method; if the first dielectric layer contains silicon oxide/silicon oxynitride of silicon oxide film, the silicon oxide film can be grown by thermal oxidation, solution or plasma enhanced chemical vapor deposition; the silicon oxynitride film is grown by plasma enhanced chemical vapor deposition.

Preferably, the method of depositing the second dielectric layer is Plasma Enhanced Chemical Vapor Deposition (PECVD) or Atomic Layer Deposition (ALD).

Preferably, the method of depositing the third dielectric layer is Plasma Enhanced Chemical Vapor Deposition (PECVD) or Atomic Layer Deposition (ALD).

Preferably, the method of depositing the fourth dielectric layer is Plasma Enhanced Chemical Vapor Deposition (PECVD) or Atomic Layer Deposition (ALD).

Preferably, the method further comprises: preparation of N ⁺⁺ Heavily diffused region and N ⁺ And depositing a fifth dielectric layer and a sixth dielectric layer.

Preferably, the method of depositing the fifth dielectric layer is plasma enhanced chemical vapor deposition.

Preferably, the method of depositing the sixth dielectric layer is plasma enhanced chemical vapor deposition.

As a further preferable technical solution of the above preparation method, the method comprises the steps of:

the method comprises the following steps: removing a mechanical damage layer of the P-type silicon substrate by using alkaline corrosive liquid, corroding the surface of the silicon substrate by using the alkaline corrosive liquid, forming a pyramid structure on the front surface of the P-type silicon substrate, and then diffusing on the front surface of the P-type silicon substrate to form N ⁺ A light diffusion region, performing laser doping to obtain N ⁺⁺ And a heavy diffusion region, removing the back junction of the P-type silicon substrate, polishing the back surface of the P-type silicon substrate, oxidizing the P-type silicon substrate to generate a first dielectric layer and a fifth dielectric layer, sequentially depositing a second dielectric layer, a third dielectric layer and a fourth dielectric layer on the first dielectric layer, depositing a sixth dielectric layer on the fifth dielectric layer, printing a back surface Ag electrode, drying, printing a back surface Al slurry, forming an aluminum back surface field, and printing a front surface Ag electrode.

Compared with the prior art, the utility model discloses following beneficial effect has:

the utility model provides a solar cell back lamination passivation structure which can effectively exert the field passivation effect of the negative charges of the film,the chemical passivation effect of the interface film is good, meanwhile, the light reflection effect of the back of the cell is greatly enhanced through the optimization of the refractive index of each dielectric film, the open-circuit voltage of the laminated passivation structure on the back of the solar cell can reach more than 694mV, and the short-circuit current is 40.80mA/cm ² Above, the conversion efficiency is as high as 23.08%. Therefore the utility model discloses a solar cell passivation structure has good passivation effect and light reflection effect.

Drawings

FIG. 1 is a schematic cross-sectional view of a passivation structure of a solar cell stack provided in example 1 (the front surface of the cell is a textured structure, and is specially drawn as a plane for simplicity)

Wherein:

a 1-P type silicon substrate is provided,

2-a first dielectric layer, a second dielectric layer,

3-a second dielectric layer, the second dielectric layer,

4-a third dielectric layer, the third dielectric layer,

5-a fourth dielectric layer, the first dielectric layer,

6-an aluminum back surface field is formed,

7-a sixth dielectric layer, the first dielectric layer,

8-N ⁺⁺ the area of heavy diffusion is formed,

9-N ⁺ the light diffusion region is formed on the substrate,

10-a fifth dielectric layer, the first dielectric layer,

11-front Ag electrode.

FIG. 2 is a schematic cross-sectional view showing a back-side-stacked passivation structure of a solar cell using the structure provided in example 1 (the front side of the cell is a textured structure, and is particularly drawn as a plane for simplicity)

Wherein:

a 1-P type silicon substrate is provided,

2-a first dielectric layer, a second dielectric layer,

3-a second dielectric layer, the second dielectric layer,

4-a third dielectric layer, the third dielectric layer,

5-fourth dielectric layer.

Detailed Description

To better explain the utility model, the technical proposal of the utility model is convenient to understand, and the utility model is further explained in detail below. However, the following embodiments are only simple examples of the present invention, and do not represent or limit the scope of the present invention, which is defined by the appended claims.

The utility model discloses in, as a specific implementation mode, solar cell stromatolite passivation structure, including P type silicon substrate, P type silicon substrate back be equipped with first SiO from inside to outside in proper order ₂ Film, al ₂ O ₃ Layer, siO _x N _y A film and a first SiNx film. The aluminum back surface field sequentially passes through the first SiN _x Film, siO _x N _y Film, al ₂ O ₃ Layer and first SiO ₂ The film is connected with a P-type silicon substrate.

First SiO ₂ The thickness of the film is 1-10nm, al ₂ O ₃ The layer is deposited by PECVD method or ALD method, the thickness is 1-50nm _x N _y The film is deposited by PECVD method with a thickness of 1-80nm and a first SiN layer _x SiN deposited by PECVD method _x The film has a thickness of 20-150nm.

Preferably, the first SiO ₂ The thickness of the film is 1-5nm ₂ O ₃ The layer is deposited by PECVD method or ALD method, the thickness is 1-50nm _x N _y The film is deposited by PECVD method with a thickness of 1-80nm and a first SiN layer _x SiN with film deposited by PECVD method _x The film has a thickness of 20-150nm.

The front surface of the P-type silicon substrate is sequentially provided with an N + + heavy diffusion region, an N + light diffusion region and a second SiO from inside to outside ₂ A film and a second SiNx film.

In this embodiment, the stacked film on the back surface of the P-type silicon substrate contains a large amount of H +, which is injected into the surface and the inside of the silicon wafer in the subsequent annealing process or sintering process to passivate the recombination center. The laminated passivation film has strong field effect passivation, and the two layers are superposed to have a very good passivation effect.

As another specific embodiment, the solar cell stack passivation structure includes a P-type silicon substrate, and the back surface of the P-type silicon substrate is sequentially provided with a first SiO from inside to outside ₂ Film, al ₂ O ₃ Layer, siO _x N _y Film and first SiN _x And (3) a membrane. Aluminum back field deviceSecond pass first SiN _x Film, siO _x N _y Film, al ₂ O ₃ Layer and first SiO ₂ The film is connected with a P-type silicon substrate.

Specifically, a KOH solution with the volume ratio of 47% is used for removing the mechanical damage layer of the P-type silicon wafer by 2-3 microns, and then the KOH solution with the volume ratio of 47% is used for corroding the surface of the silicon wafer to form a pyramid structure with the thickness of 2-3 microns.

Using a POCL ₃ And diffusing by liquid low-pressure diffusion to form a light diffusion area, wherein the diffusion temperature is 810 ℃, the process time is 90min, and the diffusion sheet resistance is controlled to be 120-170 ohm/sq.

And (3) laser SE doping, wherein the diffused phosphorus atoms in the phosphorosilicate glass are subjected to laser doping at high temperature through laser to form a local N + + heavy diffusion region, and the diffusion sheet resistance is 50-100ohm/sq.

And removing the back junction by using a chain type cleaning machine, polishing the back surface of the silicon wafer by 3-4 mu m, and removing the peripheral p-n junction.

Oxidation creates thin SiO on the back, front and edges of the wafer ₂ Film of first SiO ₂ Film and second SiO ₂ The thickness of the film is 1-5nm respectively.

PECVD deposition of backside Al ₂ O ₃ Layer with a thickness of 1-50nm.

PECVD deposition of backside SiO _x N _y The film has a thickness of 5-30nm.

And depositing a first SiNx film on the back surface by PECVD, wherein the thickness of the first SiNx film is 4-100nm.

And depositing a second SiNx film on the front surface by a PECVD method, wherein the thickness of the second SiNx film is 50-100nm.

And (3) adopting a 532nm ns laser to perform local grooving on the laminated film on the back surface, and opening the laminated passivation film.

And printing back Al slurry after drying the printed back Ag electrode to form an aluminum back field. The front side Ag cell was printed and rapidly sintered at 875 ℃ to form a good ohmic contact. And (6) testing and sorting.

As another specific embodiment, the solar cell stack passivation structure includes a P-type silicon substrate, and the back surface of the P-type silicon substrate is sequentially provided with a first SiO layer from inside to outside ₂ Film, al ₂ O ₃ Layer, siOxNy film and first SiN _x And (3) a film. The aluminum back field sequentially passes through the first SiNx film and the SiO _x N _y Film, al ₂ O ₃ Layer and first SiO ₂ The P-type silicon substrate 1 is connected behind the film.

Specifically, 3 microns of a mechanical damage layer of the P-type silicon wafer is removed by using a KOH solution with the volume ratio of 47%, and then the surface of the silicon wafer is corroded by using the KOH solution with the volume ratio of 47% to form a pyramid structure with the size of 2-3 microns.

Using a POCL ₃ Diffusing by liquid low-pressure diffusion to form a p-N junction, namely an N + light diffusion region, wherein the diffusion temperature is 810 ℃, the process time is 90min, and the diffusion sheet resistance is controlled between 150-170 ohm/sq.

And (3) laser SE doping, wherein the diffused phosphorus atoms in the phosphorosilicate glass are subjected to laser doping through laser high temperature to form a local heavily doped region, and the diffusion sheet resistance is 40-100ohm/sq.

Oxidation creates thin SiO on the back, front and edges of the wafer ₂ Film of first SiO ₂ Film and second SiO ₂ The thickness of the film is 1-10nm.

ALD method for depositing backside Al ₂ O ₃ A layer with a thickness of 5-50nm.

PECVD sequentially depositing SiO on the back _x N _y Film and first SiN _x The film thickness is 5-50nm and 40-100nm respectively.

And depositing a SiNx film on the front surface by a PECVD method, wherein the thickness is 20-120nm.

And printing back Al paste after drying the printed back Ag electrode to form an aluminum back field. The front side Ag cell was printed and rapidly sintered at 875 ℃ to form a good ohmic contact.

Testing and sorting.

As a further embodiment, the solar cell stack passivation structure comprises a P-type silicon substrate with a back side from inside to outsideA first SiO is arranged outside the first chamber in sequence ₂ Film, al ₂ O ₃ Layer, siO _x N _y Film, silicon carbide film, siO _x N _y Film and first SiN _x And (3) a film. The aluminum back field sequentially passes through the first SiNx film and the SiO _x N _y Film, silicon carbide film, siO _x N _y Film, al ₂ O ₃ Layer and first SiO ₂ The P-type silicon substrate 1 is connected behind the film.

And (3) laser SE doping, wherein laser doping is carried out on phosphorus atoms in the diffused phosphorosilicate glass at high temperature through laser to form a local heavily doped region, and the diffusion sheet resistance is 40-100ohm/sq.

PECVD sequentially depositing SiO on the back _x N _y Film, silicon carbide film, siO _x N _y Film and first SiN _x The thickness of the film is 5-50nm, 5-10nm, 40-100nm and 40-100nm respectively.

PECVD method for depositing front SiN _x The film is 20-120nm thick.

Testing and sorting.

The following are typical but non-limiting examples of the present invention:

example 1

The embodiment provides a solar cell stacked passivation structure, as shown in fig. 1 and fig. 2, the solar cell stacked passivation structure includes a P-type silicon substrate 1, a first dielectric layer 2, a second dielectric layer 3, a third dielectric layer 4 and a fourth dielectric layer 5 are sequentially disposed on the back surface of the P-type silicon substrate 1 from inside to outside, an aluminum back field 6 connected to the P-type silicon substrate 1 after sequentially passing through the fourth dielectric layer 5, the third dielectric layer 4, the second dielectric layer 3 and the first dielectric layer 2, and N sequentially disposed on the front surface of the P-type silicon substrate 1 from inside to outside ⁺⁺ Heavy diffusion regions 8, N ⁺ A light diffusion region 9, a fifth dielectric layer 10 and a sixth dielectric layer 7. The solar cell stack passivation structure provided by this embodiment further includes a front Ag electrode 11, where the front Ag electrode 11 penetrates through the sixth dielectric layer 7 and the fifth dielectric layer 10 into N ⁺⁺ In the heavy diffusion region 8.

In the solar cell stacked passivation structure provided in this embodiment, the first dielectric layer 2 is a silicon oxide film having a thickness of 2nm, the second dielectric layer 3 is an aluminum oxide film having a thickness of 10nm, the third dielectric layer 4 is a silicon oxynitride stacked film having a total thickness of 8nm and a refractive index of 1.8, the fourth dielectric layer 5 is a silicon nitride stacked film having a total thickness of 60nm and a refractive index of 2.1, n ⁺ The diffusion sheet resistance of the light diffusion region 9 was 150ohm/sq, N ⁺⁺ The diffusion sheet resistance of the heavy diffusion region 8 was 75ohm/sq, the fifth dielectric layer 10 was a silicon oxide film with a thickness of 2nm, the sixth dielectric layer 7 was a silicon nitride film with a thickness of 75nm and a refractive index of 2.0.

The third dielectric layer 4 is a three-layer silicon oxynitride laminated film, and a first film of the third dielectric layer 4, a second film of the third dielectric layer 4 and a third film of the third dielectric layer 4 are respectively arranged along the direction far away from the P-type silicon substrate 1, the refractive index of the first film of the third dielectric layer 4 is 1.7, the refractive index of the second film of the third dielectric layer 4 is 1.8, and the refractive index of the third film of the third dielectric layer 4 is 1.9.

The fourth dielectric layer 5 is a three-layer silicon nitride laminated film, a first film of the fourth dielectric layer 5, a second film of the fourth dielectric layer 5 and a third film of the fourth dielectric layer 5 are respectively arranged along the direction far away from the P-type silicon substrate 1, the refractive index of the first film of the fourth dielectric layer 5 is 2.0, the refractive index of the second film of the fourth dielectric layer 5 is 2.1, and the refractive index of the third film of the fourth dielectric layer 5 is 2.2.

In the solar cell stacked passivation structure provided by the embodiment, N ⁺ The light diffusion region 9 is a tubular liquid phosphorus source diffusion, N ⁺⁺ The heavily diffused region 8 is laser doped.

The method for preparing the passivation structure of the battery stack provided by the embodiment comprises the following specific steps:

(1) Removing the mechanically damaged layer of the P-type silicon wafer by 1.5 μm using 2% by mass of KOH solution, and then etching the surface of the silicon wafer by using 3% by mass of KOH solution to form pyramid structures having a size of 1.5 μm.

(2) Using POCl ₃ Diffusing by liquid diffusion to form N ⁺ And a light diffusion region 9, wherein the diffusion temperature is 810 ℃, and the process time is 90min.

(3) Laser SE doping, wherein the diffused phosphorus atoms in the phosphorus-silicon glass are subjected to laser doping at high temperature to form local N ⁺⁺ A heavy diffusion region 8.

(4) And removing the back junction by using a chain type cleaning machine, polishing the back surface of the silicon wafer by 3.5 mu m, and removing the peripheral p-n junction.

(5) Thermal oxidation produces a thin silicon oxide film on the back, front and edge of the silicon wafer, as the first 2 and fifth 10 dielectric layers, 2nm thick.

(6) A backside alumina film is deposited by PECVD as the second dielectric layer 3.PECVD deposits a back silicon oxynitride film as the third dielectric layer 4.PECVD deposits a back silicon nitride film as the fourth dielectric layer 5.

(7) The PECVD method deposits a front silicon nitride film as the sixth dielectric layer 7.

(8) And (3) adopting a 532nm ns laser to perform local grooving on the laminated film on the back surface, and opening the laminated passive film.

(9) And printing the front Ag paste 11 and quickly sintering at 875 ℃ to form good ohmic contact after drying the printing back Ag paste and then drying the printing back Al paste 6.

Example 2

The solar cell stacked passivation structure provided in this embodiment is different from that of embodiment 1 in that the first dielectric layer 2 is a silicon oxide/silicon oxynitride stacked film having a film thickness of 3nm, the second dielectric layer 3 is an aluminum oxide film having a film thickness of 10nm, the third dielectric layer 4 is a stacked film composed of a silicon oxynitride film, a silicon nitride film and a silicon carbide film, the stacked film has a total thickness of 20nm and a refractive index of 1.8, the fourth dielectric layer is a stacked film composed of a silicon carbide film, a silicon oxynitride film and a silicon nitride film, the stacked film has a total thickness of 60nm, the diffusion sheet resistance of the light diffusion region 9 having a refractive index of 2.1, N + is 150ohm/sq, the diffusion sheet resistance of the heavy diffusion region 8 of N + + is 75ohm/sq, the fifth dielectric layer 10 is a silicon oxide film having a thickness of 2.5nm, the sixth dielectric layer 7 is a silicon nitride film having a thickness of 75nm and a refractive index of 2.0.

The third dielectric layer 4 is a laminated film composed of a silicon oxynitride film, a silicon nitride film and a silicon carbide film, and is a first film (silicon oxynitride film) of the third dielectric layer 4, a second film (silicon nitride film) of the third dielectric layer 4 and a third film (silicon carbide film) of the third dielectric layer 4 respectively along a direction away from the P-type silicon substrate 1, wherein the refractive index of the first film of the third dielectric layer 4 is 1.7, the refractive index of the second film of the third dielectric layer 4 is 1.9, and the refractive index of the third film of the third dielectric layer 4 is 2.0.

The fourth dielectric layer 5 is a laminated film composed of a silicon carbide film, a silicon oxynitride film and a silicon nitride film, and the first film (the silicon carbide film), the second film (the silicon oxynitride film) and the third film (the silicon nitride film) of the fourth dielectric layer 5 are respectively arranged along the direction far away from the P-type silicon substrate 1, the refractive index of the first film of the fourth dielectric layer 5 is 2.05, the refractive index of the second film of the fourth dielectric layer 5 is 2.1, and the refractive index of the third film of the fourth dielectric layer 5 is 2.15.

A method for preparing a passivation structure of a battery stack provided by the embodiment comprises the following specific steps:

(1) Removing the mechanical damage layer of the P-type silicon wafer by using KOH solution with the mass ratio of 2 percent for 1.5 mu m, and then corroding the surface of the silicon wafer by using KOH solution with the mass ratio of 3 percent to form a pyramid structure with the size of 1.5 mu m.

(2) Using POCl ₃ Diffusing by liquid diffusion to form N ⁺ And in the light diffusion region 9, the diffusion temperature is 810 ℃, and the process time is 90min.

(5) Wet oxidation generates thin silicon oxide films on the front side and the edge of the back side of the silicon wafer, the thin silicon oxide films are a first dielectric layer 2 and a fifth dielectric layer 10, the thickness of the thin silicon oxide films is 1nm, a back side silicon oxynitride film is deposited by PECVD, the thin silicon oxide films are a first dielectric layer 2, and the thickness of the thin silicon oxide films is 2nm.

(6) A backside alumina film is deposited by PECVD as the second dielectric layer 3.PECVD deposits a back silicon oxynitride film, a silicon nitride film, and a silicon carbide film as the third dielectric layer 4. The PECVD deposits a back silicon carbide film, a silicon oxynitride film, and a silicon nitride film as the fourth dielectric layer 5.

(8) And (3) adopting a 532nm ns laser to perform local grooving on the laminated film on the back surface, and opening the laminated passivation film.

Example 3

The solar cell stacked passivation structure provided in this embodiment is similar to that of embodiment 1 except that the first dielectric layer 2 is a silicon oxide film having a thickness of 2nm, the second dielectric layer 3 is an aluminum oxide film having a thickness of 10nm, the third dielectric layer 4 is a silicon oxynitride film having a thickness of 20nm and a refractive index of 1.9, the fourth dielectric layer is two silicon nitride films having a thickness of 20nm and 40nm, respectively, and a refractive index of 2.0 and 2.1, respectively, n ⁺ The diffusion sheet resistance of the light diffusion region 9 was 150ohm/sq, N ⁺⁺ The diffusion sheet resistance of the heavy diffusion region 8 was 75ohm/sq, the fifth dielectric layer 10 was a silicon oxide film with a thickness of 2.5nm, and the fifth dielectric layer was a silicon oxide filmThe six dielectric layers 7 are silicon nitride films with a thickness of 75nm and a refractive index of 2.0.

Example 4

The solar cell stacked passivation structure provided in this embodiment is different from that of embodiment 2 only in that the structure of the stacked film of the fourth dielectric layer, specifically, the fourth dielectric layer is provided as the stacked film composed of the silicon oxynitride film and the silicon nitride film, the total thickness of the stacked film is 60nm, and the refractive index is 2.1.

Accordingly, the fourth dielectric layer 5 is a laminated film of a silicon oxynitride film and a silicon nitride film, and a first film (silicon oxynitride film) and a second film (silicon nitride film) of the fourth dielectric layer 5 are provided along a direction away from the P-type silicon substrate 1, respectively, the refractive index of the first film of the fourth dielectric layer 5 is 2.1, and the refractive index of the second film of the fourth dielectric layer 5 is 2.15.

The method for preparing the solar cell stack passivation structure of the present embodiment is different from that of embodiment 2 only in that: in the step (6), a back silicon oxynitride film and a silicon nitride film are deposited by PECVD, which is the fourth dielectric layer 5.

Comparative example 1

The present comparative example is different from example 1 in that the solar cell stack passivation structure provided by the present comparative example is not provided with the first dielectric layer 2.

Comparative example 2

The present comparative example is different from example 1 in that the solar cell stack passivation structure provided by the present comparative example is not provided with the third dielectric layer 4.

Comparative example 3

The present comparative example is different from example 2 in that the solar cell stack passivation structure provided by the present comparative example does not have a silicon oxynitride layer in the first dielectric layer 2, and thus does not form a stack structure.

Comparative example 4

The difference between the comparative example and the example 3 is that the solar cell laminated passivation structure provided by the comparative example is not provided with the fourth dielectric layer 5 of the laminated structure, and the fourth dielectric layer is a silicon nitride film, has the thickness of 60nm and the refractive index of 2.1.

The results for the different cell configurations are shown in the following table:

TABLE 1

The above-mentioned cell efficiency test is a standard test condition of Irradiance (Irradiance) 1000W/m ² Cell Temperature (Cell Temperature) 25 ℃, atmospheric Mass (Air Mass) AM1.5.

Compared with the example 1, the chemical passivation effect of the battery is weakened because the first dielectric layer 2 is not arranged, the Voc of the battery is lower by 2mV, and the efficiency is lower by 0.1 percent in the example 1.

Compared with the embodiment 1, the field passivation effect of the second dielectric layer is weakened, the back light reflection effect is weakened, the open-circuit voltage of the battery is lower by 3mV, and the current density is lower by 0.1mA/cm because the third dielectric layer 4 is not arranged in the embodiment 1 ² The efficiency is lower than 0.18 percent.

Comparative example 3 compared with example 2, the chemical passivation effect is unstable because the first dielectric layer 2 with a laminated structure is not provided, the Voc of the battery is lower by 1.5mV, and the efficiency is lower by 0.1%.

Comparative example 4 compared with example 3, since the fourth dielectric layer 5 having a stacked structure was not provided, the back light reflection effect was also reduced, and the current density was lowered by 0.09mA/cm ² The efficiency is lower than 0.05%.

From the above results, it can be seen that the passivation structures of the solar cell backside stack provided in examples 1 to 4 have very good chemical passivation and field passivation effects.

The applicant states that the present invention is described by the above embodiments, but the present invention is not limited to the above detailed method, that is, the present invention must not rely on the above detailed method to be implemented. It should be clear to those skilled in the art that any improvement of the present invention, to the equivalent replacement of each raw material of the present invention, the addition of auxiliary components, the selection of specific modes, etc., all fall within the protection scope and disclosure scope of the present invention.

Claims

1. The solar cell laminated passivation structure is characterized by comprising a P-type silicon substrate (1), and a first dielectric layer (2), a second dielectric layer (3), a third dielectric layer (4) and a fourth dielectric layer (5) which are sequentially arranged on the back surface of the P-type silicon substrate (1) from inside to outside;

the fourth dielectric layer (5) is a combination of at least two of a silicon oxide layer, a silicon oxynitride layer, a silicon nitride layer and a silicon carbide layer.

2. Solar cell stack passivation structure according to claim 1, characterized in that the first dielectric layer (2) is a silicon oxide layer and/or a silicon oxynitride layer.

3. Solar cell stack passivation structure according to claim 1 or 2, characterized in that the thickness of the first dielectric layer (2) is 1-10nm.

4. Solar cell stack passivation structure according to claim 1, characterized in that the second dielectric layer (3) is an aluminum oxide layer.

5. Solar cell stack passivation structure according to claim 1 or 4, characterized in that the thickness of the second dielectric layer (3) is 1-60nm.

6. Solar cell stack passivation structure according to claim 1, characterized in that the third dielectric layer (4) is any one or a combination of at least two of a silicon oxide layer, a silicon oxynitride layer, a silicon nitride layer or a silicon carbide layer.

7. Solar cell stack passivation structure according to claim 1, characterized in that the thickness of the third dielectric layer (4) is 1-80nm.

8. Solar cell stack passivation structure according to claim 1, characterized in that the refractive index of the third dielectric layer (4) is 1.5-2.4.

9. Solar cell stack passivation structure according to claim 1, characterized in that the third dielectric layer (4) is a stacked film structure of different refractive indices.

10. The solar cell stack passivation structure according to claim 9, characterized in that the third dielectric layer (4) is a stacked film structure of silicon oxynitride having a refractive index in the range of 1.6-2.2 and silicon oxynitride having a refractive index in the range of 1.7-2.4.

11. The solar cell stack passivation structure according to claim 9, characterized in that the third dielectric layer (4) is a laminated film structure of a silicon oxynitride layer having a refractive index in the range of 1.5-2.35 and a silicon carbide layer having a refractive index in the range of 1.6-2.4.

12. The solar cell stack passivation structure according to claim 9, characterized in that in the stacked film structure of the third dielectric layer (4), the film refractive index of each of the stacked films increases sequentially in a direction away from the P-type silicon substrate (1).

13. Solar cell stack passivation structure according to claim 1, characterized in that the thickness of the fourth dielectric layer (5) is 1-200nm.

14. Solar cell stack passivation structure according to claim 1, characterized in that the refractive index of the fourth dielectric layer (5) is 1.5-2.4.

15. Solar cell stack passivation structure according to claim 1, characterized in that the fourth dielectric layer (5) is a stacked film structure of different refractive indices.

16. The solar cell stack passivation structure according to claim 15, characterized in that the fourth dielectric layer (5) is a laminated film structure of a silicon oxynitride layer having a refractive index in the range of 1.6-2.2 and a silicon nitride layer having a refractive index in the range of 1.9-2.4.

17. The solar cell stack passivation structure according to claim 15, characterized in that the stacked film structure of the fourth dielectric layer (5) has sequentially increasing film refractive indices along a direction away from the P-type silicon substrate (1).

18. Solar cell stack passivation structure according to claim 1, characterized in that the refractive index of the third dielectric layer (4) is smaller than the refractive index of the fourth dielectric layer (5).

19. The solar cell stack passivation structure according to claim 1, further comprising N sequentially disposed from inside to outside on the front side of the P-type silicon substrate (1) ⁺⁺ Heavy diffusion region (8), N ⁺ A light diffusion region (9), a fifth dielectric layer (10) and a sixth dielectric layer (7).

20. Solar cell stack passivation structure according to claim 19, characterized in that the fifth dielectric layer (10) is a silicon oxide layer.

21. Solar cell stack passivation structure according to claim 19, characterized in that the thickness of the fifth dielectric layer (10) is 1-10nm.

22. The solar cell stack passivation structure according to claim 19, characterized in that the sixth dielectric layer (7) is any one or a combination of at least two of a silicon oxide layer, a silicon oxynitride layer, a silicon nitride layer or a silicon carbide layer.

23. Solar cell stack passivation structure according to claim 19, characterized in that the thickness of the sixth dielectric layer (7) is 50-150nm.

24. The solar cell stack passivation structure of claim 19, further comprising a sixth dielectric layer (7), a fifth dielectric layer (10), and N ⁺⁺ A front Ag electrode (11) in contact with the heavy diffusion region (8).

25. The solar cell stack passivation structure according to claim 1, characterized in that it further comprises an aluminum back field (6) connected to the P-type silicon substrate (1) through a first dielectric layer (2), a second dielectric layer (3), a third dielectric layer (4) and a fourth dielectric layer (5) in sequence.