TWI705572B - Solar cell having silicon oxynitride passivation layer and method for manufacturing the same - Google Patents

Abstract

The present invention provides a solar cell with a ruthenium oxynitride passivation layer, which includes a first conductive type silicon substrate, a second conductive type electric field layer, a back passivation layer, a back passivation protective layer and a back aluminum metal layer. The first conductive type silicon substrate has an upper surface and a lower surface, the second conductive type electric field layer is disposed on the upper surface of the first conductive type silicon substrate, and the back passivation layer is disposed on the lower surface of the first conductive type silicon substrate, the back passivation protective layer is disposed on the other side of the back passivation layer opposite to the first conductive type silicon substrate, and the back passivation protective layer includes a silicon oxynitride passivation layer. The back aluminum metal layer is disposed on the other side of the back passivation protective layer opposite to the back passivation layer, and includes a plurality of contacts, the back passivation layer and the back passivation protective layer have a plurality of through holes, and the plurality of contacts respectively correspond to Set through the hole.

Description

Solar cell with silicon oxynitride passivation layer and manufacturing method thereof

The invention relates to a solar cell and a manufacturing method thereof, in particular to a solar cell with a silicon oxynitride passivation layer and a manufacturing method thereof.

At present, the existing solar cell products on the market belong to the front junction solar cell, which uses a silicon wafer as the base material, and the emitter is formed on the front side of the silicon wafer by diffusion, and the entire surface is formed on the back side. The aluminum paste is sintered, so that aluminum atoms diffuse into the p-type silicon wafer during the sintering process to form a full-surface back electric field. However, the design of the aforementioned full-surface back electric field of this type of solar cell prevents the aluminum-silicon interface from being properly passivated. It serves as a full-surface back electric field and also a carrier recombination center, thereby limiting the overall conversion efficiency of the solar cell.

Silicon crystalline solar cells currently have the highest market share and also have a variety of structures. The current research and development goal is to improve conversion efficiency while minimizing manufacturing costs. In recent years, the industry has begun to focus on high-efficiency cells on the passivation layer on the back of the cell. Therefore, in recent years, Passivated Emitter and Rear Cell (PERC) solar cells have been developed to improve the conversion efficiency of solar cells. . Alumina or silicon oxynitride is added to the back of the PERC solar cell as a passivation layer, and a local back electric field is formed by sintering aluminum paste in a partially open manner.

On the other hand, PERC solar cells can improve long-wavelength absorption, so the improvement of cell efficiency can be better reflected in the improvement of module efficiency. Generally speaking, the efficiency of solar cells is limited by the degree of recombination of electron holes during photoelectric conversion. In PERC solar cells, a dielectric passivation layer is added to the back of the cell to improve the conversion efficiency. The PERC battery maximizes the potential gradient across the PN junction, which enables a more stable flow of electrons and reduces the recombination of electron holes to achieve a higher efficiency level.

Therefore, there is an urgent need in the art for a solar cell and its manufacturing method that can be optimized for the passivation layer to improve cell efficiency.

The technical problem to be solved by the present invention is to provide a solar cell with a silicon oxynitride passivation layer and a manufacturing method thereof in view of the shortcomings of the prior art.

In order to solve the above technical problems, one of the technical solutions adopted by the present invention is to provide a solar cell with a silicon oxynitride passivation layer, which includes a first conductivity type silicon substrate, a second conductivity type electric field layer, a back passivation layer, The back passivation protective layer and the back aluminum metal layer. The first conductivity type silicon substrate has an upper surface and a lower surface, the second conductivity type electric field layer is arranged on the upper surface of the first conductivity type silicon substrate, and the back passivation layer is arranged on the lower surface of the first conductivity type silicon substrate The back passivation protection layer is disposed on the other side of the back passivation layer opposite to the first conductivity type silicon substrate, wherein the back passivation protection layer includes a silicon oxynitride passivation layer. The back aluminum metal layer is disposed on the other side of the back passivation protection layer relative to the back passivation layer, and includes a plurality of contacts. The back passivation layer and the back passivation protection layer have a plurality of through holes, and the contacts correspond to some Set through holes.

In order to solve the above technical problem, another technical solution adopted by the present invention is to provide a method for manufacturing a solar cell with a silicon oxynitride passivation layer, which includes forming a first conductivity type silicon substrate, the first conductivity type The silicon substrate has an upper surface and a lower surface; a second conductivity type electric field layer is formed on the upper surface of the first conductivity type silicon substrate through a diffusion process; a back passivation layer is deposited on the first conductivity type through a deposition process On the lower surface of the conductive silicon substrate; a back passivation layer is plated on the other side of the back passivation layer opposite to the first conductive silicon substrate through a coating process, wherein the back passivation layer includes an oxynitride Silicon passivation layer; forming a plurality of through holes in the back passivation layer and the back protective passivation layer by a laser process; and printing a back aluminum metal layer on the back protective passivation layer relative to the back passivation layer by a screen printing process On the other side of the back passivation layer, a plurality of contacts corresponding to the through holes are formed.

One of the beneficial effects of the present invention is that the solar cell with a silicon oxynitride passivation layer and its manufacturing method provided by the present invention uses an aluminum oxide passivation layer and a silicon oxynitride passivation layer in the existing manufacturing process to improve back reflectivity. To increase the short-circuit current and reduce the series resistance, thereby increasing the efficiency by about 0.1% compared to the sample. In addition, the protection layer process integration can reduce the risk of automated fragmentation.

In order to further understand the features and technical content of the present invention, please refer to the following detailed description and drawings about the present invention. However, the provided drawings are only for reference and description, and are not used to limit the present invention.

The following are specific examples to illustrate the implementation of the “solar cell with silicon oxynitride passivation layer and its manufacturing method” disclosed in the present invention. Those skilled in the art can understand the advantages of the present invention from the content disclosed in this specification. And effect. The present invention can be implemented or applied through other different specific embodiments, and various details in this specification can also be modified and changed based on different viewpoints and applications without departing from the concept of the present invention. In addition, the drawings of the present invention are merely schematic illustrations, and are not drawn according to actual dimensions, and are stated in advance. The following embodiments will further describe the related technical content of the present invention in detail, but the disclosed content is not intended to limit the protection scope of the present invention.

It should be understood that although terms such as “first”, “second”, and “third” may be used herein to describe various elements or signals, these elements or signals should not be limited by these terms. These terms are mainly used to distinguish one element from another, or one signal from another signal. In addition, the term "or" used in this document may include any one or a combination of more of the associated listed items depending on the actual situation.

[First Embodiment]

FIG. 1 is a schematic cross-sectional view of an n-type back emitter bifacial solar cell provided by an embodiment of the present invention. Referring to FIG. 1, the first embodiment of the present invention provides a solar cell 10 with a silicon oxynitride passivation layer. The solar cell 10 is specifically a Passivated Emitter and Rear Cell (PERC) solar cell. It includes a first conductive type silicon substrate 100, a second conductive type electric field layer 102, a back passivation layer 104, a back passivation protection layer 106, a back aluminum metal layer 108, and a front passivation layer 110. The first conductive type silicon substrate 100 can be, for example, a P-type silicon substrate, which has an upper surface S1 and a lower surface S2. In the embodiment of the present invention, the direction of the upper surface S1 is defined as the front surface of the solar cell 10, and the direction of the lower surface S2 is defined as the back surface of the solar cell 10. In the solar cell 10, the upper surface S1 of the first conductivity type silicon substrate 100 can be used as a light-receiving surface, and the lower surface S2 can be used as a non-light-receiving surface. The upper surface S1 has a textured structure to capture incident sunlight, which can improve sunlight absorption efficiency.

Further, the first conductive type silicon substrate 100 may be a polycrystalline silicon substrate, a single crystal-like silicon substrate or a single crystal silicon substrate, and the present invention is not limited thereto. A plurality of local back electric fields 114 are formed between the first conductive type silicon substrate 100, the back passivation layer 104 and the back aluminum metal layer 108.

The second conductivity type electric field layer 102 is disposed on the upper surface S1 of the first conductivity type silicon substrate 100. The second conductivity type electric field layer 102 may also be called a front surface field (FSF), and the second conductivity type electric field A PN junction can be formed between the layer 102 and the first conductive silicon substrate 100 to convert light energy into electrical energy. Compared to the first conductivity type silicon substrate 100 which is a P-type silicon substrate, the second conductivity type electric field layer 102 may be an N-type emitter layer.

On the other hand, the back passivation layer 104 is disposed on the lower surface S2 of the first conductivity type silicon substrate 100, and the back passivation layer 104 may have a passivation ability. Specifically, impurities and defects in the silicon substrate and on the surface of the silicon substrate will negatively affect the performance of the solar cell. Passivation technology reduces the impact of defects by reducing the recombination of surface carriers, thereby ensuring the efficiency of the cell. The back passivation layer 104 may include an aluminum oxide (Al ₂ O ₃ ) layer, and the thickness of the aluminum oxide layer may be in the range of 3 nm to 15 nm, preferably in the range of 4 nm to 10 nm. In the selection of the material for the back passivation layer, aluminum oxide (Al ₂ O ₃ ) can provide good passivation to the P-type surface due to its high charge density, and is currently widely used as a back passivation material for mass production of PERC cells.

Furthermore, the back passivation protection layer 106 is disposed on the other side of the back passivation layer 104 opposite to the first conductivity type silicon substrate 100, where the back passivation protection layer 106 includes a silicon oxynitride passivation layer 106-1 and a silicon nitride layer 106- 2. In order to fully meet the back passivation conditions, it is also necessary to cover a silicon nitride (SiNx) layer on the surface of the aluminum oxide layer to protect the back passivation layer 104 and ensure the optical performance of the back of the battery. Therefore, the back passivation of existing PERC batteries mostly adopts Al ₂ O ₃ /SiN double-layer structure.

In the present invention, the Al ₂ O ₃ /SiON/SiN three-layer structure is adopted. Please further refer to FIG. 2, which shows a graph of the influence of forming a silicon oxynitride passivation layer on reflectivity according to an embodiment of the present invention. As shown in the figure, the curves REF and INX respectively represent the reference sample without the silicon oxynitride passivation layer and the sample with the silicon oxynitride passivation layer, which shows that the formation of the silicon oxynitride passivation layer can make the coating uniformity better. In addition, the silicon oxynitride passivation layer 106-1 can increase the reflectivity when used as a back reflection layer, can increase the internal reflection current of the solar cell 10, and increase the short-circuit current. In addition, by forming the silicon oxynitride passivation layer 106-1, the back passivation protective layer 106 can obtain better coating uniformity, thereby reducing the series resistance.

Among them, the thickness of the silicon oxynitride passivation layer 106-1 is in the range of 50 nm to 200 nm, preferably 100 nm to 150 nm, and the thickness of the silicon nitride layer 106-2 is in the range of 50 nm to 250 nm. Preferably, it may be in the range of 100 nm to 200 nm.

The front passivation layer 110 is disposed on the second conductivity type electric field layer 102, and can passivate the material of the n-type second conductivity type electric field layer 102. The front passivation layer 110 may be selected from the group consisting of silicon nitride (SiN), silicon oxide (SiOx), silicon oxynitride (SiON), aluminum oxide (AlOx), aluminum nitride (AlN), and combinations thereof Group of materials formed. In the present invention, the method of forming the front passivation layer 110 is not limited.

In addition, the back aluminum metal layer 108 is disposed on the other side of the back passivation protection layer 106 relative to the back passivation layer 104, and includes a plurality of contacts C, wherein the back passivation layer 104 and the back passivation protection layer 106 have a plurality of through holes TH, the contacts C are respectively provided corresponding to the through holes TH.

The back aluminum metal layer 108 is used to form the back electrode of the solar cell 10, and the through hole TH on the back passivation layer 106 is covered by a conductive contact C containing aluminum to form a local back electric field 114 and a conductive layer (metal layer), And the aluminum metal layer covers the through holes TH of the back passivation layer 104 to form the back aluminum metal layer 108. The back aluminum metal layer 108 may overlap a part of the back busbar to further enable the charge to be collected on the back busbar.

A plurality of front electrodes 112 are separately disposed on the surface of the front passivation layer 110, wherein the front electrodes 112 pass through the front passivation layer 110 to be electrically connected to the second conductivity type electric field layer 102. For example, the front electrode 112 and the back aluminum metal layer 108 may be formed of metal glue. For example, the front electrode 112 is formed of silver paste, and the back aluminum metal layer 108 is formed of aluminum paste, which can be formed by screen printing, evaporation, sputtering or electroplating.

Therefore, please refer to Table 1 below. Compared with the sample without the silicon oxynitride passivation layer using the Al ₂ O ₃ /SiON/SiN three-layer structure, the solar cell with the silicon oxynitride passivation layer provided by the present invention is The aluminum oxide passivation layer combined with the silicon oxynitride passivation layer and the silicon nitride protective layer are used in the process to increase the short-circuit current and reduce the series resistance by increasing the back reflectivity, thereby improving the efficiency. Among them, when an aluminum oxide layer with a thickness in the range of 4nm to 10nm is used as the back passivation layer 104, a silicon oxynitride passivation layer 106-1 with a thickness in the range of 100nm to 150nm, and a thickness in the range of 100nm to 200nm The silicon nitride layer 106-2 can increase the efficiency by about 0.1% compared to the sample.

Table 1 effectiveness Open circuit voltage (Voc) Short circuit current (Isc) Series resistance (Rs) Fill factor (FF) sample 20.861% 0.6602 9.8229 0.00297 78.587 Al ₂ O ₃ /SiON/SiN 20.951% 0.6599 9.8380 0.00288 78.839

Refer to FIG. 3, which is a flowchart of a method for manufacturing a solar cell according to an embodiment of the present invention. As shown in the figure, the first embodiment of the present invention provides a method for manufacturing a solar cell with a silicon oxynitride passivation layer, which at least includes the following steps:

Step S100: forming a first conductivity type silicon substrate. In detail, the first conductive type silicon substrate, such as a p-type silicon wafer, has an upper surface and a lower surface. An inverted pyramid structure, that is, a textured structure, can be formed on the upper surface by alkali etching to capture incident light. Sunlight can improve the efficiency of sunlight absorption.

Step S101: forming a second conductivity type electric field layer on the upper surface of the first conductivity type silicon substrate through a diffusion process. For example, phosphorus diffusion is performed to form the second conductivity type electric field layer 102, which can be an N-type emitter layer, and then forms a PN junction to convert light energy into electrical energy. The diffusion process may include gas diffusion, ion implantation, vapor deposition or other doping methods to form the second conductivity type electric field layer.

Step S102: Depositing the back passivation layer on the lower surface of the first conductivity type silicon substrate through a deposition process. Specifically, the back passivation layer may be an aluminum oxide layer, which may be deposited on the lower surface of the first conductivity type silicon substrate by a deposition process such as atomic layer deposition (ALD) technology as the back passivation layer. Alumina (Al ₂ O ₃ ) can provide good passivation to the P-type surface due to its high charge density.

Step S103: Depositing the front passivation layer on the second conductivity type electric field layer through a deposition process. Similarly, the front passivation layer can be formed by a deposition process such as atomic layer deposition (ALD) technology to passivate the material of the n-type second conductivity type electric field layer. The front passivation layer can be selected from the group consisting of silicon nitride (SiN), silicon oxide (SiOx), silicon oxynitride (SiON), aluminum oxide (AlOx), aluminum nitride (AlN), and combinations thereof Group of materials formed. In the present invention, the method of forming the front passivation layer is not limited.

Then, the back passivation layer is plated on the other side of the back passivation layer opposite to the first conductivity type silicon substrate through a coating process, for example, the following steps may be included:

Step S104: plating a silicon oxynitride passivation layer on the other side of the back passivation layer opposite to the first conductivity type silicon substrate by a coating process.

Step S105: plating the silicon nitride layer on the other side of the silicon oxynitride passivation layer opposite to the back passivation layer by a coating process.

Among them, the thickness of the silicon oxynitride passivation layer is in the range of 50 nm to 200 nm, preferably 100 nm to 150 nm, and the thickness of the silicon nitride layer is in the range of 50 nm to 250 nm, preferably 100 nm to Within the range of 200nm.

It should be noted that both the silicon oxynitride passivation layer and the silicon nitride layer can be formed by a chemical vapor deposition (CVD) process, so they can be combined and completed in the site where the backside protective passivation layer is formed. The integration of the process can reduce automation Risk of fragmentation.

Step S106: forming a plurality of through holes in the back passivation layer and the back protection passivation layer through a laser process. Wherein, the back passivation layer and the back protection passivation layer may be penetrated by physical or chemical methods to form a plurality of through holes. The shape of the through holes may be various geometric patterns, and the forming method is not limited to the laser process.

Step S107: Print the back aluminum metal layer on the other side of the back protective passivation layer relative to the back passivation layer through a screen printing process, and form a plurality of contacts corresponding to the through holes.

Step S108: Print a plurality of front electrodes on the surface of the front passivation layer separately from each other through a screen printing process. Wherein, the front electrodes are electrically connected with the second conductivity type electric field layer through the front passivation layer.

For example, the front electrode and the back aluminum metal layer may be formed of metal glue. For example, the front electrode is formed of silver paste, and the back aluminum metal layer is formed of aluminum paste. In addition to the screen printing process, it can also be formed by an evaporation process, a sputtering process, or an electroplating process.

In detail, after the front electrodes and the back aluminum metal layer are formed, sintering can be used to make the back aluminum metal layer react with the first conductive silicon substrate through the through holes to form a local back electric field.

[Beneficial effects of the embodiment]

One of the beneficial effects of the present invention is that the solar cell with a silicon oxynitride passivation layer and its manufacturing method provided by the present invention uses an aluminum oxide passivation layer and a silicon oxynitride passivation layer in the existing manufacturing process to improve back reflectivity. To increase the short-circuit current and reduce the series resistance, thereby increasing the efficiency by about 0.1% compared to the sample. In addition, the protection layer process integration can reduce the risk of automated fragmentation.

The content disclosed above is only a preferred and feasible embodiment of the present invention, and does not limit the scope of the patent application of the present invention. Therefore, all equivalent technical changes made using the description and schematic content of the present invention are included in the application of the present invention. Within the scope of the patent.

10: Solar battery 100: The first conductivity type silicon substrate 102: second conductivity type electric field layer 104: back passivation layer 106: back passivation protective layer 106-1: Silicon oxynitride passivation layer 106-2: Silicon nitride layer 108: Aluminum metal layer on the back 110: Front passivation layer 112: front electrode 114: Backside electric field S1: upper surface S2: lower surface C: Contact TH: Through hole REF, INX: curve

FIG. 1 is a schematic cross-sectional view of an n-type back emitter bifacial solar cell provided by an embodiment of the present invention.

FIG. 2 is a graph showing the influence of forming a silicon oxynitride passivation layer at different speeds on reflectivity according to an embodiment of the present invention.

Fig. 3 is a flowchart of a method for manufacturing a solar cell according to an embodiment of the present invention.

10: Solar battery

100: The first conductivity type silicon substrate

102: second conductivity type electric field layer

104: back passivation layer

106: back passivation protective layer

106-1: Silicon oxynitride passivation layer

106-2: Silicon nitride layer

108: Aluminum metal layer on the back

110: Front passivation layer

112: front electrode

114: Backside electric field

S1: upper surface

S2: lower surface

C: Contact

TH: Through hole

Claims (10)

A solar cell with a passivation layer of silicon oxynitride, comprising: a first conductivity type silicon substrate, the first conductivity type silicon substrate having an upper surface and a lower surface; a second conductivity type electric field layer disposed on the first On the upper surface of the conductive silicon substrate; a back passivation layer is disposed on the lower surface of the first conductive silicon substrate; a back passivation protection layer is disposed on the back passivation layer opposite to the first conductive silicon On the other side of the substrate, the back passivation protection layer includes a silicon oxynitride passivation layer, the thickness of the silicon oxynitride passivation layer is in the range of 100 nm to 150 nm; and a back aluminum metal layer is disposed on the back passivation protection layer Relative to the other side of the back passivation layer, it includes a plurality of contacts, wherein the back passivation layer and the back passivation protection layer have a plurality of through holes, and the contacts are respectively arranged corresponding to the through holes. The solar cell with a silicon oxynitride passivation layer as described in the first item of the patent application, wherein the back passivation layer further comprises an aluminum oxide layer disposed between the silicon oxynitride passivation layer and the silicon substrate. The solar cell with a silicon oxynitride passivation layer as described in the first item of the patent application, wherein the back passivation protection layer further includes a silicon nitride layer. The solar cell with a silicon oxynitride passivation layer as described in item 3 of the scope of patent application, wherein the thickness of the aluminum oxide layer is in the range of 5 nm to 15 nm. The solar cell with a silicon oxynitride passivation layer as described in item 1 of the scope of the patent application further includes: a front passivation layer disposed on the second conductivity type electric field layer; and a plurality of front electrodes disposed separately from each other On the surface of the front passivation layer, wherein the front electrodes pass through the front passivation layer to interact with the second conductivity type electric field Layer electrical connection. A method for manufacturing a solar cell with a silicon oxynitride passivation layer includes: forming a first conductivity type silicon substrate, the first conductivity type silicon substrate having an upper surface and a lower surface; and performing a diffusion process on the first conductive silicon substrate. A second conductivity type electric field layer is formed on the upper surface of the type silicon substrate; a back passivation layer is deposited on the lower surface of the first conductivity type silicon substrate through a deposition process; a back protection passivation is performed through a coating process A layer is plated on the other side of the back passivation layer opposite to the first conductivity type silicon substrate, wherein the back protection passivation layer includes a silicon oxynitride passivation layer, and the thickness of the silicon oxynitride passivation layer is in the range of 100nm to 150nm A plurality of through holes are formed in the back passivation layer and the back passivation layer through a laser process; and a back aluminum metal layer is printed on the back passivation layer relative to the back passivation layer through a screen printing process On the other side of the hole, a plurality of contacts corresponding to the through holes are formed. The method for manufacturing a solar cell with a silicon oxynitride passivation layer as described in item 6 of the scope of patent application further includes depositing an aluminum oxide layer on the lower surface of the first conductive silicon substrate by the deposition process. The back passivation layer. According to the method for manufacturing a solar cell with a silicon oxynitride passivation layer described in item 7 of the scope of patent application, the thickness of the aluminum oxide layer is in the range of 4 nm to 15 nm. The method for manufacturing a solar cell with a silicon oxynitride passivation layer as described in item 6 of the scope of the patent application, wherein the step of forming the backside protective passivation layer by the coating process further includes: using the coating process to the silicon oxynitride The passivation layer is plated on the back passivation layer relative to the The other side of the first conductivity type silicon substrate; and a silicon nitride layer is plated on the other side of the silicon oxynitride passivation layer opposite to the back passivation layer by the coating process. The method for manufacturing a solar cell with a silicon oxynitride passivation layer as described in item 6 of the scope of the patent application further includes: depositing a front passivation layer on the second conductivity type electric field layer through another deposition process; The printing process separates and prints a plurality of front electrodes on the surface of the front passivation layer, wherein the front electrodes pass through the front passivation layer to be electrically connected to the second conductivity type electric field layer.

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