CN115036374A - Solar cell and method for making the same, photovoltaic module - Google Patents

Abstract

Embodiments of the present invention provide a solar cell, a manufacturing method thereof, and a photovoltaic assembly. The solar cell includes: an N-type substrate and a P-type emitter located on the front surface of the substrate; a solar cell located on the front surface of the substrate and away from the P-type A first passivation layer, a second passivation layer, a third passivation layer and a fourth passivation layer are stacked in sequence in the direction of the emitter, the first passivation layer includes a silicon oxide material, and the second passivation layer The layer includes a first silicon _{oxynitride SiOxNy} material, the third passivation layer includes a silicon _{nitride SimNn} material, and the fourth passivation layer includes a second silicon _{oxynitride SiOiNj} material, so The second passivation layer includes a first part close to the first passivation layer and a second part close to the third passivation layer, and the nitrogen atom concentration of the first part is smaller than the nitrogen atom concentration of the second part ; a passivation contact structure on the back surface of the substrate. The embodiments of the present invention are beneficial to improve the light utilization rate of the solar cell.

Description

Solar cell and method for making the same, photovoltaic module

technical field

Embodiments of the present invention relate to the field of photovoltaics, and in particular, to a solar cell, a manufacturing method thereof, and a photovoltaic assembly.

Background technique

The reflectivity or absorption of sunlight is a key factor in cell efficiency. At present, for passivating crystalline silicon solar cells in the industry, an aluminum oxide/silicon nitride (AlO _x /SiN _y ) stack is often used as the emitter passivation layer. The high cost of coating equipment and precursor gas sources (trimethyl aluminum, etc.) required for the deposition of aluminum oxide materials is not conducive to mass production in modern industrialization; the high refractive index of silicon nitride materials is not conducive to the anti-reflection of the front of the battery , After using ethylene-vinyl acetate (EVA) or polyolefin (POE) and other packaging materials, the appearance of solar modules is blue, which is not conducive to the production of black modules.

Therefore, it is hoped to develop a new type of N-type cell with non-alumina passivation system, low cost and high light utilization rate to replace the N-type cell of the alumina passivation system.

SUMMARY OF THE INVENTION

Embodiments of the present invention provide a solar cell, a manufacturing method thereof, and a photovoltaic assembly, which are beneficial to improve the utilization rate of sunlight of the solar cell.

To solve the above problem, an embodiment of the present invention provides a solar cell, comprising: an N-type substrate and a P-type emitter located on the front surface of the substrate; a solar cell located on the front surface of the substrate and in a direction away from the P-type emitter a first passivation layer, a second passivation layer, a third passivation layer and a fourth passivation layer stacked in sequence, the first passivation layer includes a silicon oxide material, and the second passivation layer includes a first passivation layer Silicon oxynitride SiO _x N _y material, the third passivation layer includes silicon nitride Si _m N _n material, the fourth passivation layer includes a second silicon oxynitride SiO _i N _j material, the second passivation layer The passivation layer includes a first part close to the first passivation layer and a second part close to the third passivation layer, the nitrogen atom concentration of the first part is smaller than the nitrogen atom concentration of the second part; Passivated contact structures on the back surface of the substrate.

In addition, in the direction of the substrate toward the third passivation layer, the nitrogen atom concentration in different regions in the second passivation layer increases.

In addition, in the second passivation layer x/y∈[1.51, 2.58], the second refractive index of the second passivation layer is 1.60˜1.71.

In addition, in a direction perpendicular to the front surface of the substrate, the thickness of the second passivation layer is 1 nm˜25 nm.

In addition, in the direction of the substrate toward the fourth passivation layer, the nitrogen atom concentration in different regions in the third passivation layer increases.

In addition, in the third passivation layer, m/n∈[3.12, 5.41], and the third refractive index of the third passivation layer is 1.98˜2.20.

In addition, in the fourth passivation layer i/j∈[1.98, 8.47], the fourth refractive index of the fourth passivation layer is 1.50˜1.70.

Correspondingly, an embodiment of the present invention further provides a solar module, including any one of the solar cells described above.

Correspondingly, an embodiment of the present invention also provides a method for fabricating a solar cell, including: providing an N-type substrate and a P-type emitter on the front surface of the substrate; and on the front surface of the substrate and away from the P-type emitter A first passivation layer, a second passivation layer, a third passivation layer and a fourth passivation layer are sequentially stacked in the direction of the pole, the first passivation layer includes a silicon oxide material, and the second passivation layer is The layer includes a first silicon _{oxynitride SiOxNy} material, the third passivation layer includes a silicon _{nitride SimNn} material, and the fourth passivation layer includes a second silicon _{oxynitride SiOiNj} material, so The second passivation layer includes a first part close to the first passivation layer and a second part close to the third passivation layer, and the nitrogen atom concentration of the first part is smaller than the nitrogen atom concentration of the second part ; A passivation contact structure is formed on the rear surface of the substrate.

In addition, the process step of forming the second passivation layer includes: feeding silane, nitrous oxide and ammonia gas into the reaction chamber, and performing a plasma vapor deposition process under the action of the first pulse power to form a material comprising silicon oxynitride The second passivation film; wherein, the flow ratio of silane and nitrous oxide is not less than 1/10, the first pulse power is 30 ~ 40mW/cm ² ; ammonia gas is introduced into the reaction chamber, and in the second pulse An ion implantation process of nitrogen ions is performed on the second passivation film under the action of power to form the second passivation layer; wherein, the second pulse power is 15-25 mW/cm ² , and the ion implantation time is 300s-600s.

Compared with the prior art, the technical solutions provided by the embodiments of the present invention have the following advantages:

In the above technical solution, the first part has a lower nitrogen atom concentration, and the material properties are closer to the silicon oxide material in the first passivation layer; the second part has a higher nitrogen atom concentration, and the material properties are closer to the third passivation layer. In this way, the second passivation layer and the adjacent first passivation layer and the third passivation layer have better lattice matching effect and lower interface defect density, which is beneficial to reduce the film layer In addition, the use of silicon oxynitride material with a relatively low refractive index as the fourth passivation layer is beneficial to reduce the refractive index difference between the outer layer of the solar cell and the packaging material, Thereby, light reflection is reduced, light utilization rate is improved, and the short-circuit current of the solar cell is improved.

In addition, in the direction of the substrate toward the fourth passivation layer, the nitrogen atom concentration in different regions of the third passivation layer increases, and the refractive index in different regions of the third passivation layer decreases, which is beneficial to improve the light utilization rate.

Description of drawings

One or more embodiments are exemplified by the pictures in the accompanying drawings, which do not constitute a scale limitation unless otherwise stated.

1 is a schematic structural diagram of a solar cell provided by an embodiment of the present invention;

FIG. 2 is a schematic diagram of a partial structure of the solar cell shown in FIG. 1;

3 is a schematic view of the appearance of a solar module provided by an embodiment of the present invention;

FIG. 4 is a schematic diagram of a change in reflectivity of a solar cell according to an embodiment of the present invention;

5 to 14 are schematic structural diagrams corresponding to each step of the method for fabricating a solar cell according to an embodiment of the present invention.

Detailed ways

In order to make the objectives, technical solutions and advantages of the embodiments of the present invention clearer, each embodiment of the present invention will be described in detail below with reference to the accompanying drawings. However, those of ordinary skill in the art can appreciate that, in various embodiments of the present invention, many technical details are provided for the reader to better understand the present application. However, even without these technical details and various changes and modifications based on the following embodiments, the technical solutions claimed in the present application can be realized.

Referring to FIGS. 1 and 2 , the solar cell includes: an N-type substrate 100 and a P-type emitter 111 located on the front surface of the substrate 100 ; The passivation layer 112, the second passivation layer 113, the third passivation layer 114 and the fourth passivation layer 115, the first passivation layer 112 includes a silicon oxide material, and the second passivation layer 113 includes a first silicon oxynitride SiO _x N _y material, the third passivation layer 114 includes a silicon nitride Si _m N _n material, the fourth passivation layer 115 includes a second silicon oxynitride SiO _i N _j material, and the second passivation layer 113 includes a material close to the first passivation The first part 113a of the layer 112 and the second part 113b near the third passivation layer 114, the nitrogen atom concentration of the first part 113a is lower than that of the second part 113b; the passivation contact structure 125 on the back surface of the substrate 100.

The first portion 113a is in contact with the first passivation layer 112, and the second portion 113b is in contact with the third passivation layer 114. In the direction perpendicular to the front surface of the substrate 100, the first portion 113a and the second portion 113b have a certain depth .

In some embodiments, the substrate 100 is a silicon substrate doped with N-type ions (eg, five main group elements such as phosphorus), the front surface of the substrate 100 is the surface of the substrate 100 facing the sunlight, and the rear surface of the substrate 100 is the substrate 100 facing away from sunlight The P-type emitter 111 is located in at least part of the surface space on the sun-facing side of the substrate 100, the P-type emitter 111 is doped with P-type ions (eg, three main group elements such as boron), and the P-type emitter 111 and N-type The substrate 100 forms a PN junction.

The material of the silicon substrate includes monocrystalline silicon, polycrystalline silicon, amorphous silicon and microcrystalline silicon. The silicon oxide material in the first passivation layer 112 is formed by in-situ generation or separate deposition based on the silicon substrate, in the direction perpendicular to the front surface of the substrate 100 On the top, the thickness of the first passivation layer 112 is 1-3 nm, such as 1.5 nm, 2 nm or 2.5 nm; in other embodiments, the material of the substrate can also be carbon element, organic material and multi-component compound, and the multi-component compound includes arsenic gallium, cadmium telluride, copper indium selenide, etc.

In some embodiments, in the direction of the substrate 100 toward the third passivation layer 114 , the nitrogen atom concentration in different regions in the second passivation layer 113 increases. The x/ _y value of the silicon oxynitride _SiOxNy material gradually decreases. Since oxygen atoms in the first part 113a account for a relatively large proportion and nitrogen atoms in a relatively small proportion, the material properties of the first part 113a are closer to those of silicon oxide; since oxygen atoms in the second part 113b account for a relatively small proportion, nitrogen atoms occupy a relatively small proportion. The proportion is relatively large, so the material properties of the second portion 113b are closer to silicon nitride.

Since the material properties of the silicon oxide material are between those of the silicon substrate and the first silicon _{oxynitride SiOxNy} material, the first passivation layer 112 is provided as an intermediate layer between the second passivation layer 113 and the substrate 100, and the first part is provided at the same time 113a has a high concentration of oxygen atoms, which is conducive to further improving the matching between the second passivation layer 113 and the substrate 100, avoiding the formation of a film-layer interface with a large defect density due to the large difference in film material characteristics, and ensuring the substrate 100. It has better lattice matching characteristics with the first passivation layer 112, the first passivation layer 112 and the second passivation layer 113, which reduces the light incident loss and carrier transmission loss caused by interface defects, and improves the photoelectric conversion. efficiency.

Correspondingly, setting the second portion 113b to have a higher concentration of nitrogen atoms is beneficial to make the second passivation layer 113 and the third passivation layer 114 have a good lattice matching effect, and reduce the amount of the second passivation layer 113 and the third passivation layer 114. The interface state defect density between the passivation layers 114 reduces the solar light incident loss and carrier transmission loss caused by the interface defects, and improves the photoelectric conversion efficiency.

Taking the value of x/y as the first ratio, since the size of the first ratio of the different regions in the second passivation layer 113 determines the size of the refractive index of the region, therefore, based on the second refractive index of the second passivation layer 113 As required, the range of the first ratio in the second passivation layer 113 needs to be defined. Theoretically, the larger the first ratio, that is, the smaller the nitrogen atom concentration, the smaller the refractive index of the first silicon oxynitride material, and the smaller the first ratio, that is, the larger the nitrogen atomic concentration, the smaller the refractive index of the first silicon oxynitride material. bigger.

In some embodiments, by adjusting the size of the first ratio, the first silicon oxynitride material and the second passivation layer 113 have a relatively high second refractive index. In this way, when the fourth passivation layer 115 is subsequently introduced, the second index of refraction of the second passivation layer 113 can be made larger than the fourth index of refraction of the fourth passivation layer 115, or similar to the fourth index of refraction, thereby increasing the incidence of incident The utilization efficiency of light and the photoelectric conversion efficiency of solar cells; correspondingly, on the premise of ensuring the utilization efficiency of incident light, the fourth refractive index of the fourth passivation layer 115 has a relatively large optional range, which is conducive to expanding the The material selection range of the fourth passivation layer 115 and the flexibility of the fourth index of refraction of the fourth passivation layer 115 to be adjusted within a certain range are improved, so as to better adapt to the index of refraction of the encapsulation component of the solar cell, so that the fourth index of refraction of the fourth passivation layer 115 can be adjusted within a certain range. The four passivation layer 115 can further match the refractive index of the material of the encapsulation component, reduce the light reflection of the solar component facing the sun, optimize the absorption performance of the solar component for different wavelengths of sunlight, and improve the short-circuit current and battery efficiency of the solar cell.

Wherein, the first ratio in the second passivation layer 113 is 1.51˜2.58, and correspondingly, the second refractive index of the second passivation layer 113 determined by the first ratio is 1.60˜1.71. In this way, the second passivation layer 113 has better lattice matching with the adjacent film layers, the second passivation layer 113 has a higher utilization rate of incident light, and the fourth passivation layer 115 has a refractive index Flexibility to adjust the rate within a certain range.

The thickness of the second passivation layer 113 is related to the passivation effect of the second passivation layer 113 and the utilization rate of incident light. Specifically, the thinner the thickness of the second passivation layer 113 is, the smaller the stress exerted by the second passivation layer 113 on the first passivation layer 112 is, and the interface between the first passivation layer 112 and the second passivation layer 113 is smaller. The lower the state defect density, the better the passivation effect of the second passivation layer 113; at the same time, the thinner the thickness of the second passivation layer 113, the weaker the light trapping ability of the second passivation layer 113, and the second passivation layer 113 The lower the light loss of 113, the higher the utilization rate of incident light of the solar cell; the thicker the thickness of the second passivation layer 113, the easier it is to adjust the concentration of nitrogen atoms in different regions in the second passivation layer 113, so as to improve the The lattice matching of the film layer reduces light loss.

Wherein, in the direction perpendicular to the front surface of the N-type substrate 100 , the thickness of the second passivation layer 113 can be set to be 1 nm˜25 nm, for example, 5 nm, 10 nm, 15 nm or 20 nm. In this way, it is beneficial to make the second passivation layer 113 have a weaker light trapping ability, and to make the opposite surface layers of the second passivation layer 113 have a large difference in nitrogen atom concentration, so as to improve the lattice with the adjacent film layer. matching properties.

The third passivation layer 114 is composed of a silicon nitride Si _m N _n material. The number of silicon atoms of silicon nitride in the silicon nitride Si _m N _n material has a second ratio to the number of nitrogen atoms. By adjusting the second ratio , the refractive index of the third passivation layer 114 can be adjusted.

In some embodiments, the second ratio is 3-5, specifically 3.12-5.41, such as 3.72, 4.32 or 4.92, and correspondingly, the third refractive index of the third passivation layer 114 is 1.98-2.20, such as 2.05 , 2.1 or 2.15. Silicon nitride with the above atomic number ratio has a higher refractive index, which is beneficial to reduce the reflection and emission of light, enhance the absorption of visible light, and facilitate the preparation of dark blue or even black solar cells to meet the requirements of black components.

It should be noted that the second ratio is set on the basis of the first ratio, so that under the influence of the surface charge of the second passivation layer 113, the third passivation layer 114 has a good hydrogen passivation effect, and Make the third index of refraction of the third passivation layer 114 greater than the second index of refraction of the second passivation layer 113 and the fourth index of refraction of the fourth passivation layer 115 to ensure that the second passivation layer 113 and the third passivation layer Compared with the fourth passivation layer 115, the 114 as a whole has a higher refractive index, thereby reducing the reflection and emission of light, and improving the photoelectric conversion efficiency of the solar cell.

The thickness of the third passivation layer 114 is related to the hydrogen passivation effect and cost of the third passivation layer 114 . In theory, the thicker the thickness, the stronger the hydrogen passivation effect. Meanwhile, the thicker the thickness, the stronger the hydrogen passivation effect is. slow; in addition, the thicker the thickness, the higher the cost, and the thicker the package size of the solar cell.

In some embodiments, in the direction perpendicular to the N-type substrate 100 , the thickness of the third passivation layer 114 is 40 nm˜60 nm, for example, 45 nm, 50 nm or 55 nm. When the thickness of the third passivation layer 114 is in the range of 40 nm to 60 nm, it is beneficial to ensure that the number of positive charges carried by the third passivation layer 114 meets the requirements of interface hydrogen passivation, and reduces the surface recombination rate of carriers; in addition, it is beneficial to The manufacturing cost of the third passivation layer 114 is reduced, and the package size of the solar cell is reduced.

It should be noted that the limitation on the refractive index and thickness of the third passivation layer 114 belongs to the overall limitation on the third passivation layer 114. In fact, the third passivation layer 114 may be either a single-layer film layer or a It is composed of multiple layers stacked in sequence. Specifically, the third passivation layer 114 may be composed of 2 to 5 sub-layers. In the direction of the substrate 100 toward the third passivation layer 114 , the nitrogen atom concentration of different sub-layers increases, and the refractive index decreases. The refractive index of a sub-film layer all meets the definition of the refractive index of the third passivation layer 114 , which is beneficial to further improve the utilization rate of incident light.

The fourth passivation layer 115 is composed of a second silicon oxynitride SiO _i N _j material, and the number of oxygen atoms in the second silicon oxynitride SiO _i N _j material has a third ratio to the number of nitrogen atoms, and the third ratio is adjusted by adjusting the third ratio. , the refractive index of the fourth passivation layer 115 can be adjusted.

In some embodiments, the third ratio is 1.98˜8.47, such as 2.5, 5 or 6.5, and the fourth refractive index of the fourth passivation layer 115 is 1.50˜1.70, such as 1.55, 1.60 or 1.65. In this way, it is beneficial to make the fourth refractive index of the fourth passivation layer 115 smaller than or similar to the second refractive index of the second passivation layer 113, thereby improving the utilization efficiency of incident light and the photoelectric conversion efficiency of the solar cell; in addition, there are It is beneficial to make the fourth index of refraction of the fourth passivation layer 115 greater than the index of refraction of the packaging component material and smaller than the third index of refraction of the third passivation layer 114, so as to avoid the excessive difference in the refractive index between the solar cell surface layer material and the packaging component material. The resulting light reflection enhances the absorption of light and facilitates the preparation of black or dark blue solar modules.

The packaging component materials are usually transparent materials such as ethylene-vinyl acetate (EVA) or polyolefin (POE). For example, the refractive index of the third passivation layer 114 is 1.98˜2.20, and setting the fourth passivation layer 115 with the refractive index in the middle value is beneficial to enhance the absorption of light. Compared with the traditional aluminum oxide/silicon nitride passivation anti-reflection layer, referring to Figure 3, the encapsulated solar modules appear dark blue or even black under sunlight.

The ability of the solar cell to absorb light is mainly reflected in the refractive index and thickness of the third passivation layer 114 and the refractive index and thickness of the fourth passivation layer 115 . Since the refractive index and thickness of the third passivation layer 114 and the refractive index of the fourth passivation layer 115 have been determined, in order to further ensure that the solar cell has a higher light absorbing ability, the thickness of the fourth passivation layer 115 can be set to be 40 nm~ 60 nm, for example 45 nm, 50 nm or 55 nm.

In the above-mentioned embodiment, by setting the material properties of the first passivation layer 112 between the substrate 100 and the second passivation layer 113, the second passivation layer 113 and the third passivation layer 114 with a graded nitrogen atomic concentration, and the The fourth passivation layer 115 with an intermediate refractive index optimizes the incident and absorption of sunlight in different wavelength bands by the solar cell, thereby improving the short-circuit current and cell efficiency of the solar cell. Referring to FIG. 4 , compared with the existing aluminum oxide/silicon nitride passivation anti-reflection layer, the improved passivation stack provided by the present application has a lower reflectivity for the near-ultraviolet visible light band and the ultraviolet light band, for example, the wavelength is about The reflectivity of light with a wavelength of 350 nm dropped from about 20% to about 5%, a drop of nearly 4 times. Further, the average reflectivity of light with a wavelength range of 350 nm to 1050 nm dropped from 2.1% to 2.3%. 1.4% to 1.6 %, the light utilization rate of the improved passivation stack is higher; further, the short-circuit current I _sc of the solar cell provided by the present invention can be increased by about 30 mA.

In some embodiments, the passivation contact structure 125 at least includes: an interface passivation layer 121 and a field passivation layer 122 which are sequentially arranged in a direction away from the substrate 100 . The material of the interface passivation layer 121 is a dielectric material, which is used to realize the interface passivation on the backside of the substrate 100. For example, the interface passivation layer 121 is a tunnel oxide layer (eg, a silicon oxide layer); The material is a material that realizes the field passivation effect, such as a doped silicon layer, and the doped silicon layer may specifically be one or more of a doped polysilicon layer, a doped microcrystalline silicon layer, or a doped amorphous silicon layer. For the N-type silicon substrate 100, the field passivation layer 122 may be an N-type doped polysilicon layer.

In some embodiments, a fifth passivation layer 123 is further provided on the surface of the field passivation layer 122 away from the substrate 100 . The material of the fifth passivation layer 123 includes a material that realizes an anti-reflection function, such as silicon nitride. Wherein, the fifth passivation layer 123 may be a multi-layer sub-layer similar to the third passivation layer 114, that is, in the direction of the substrate 100 toward the fifth passivation layer 123, the refractive index of different sub-layers gradually decreases, Each sub-layer is limited by the overall refractive index of the fifth passivation layer 123 .

In addition, the solar cell further includes a first electrode 116 and a second electrode 124 , the first electrode 116 is electrically connected to the P-type emitter 111 , and the second electrode 124 penetrates the fifth passivation layer 123 and is electrically connected to the field passivation layer 122 . In some embodiments, the first electrode 116 and/or the second electrode 124 may be sintered and printed with a conductive paste (silver paste, aluminum paste, or silver-aluminum paste).

In some embodiments, the first portion has a lower nitrogen atomic concentration and material properties closer to the silicon oxide material in the first passivation layer, and the second portion has a higher nitrogen atomic concentration and material properties closer to the third passivation layer The silicon nitride material in the layer, so that the second passivation layer and the adjacent first passivation layer and the third passivation layer have better lattice matching effect and lower interface defect density, which is beneficial to reduce solar energy. The interface loss of light and the improvement of the utilization rate of sunlight; in addition, the use of silicon oxynitride material with a relatively low refractive index as the fourth passivation layer is beneficial to reduce the refractive index difference between the fourth passivation layer and the packaging material , thereby reducing the light reflection and improving the light utilization rate, and improving the short-circuit current of the solar cell.

Correspondingly, an embodiment of the present invention also provides a solar module, the solar module includes the above-mentioned solar cell, the solar cell has a P-type emitter, and adopts a non-alumina passivation system, compared with N-type emitter and alumina passivation With the combination of the systems, the solar modules provided by the embodiments of the present invention have lower light reflectivity and lower light loss, and finally exhibit higher photoelectric conversion efficiency and larger short-circuit current.

Correspondingly, an embodiment of the present invention also provides a method for fabricating a solar cell, which can be used to fabricate the above-mentioned solar cell.

Referring to FIGS. 5 to 7 , an N-type substrate 100 is provided and double-sided texturing is performed to form a P-type emitter 111 .

Specifically, the N-type substrate 100 is cleaned, and the pyramid textured surface is prepared by wet chemical etching. The pyramid textured surface can reduce the reflection of light on the surface of the substrate 100, thereby increasing the absorption and utilization rate of light by the substrate 100 and improving the solar energy The conversion efficiency of the battery; in addition, the suede preparation can use the mature production line alkali texturing process to form a 45-degree positive pyramid suede.

After double-sided texturing, the front surface of the substrate 100 is subjected to boron diffusion treatment to form a P-type emitter 111 . The P-type emitter 111 occupies part of the surface space on the sun-facing side of the substrate 100 , and the P-type emitter 111 and the substrate 100 form a PN junction .

It should be noted that the boron diffusion treatment will also generate unnecessary borosilicate glass on the front surface, the rear surface and the side surface of the substrate 100 at the same time. The borosilicate glass has a certain protective effect on the substrate 100 and can avoid certain processes from affecting the substrate 100. surface damage. In other words, unnecessary borosilicate glass can be used as a mask layer for the substrate 100 .

Referring to FIG. 8 , a planarization process (eg, polishing) is performed on the rear surface of the substrate 100 .

The back surface is the side of the solar cell facing away from sunlight, and the planarization process can form the flat surface required for depositing the film layer on the back surface. During the planarization process, the borosilicate glass on the back surface is removed together.

Referring to FIG. 9 and FIG. 10 , an interface passivation layer 121 and a field passivation layer 122 are formed to form a passivation contact structure.

In some embodiments, the interface passivation layer 121 is formed by a deposition process. Specifically, the material of the interface passivation layer 121 includes silicon oxide, and the deposition process includes a chemical vapor deposition process; in other embodiments, in-situ can also be used. The generation process forms the interface passivation layer. Specifically, the interface passivation layer can be formed in-situ by a thermal oxidation process and a nitric acid passivation process on the basis of the silicon substrate.

In some embodiments, after the interface passivation layer 121 is formed, intrinsic polysilicon is deposited to form a polysilicon layer, and phosphorus ions are doped by means of ion implantation and source diffusion to form an N-type doped polysilicon layer, and the doped polysilicon layer is as the field passivation layer 122 .

When the deposition process is used to form the interface passivation layer 121 and the field passivation layer 122, since borosilicate glass is used as a mask layer on the front surface to protect the front surface of the substrate 100, there is no need to pass the mask during the deposition process. The area is defined on the back surface, and the same process can be used to remove the borate glass on the front surface and the silicon oxide and polysilicon deposited on the front surface at the same time. In this way, there is no need to set an additional mask, which is beneficial to reduce the process steps, shorten the process flow, and reduce the process cost.

In other embodiments, when the interface passivation layer is formed by an in-situ generation process, only polysilicon is deposited on the surface of the borosilicate glass on the front surface of the substrate.

Referring to FIG. 11 , a first passivation layer 112 is formed on the front surface of the substrate 100 .

In some embodiments, before forming the first passivation layer 112, it is necessary to remove excess borosilicate glass, silicon oxide and polysilicon coated on the front surface of the substrate 100; in other embodiments, after forming the first passivation layer Previously, the excess borosilicate glass and polysilicon plated around the front surface of the substrate needed to be removed.

In some embodiments, after removing excess material, oxidation is performed at 450° C.˜500° C. in an oxygen-containing atmosphere for 15 min˜30 min to form an ultra-thin silicon oxide layer with a thickness of 1 nm˜3 nm on the front surface of the substrate 100 , as the first Passivation layer 112 ; in other embodiments, the formation process of the ultra-thin silicon oxide layer further includes natural oxidation, deposition process, ozone oxidation or nitric acid passivation.

Referring to FIG. 12 , a second passivation layer 113 is formed on the surface of the first passivation layer 112 .

In some embodiments, the second passivation layer 113 , the third passivation layer 114 and the fourth passivation layer 115 are sequentially deposited on the surface of the first passivation layer 112 by using a plasma enhanced chemical vapor deposition process (PECVD). Taking tubular PECVD as an example, the deposition temperature of different passivation layers is generally set to 450°C to 500°C.

Specifically, the process steps of forming the second passivation layer 113 include: feeding silane, nitrous oxide and ammonia gas into the reaction chamber, and performing a plasma vapor deposition process under the action of the first pulse power to form a material comprising silicon oxynitride The second passivation film; wherein, the flow ratio of silane and nitrous oxide is not less than 1/10, the first pulse power is 30 ~ 40mW/cm ² ; ammonia gas is introduced into the reaction chamber, and the second pulse power acts Next, an ion implantation process of nitrogen ions is performed on the second passivation film to form a second passivation layer 113; wherein, the second pulse power is 15-25 mW/cm ² , and the ion implantation time is 300s-600s. It should be noted that the above-mentioned pulse power is the pulse power per unit area.

The second passivation layer 113 includes a first portion 113a close to the first passivation layer 112 and a second portion 113b away from the first passivation layer 112. Through the above process, the concentration of nitrogen atoms in the first portion 113a can be made smaller than that in the second portion The nitrogen atom concentration in 113b, specifically, in the direction of the substrate 100 toward the third passivation layer 114, the nitrogen ion concentration in different regions in the second passivation layer 113 increases, so that the second passivation layer 113 and the third passivation layer 113. A passivation layer 112 and a third passivation layer formed subsequently have high lattice matching properties.

Referring to FIG. 13 , a third passivation layer 114 covering the surface of the second passivation layer 113 is formed.

In some embodiments, the process steps of forming the third passivation layer 114 include: passing silane and ammonia gas into the reaction chamber, and performing a plasma vapor deposition process under the action of a third pulse power to form a material comprising silicon nitride The third passivation layer 114; wherein, the flow ratio of silane and ammonia gas is 1/10-1/5, and the third pulse power is 30-40 mW/cm ² . In the direction perpendicular to the front surface of the substrate 100 , the thickness of the third passivation layer 114 is 40 nm˜60 nm, and the overall refractive index of the third passivation layer 114 is 2.00˜2.10, for example, 2.25, 2.5 or 2.75.

In some embodiments, the process equipment for forming the second passivation layer 113 is the same as the process equipment for forming the third passivation layer 114 , and no additional equipment is required to form the aluminum oxide layer, which is beneficial to reduce hardware costs.

Referring to FIG. 14 , a fourth passivation layer 115 covering the surface of the third passivation layer 114 is formed, and a fifth passivation layer 123 is formed on the surface of the field passivation layer 122 away from the substrate 100 .

In some embodiments, the process steps of forming the fourth passivation layer 115 include: passing silane, nitrous oxide and ammonia gas into the reaction chamber, and performing a plasma vapor deposition process under the action of a fourth pulse power to form a nitrogen-containing gas The fourth passivation layer 115 of silicon oxide material; wherein, the flow ratio of silane and nitrous oxide is not less than 1/10, and the fourth pulse power is 25-40 mW/cm 2 . In the direction perpendicular to the front surface of the substrate 100 , the thickness of the fourth passivation layer 115 is 40 nm˜60 nm, and the overall refractive index of the fourth passivation layer 115 is 1.50˜1.70, for example, 1.55, 1.60 or 1.65.

In some embodiments, the fifth passivation layer 123 may be divided into multiple sub-layers, for example, 2-4 layers. In the direction of the fifth passivation layer 123 facing the substrate 100, the refractive indices of different sub-layers In this way, it is beneficial to improve the antireflection effect of the solar cell, so that the rear surface of the solar cell presents a completely black effect. The material of the fifth passivation layer 123 includes silicon nitride.

Referring to FIG. 1, a first electrode 116 and a second electrode 124 are formed.

After the fifth passivation layer 123 is formed, a metallization process is performed, including a screen printing process and a high-temperature sintering process, to form the first electrode 116 connected to the emitter 111 and the second electrode connected to the field passivation layer 122 124.

In some embodiments, the first portion has a lower nitrogen atomic concentration and material properties closer to the silicon oxide material in the first passivation layer, and the second portion has a higher nitrogen atomic concentration and material properties closer to the third passivation layer The silicon nitride material in the layer, so that the second passivation layer and the adjacent first passivation layer and the third passivation layer have better lattice matching effect and lower interface defect density, which is beneficial to reduce solar energy. The interface loss of light and the improvement of the utilization rate of sunlight; in addition, the use of silicon oxynitride material with a relatively low refractive index as the fourth passivation layer is beneficial to reduce the refractive index difference between the fourth passivation layer and the packaging material , thereby reducing the light reflection and improving the light utilization rate, and improving the short-circuit current of the solar cell.

Those skilled in the art can understand that the above-mentioned embodiments are specific examples for realizing the present invention, and in practical applications, various changes in form and details can be made without departing from the spirit and the spirit of the present invention. scope. Any person skilled in the art can make respective changes and modifications without departing from the spirit and scope of the present invention. Therefore, the protection scope of the present invention should be based on the scope defined by the claims.

Claims (10)

1. A solar cell, comprising:

the device comprises an N-type substrate and a P-type emitter positioned on the front surface of the substrate;

the first passivation layer, the second passivation layer, the third passivation layer and the fourth passivation layer are sequentially stacked on the front surface of the substrate and in the direction far away from the P-type emitter, the first passivation layer comprises a silicon oxide material, and the second passivation layer comprises a first silicon oxynitride SiO _x N _y Material, the third passivation layer comprising silicon nitride Si _m N _n Material, the fourth passivation layer comprising a second silicon oxynitride SiO _i N _j A material, the second passivation layer including a first portion proximate the first passivation layer and a second portion proximate the third passivation layer, the first portion having a nitrogen atom concentration that is less than a nitrogen atom concentration of the second portion;

a passivation contact structure on the rear surface of the substrate.

2. The solar cell of claim 1, wherein the concentration of nitrogen atoms in different regions of the second passivation layer increases in a direction of the substrate toward the third passivation layer.

3. The solar cell according to claim 1 or 2, wherein the second passivation layer has a second refractive index of 1.60 to 1.71 in x/y e [1.51, 2.58 ].

4. The solar cell of claim 1, wherein the second passivation layer has a thickness of 1nm to 25nm in a direction perpendicular to the front surface of the substrate.

5. The solar cell of claim 1, wherein the concentration of nitrogen atoms in different regions of the third passivation layer increases in a direction from the substrate toward the fourth passivation layer.

6. The solar cell of claim 5, wherein the third passivation layer has a third refractive index of 1.98-2.20 in m/n e [3.12, 5.41 ].

7. The solar cell according to claim 1 or 6, wherein i/j e [1.98, 8.47] in the fourth passivation layer has a fourth refractive index of 1.50 to 1.70.

8. A photovoltaic module comprising the solar cell of any one of claims 1 to 7.

9. A method for manufacturing a solar cell, comprising:

providing an N-type substrate and a P-type emitter positioned on the front surface of the substrate;

forming a first passivation layer, a second passivation layer, a third passivation layer and a fourth passivation layer which are sequentially stacked on the front surface of the substrate and in the direction far away from the P-type emitter, wherein the first passivation layer comprises a silicon oxide material, and the second passivation layer comprises a first silicon oxynitride SiO _x N _y Material, the third passivation layer comprising silicon nitride Si _m N _n Material, the fourth passivation layer comprising a second silicon oxynitride SiO _i N _j A material, the second passivation layer including a first portion adjacent the first passivation layer and a second portion adjacent the second passivation layerA second portion of the triple passivation layer, the first portion having a nitrogen atom concentration less than a nitrogen atom concentration of the second portion;

and forming a passivation contact structure on the rear surface of the substrate.

10. The method for manufacturing a solar cell according to claim 9, wherein the process step for forming the second passivation layer comprises:

introducing silane, laughing gas and ammonia gas into the reaction chamber, and performing a plasma vapor deposition process under the action of first pulse power to form a second passivation film containing silicon oxynitride material; wherein the flow ratio of the silane to the laughing gas is not less than 1/10, and the first pulse power is 30-40 mW/cm ² ；

Introducing ammonia gas into the reaction chamber, and performing an ion implantation process of nitrogen ions on the second passivation film under the action of second pulse power to form the second passivation layer; wherein the second pulse power is 15-25 mW/cm ² The ion implantation time is 300 s-600 s.

Images