CN114744055A

CN114744055A - Solar cell and contact structure thereof, cell module and photovoltaic system

Info

Publication number: CN114744055A
Application number: CN202210242904.XA
Authority: CN
Inventors: 王永谦; 许文理; 陈刚
Original assignee: Zhejiang Aiko Solar Energy Technology Co Ltd; Guangdong Aiko Technology Co Ltd; Tianjin Aiko Solar Energy Technology Co Ltd; Zhuhai Fushan Aixu Solar Energy Technology Co Ltd
Current assignee: Zhejiang Aiko Solar Energy Technology Co Ltd; Guangdong Aiko Technology Co Ltd; Tianjin Aiko Solar Energy Technology Co Ltd; Zhuhai Fushan Aixu Solar Energy Technology Co Ltd
Priority date: 2022-03-11
Filing date: 2022-03-11
Publication date: 2022-07-12
Anticipated expiration: 2042-03-11
Also published as: CN114744055B

Abstract

The application is suitable for the technical field of solar cells, and provides a solar cell, a contact structure of the solar cell, a cell module and a photovoltaic system. The contact structure of a solar cell includes: a doped region disposed on the silicon substrate; the surface passivation layer is arranged on the doped region, and a first opening region is arranged on the surface passivation layer; the functional layer is arranged on the first opening area, and a second opening area is arranged on the functional layer; and a metal electrode disposed on the second opening region. Therefore, the functional layer can not only produce a barrier effect, but also be used as a seed to realize the preparation of the metal electrode. Moreover, the functional layer and the metal electrode are bonded more firmly, so that the adhesion of the metal electrode and the solar cell is improved.

Description

Solar cell and contact structure thereof, cell module and photovoltaic system

Technical Field

The application belongs to the technical field of solar cells, and particularly relates to a solar cell and a contact structure, a cell module and a photovoltaic system thereof.

Background

Solar cell power generation is a sustainable clean energy source that can convert sunlight into electrical energy using the photovoltaic effect of semiconductor p-n junctions.

The solar cell in the related art generally provides a metal electrode on a transparent conductive film to increase the amount of current output conducted to the metal electrode. Specifically, the photogenerated carriers in the solar cell can flow to the metal electrode through the transparent conductive film, so that the residence time of the photogenerated carriers in the cell is reduced, and the current can be more effectively output. However, the adhesion between the metal electrode and the transparent conductive film is poor, and the metal electrode is easily detached from the solar cell.

Therefore, how to design a contact structure of a solar cell to improve the adhesion of a metal electrode becomes a technical problem to be solved urgently.

Disclosure of Invention

The application provides a solar cell, a contact structure of the solar cell, a cell module and a photovoltaic system, and aims to solve the problem of how to design the contact structure of the solar cell to improve the adhesiveness of a metal electrode.

In a first aspect, the present application provides a contact structure for a solar cell. The contact structure of a solar cell includes:

a doped region disposed on the silicon substrate;

the surface passivation layer is arranged on the doped region, and a first opening region is arranged on the surface passivation layer;

the functional layer is arranged on the first opening area, and a second opening area is arranged on the functional layer; and

and a metal electrode disposed on the second opening region.

In a second aspect, the present application provides a solar cell. The solar cell is a back contact cell, the back contact cell comprises a silicon substrate, a first contact region and a second contact region, the first contact region and the second contact region are opposite in polarity and are alternately arranged on the back surface of the silicon substrate, and the first contact region and/or the second contact region adopt any one of the contact structures.

In a third aspect, the present application provides a solar cell. The solar cell is a double-sided contact cell, the double-sided contact cell comprises a silicon substrate, a third contact region and a fourth contact region, the third contact region and the fourth contact region are opposite in polarity and are respectively arranged on the front surface and the back surface of the silicon substrate, and the third contact region and/or the fourth contact region adopt any one of the contact structures.

In a fourth aspect, the present application provides a battery module comprising the solar cell of any one of the above.

In a fifth aspect, the present application provides a photovoltaic system comprising any of the above cell assemblies.

In the solar cell and the contact structure thereof, the cell module and the photovoltaic system in the embodiment of the application, the functional layer is arranged at the first opening region formed in the surface passivation layer, and the metal electrode is arranged at the second opening region formed in the functional layer, so that the functional layer can not only produce a blocking effect, but also be used as a seed to realize the preparation of the metal electrode. Moreover, the functional layer and the metal electrode are bonded more firmly, so that the adhesion of the metal electrode and the solar cell is improved.

Drawings

Fig. 1 is a schematic structural diagram of a solar cell according to an embodiment of the present application;

FIG. 2 is a schematic diagram of another embodiment of the present application;

fig. 3 to 6 are schematic structural views of contact structures of solar cells according to embodiments of the present application.

Description of the main element symbols:

the solar cell comprises a back contact cell 1001, a double-sided contact cell 1002, a contact structure 100, a silicon substrate 101, a doped region 10, a first doped layer 11, a first passivation layer 12, a second doped layer 13, a second passivation layer 14, a third doped layer 15, a surface passivation layer 20, a first opening region 21, a functional layer 30, a second opening region 31, a metal electrode 40, a first conductive part 41 and a second conductive part 42.

Detailed Description

In order to make the objects, technical solutions and advantages of the present application more apparent, the present application is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the present application and are not intended to limit the present application.

In the related art, the metal electrode has poor adhesiveness, and the functional layer can generate a blocking effect and can be used as a seed to realize the preparation of the metal electrode because the functional layer is arranged in the first opening region formed in the surface passivation layer and the metal electrode is arranged in the second opening region formed in the functional layer. Moreover, the functional layer and the metal electrode are bonded more firmly, so that the adhesion between the metal electrode and the solar cell is improved.

Example one

The photovoltaic system of the embodiment of the present application includes the cell assembly of the second embodiment.

In the photovoltaic system of the embodiment of the application, the contact structure of the solar cell in the cell module is provided with the functional layer in the first opening region formed in the surface passivation layer and the metal electrode in the second opening region formed in the functional layer, so that the functional layer can not only produce a blocking effect, but also be used as a seed to realize the preparation of the metal electrode. Moreover, the functional layer and the metal electrode are bonded more firmly, so that the adhesion of the metal electrode and the solar cell is improved.

Specifically, the photovoltaic system may further include a combiner box connecting the battery modules and an inverter connecting the combiner box. It can be understood that the battery assembly converts solar energy into direct current, the direct current is converged by the combiner box, the voltage level of the photovoltaic system connected to the power station is determined after the direct current and alternating current inversion of the inverter, and the voltage level is boosted by the transformer and then is connected to a medium-voltage or high-voltage power grid.

For further explanation and explanation of this embodiment, reference may be made to other parts of the present document, and further explanation is omitted here to avoid redundancy.

Example two

The cell module of the embodiment of the present application includes the solar cell of the third embodiment or the fourth embodiment.

In the battery module of the embodiment of the application, the contact structure of the solar battery is provided with the functional layer in the first opening region formed in the surface passivation layer and the metal electrode in the second opening region formed in the functional layer, so that the functional layer can not only produce a blocking effect, but also be used as a seed to realize the preparation of the metal electrode. Moreover, the functional layer and the metal electrode are bonded more firmly, so that the adhesion between the metal electrode and the solar cell is improved.

Specifically, the battery assembly can further comprise photovoltaic glass, adhesive colloid, solder strips, a back plate, silica gel and a junction box. The light transmittance of the photovoltaic glass can be greater than 92%. The adhesive colloid comprises but not limited to EVA or POE, has better light transmission performance and aging resistance, and can bond the photovoltaic glass and the solar cell into a whole. The solder strip can be a copper solder strip used for connecting solar cells in series to conduct current. The back plate is positioned on the back surface of the solar cell, plays a role in protecting and supporting the solar cell, and has reliable insulativity, water resistance and aging resistance. The silica gel can seal photovoltaic glass and solar cells, is waterproof and moistureproof, bonds the battery assembly and the frame, protects the battery assembly and reduces the impact of external force. The junction box can be connected with and protect the battery assembly and conduct the current generated by the battery assembly out for the user to use.

EXAMPLE III

Referring to fig. 1, the solar cell of the embodiment of the present application is a back contact cell 1001, the back contact cell 1001 includes a silicon substrate 101, a first contact region 110 and a second contact region 120, the first contact region 110 and the second contact region 120 have opposite polarities and are alternately disposed on the back surface of the silicon substrate 101, and the first contact region 110 and/or the second contact region 120 adopt the contact structure 100 of the fifth embodiment.

In the solar cell according to the embodiment of the present application, since the contact structure 100 has the functional layer in the first opening region formed in the surface passivation layer and has the metal electrode in the second opening region formed in the functional layer, the functional layer can not only produce a blocking effect, but also be used as a seed to implement the preparation of the metal electrode. Moreover, the functional layer and the metal electrode are bonded more firmly, so that the adhesion between the metal electrode and the solar cell is improved.

Specifically, the front surface of the silicon substrate 101 may be provided with a front surface passivation layer. The explanation and description of this section can refer to the description of the surface passivation layer later, and will not be repeated here to avoid redundancy.

Specifically, in the example of fig. 1, the first contact region 110 and the second contact region 120 each employ the contact structure 100 in embodiment five.

Specifically, one of the first and

second contact regions

110 and 120 is a P-type contact region, and the other is an N-type contact region.

It is understood that in other examples, the contact structure 100 of the fifth embodiment may be adopted for the first contact region 110, and the contact structure 100 of the fifth embodiment may not be adopted for the second contact region 120; alternatively, the first contact region 110 may not adopt the contact structure 100 of the fifth embodiment, and the second contact region 120 may adopt the contact structure 100 of the fifth embodiment.

For further explanation and explanation of the embodiment, reference may be made to other parts of the text, and in order to avoid redundancy, further description is omitted here.

Example four

Referring to fig. 2, the solar cell of the embodiment of the present application is a double-sided contact cell 1002, the double-sided contact cell 1002 includes a silicon substrate 101, a third contact region 130 and a fourth contact region 140, the third contact region 130 and the fourth contact region 140 have opposite polarities and are respectively disposed on the front surface and the back surface of the silicon substrate 101, and the third contact region 130 and/or the fourth contact region 140 adopt the contact structure 100 of the fifth embodiment.

In the solar cell according to the embodiment of the present application, since the contact structure 100 has the functional layer in the first opening region formed in the surface passivation layer and has the metal electrode in the second opening region formed in the functional layer, the functional layer can not only produce a blocking effect, but also be used as a seed to implement the preparation of the metal electrode. Moreover, the functional layer and the metal electrode are bonded more firmly, so that the adhesion of the metal electrode and the solar cell is improved.

Specifically, the front surface of the silicon substrate 101 may be provided with a front surface passivation layer. For explanation and explanation of this part, reference may be made to the description of the surface passivation layer to avoid redundancy, which is not described herein.

Specifically, in the example of fig. 2, the third contact region 130 and the fourth contact region 140 each employ the contact structure 100 in embodiment five.

Specifically, one of the third contact region 130 and the fourth contact region 140 is a P-type contact region, and the other is an N-type contact region.

It is understood that, in other examples, the contact structure 100 of the fifth embodiment may be adopted for the third contact region 130, and the contact structure 100 of the fifth embodiment may not be adopted for the fourth contact region 140; alternatively, the third contact region 130 may not adopt the contact structure 100 of the fifth embodiment, and the fourth contact region 140 adopts the contact structure 100 of the fifth embodiment.

EXAMPLE five

Referring to fig. 3, a contact structure 100 of a solar cell according to an embodiment of the present disclosure includes: a doped region 10 disposed on a silicon substrate 101; a surface passivation layer 20 disposed on the doped region 10, the surface passivation layer 20 having a first opening region 21; a functional layer 30 disposed on the first opening region 21, a second opening region 31 being provided on the functional layer 30; and a metal electrode 40 disposed on the second opening region 31.

In the contact structure 100 of the solar cell according to the embodiment of the present application, since the functional layer 30 is disposed in the first opening region 21 formed in the surface passivation layer 20 and the metal electrode 40 is disposed in the second opening region 31 formed in the functional layer 30, the functional layer 30 can not only generate a blocking effect, but also serve as a seed to implement the preparation of the metal electrode 40. Furthermore, this makes the functional layer 30 and the metal electrode 40 more firmly bonded, thereby improving the adhesion of the metal electrode 40 to the solar cell.

It can be understood that the functional layer 30 is a dense structure, which can block the diffusion of the metal electrode 40, and meanwhile, the functional layer 30 has a better electroplating effect due to the conductive effect under the combined action of the seed layer and the functional layer during electroplating.

In particular, the silicon substrate 101 has a front side facing the sun and a back side facing away from the sun during normal operation. The front surface is a light receiving surface of the solar cell, and the back surface is arranged on the other side of the silicon substrate 101 away from the front surface. That is, the front surface and the back surface are located on opposite sides of the silicon substrate 101. In this embodiment, the silicon substrate 101 is an N-type single crystal silicon wafer. It is understood that in other embodiments, the silicon substrate 101 may also be a polysilicon wafer or a quasi-monocrystalline silicon wafer, and the silicon substrate 101 may also be P-type. In this way, the silicon substrate 101 may be provided according to actual use requirements, and the specific form of the silicon substrate 101 is not limited herein.

Alternatively, the front surface of the silicon substrate 101 may be formed with an anti-reflection structure. Such as random pyramid structures, inverted pyramid structures, spherical cap structures, V-groove structures. The anti-reflection structure may be formed by texturing on the front surface of the silicon substrate 101. Therefore, the reflection of sunlight from the front can be reduced, and the photoelectric conversion efficiency can be improved.

Alternatively, the back surface of the silicon substrate 101 may be a polished surface. For example, an alkaline polishing surface, an acid polishing surface, a mechanical polishing surface, and the like.

Referring to fig. 3, the width of the first opening region 21 is optionally 30 μm to 2000 μm. Examples thereof include 30 μm, 32 μm, 50 μm, 100 μm, 800 μm, 1000 μm, 1300 μm, 1500 μm and 2000 μm. In this way, the width of the first open region 21 is made to be in a suitable range, providing sufficient space for the functional layer 30 and the second open region 31.

Preferably, the width of the first opening region 21 is 800 μm to 1200 μm. For example, 800. mu.m, 850. mu.m, 900. mu.m, 960. mu.m, 1000. mu.m, 1100. mu.m, 1150. mu.m, 1200. mu.m.

Specifically, the first opening region 21 may be in a long strip shape, and the doped region 10 and the surface passivation layer 20 enclose a groove; alternatively, the surface passivation layer 20 is provided with a plurality of spaced through holes, and the plurality of spaced through holes form the first opening region 21.

Further, the bottom surface of the groove may be rectangular. Thus, the shape of the groove is regular, which facilitates the manufacture of the groove on the surface passivation layer 20 and the arrangement of the functional layer 30 in the groove. It will be appreciated that in other embodiments the floor of the recess may be oval, racetrack, or other irregular shape.

In particular, a plurality of spaced through holes may be located in a common line. Thus, the through holes have regular shapes, which facilitates the fabrication of the through holes on the surface passivation layer 20 and the arrangement of the functional layer 30 in the through holes. It is understood that in other embodiments, the plurality of spaced vias may not be aligned.

Referring to fig. 3, the functional layer 30 may optionally include a semiconductive or conductive film. In this way, the functional layer 30 can conduct electricity, and the photogenerated carriers generated inside the solar cell can flow not only to the metal electrode 40 directly, but also to the metal electrode 40 through the functional layer 30, so that the residence time of the photogenerated carriers inside the solar cell can be reduced, and the current can be output more effectively.

In particular, the semiconducting film is a doped semiconducting film. Such as doped polysilicon, doped amorphous silicon, doped silicon carbide, etc.

Specifically, the conductive film is a transparent conductive film, and the transparent conductive film is formed by one or more stacked layers of an ITO (indium tin oxide) thin film, an AZO (aluminum-doped zinc oxide) thin film, a GZO (gallium zinc oxide) thin film, an FTO (fluorine-doped tin oxide) thin film, an IWO (indium tin oxide) thin film and a graphene thin film. Therefore, the transparent conductive film has high permeability and can reflect light, and the loss of sunlight can be reduced. Thus, the photoelectric conversion efficiency is advantageously improved.

For example, the transparent conductive film is an ITO thin film; as another example, the transparent conductive film includes a stacked ITO thin film and AZO thin film; for another example, the transparent conductive film includes a GZO film, an FTO film, and an IWO film that are laminated. The specific form of the conductive film is not limited herein.

Optionally, the functional layer 30 has a thickness of less than 200 nm. For example, 0.2nm, 1nm, 10nm, 30nm, 50nm, 80nm, 100nm, 150nm, 190nm, 199 nm. Thus, the thickness of the functional layer 30 is made to be in a suitable range, thereby ensuring the barrier function, the seed function, and the adhesion function of the functional layer 30.

Preferably, the functional layer 30 has a thickness in the range of 80nm to 120 nm. For example, 80nm, 85nm, 90nm, 96nm, 100nm, 107nm, 110nm, 120 nm.

Specifically, the functional layers 30 are continuously distributed in the regions of the first opening regions 21 other than the second opening regions 31. Thus, the functional layer 30 is fully contacted with the doped region 10, which is beneficial to fully leading out current.

Referring to fig. 3, optionally, a ratio of an area of the second opening region 31 to an area of the first opening region 21 is less than 0.3. For example, 0.1, 0.13, 0.15, 0.18, 0.2, 0.21, 0.225, 0.28, 0.29. In this way, the area ratio of the second opening region 31 is prevented from being too large, and thus the functional layer 30 is prevented from being poor in effect.

Preferably, the ratio of the area of the second opening region 31 to the area of the first opening region 21 is 0.13-0.17. For example, 0.13, 0.14, 0.15, 0.16, 0.17.

Referring to fig. 3, the second opening region 31 is optionally a continuous groove or a spaced through hole. In other words, the second opening region 31 is in a long strip shape, and the doped region 10 and the functional layer 30 enclose a groove; alternatively, the functional layer 30 is provided with a plurality of spaced through holes, and the plurality of spaced through holes form the second opening region 31. In this way, the metal electrode 40 contacts the doped region 10 through the groove or the through hole on the functional layer 30, so as to extract the current.

In particular, the bottom surface of the groove may be rectangular. Thus, the shape of the groove is regular, so that the groove can be conveniently manufactured on the functional layer 30, and the metal electrode 40 can be conveniently arranged in the groove. It will be appreciated that in other embodiments, the bottom surface of the groove may also be oval, racetrack, or other irregular shapes.

In particular, a plurality of spaced through holes may be located in a common line. Thus, the through holes are regular in shape, so that the through holes can be conveniently manufactured on the functional layer 30, and the metal electrodes 40 can be conveniently arranged in the through holes. It is understood that in other embodiments, the plurality of spaced vias may not be aligned.

In particular, the diameter of the through-hole is less than 50 μm. For example, 2 μm, 10 μm, 15 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 49 μm.

Preferably, the diameter of the through-hole is 20 μm to 30 μm. For example, 20 μm, 22 μm, 25 μm, 28 μm, and 30 μm.

Referring to fig. 3, the metal electrode 40 optionally includes a seed layer and a metal layer, wherein the seed layer is located between the metal layer and the doped region. Thus, the seed layer can form many core centers on the doped region 10, so as to avoid island-shaped distribution of metal without seed layer, and make the metal layer more uniformly distributed in the second opening region 31.

Specifically, the metal layer is one or more of magnesium, copper, tin, aluminum, silver, gold, chromium, iron, nickel, zinc, ruthenium, palladium, and platinum. For example, the metal layer is aluminum; as another example, the metal layer is a stack of aluminum and silver; for another example, the metal layer is a stack of aluminum, silver, and gold.

Specifically, the metal electrodes 40 are continuously distributed in the second opening region 31. Therefore, the metal electrode 40 is fully contacted with the doped region 10, which is beneficial to fully extracting current.

Specifically, the seed layer is one or more of copper, tin, aluminum, silver, gold, chromium, iron, nickel, zinc, ruthenium, palladium, and platinum. For example, the seed layer is copper; as another example, the seed layer is a stack of copper and tin; for another example, the seed layer is a stack of copper, tin, and aluminum.

Specifically, the seed layer may also be an alloy material, the seed layer includes a main component and a reinforcing component, the main component is one or more metals having a wavelength range of 850-.

Therefore, the seed layer formed by fusing the main component and the strengthening component, the metal layer and the silicon substrate have strong binding force, and the light trapping effect of the solar cell is improved.

The main component has a wavelength of, for example, 850, 880, 900, 950, 1000, 1100, 1200. The average refractive index of the main component is, for example, 1.9, 1.8, 1.7, 1.6, 1.5, 1.4, 1.3, 1.2, 1.1. The content of the main component is, for example, 51%, 55%, 60%, 70%, 80%, 90%, 100%.

Furthermore, the main component is aluminum (Al), and the content is more than or equal to 70 percent. For example, 70%, 72%, 75%, 80%, 85%, 90%, 95%, 100%. The strengthening component is one or more of molybdenum (Mo), nickel (Ni), titanium (Ti) and tungsten (W), and the content is less than or equal to 30 percent. For example, 30%, 29%, 25%, 20%, 15%, 10%, 5%, 100%.

In the prior art, Ni (nickel) is usually used as a barrier layer for Cu (copper) diffusion, and can well adhere to a silicon substrate and a Cu electrode, and the general flow of the implementation scheme is as follows: preparing a silicon substrate after film coating, laser film opening, Ni electroplating and Cu electroplating. However, in the research process, the Ni serving as a barrier layer of Cu has a large defect, the long-wave band reflection effect of the Ni is low, the light trapping effect of the cell is reduced, and the conversion efficiency of the cell is further reduced.

The comparative data of the optical performance of the battery using Ni + Cu and Ag as electrode materials are shown in the following table:

as can be seen from the above table, the combination of Ni + Cu greatly reduces the short-circuit current of the battery, wherein the simulation result predicts that the short-circuit current density will be reduced by 0.75mA/cm²And the experimental result is reduced by 1.36mA/cm²Is greater than theoretically predicted.

We analyze the common metal trapping effect as follows:

at present, the thickness of the finished product battery silicon wafer is about 150um, light with the wavelength of more than 850nm can effectively penetrate through the thickness, and meanwhile, because the forbidden bandwidth of Si is 1.12eV, the light with the wavelength of more than 1200nm can hardly excite electron-hole pairs, so that the light trapping effect is mainly considered to be in a 850-1200nm waveband. The following table shows the interface reflectivity for different metals and the market price found in 2 months of 2022:

as can be seen from the above table, the difference of the reflectivity of the interface between different metals is large, wherein the four metals of Ag/Al/Cu/Mg can obtain relatively ideal short-circuit current results, and can form effective light trapping effect when used in a seed layer; further analysis: cu cannot be applied as a seed layer because one important function of the seed layer is to block Cu; mg is not a good choice if it is too reactive chemically; the price of Ag is higher, and the Ag is not a better choice; al is an ideal seed layer metal, which has excellent back-reflection effect, relatively stable chemical properties, and low price, which is 1/223 for Ag and 1/3 for Cu.

However, the use of Al as a seed layer introduces another problem: the adhesion between Al and other metals is weak, the product reliability can not reach the standard by using the technology of using pure Al as a seed layer, and the product is separated from the outer metal layer under the condition of cold and hot alternation or bending, or the stress of welding spots in component welding can cause the separation of Al and the outer metal layer, so that the separation is generated, and the failure is caused.

The bonding force between Al and Cu is poor, and a piece of grid line is easy to form and fall off. In order to solve the problem, various improving methods are tried, such as increasing the contact area of an Al/silicon substrate, raising the temperature of a sample to promote inter-metal diffusion, inserting a new material such as TiW between Al/Cu materials and the like, and the effect is not ideal; finally, if a strengthening component capable of forming good interconnection with Cu is added into the Al material to be used as a seed layer, even no additional annealing treatment is needed after Cu electroplating, namely good seed layer/electroplated layer connection is formed, so that the adhesion of the electroplated layer is greatly improved, and the problem is finally solved.

Experiments prove that the four strengthening components of Ni, Mo, Ti and W have obvious adhesion promotion effect.

Further, it is understood from the table that the reflectance of four materials, Ni, Mo, Ti, and W, is low, and if the reflectance is too high, the optical properties are deteriorated, and in the case of W, the properties of the alloy components are simply assumed to be the reinforced average values of the components, and the estimated results shown in the following table are obtained:

wherein when the W content is 30%, the current loss is 0.36mA/cm²This causes a reduction in the cell conversion efficiency of about 0.2%, which is acceptable in view of cost reduction by substitution of Ag with Cu and solution of the reliability problem, though large, and therefore, it is considered that 30% or less of the strengthening component is a recommended value.

Further, the ratio of the strengthening components in the seed layer can be unevenly distributed, so that better performance effect can be obtained, and the principle is as follows: the portion adjacent to the silicon substrate may have a reduced content of the reinforcing component, which may enhance the reflection of light, and the portion in contact with the metal layer may have a relatively higher content of the reinforcing component to improve the bonding force with the metal layer.

The following table shows the welding tension comparison for different electrode technologies:

the solar cell manufactured by the Al alloy seed layer has higher welding tension even than the conventional Ag electrode.

Furthermore, the thickness of the seed layer is preferably not less than 30nm, experiments show that the seed layer with the thickness of 30nm is enough to block the diffusion of Cu metal, and the thickness is not more than 300nm, and the main consideration is to control the cost, for example, the seed layer is manufactured by adopting a physical vapor deposition method, even if Al is lower than other metals, the cost influence of an Al target material is still not negligible, and in addition, the higher the thickness of the seed layer is, the lower the productivity of the equipment side is, the difficulty in popularization in large-scale production is caused, so the thickness of the seed layer is preferably between 30nm and 300 nm.

Referring to fig. 3, optionally, a metal electrode 40 is further disposed on the functional layer 30. In other words, the metal electrode 40 includes a first conductive portion 41 and a second conductive portion 42, the first conductive portion 41 protrudes from the second conductive portion 42 toward the doped region 10, and the first conductive portion 41, the second conductive portion 42 and the doped region 10 enclose a gap in which the functional layer 30 is disposed. Thus, the metal electrode 40 is not only disposed on the doped region 10, but also disposed on the functional layer 30, which can increase the contact between the metal electrode 40 and the functional layer 30, so that the effect of conducting current is better.

Specifically, the functional layer 30 entirely fills the gap. Thus, the metal electrode 40 and the functional layer 30 are in close contact with each other, the current extraction effect is improved, and dust, moisture and the like can be prevented from accumulating in the gap.

It is understood that in other embodiments, the functional layer 30 may also partially fill the gap. Thus, the reflected sunlight can be reflected back to the silicon substrate 101 through the metal electrode 40, thereby improving the photoelectric conversion efficiency.

Specifically, the first conductive portion 41 completely overlaps the second opening region 31 or is located in the second opening region 31, and the width of the orthographic projection of the second conductive portion 42 on the silicon substrate 10 is greater than the width of the orthographic projection of the first conductive portion 41 on the silicon substrate 10. Thus, the width of the second conductive portion 42 is wide, which facilitates the fabrication of the metal electrode 40. It is understood that the area where the first conductive portion 41 contacts the doped region 10 is a conductive contact area.

Specifically, "first conductive portions 41 completely overlap with second opening region 31 or are located in second opening region 31" means that all first conductive portions 41 completely overlap with corresponding second opening regions 31; alternatively, all of the first conductive portions 41 are located in the corresponding second opening regions 31; or, part of the first conductive portions 41 completely overlap the corresponding second opening regions 31, and part of the first conductive portions 41 are located in the corresponding second opening regions 31.

Specifically, in fig. 3, the first conductive portion 41 is located at the middle position of the second conductive portion 42. It is understood that in other embodiments, the first conductive portion 41 may be located at an edge position of the second conductive portion 42.

Specifically, the thickness of the first conductive portion 41 is 10nm to 1000 nm. For example, 10nm, 12nm, 50nm, 100nm, 300nm, 500nm, 700nm, 980nm, and 1000 nm.

Specifically, the seed layer thickness is generally smaller than the first conductive portion 41 thickness.

Specifically, the second conductive portion 42 has a thickness of 1 μm to 800 μm. For example, 1 μm, 2 μm, 10 μm, 50 μm, 100 μm, 300 μm, 500 μm, 780 μm, 800 μm.

Referring to fig. 3, the doped region 10 may alternatively be a monocrystalline doped layer. Further, the monocrystalline doped layer may be formed by diffusion, ion implantation, source diffusion, or other processes. It is understood that the doped region 10 is a diffusion structure formed on the silicon substrate 101 by doping different types of diffusion sources, and the doped region 10 is not grown on the basis of the silicon substrate 101, but the silicon substrate 101 is partially diffused into the doped region 10. Thus, the doped region 10 has a simple structure, which is beneficial to improving the production efficiency.

Referring to fig. 4, the doped region 10 may be a passivation contact structure. Specifically, the doped region 10 includes a first doped layer 11, a first passivation layer 12, and a second doped layer 13, which are sequentially stacked. Therefore, the arrangement of the passivation contact structure is realized, and double gettering can be performed through the first doping layer 11 and the second doping layer 13, so that the gettering effect is better.

Specifically, the thickness of the first doped layer 11 ranges from 50nm to 2000 nm. For example, 50nm, 51nm, 60nm, 100nm, 500nm, 1000nm, 1500nm, 1900nm, 2000 nm. In this way, contact resistance can be reduced and a field passivation effect can be provided.

Specifically, the first doped layer 11 is a doped monocrystalline silicon layer. Further, the first doping layer 11 may be formed by diffusion, ion implantation, source diffusion, or other processes; it is also possible to form the first doped layer 11 in the silicon substrate 101 by making the doping source directly through the first passivation layer 12 or through a hole in the porous structure when the second doped layer 13 is prepared.

Specifically, the thickness of the first passivation layer 12 is 0.5nm to 20 nm. For example, 0.5nm, 0.6nm, 1nm, 1.5nm, 5nm, 10nm, 12nm, 15nm, 18nm, 20 nm.

Specifically, the first passivation layer 12 includes one or more of an oxide layer, a nitride oxide layer, a silicon carbide layer, and an amorphous silicon layer. Further, the oxide layer comprises one or more of a silicon oxide layer and an aluminum oxide layer. Thus, an excellent interface passivation effect can be provided.

Further, the silicon carbide layer comprises a hydrogenated silicon carbide layer. Thus, hydrogen in the hydrogenated silicon carbide layer enters the silicon substrate 101 under the action of a diffusion mechanism and a thermal effect, dangling bonds on the back surface of the silicon substrate 101 can be neutralized, and defects of the silicon substrate 101 are passivated, so that defect energy levels in forbidden bands are reduced, and the probability that carriers enter the second doped layer 13 through the first passivation layer 12 is improved.

Referring to fig. 5, optionally, the first passivation layer 12 is a porous structure, the hole region of the first passivation layer 12 has the first doped layer 11 and/or the second doped layer 13, and the first doped layer 11 and the second doped layer 13 are connected by the doped hole region. Further, the second doped layer 13 is connected to the silicon substrate 101 through the doped hole region and the first doped layer 11.

In this way, a conductive channel is formed in the hole region of the first passivation layer 12, so that the first passivation layer 12 has good resistivity, and the sensitivity of the thickness of the first passivation layer 12 to the influence of resistance is reduced, thereby reducing the control requirement on the thickness of the first passivation layer 12. Meanwhile, the first doping layer 11 disposed between the silicon substrate 101 and the first passivation layer 12 may form a separation electric field for enhancing surface electron holes, thereby improving a field passivation effect. Meanwhile, since the fermi level of the first doping layer 11 is different from that of the silicon substrate 101, the first doping layer 11 changes the fermi level, increases the solid concentration of impurities (transition group metals), and may form an additional gettering effect. Meanwhile, the second doping layer 13 is connected with the silicon substrate 101 through the doped hole region and the first doping layer 11 on the porous structure, so that the overall resistance of the prepared battery is further reduced, and the conversion efficiency of the battery is finally improved.

In one example, the hole region has the first doped layer 11 therein and no second doped layer 13 therein; in another example, the hole region has the second doped layer 13 therein and does not have the first doped layer 11; in yet another example, the hole region has a first doped layer 11 and a second doped layer 13 therein. In addition, the first doped layer 11 and/or the second doped layer 13 may fill one or more holes, or may fill a part of one or more holes, or may not fill a part of the holes in the first doped layer 11 and the second doped layer 13. The specific doping profile of the void region is not limited herein.

It is understood that in other embodiments, the first passivation layer 12 may also be a completely continuous structure. In other words, the first passivation layer 12 may not include holes.

Optionally, the average pore diameter of the pores of the first passivation layer 12 is less than 1000 nm. Examples thereof include 4nm, 10nm, 16nm, 50nm, 480nm, 830nm, 960nm and 999 nm. In this way, the average pore diameter of the porous structure is on the order of nanometers, so that the total contact area of second doped layer 13 and silicon substrate 101 is greatly reduced, and recombination loss can be reduced. Still further, the porous structure has an average pore size of less than 500 nm. In this manner, the overall contact area of second doped layer 13 with silicon substrate 101 is further reduced, thereby further reducing recombination losses. Still further, 90% of the through-holes may have an average pore size of less than 1000 nm. Therefore, a certain floating space is provided, the product yield can be guaranteed under the condition of ensuring small composite loss, the production efficiency is improved, extra processes such as laser hole opening are not needed to be added, and the preparation process is simple.

Optionally, the ratio of the area of the hole region of the first passivation layer 12 to the entire area of the first passivation layer 12 is less than 20%. In this way, by controlling the total area of the hole region according to the area ratio of the hole region, the total contact area between second doped layer 13 and silicon substrate 101 can be made smaller, and the recombination loss can be reduced while ensuring low contact resistance.

Alternatively, the holes of the first passivation layer 12 are formed by thermal diffusion impact. Specifically, the temperature range of the thermal diffusion impact is 500 ℃ to 1200 ℃. For example, 500 deg.C, 510 deg.C, 550 deg.C, 600 deg.C, 700 deg.C, 800 deg.C, 820 deg.C, 900 deg.C, 950 deg.C, 1000 deg.C, 1050 deg.C, 1100 deg.C, 1150 deg.C, 1200 deg.C. Preferably, the thermal diffusion impact temperature is from 800 ℃ to 1100 ℃. For example, 800 deg.C, 820 deg.C, 900 deg.C, 950 deg.C, 1000 deg.C, 1050 deg.C, 1100 deg.C. Therefore, the formed porous structure has smaller holes, the average pore diameter is less than 1000nm, and the reduction of recombination loss is facilitated. Moreover, the surface density of the holes is higher and can reach 10⁶-10⁸/cm²The transverse transport distance can be reduced, the current crowding effect is eliminated, the resistance loss is reduced, and the resistance reducing effect is better. It is understood that in other embodiments, the porous structure may be formed by chemical etching, dry etching, or other means.

Optionally, the holes of the first passivation layer 12 are distributed sparsely on the first passivation layer 12. Therefore, the distribution state of the holes does not need to be strictly controlled, and the production efficiency is favorably improved.

Further, the first doped layer 11 is discretely and locally distributed in each hole region of the first passivation layer 12. Thus, under the condition that the first doping layers 11 are distributed discretely, the orthographic projection of the holes of the first passivation layer 12 on the silicon substrate 101 can be covered by the orthographic projection of the first doping layers 11 on the silicon substrate 101, so that the second doping layers 13 can not be in direct contact with the silicon substrate 101, and serious recombination caused by the fact that the second doping layers 13 are in direct contact with the silicon substrate 101 is avoided.

Further, the first doped layer 11 is completely continuously disposed between the silicon substrate 101 and the first passivation layer 12. Thus, since the first doping layer 11 is completely and continuously disposed, the orthographic projection of the hole of the first passivation layer 12 on the silicon substrate 101 is inevitably covered by the orthographic projection of the first doping layer 11 on the silicon substrate 101, and the second doping layer 13 cannot be in direct contact with the silicon substrate 101, thereby avoiding the serious recombination caused by the direct contact of the second doping layer 13 with the silicon substrate 101.

Further, the distribution of the first doped layer 11 can be controlled by the doping duration. The longer the doping time, the greater the amount of doping, the higher the proportion of first doped layer 11 that continues until a completely covered layer of first doped layer 11 is formed on the silicon substrate 101. Further, the junction depth of the first doped layer 11 is less than 1.5 μm. Thus, contact resistance can be reduced, and field effect passivation can be improved.

Specifically, the thickness of the second doped layer 13 ranges from 0nm to 500 nm. For example, 0.1nm, 50nm, 100nm, 150nm, 200nm, 250nm, 300nm, 350nm, 400nm, 450nm, 500 nm. Thus, the thickness range of the second doped layer 13 is wide, and the second doped layer can meet different requirements in actual production.

Preferably, the thickness of second doped layer 13 ranges from 100nm to 500 nm. Examples thereof include 100nm, 150nm, 200nm, 250nm, 300nm, 350nm, 400nm, 450nm and 500 nm. Therefore, the thicker second doping layer 13 can prevent the conducting layer from burning through the second doping layer 13, reduce contact recombination, improve open-circuit voltage, improve process width and ensure product yield.

Specifically, the second doping layer 13 includes a doped polysilicon layer, a doped silicon carbide layer, or a doped amorphous silicon layer. Preferably, second doped layer 13 comprises a doped silicon carbide layer. Thus, the silicon carbide material has wide optical band gap and low absorption coefficient, so that parasitic absorption can be reduced, and the short-circuit current density can be effectively improved. Further, the doped silicon carbide layer is composed of at least one doped silicon carbide film having different refractive indexes, and the refractive indexes of the doped silicon carbide films are sequentially decreased from the silicon substrate 101 to the outside. Thus, a gradient of refractive index can be formed, and a gradient extinction effect can be formed. Further, the doped silicon carbide layer in second doped layer 13 comprises a doped hydrogenated silicon carbide layer having a conductivity greater than 0.01S-cm and a thickness greater than 10 nm. Thus, the conductivity requirement of the second doped layer 13 can be satisfied, and the parasitic absorption is lower, and the short-circuit current is improved.

Referring to fig. 6, the doped region 10 may be a passivation contact structure. Specifically, the doped region 10 includes a second passivation layer 14 and a third doped layer 15, which are sequentially stacked.

Thus, the arrangement of the front passivation contact structure is realized. It will be appreciated that the second passivation layer 14 is provided between the substrate 101 and the third doped layer 15, and as a tunneling structure is used, the second passivation layer 14 allows selective transport of one carrier by the tunneling principle, while the other carrier is difficult to tunnel through the second passivation layer 14 due to the presence of the potential barrier and the field effect of the third doped layer 15. In this way, one type of carriers can tunnel into the third doped layer 15 and block the other type of carriers from passing through, and recombination at the interface can be significantly reduced, so that the solar cell 100 has higher open-circuit voltage and short-circuit current, thereby improving the photoelectric conversion efficiency.

Specifically, the thickness of the second passivation layer 14 ranges from 0.1nm to 20 nm. For example, 0.1nm, 0.2nm, 0.5nm, 1nm, 5nm, 10nm, 15nm, 19nm, 20 nm.

Specifically, the second passivation layer 14 includes one or more of intrinsic amorphous silicon, intrinsic silicon carbide. Preferably, the second passivation layer 14 is an intrinsic silicon carbide layer. Thus, the silicon carbide material has wide optical band gap and low absorption coefficient, so that parasitic absorption can be reduced, and the short-circuit current density can be effectively improved.

Further, when the second passivation layer 14 is an intrinsic silicon carbide layer, it can be prepared by Hot filament chemical vapor deposition (HWCVD, Hot Wire CVD), wherein the Hot filament temperature is preferably 1500-1800 ℃, the deposition pressure is 0.05-2mbar, the substrate temperature is RT-400 ℃, and SiH is used as deposition gas₃(CH₃) And H₂Or may also include N₂At this time N₂Does not participate in the reaction at a temperature lower than 1800 ℃.

Further, when the second passivation layer 14 is an intrinsic silicon carbide layer, it can be prepared by Plasma Enhanced Chemical Vapor Deposition (PECVD), wherein the Deposition temperature is 100-₄And CH₄And its CH₄Flow rate of (1) and SiH₄And CH₄Total flow ratio of CH₄/(SiH₄+CH₄) Is 0.1-1.

Specifically, the thickness of the third doped layer 15 ranges from 10nm to 300 nm. For example, 10nm, 11nm, 15nm, 20nm, 50nm, 100nm, 150nm, 180nm, 200nm, 250nm, 290nm, 300 nm.

Specifically, the third doped layer 15 includes one or more of doped amorphous silicon, doped silicon carbide. Preferably, the third doped layer 15 is a doped silicon carbide layer. Because the silicon carbide material has wide optical band gap and low absorption coefficient, the parasitic absorption can be reduced, and the short-circuit current density can be effectively improved. Further, the doped silicon carbide layer is composed of at least one doped silicon carbide film having different refractive indexes, and the refractive indexes of the doped silicon carbide films are sequentially decreased from the silicon substrate 101 to the outside. Thus, a gradient of refractive index can be formed, and a gradient extinction effect can be formed. Further, the doped silicon carbide layer in the third doped layer 15 comprises a doped hydrogenated silicon carbide layer having a conductivity greater than 0.01S · cm and a thickness greater than 10 nm. Thus, the conductivity requirement of the third doped layer 15 can be satisfied, and the parasitic absorption is lower, and the short-circuit current is increased.

Specifically, the surface of the silicon substrate 101 in contact with the second passivation layer 14 forms a plurality of inner diffusion regions corresponding to the third doping layer 15. It can be understood that, during the process of preparing the third doped layer 15, due to the high temperature process, the thinner second passivation layer 14 may be partially broken, and at this time, the second passivation layer 14 and the silicon substrate 101 may be attached at the broken position during the high temperature diffusion process, so that a plurality of inner diffusion regions corresponding to the third doped layer 15 are formed on the surface of the silicon substrate 101 in contact with the second passivation layer 14.

In particular, a tunnel oxide layer may also be provided between the second passivation layer 14 and the substrate 101.

Further, the thickness of the tunneling oxide layer is less than 3 nm. For example, 0.1nm, 0.5nm, 0.8nm, 1nm, 1.2nm, 1.5nm, 2nm, 2.3nm, 2.8nm, 3 nm.

Further, the tunneling oxide layer comprises one or more of a silicon oxide layer and an aluminum oxide layer. Preferably, the tunnel oxide layer is a silicon oxide layer. As such, the silicon oxide layer and the second passivation layer 14 may reduce the interface state density between the substrate 101 and the third doped layer 15 through chemical passivation.

Further, the tunnel oxide layer may be prepared by thermal oxidation and solution oxidation. Further, in the case of preparing the tunnel oxide layer by thermal oxidation, oxygen and nitrogen may be introduced at 800 ℃ and 500 ℃ for thermal oxidation for 5-30min, so as to form a silicon oxide layer on the substrate 101. In the case of preparing the tunneling oxide layer by solution oxidation, H in a solution ratio of 4:1 to 1:4 may be used₂SO₄And H₂O₂The mixed solution of the solutions is subjected to oxidation preparation, thereby forming a silicon oxide layer on the substrate 101.

Referring to fig. 3, the surface passivation layer 20 may optionally include one or more of an aluminum oxide layer, a silicon nitride layer, a silicon oxynitride layer, a silicon carbide layer, an amorphous silicon layer, and a silicon oxide layer.

Alternatively, the surface passivation layer 20 may be composed of at least one passivation film having different refractive indexes, and the refractive indexes of the respective passivation films are sequentially decreased from the silicon substrate 101 outward. Thus, a gradient of refractive index can be formed, and a gradient extinction effect can be formed.

Optionally, the surface passivation layer 20 covers the entire area of the doped region 10 except for the functional layer 30 and the metal electrode 40. Thus, leakage current can be avoided.

The present invention is not intended to be limited to the particular embodiments shown and described, but is to be accorded the widest scope consistent with the principles and novel features herein disclosed.

Claims

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

a doped region disposed on the silicon substrate;

the surface passivation layer is arranged on the doped region, and a first opening region is formed in the surface passivation layer;

and a metal electrode disposed on the second opening region.

2. The contact structure of claim 1, wherein said metal electrode is further disposed on said functional layer.

3. The contact structure of claim 1, wherein the functional layer comprises a semiconductive or conductive film.

4. The contact structure according to claim 3, wherein the conductive film is a transparent conductive film, and the transparent conductive film is formed by stacking one or more of an ITO thin film, an AZO thin film, a GZO thin film, an FTO thin film, an IWO thin film, and a graphene thin film.

5. The contact structure of claim 1, wherein the functional layer has a thickness of less than 200 nm.

6. The contact structure of claim 1, wherein the width of the first open region is 30 μ ι η to 2000 μ ι η.

7. The contact structure of claim 1, wherein a ratio of an area of said second open region to an area of said first open region is less than 0.3.

8. The contact structure of claim 1 wherein said second open area is a continuous groove or spaced through holes.

9. The contact structure of claim 8, wherein the via has a diameter of less than 50 μm.

10. The contact structure of claim 1, wherein the doped region comprises a first doped layer, a first passivation layer, and a second doped layer, which are sequentially stacked.

11. The contact structure according to claim 10, wherein the first passivation layer is a porous structure, the first and/or second doped layers are provided in the hole region of the first passivation layer, and the first and second doped layers are connected by a doped hole region.

12. The contact structure of claim 11, wherein the pores of the first passivation layer have an average pore size of less than 1000 nm.

13. The contact structure of claim 11, wherein a ratio of an area of the hole region of the first passivation layer to an overall area of the first passivation layer is less than 20%.

14. The contact structure of claim 11, wherein the hole of the first passivation layer is formed by thermal diffusion bombardment.

15. The contact structure of claim 11, wherein the holes of the first passivation layer are sparsely distributed on the first passivation layer.

16. The contact structure of claim 1, wherein the doped region comprises a second passivation layer and a third doped layer sequentially stacked.

17. The contact structure of claim 1, wherein the metal electrode comprises a seed layer and a metal layer, the seed layer being between the metal layer and the doped region.

18. The contact structure of claim 17, wherein the seed layer is a stack of one or more of copper, tin, aluminum, silver, gold, chromium, iron, nickel, zinc, ruthenium, palladium, and platinum.

19. The contact structure of claim 17, wherein the seed layer is an alloy material, the seed layer comprises a main component and an enhancing component, the main component is one or more metals with a wavelength range of 850-.

20. The contact structure of claim 19, wherein said main component is aluminum in an amount of 70% or more; the strengthening component is one or more of molybdenum, nickel, titanium and tungsten, and the content is less than or equal to 30 percent.

21. The contact structure of claim 17, wherein the metal layer is a stack of one or more of magnesium, copper, tin, aluminum, silver, gold, chromium, iron, nickel, zinc, ruthenium, palladium, and platinum.

22. A solar cell, characterized in that the solar cell is a back contact cell, the back contact cell comprises a silicon substrate, a first contact region and a second contact region, the first contact region and the second contact region have opposite polarities and are alternately arranged on the back side of the silicon substrate, and the first contact region and/or the second contact region adopt the contact structure of any of claims 1-21.

23. A solar cell, characterized in that the solar cell is a double-sided contact cell, the double-sided contact cell comprises a silicon substrate, a third contact region and a fourth contact region, the third contact region and the fourth contact region have opposite polarities and are respectively disposed on the front surface and the back surface of the silicon substrate, and the third contact region and/or the fourth contact region adopt the contact structure of any one of claims 1 to 21.

24. A battery module comprising the solar cell of claim 22 or 23.

25. A photovoltaic system comprising the cell assembly of claim 24.