Passivated contact cell with selective polysilicon layer and photovoltaic module and system
By adopting a double-layer polysilicon layer stack structure in TOPCon batteries, the inner layer of the selective polysilicon layer doped with carbon elements solves the problems of ineffective absorption and high contact resistivity of heavily doped polysilicon, and achieves higher photoelectric conversion efficiency and surface passivation performance.
Patent Information
- Application Number
- CN202422048502.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-08-22
- Publication Date
- 2025-08-26
- Estimated Expiration
- 2034-08-22
AI Technical Summary
The selective polysilicon layer of the existing TOPCon battery has the problem that the heavily doped polysilicon has no effect on long-wave light absorption by heavy doped polysilicon, the inability to form C-H chemical bonds to suppress H escape, and the contact resistivity of the phosphorus doped polysilicon layer and the metal electrode is high.
A double-layer polysilicon layer stacking structure is adopted, and the inner layer is a phosphorus heavily doped polysilicon layer and a carbon/phosphorus medium-doped polysilicon layer. The C-H chemical bond is formed by doping carbon to inhibit H escape, and a high concentration doping is formed in the metallized region to reduce contact resistivity.
It improves the photoelectric conversion efficiency, reduces the contact resistivity, enhances the surface passivation performance, and improves the short-circuit current density and filling factor.
Smart Images
Figure CN223274432U_ABST
Abstract
Description
Technical Field
[0001] The utility model belongs to the technical field of solar cells, and in particular relates to a passivation contact cell with a selective polysilicon layer, and also relates to a photovoltaic component and a photovoltaic system. Background Art
[0002] Currently, TOPCon cells use a tunneling oxide layer + doped polysilicon layer passivation contact structure. Due to the serious parasitic absorption of the doped polysilicon layer itself, this tunneling layer + passivation layer structure is only used on the back of the TOPCon cell. The current industrialized tunneling oxide layer thickness is 1-2nm, and the doped polysilicon layer thickness is 100-150nm. In other words, the selective polysilicon layer structure reduces the free carrier absorption and direct band gap absorption on the back of the cell. Compared with the conventional cell structure, the short-circuit current density (Jsc) is increased by about 1.2mA / cm 2 At the same time, in order to further reduce the negative impact of the parasitic absorption of the doped polysilicon layer itself on the electrical performance of the battery, some processing technologies that can form selectively doped polysilicon layers have emerged in recent years. At present, the mainstream of this type of technology is mainly divided into two categories: one is to use an ultraviolet picosecond laser to oxidize the surface of the phosphorus-doped polysilicon layer using laser to form a SiOx mask layer, and then use tetramethylammonium hydroxide (TMAH) solution to etch away the polysilicon layer without mask blocking, and finally use hydrofluoric acid (HF) solution to etch away the SiOx mask layer to form phosphorus-doped polysilicon layers of different thicknesses; the second is to use a picosecond laser to directly use laser to thin and ablate the doped polysilicon layer, thereby forming phosphorus-doped polysilicon layers of different thicknesses.
[0003] Therefore, the formation of the selective polysilicon layer structure has the following technical defects:
[0004] (1) Heavily doped polysilicon covers the entire back surface of the TOPCon cell. This part of the structure has a large light absorption coefficient for long-wavelength light. This type of absorption is called free carrier absorption (FCA), which is ineffective absorption. The thicker the doped polysilicon or the higher the doping concentration, the more severe the FCA absorption and the lower the photoelectric conversion efficiency.
[0005] (2) Conventional phosphorus-doped polysilicon layers cannot form C—H chemical bonds to suppress H escape, resulting in an inability to effectively improve surface passivation performance;
[0006] (3) The phosphorus-doped polysilicon layer cannot form a better ohmic contact with the metal electrode, thereby failing to reduce the contact resistivity. Utility Model Content
[0007] The technical problem to be solved by the utility model is to overcome the deficiencies of the prior art and provide an improved passivation contact cell with a selective polysilicon layer.
[0008] At the same time, the utility model also relates to a photovoltaic component and a photovoltaic system.
[0009] In order to solve the above technical problems, the technical solutions adopted by the present invention are as follows:
[0010] A passivation contact cell with a selective polysilicon layer comprises a silicon wafer body, a front structural layer, a back structural layer, a front metal electrode and a back metal electrode, wherein the back structural layer comprises a tunneling oxide layer formed on the back of the silicon wafer body, a selective polysilicon layer, a back passivation layer and a back anti-reflection layer, wherein the selective polysilicon layer comprises a phosphorus-heavy doped polysilicon layer, a carbon / phosphorus-medium doped polysilicon layer and a phosphorus-lightly doped polysilicon layer in which the concentrations of phosphorus atoms are arranged in descending order, and the phosphorus-heavy doped polysilicon layer, the carbon / phosphorus-medium doped polysilicon layer and the phosphorus-lightly doped polysilicon layer constitute inner and outer doped structural layers, and the back metal electrode corresponds to the phosphorus-heavy doped polysilicon layer and the back metal electrode is formed on the phosphorus-heavy doped polysilicon layer.
[0011] According to a specific implementation and preferred aspect of the present invention, a lightly phosphorus-doped polysilicon layer constitutes an inner doped structural layer, and a heavily phosphorus-doped polysilicon layer and a carbon / phosphorus medium-doped polysilicon layer constitute an outer doped structural layer. Since the polysilicon is doped with carbon, this helps suppress the activity of phosphorus atoms doped in subsequent processes. This allows for a structure in which the metallized region has a high doping concentration and the non-metallized region has a low doping concentration, reducing the parasitic absorption of long-wavelength photons by the heavily doped polysilicon layer and maximizing the current value of photoelectric conversion. At the same time, in the metallized region, a higher doping concentration forms a better ohmic contact with the metal electrode. This is because the resistivity of the highly doped region is greatly reduced, reducing the resistance at the interface between the semiconductor and the metal electrode.
[0012] Preferably, the thicknesses of the heavily phosphorus-doped polysilicon layer and the carbon / phosphorus-medium-doped polysilicon layer are equal, wherein the heavily phosphorus-doped polysilicon layer corresponds to the metal region, and the carbon / phosphorus-medium-doped polysilicon layer corresponds to the non-metal region.
[0013] Alternatively, a phosphorus-heavy doped polysilicon layer is formed in the metal area corresponding to the inner doped structural layer to fill the back side, and the inner doped structural layer separates the phosphorus-heavy doped polysilicon layer and the tunneling oxide layer, and a carbon / phosphorus-medium doped polysilicon layer is formed in the non-metal area corresponding to the inner doped structural layer.
[0014] In some specific embodiments, the concentration of phosphorus heavily doped polysilicon layer is 4.0 to 8.0E+20 cm -3 The concentration of carbon / phosphorus doped polysilicon layer is 0.8~1.0E+20cm -3The concentration of phosphorus lightly doped polysilicon layer is 1.0~4.0E+19cm -3 .
[0015] According to another specific embodiment and preferred aspect of the present invention, the thickness of the inner doped structure layer and the outer doped structure layer are both 30 to 60 nm. Currently, the industry widely adopts a passivation contact structure of a tunnel oxide layer + phosphorus-doped polysilicon layer, where the phosphorus-doped polysilicon layer is currently approximately 100 to 150 nm thick. The present invention adopts a double-layer polysilicon stacking method, with the thickness of the inner intrinsic polysilicon layer maintained at 30-60nm, and the outer polysilicon layer doped with carbon elements, and the thickness maintained at 30-60nm. This technology is beneficial for suppressing the escape of H by forming C-H chemical bonds, which is beneficial for promoting surface passivation. In addition, doping carbon elements in the polysilicon layer can reduce the activity of phosphorus atoms, reduce Auger recombination and SRH recombination, and thus inhibit the advancement of phosphorus atoms in non-metallized areas during the phosphorus diffusion process. In the metallized area, since there is no carbon-doped polysilicon, phosphorus atoms can be doped to the maximum extent. A higher doping concentration will form a better ohmic contact. This is because the resistivity of the high-concentration doped area is greatly reduced, reducing the resistance of the contact interface between the semiconductor and the metal electrode. The parasitic absorption of the low-concentration carbon-doped area of the non-metallized part is also reduced compared with traditional solar cells.
[0016] According to another specific implementation and preferred aspect of the present invention, the front structural layer includes a boron-doped emitter, a front passivation layer and a front anti-reflection layer, which are sequentially arranged from the inside to the outside.
[0017] Preferably, the boron-doped emitter, the front passivation layer and the front anti-reflection layer have the same shape and their surfaces are all in a pyramid velvet shape.
[0018] According to another specific implementation and preferred aspect of the present invention, the front passivation layer is an aluminum oxide layer, wherein the thickness of the aluminum oxide layer is 2 to 10 nm; and / or, the front anti-reflection layer is a silicon carbide layer, wherein the thickness of the silicon nitride layer is 20 to 50 nm, and the refractive index of the silicon nitride layer is 2.1 to 2.2. Preferably, the stack formed by the back passivation layer and the back anti-reflection layer is the same as the stack formed by the front passivation layer and the front anti-reflection layer. In short, the passivation anti-reflection film on the front and back surfaces adopts a stacked film design, which is a combination of two materials such as aluminum oxide, silicon nitride, silicon dioxide, and silicon oxynitride. As a preference, a passivation anti-reflection film stack design of aluminum oxide + silicon carbide is adopted, wherein the preferred thickness of aluminum oxide is 2 to 10 nm, the preferred thickness of silicon nitride is 20 to 50 nm, and the refractive index of silicon nitride is 2.1 to 2.2.
[0019] Preferably, the silicon wafer body is an N-type silicon wafer substrate. The N-type single crystal silicon wafer is wet cleaned to remove the damaged layer on the surface of the wafer, clean the surface metal impurities and oil stains, and produce a velvet surface. At a reaction temperature of 70±10°C, a 10% volume fraction of sodium hydroxide solution is used to etch the damaged layer on the surface of the silicon wafer caused by wire cutting. The etching thickness on both sides is approximately 10μm. A random pyramid surface texture is then generated using a wet chemical process using an alkaline solution and a velvet additive. Standard RCA wet cleaning is then performed, and the resulting random pyramid height is approximately 0.5 to 2μm.
[0020] In some specific embodiments, the front metal electrode and the back metal electrode are formed to have a width of 10 to 60 μm and a height of 3 to 10 μm.
[0021] In addition, the carbon / phosphorus doped polysilicon layer is an oxygen / phosphorus doped polysilicon layer or a nitrogen / phosphorus doped polysilicon layer. That is, the selective polysilicon layer formed by doping carbon elements can be replaced by doping with elements such as oxygen and nitrogen.
[0022] Another technical solution of the present invention is: a photovoltaic module, which includes a front encapsulation layer, a photovoltaic cell, and a back encapsulation layer, wherein the photovoltaic cell is the above-mentioned passivated contact cell.
[0023] Another technical solution of the present invention is: a photovoltaic system, which includes the above-mentioned photovoltaic module, wherein there are one or more photovoltaic modules, and when there are multiple photovoltaic modules, the multiple photovoltaic modules are connected to each other. In short, the multiple photovoltaic modules are connected to each other (in series).
[0024] Due to the implementation of the above technical solution, the utility model has the following advantages compared with the prior art:
[0025] In the existing passivation contact cell with polysilicon layer, heavily doped polysilicon covers the entire area on the back of the TOPCon cell. This part of the structure has a large light absorption coefficient for long-wave light. This type of absorption is called free carrier absorption (FCA), which is ineffective absorption. The thicker the doped polysilicon or the higher the doping concentration, the more severe the FCA absorption and the lower the photoelectric conversion efficiency. Conventional phosphorus-doped polysilicon layer cannot form C—H chemical bonds to suppress the escape of H, resulting in the inability to effectively improve the surface passivation performance. The phosphorus-doped polysilicon layer cannot form a better ohmic contact with the metal electrode, thereby failing to reduce the contact resistivity and other shortcomings. The overall design of the passivation contact cell of the present invention cleverly solves the various shortcomings of the existing structure. The passivated contact cell adopts a double-layer stacked structure of different types of polysilicon layers, and the inner and outer polysilicon layers are selective. At the same time, carbon doping is beneficial to suppress the escape of H by forming C—H chemical bonds, which is beneficial to promote surface passivation. In addition, the activity of phosphorus atoms can be reduced, reducing Auger recombination and SRH recombination, thereby suppressing the advancement of phosphorus atoms in non-metallized areas during the phosphorus diffusion process. In the metallized area, due to the absence of carbon-doped polysilicon, phosphorus atoms can be doped to the maximum extent. A higher doping concentration will form a better ohmic contact. This is because the high-concentration doping area has a higher electrical conductivity. The resistivity is greatly reduced, which reduces the resistance of the contact interface between the semiconductor and the metal electrode. The parasitic absorption of the low-concentration carbon-doped area in the non-metallic part is also lower than that of the traditional solar cell. Therefore, on the one hand, the utility model not only reduces the parasitic absorption of light by the polysilicon layer in the non-metallic area due to heavy doping, improves the utilization rate of light, and thus improves the photoelectric conversion efficiency of the battery; on the other hand, it forms a CH chemical bond to suppress the escape of H, resulting in a significant increase in the surface passivation performance. Moreover, because the metal area adopts a heavy doping method, it is more conducive to forming a better ohmic contact with the metal electrode, thereby reducing the contact resistivity. BRIEF DESCRIPTION OF THE DRAWINGS
[0026] Figure 1 Schematic diagram of the structure of a passivation contact cell with a selective polysilicon layer according to Example 1;
[0027] Figure 2 Schematic diagram of the structure of a passivation contact cell with a selective polysilicon layer according to Example 2;
[0028] Figure 3 Schematic diagram of the structure of a passivated contact battery of a comparative example;
[0029] Among them: 1. Silicon wafer body;
[0030] 2. Front structural layer; 20. Boron-doped emitter; 21. Front passivation layer; 22. Front anti-reflection layer;
[0031] 3. Back structural layer; 30. Tunneling oxide layer; 31. Selective polysilicon layer; 310. Phosphorus-heavily doped polysilicon layer; 311. Carbon / phosphorus-medium doped polysilicon layer; 312. Phosphorus-lightly doped polysilicon layer; 32. Back passivation layer; 33. Back anti-reflection layer;
[0032] 4. Front metal electrode;
[0033] 5. Back metal electrode. DETAILED DESCRIPTION
[0034] To make the above-mentioned objects, features, and advantages of the present invention more clearly understood, the present invention is described in detail below with reference to the accompanying drawings and specific embodiments. The following description sets forth many specific details to facilitate a full understanding of the present invention. However, the present invention can be implemented in many other ways than those described herein, and those skilled in the art can make similar improvements without violating the scope of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.
[0035] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc., indicating the orientation or position relationship, are based on the orientation or position relationship shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.
[0036] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of the technical features being referred to. Thus, a feature specified as "first" or "second" may explicitly or implicitly include at least one such feature. In the description of this utility model, "plurality" means at least two, for example, two, three, etc., unless otherwise specifically defined.
[0037] In this utility model, unless otherwise specified or limited, the terms "installed," "connected," "connected," "fixed," etc. should be understood in a broad sense. For example, they can refer to fixed connection, detachable connection, or integration; they can refer to direct connection or indirect connection through an intermediate medium; they can refer to internal communication between two components or interaction between two components, unless otherwise specified. For those skilled in the art, the specific meanings of the above terms in this utility model can be understood according to specific circumstances.
[0038] In utility models, unless otherwise expressly specified or limited, a first feature being "above" or "below" a second feature may mean that the first and second features are in direct contact, or that the first and second features are in indirect contact through an intermediary. Furthermore, a first feature being "above," "above," or "above" a second feature may mean that the first feature is directly above or diagonally above the second feature, or simply means that the first feature is at a higher level than the second feature. A first feature being "below," "below," or "below" a second feature may mean that the first feature is directly below or diagonally below the second feature, or simply means that the first feature is at a lower level than the second feature.
[0039] It should be noted that when an element is referred to as being "fixed to" or "disposed on" another element, it may be directly on the other element or there may be an intermediate element. When an element is referred to as being "connected to" another element, it may be directly connected to the other element or there may be an intermediate element. The terms "vertical," "horizontal," "upper," "lower," "left," "right," and similar expressions used herein are for illustrative purposes only and do not represent the only implementation methods.
[0040] Example 1
[0041] like Figure 1 As shown, the passivation contact cell with a selective polysilicon layer provided in this embodiment includes a silicon wafer body 1, a front structure layer 2, a back structure layer 3, a front metal electrode 4 and a back metal electrode 5, wherein the back structure layer 3 includes a tunneling oxide layer 30, a selective polysilicon layer 31, a back passivation layer 32 and a back anti-reflection layer 33 formed on the back of the silicon wafer body 1, and the front structure layer 2 includes a boron-doped emitter 20, a front passivation layer 21 and a front anti-reflection layer 22 arranged in sequence from the inside to the outside.
[0042] Specifically, the selective polysilicon layer 31 includes a phosphorus-heavy doped polysilicon layer 310, a carbon / phosphorus-medium doped polysilicon layer 311, and a phosphorus-lightly doped polysilicon layer 312, in which the concentrations of phosphorus atoms are arranged in descending order, and the phosphorus-heavy doped polysilicon layer 310, the carbon / phosphorus-medium doped polysilicon layer 311, and the phosphorus-lightly doped polysilicon layer 312 constitute internal and external doping structural layers, and the back metal electrode 5 corresponds to the phosphorus-heavy doped polysilicon layer 310 and the back metal electrode 5 is formed on the phosphorus-heavy doped polysilicon layer 310.
[0043] In some specific embodiments, the lightly phosphorus-doped polysilicon layer 312 constitutes an inner doped structural layer, and the heavily phosphorus-doped polysilicon layer 310 and the carbon / phosphorus medium-doped polysilicon layer 311 constitute an outer doped structural layer. The metal region corresponding to the inner doped structural layer is formed with the heavily phosphorus-doped polysilicon layer 312 that fills the back surface. The inner doped structural layer separates the heavily phosphorus-doped polysilicon layer 312 from the tunneling oxide layer 30. The carbon / phosphorus medium-doped polysilicon layer 311 is formed in the non-metallic region corresponding to the inner doped structural layer. That is, the heavily phosphorus-doped polysilicon layer 310 and the carbon / phosphorus medium-doped polysilicon layer 311 are formed in the metal region and non-metallic region of the inner and outer layers, respectively. Since carbon is doped into polysilicon, this helps to suppress the activity of phosphorus atoms doped in subsequent processes, thus forming a structure with high doping concentration in the metallized area and low doping concentration in the non-metallized area, reducing the parasitic absorption of long-wave photons by the heavily doped polysilicon layer, and maximizing the current value of photoelectric conversion. At the same time, in the metallized area, a higher concentration of doping will form a better ohmic contact with the metal electrode. This is because the resistivity of the high-concentration doping area is greatly reduced, reducing the resistance of the contact interface between the semiconductor and the metal electrode.
[0044] Furthermore, the thickness of the inner doped structure layer and the outer doped structure layer is equal, both 30 to 60 nm. Currently, the industry widely adopts a passivation contact structure of a tunnel oxide layer + phosphorus-doped polysilicon layer, where the phosphorus-doped polysilicon layer is currently in the range of about 100 to 150 nm in thickness. The present invention adopts a double-layer polysilicon stacking method, with the thickness of the inner intrinsic polysilicon layer maintained at 30-60nm, and the outer polysilicon layer doped with carbon elements, and the thickness maintained at 30-60nm. This technology is beneficial for suppressing the escape of H by forming C-H chemical bonds, which is beneficial for promoting surface passivation. In addition, doping carbon elements in the polysilicon layer can reduce the activity of phosphorus atoms, reduce Auger recombination and SRH recombination, and thus inhibit the advancement of phosphorus atoms in non-metallized areas during the phosphorus diffusion process. In the metallized area, since there is no carbon-doped polysilicon, phosphorus atoms can be doped to the maximum extent. A higher doping concentration will form a better ohmic contact. This is because the resistivity of the high-concentration doped area is greatly reduced, reducing the resistance of the contact interface between the semiconductor and the metal electrode. The parasitic absorption of the low-concentration carbon-doped area of the non-metallized part is also reduced compared with traditional solar cells.
[0045] In some specific embodiments, the silicon wafer body is an N-type silicon wafer substrate, and the N-type single crystal silicon wafer is wet cleaned to remove the surface damage layer of the silicon wafer, clean the surface metal impurities and oil stains, and produce a velvet surface. At a reaction temperature of 70±10°C, a 10% volume fraction of sodium hydroxide solution is used to etch the surface damage layer of the silicon wafer caused by wire cutting. The etching thickness on both sides is about 10μm. Then, a wet chemical process using an alkaline solution + a velvet additive is used to produce a random pyramid surface texture. A standard RCA wet cleaning is performed. The height of the resulting random pyramids is about 0.5 to 2μm. The boron-doped emitter 20, the front passivation layer 21, and the front anti-reflection layer 22 are all of the same shape and have a pyramid velvet surface. The back passivation layer 32 and the back anti-reflection layer 33 form a stack that is the same as the stack formed by the front passivation layer 21 and the front anti-reflection layer 22. In short, the passivation anti-reflection film on the front and back surfaces adopts a laminated film design, which is a combination of two materials such as aluminum oxide, silicon nitride, silicon dioxide, and silicon oxynitride. As a preference, a passivation anti-reflection film laminated design of aluminum oxide + silicon carbide is adopted, wherein the preferred thickness of aluminum oxide is 2 to 10 nm, the preferred thickness of silicon nitride is 20 to 50 nm, and the refractive index of silicon nitride is 2.1 to 2.2. The width of the front metal electrode and the back metal electrode is 10 to 60 μm and the height is 3 to 10 μm. The metal electrodes on the front and back surfaces are printed and sintered, wherein the printing adopts screen printing or laser transfer, and the width of the front and back metal grid lines is 10 to 60 μm and the height is 3 to 10 μm, and the sintering temperature is 700 to 850 ° C. The metallized pattern is printed on the front and back sides (printing is performed by screen printing or laser transfer, etc.). The metal grid lines can be made of silver paste, silver aluminum paste or other metal materials (aluminum, copper, titanium, nickel, etc.). The width of the metal grid lines on the front and back sides is 10 to 60 μm, the height is 3 to 10 μm, and the sintering temperature is 700 to 850 ° C; or a laser-assisted enhanced sintering process is used to enhance contact and reduce contact resistivity.
[0046] In addition, the carbon / phosphorus doped polysilicon layer is an oxygen / phosphorus doped polysilicon layer or a nitrogen / phosphorus doped polysilicon layer. That is, the selective polysilicon layer formed by doping carbon elements can be replaced by doping with elements such as oxygen and nitrogen, and the concentration of the heavily phosphorus doped polysilicon layer is 4.0 to 8.0E+20 cm -3 The concentration of carbon / phosphorus doped polysilicon layer is 0.8~1.0E+20cm -3 The concentration of phosphorus lightly doped polysilicon layer is 1.0~4.0E+19cm -3 .
[0047] Example 2
[0048] like Figure 2As shown, the passivation contact cell with a selective polysilicon layer provided in this embodiment includes a silicon wafer body 1, a front structure layer 2, a back structure layer 3, a front metal electrode 4 and a back metal electrode 5, wherein the back structure layer 3 includes a tunneling oxide layer 30, a selective polysilicon layer 31, a back passivation layer 32 and a back anti-reflection layer 33 formed on the back of the silicon wafer body 1, and the front structure layer 2 includes a boron-doped emitter 20, a front passivation layer 21 and a front anti-reflection layer 22 arranged in sequence from the inside to the outside, and the main difference compared with Example 1 is that the structure of the selective polysilicon layer 31 is different, and the others are the same. The specific structure is as follows.
[0049] In this example, the lightly phosphorus-doped polysilicon layer 312 constitutes an inner doped structural layer, the heavily phosphorus-doped polysilicon layer 310 and the carbon / phosphorus-medium-doped polysilicon layer 311 constitute an outer doped structural layer, and the thicknesses of the heavily phosphorus-doped polysilicon layer 310 and the carbon / phosphorus-medium-doped polysilicon layer 311 are equal, wherein the heavily phosphorus-doped polysilicon layer 310 corresponds to the metal area, and the carbon / phosphorus-medium-doped polysilicon layer 311 corresponds to the non-metal area (at this point, it is necessary to distinguish from Example 1, the heavily phosphorus-doped polysilicon layer 310 and the carbon / phosphorus-medium-doped polysilicon layer 311 are located in the same outer layer, not the inner and outer layers).
[0050] Comparative Example 1
[0051] like Figure 3 As shown, the passivated contact cell involved in this comparative example 1 includes an N-type single crystal silicon wafer 1, a front structure layer 2 formed on the front side of the N-type single crystal silicon wafer 1, a back structure layer 3 formed on the back side of the N-type single crystal silicon wafer 1, a front metal electrode 4 and a back metal electrode 5, wherein the back structure layer 3 is a single layer of polycrystalline silicon deposited and covers the entire area of the back side of the cell, that is, the front structure layer 2 includes a boron-doped emitter 20, a front passivation layer 21 and a front anti-reflection layer 22 arranged in sequence from the inside to the outside, and the back structure layer 3 includes a tunneling oxide layer 30, a phosphorus-doped polycrystalline silicon layer 31, a front passivation layer 32, and a front anti-reflection layer 33 arranged in sequence from the inside to the outside, that is, the phosphorus-doped polycrystalline silicon layer 31 is deposited and covers the entire area of the back side of the cell.
[0052] Performance Testing: The cells obtained in Examples 1 and 2 and Comparative Example 1 were subjected to the following performance testing: Using an IV tester, the cells' photoelectric conversion efficiency and related electrical performance parameters were measured under standard illumination power, using a simulated solar light source. The electrical performance data are average values for 100 cells per sample. Specific test results are shown in Table 1 (Eta: conversion efficiency, Voc: open-circuit voltage, Jsc: short-circuit current density, FF: fill factor).
[0053] Table 1
[0054] sample Eta(%) Voc(mV) <![CDATA[Jsc(mA / cm 2 )]]> FF(%) Example 1 25.03 725 40.84 84.52 Example 2 25.00 724 40.85 84.53 Comparative Example 1 24.77 722 40.60 84.50
[0055] Based on the data in Table 1, it can be seen that Examples 1 to 3 have at least the following advantages compared with Comparative Example 1:
[0056] 1. Due to the doping of carbon elements, it is beneficial to suppress the escape of H by forming C—H chemical bonds, which is more conducive to promoting surface passivation. The open circuit voltage Voc is improved compared with the control ratio.
[0057] 2. Due to the reduction of doping concentration, the parasitic absorption coefficient of the polysilicon layer in the non-metallized area decreases, which improves the utilization rate of light. Therefore, the short-circuit current density Jsc will be 0.2+mA / cm 2 Advantages of left and right;
[0058] 3. The heavily doped structure of the metallized area helps to form a better ohmic contact with the metal electrode and reduce the contact resistivity. The fill factor (FF) of this structure has a certain advantage over the comparative example.
[0059] 4. The photoelectric conversion efficiency Eta formed by this structure is also improved by 0.19-0.26%.
[0060] Example 3
[0061] The photovoltaic module involved in this embodiment includes a front encapsulation layer, a photovoltaic cell, and a back encapsulation layer, wherein the photovoltaic cell is the passivated contact cell in the above-mentioned embodiment 1 or 2.
[0062] Example 4
[0063] The photovoltaic system involved in this embodiment includes the photovoltaic components involved in Example 3, wherein there are two, three or more photovoltaic components, and the multiple photovoltaic components are interconnected (generally connected in series).
[0064] Meanwhile, there may be only one photovoltaic module, that is, a photovoltaic system consisting of a single photovoltaic module; or there may be two, three or more photovoltaic modules, and the multiple photovoltaic modules may be connected in series and / or in parallel.
[0065] In summary, the passivation contact cell adopts a double-layer stacked structure of different types of polysilicon layers, and the inner and outer polysilicon layers are selective. At the same time, carbon doping is beneficial to suppress the escape of H by forming CH chemical bonds, which is beneficial to promote surface passivation; in addition, the activity of phosphorus atoms can be reduced, and Auger recombination and SRH recombination can be reduced, thereby suppressing the advancement of phosphorus atoms in non-metallized areas during the phosphorus diffusion process. In the metallized area, due to the absence of carbon-doped polysilicon, phosphorus atoms can be doped to the maximum extent, and a higher doping concentration will form a better ohmic contact. This is because the resistivity of the high-concentration doped area is greatly reduced, reducing the contact interface between the semiconductor and the metal electrode. The resistance of the surface, the parasitic absorption of the low-concentration carbon-doped area of the non-metallic part will also be lower than that of the traditional solar cell. Therefore, on the one hand, the utility model not only reduces the parasitic absorption of light by the heavy doping in the polysilicon layer in the non-metallic area, improves the utilization rate of light, and thus improves the photoelectric conversion efficiency of the battery; on the other hand, it forms a CH chemical bond to inhibit the escape of H, resulting in a significant increase in the surface passivation performance, and the metal area is more conducive to forming a better ohmic contact with the metal electrode because of the heavy doping method, thereby reducing the contact resistivity; thirdly, a double-layer polysilicon stacking method is adopted, the thickness of the inner intrinsic polysilicon layer is maintained at 30-60nm, and the outer polysilicon is kept at 100-200nm. Doping carbon elements with a thickness of 30 to 60 nm is beneficial for suppressing the escape of H by forming CH chemical bonds, which is beneficial for promoting surface passivation. In addition, doping carbon elements in the polysilicon layer can reduce the activity of phosphorus atoms, reduce Auger recombination and SRH recombination, and thus inhibit the advancement of phosphorus atoms in the non-metallized area during the phosphorus diffusion process. In the metallized area, due to the absence of carbon-doped polysilicon, phosphorus atoms can be doped to the maximum extent. A higher doping concentration will form a better ohmic contact. This is because the resistivity of the high-concentration doped area is greatly reduced, reducing the resistance of the contact interface between the semiconductor and the metal electrode. The low carbon doping in the non-metallized part The parasitic absorption in the concentration area will also be lower than that of traditional solar cells; fourthly, the passivation anti-reflection film on the front and back surfaces adopts a laminated film design, which is a combination of two materials such as aluminum oxide, silicon nitride, silicon dioxide, and silicon oxynitride. Preferably, a passivation anti-reflection film laminated design of aluminum oxide + silicon carbide is adopted, wherein the preferred thickness of aluminum oxide is 2 to 10 nm, the preferred thickness of silicon nitride is 20 to 50 nm, and the refractive index of silicon nitride is 2.1 to 2.2; fifthly, the carbon / phosphorus doped polysilicon layer is an oxygen / phosphorus doped polysilicon layer or a nitrogen / phosphorus doped polysilicon layer, that is, the selective polysilicon layer formed by doping carbon elements can be replaced by doping with elements such as oxygen and nitrogen.
[0066] The above detailed description of the utility model is intended to enable people familiar with the technology in this field to understand the content of the utility model and implement it. It is not intended to limit the scope of protection of the utility model. Any equivalent changes or modifications made according to the spirit of the utility model should be included in the scope of protection of the utility model.
Claims
1. A passivation contact cell with a selective polysilicon layer, comprising a silicon wafer body (1), a front structural layer (2), a back structural layer (3), a front metal electrode (4) and a back metal electrode (5), characterized in that: The back structure layer (3) includes a tunneling oxide layer (30), a selective polysilicon layer (31), a back passivation layer (32) and a back anti-reflection layer (33) formed on the back of the silicon wafer body (1), wherein the selective polysilicon layer (31) includes a phosphorus heavily doped polysilicon layer (310), a carbon / phosphorus medium doped polysilicon layer (311), and a phosphorus lightly doped polysilicon layer (312) in which the concentration of phosphorus atoms is arranged in descending order, and the phosphorus heavily doped polysilicon layer (310), the carbon / phosphorus medium doped polysilicon layer (311), and the phosphorus lightly doped polysilicon layer (312) constitute an inner and outer doping structure layer, and the back metal electrode (5) corresponds to the phosphorus heavily doped polysilicon layer (310) and the back metal electrode (5) is formed on the phosphorus heavily doped polysilicon layer (310).
2. The passivation contact cell with a selective polysilicon layer according to claim 1, characterized in that: The lightly phosphorus-doped polysilicon layer (312) constitutes an inner doping structure layer, and the heavily phosphorus-doped polysilicon layer (310) and the carbon / phosphorus medium-doped polysilicon layer (311) constitute an outer doping structure layer.
3. The passivation contact cell with a selective polysilicon layer according to claim 2, characterized in that: The phosphorus heavily doped polysilicon layer (310) and the carbon / phosphorus medium doped polysilicon layer (311) have the same thickness, wherein the phosphorus heavily doped polysilicon layer (310) corresponds to the metal region, and the carbon / phosphorus medium doped polysilicon layer (311) corresponds to the non-metal region.
4. The passivation contact cell with a selective polysilicon layer according to claim 2, characterized in that: A phosphorus heavily doped polysilicon layer (310) is formed in the metal region corresponding to the inner doping structure layer to fill the back surface, and the inner doping structure layer separates the phosphorus heavily doped polysilicon layer (310) from the tunneling oxide layer (30), and the carbon / phosphorus medium doped polysilicon layer (311) is formed in the non-metal region corresponding to the inner doping structure layer.
5. The passivation contact cell with a selective polysilicon layer according to any one of claims 2 to 4, characterized in that: The thickness of the inner doping structure layer and the outer doping structure layer are both 30-60 nm.
6. The passivation contact cell with a selective polysilicon layer according to claim 1, characterized in that: The front structural layer (2) comprises a boron-doped emitter (20), a front passivation layer (21) and a front anti-reflection layer (22) which are arranged in sequence from the inside to the outside.
7. The passivation contact cell with a selective polysilicon layer according to claim 6, characterized in that: The boron-doped emitter (20), the front passivation layer (21) and the front anti-reflection layer (22) have the same shape and all have pyramid velvet surfaces.
8. The passivation contact cell with a selective polysilicon layer according to claim 7, characterized in that: The front passivation layer (21) is an aluminum oxide layer, wherein the thickness of the aluminum oxide layer is 2 to 10 nm.
9. The passivation contact cell with a selective polysilicon layer according to claim 6, characterized in that: The front anti-reflection layer (22) is a silicon carbide layer, wherein the thickness of the silicon nitride layer is 20 to 50 nm, and the refractive index of the silicon nitride layer is 2.1 to 2.
2.
10. The passivation contact cell with a selective polysilicon layer according to claim 9, characterized in that: The stack formed by the back passivation layer (32) and the back anti-reflection layer (33) is the same as the stack formed by the front passivation layer (21) and the front anti-reflection layer (22).
11. The passivation contact cell with a selective polysilicon layer according to claim 1, characterized in that: The silicon wafer body (1) is an N-type silicon wafer substrate.
12. The passivation contact cell with a selective polysilicon layer according to claim 1, characterized in that: The front metal electrode (4) and the back metal electrode (5) are formed to have a width of 10 to 60 μm and a height of 3 to 10 μm.
13. The passivation contact cell with a selective polysilicon layer according to claim 1, characterized in that: The carbon / phosphorus doped polysilicon layer is an oxygen / phosphorus doped polysilicon layer or a nitrogen / phosphorus doped polysilicon layer.
14. A photovoltaic module comprising a front encapsulation layer, a photovoltaic cell, and a back encapsulation layer, characterized in that: The photovoltaic cell is a passivated contact cell with a selective polysilicon layer according to any one of claims 1 to 13.
15. A photovoltaic system, characterized in that: The photovoltaic system includes the photovoltaic assembly according to claim 14, wherein there are one or more photovoltaic assemblies, and when there are multiple photovoltaic assemblies, the multiple photovoltaic assemblies are connected to each other.