Silicon rod, silicon wafer, solar cell, cell module and photovoltaic system

Abstract

The invention discloses a silicon rod and a preparation method thereof, a silicon wafer, a solar cell, a cell module and a photovoltaic system, and the silicon rod comprises a central region and an edge region; the conduction type of the central region is N type, and the conduction type of the edge region is P type; or, the conduction type of the central region is P type, and the conduction type of the edge region is N type. According to the invention, P-type and N-type silicon rods or silicon wafers can be prepared.

Description

Technical Field

[0001] The present invention relates to the technical field of solar cells, and in particular to a silicon rod, a silicon wafer, a solar cell, a battery assembly, and a photovoltaic system. Background Art

[0002] N-type silicon wafers are semiconductors formed by doping a small amount of pentavalent elements into pure silicon materials. These pentavalent elements replace part of the tetravalent elements in the silicon lattice, causing the excess valence electrons to become free electrons, making the free electron concentration in the N-type semiconductor much greater than the hole concentration. P-type silicon wafers are semiconductors formed by doping a small amount of trivalent elements into pure silicon materials. These trivalent elements form holes in the silicon lattice, making the hole concentration in the P-type semiconductor much greater than the free electron concentration. Conventional silicon wafers are often N-type silicon wafers or P-type silicon wafers. The present invention proposes a silicon wafer that has both P-type and N-type properties. Summary of the invention

[0003] The technical problem to be solved by the present invention is to provide a silicon rod which has both P-type and N-type.

[0004] The technical problem to be solved by the present invention is also to provide a method for preparing a silicon rod, wherein the prepared silicon rod has both P-type and N-type.

[0005] The technical problem to be solved by the present invention is also to provide a solar cell, a battery assembly, and a photovoltaic system.

[0006] In order to solve the above problems, the present invention provides a silicon rod, characterized in that it includes a central area and an edge area;

[0007] The conductivity type of the central region is N-type, and the conductivity type of the edge region is P-type;

[0008] Alternatively, the conductivity type of the central region is P type, and the conductivity type of the edge region is N type.

[0009] In some embodiments, the surface of the central region in the cross-sectional direction of the silicon rod is circular, and the center of the circle is the center point of the cross-sectional direction of the silicon rod;

[0010] The surface of the edge region in the cross-sectional direction of the silicon rod is in the shape of a circular ring, and the center of the circle is the central point of the cross-sectional area of ​​the silicon rod.

[0011] In some embodiments, the P-type doping concentration is ≤9×10 18 atoms / cm 3 ; The N-type doping concentration is ≤5×10 17 atoms / cm 3 .

[0012] In order to solve the above problems, the present invention also provides a method for preparing a silicon rod, comprising the following steps:

[0013] melting silicon raw materials to obtain silicon liquid;

[0014] Adding a first concentration of an N-type dopant and a second concentration of a P-type dopant into the silicon liquid to obtain a doped silicon liquid;

[0015] Placing a seed crystal on the doped silicon liquid, pulling up the seed crystal to allow the doped silicon liquid to crystallize on the seed crystal, and obtaining a silicon rod after the crystalline silicon is grown;

[0016] During the growth of crystalline silicon, the growth rate of the central area of ​​the silicon rod is greater or less than the growth rate of the edge area;

[0017] The concentration of the N-type dopant in the central region is higher than that of the P-type dopant, and the concentration of the P-type dopant in the edge region is higher than that of the N-type dopant;

[0018] Alternatively, the concentration of the P-type dopant in the central region is higher than that of the N-type dopant, and the concentration of the N-type dopant in the edge region is higher than that of the P-type dopant.

[0019] In some embodiments, during the growth of crystalline silicon, the interface shape of the silicon rod growth is convex or concave.

[0020] In some embodiments, the first concentration and the second concentration satisfy:

[0021] The effective segregation coefficient of the N-type dopant at the minimum growth rate of the crystalline silicon / the effective segregation coefficient of the P-type dopant at the minimum growth rate of the crystalline silicon < the second concentration / the first concentration < the effective segregation coefficient of the N-type dopant at the maximum growth rate of the crystalline silicon / the effective segregation coefficient of the P-type dopant at the maximum growth rate of the crystalline silicon.

[0022] In some embodiments, during the growth of crystalline silicon, the growth rate of the central region is greater than the growth rate of the edge region, the interface shape of silicon rod growth is convex, the conductivity type of the central region is N-type, and the conductivity type of the edge region is P-type.

[0023] In some embodiments, during the growth of crystalline silicon, the growth rate of the central region is lower than that of the edge region, the interface shape of silicon rod growth is concave, the conductivity type of the central region is P type, and the conductivity type of the edge region is N type.

[0024] In some embodiments, the first concentration and the second concentration satisfy:

[0025] The effective segregation coefficient of the P-type dopant at the minimum growth rate of the crystalline silicon / the effective segregation coefficient of the N-type dopant at the minimum growth rate of the crystalline silicon < the first concentration / the second concentration < the effective segregation coefficient of the P-type dopant at the maximum growth rate of the crystalline silicon / the effective segregation coefficient of the N-type dopant at the maximum growth rate of the crystalline silicon.

[0026] In some embodiments, during the growth of crystalline silicon, the growth rate of the central region is greater than the growth rate of the edge region, the interface shape of silicon rod growth is convex, the conductivity type of the central region is P type, and the conductivity type of the edge region is N type.

[0027] In some embodiments, during the growth of crystalline silicon, the growth rate of the central region is lower than that of the edge region, the interface shape of silicon rod growth is concave, the conductivity type of the central region is N-type, and the conductivity type of the edge region is P-type.

[0028] In some embodiments, the surface of the central region in the cross-sectional direction of the silicon rod is circular, and the center of the circle is the central point of the cross-sectional direction of the silicon rod.

[0029] In some embodiments, the surface of the edge region in the cross-sectional direction of the silicon rod is in the shape of a circular ring, and the center of the circle is the center point of the cross-sectional direction of the silicon rod.

[0030] In some embodiments, the N-type dopant includes at least one of a fifth main group element and a sixth main group element.

[0031] In some embodiments, the P-type dopant includes at least one of the third main group elements.

[0032] In order to solve the above problems, the present invention provides a silicon wafer cut from the above silicon rod;

[0033] Alternatively, the silicon rod is cut from the silicon rod prepared by the above-mentioned silicon rod preparation method.

[0034] In order to solve the above problems, the present invention provides a solar cell, which is made based on the above silicon wafer.

[0035] In order to solve the above problems, the present invention provides a battery assembly, including the above solar cell.

[0036] In order to solve the above problems, the present invention provides a photovoltaic system including the above battery assembly.

[0037] The implementation of the present invention has the following beneficial effects:

[0038] The silicon rod provided by the present invention has both P-type and N-type, and includes a central area and an edge area; the conductivity type of the central area is N-type, and the conductivity type of the edge area is P-type; or, the conductivity type of the central area is P-type, and the conductivity type of the edge area is N-type. In the process of making solar cells based on the PN-type silicon wafer prepared by the present invention, a PN junction can be formed in the silicon wafer. After the solar cell is made, a better field passivation effect can be formed in the solar cell, which is beneficial to carrier transmission and helps to improve the photoelectric conversion efficiency of the solar cell. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 is a structural schematic diagram of a cross section of a silicon rod provided by the present invention;

[0040] Figure 2 is another structural schematic diagram of the cross section of the silicon rod provided by the present invention;

[0041] Figure 3 It is a schematic structural diagram of a convex interface shape of silicon rod growth provided by the present invention;

[0042] Figure 4 It is a structural schematic diagram of a silicon rod growth interface provided by the present invention having a concave shape. DETAILED DESCRIPTION

[0043] In order to make the purpose, technical scheme and advantages of the present invention clearer, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. Examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements with the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention. In addition, it should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0044] In the description of the present invention, it is necessary to understand that the orientations or positional relationships indicated by the terms "upper", "lower", "back surface", "front surface", etc. are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying 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.

[0045] In the present invention, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may include that the first and second features are in direct contact, or may include that the first and second features are not in direct contact but are in contact through another feature between them. Moreover, a first feature being "above", "above" and "above" a second feature includes that the first feature is directly above and obliquely above the second feature, or simply indicates that the first feature is higher in level than the second feature. A first feature being "below", "below" and "below" a second feature includes that the first feature is directly below and obliquely below the second feature, or simply indicates that the first feature is lower in level than the second feature.

[0046] In the present invention, “preferred” is only used to describe an implementation method or example with better effects, and it should be understood that it does not constitute a limitation on the protection scope of the present invention.

[0047] In the present invention, the technical features described in an open manner include closed technical solutions composed of the listed features, and also include open technical solutions containing the listed features.

[0048] The present invention provides a silicon rod, comprising a central region 100 and an edge region 200; in some embodiments, the surface of the central region 100 in the cross-sectional direction of the silicon rod is circular, and the center of the circle is the center point of the cross section of the silicon rod. In some embodiments, the surface of the edge region 200 in the cross-sectional direction of the silicon rod is annular, and the center of the circle is the center point of the cross section of the silicon rod.

[0049] like Figure 1 As shown, the conductivity type of the central region 100 is N-type, and the conductivity type of the edge region 200 is P-type; or Figure 2 As shown, the conductivity type of the central region 100 is P type, and the conductivity type of the edge region 200 is N type. It should be noted that, Figure 1 or Figure 2 In the figure, the slash filled part represents the conductivity type is N type, and the plus sign filled part represents the conductivity type is P type. In some embodiments, the doping concentration of the P type is ≤9×10 18 atoms / cm 3 ; The N-type doping concentration is ≤5×10 17 atoms / cm 3 .

[0050] The present invention also provides a method for preparing a silicon rod, comprising the following steps:

[0051] S1, melting silicon raw materials to obtain silicon liquid;

[0052] S2, adding a first concentration of an N-type dopant and a second concentration of a P-type dopant to the silicon liquid to obtain a doped silicon liquid;

[0053] In some embodiments, the N-type dopant includes at least one of a Group V element and a Group VI element. Preferably, the N-type dopant is arsenic and / or phosphorus; more preferably, the N-type dopant is phosphorus.

[0054] In some embodiments, the P-type dopant includes at least one of the elements of the third main group. Preferably, the P-type dopant is one or more of aluminum, boron, and gallium; more preferably, the P-type dopant is gallium.

[0055] S3, placing a seed crystal on the doped silicon liquid, pulling up the seed crystal to allow the doped silicon liquid to crystallize on the seed crystal, and obtaining a silicon rod after the crystalline silicon is grown;

[0056] In order to obtain a silicon rod having both P-type and N-type properties, the present invention controls the growth of the silicon rod according to the following requirements during the growth of the silicon rod:

[0057] First, during the growth of crystalline silicon, the growth rate of the central region of the silicon rod is greater than or less than the growth rate of the edge region; in some embodiments, during the growth of crystalline silicon, the interface shape of the silicon rod growth is convex or concave. Figure 3 As shown, when the shape of the interface 300 of the silicon rod growth is convex, the growth rate of the central region of the silicon rod is greater than the growth rate of the edge region; Figure 4 As shown, when the shape of the interface 300 of the silicon rod growth is concave, the growth rate of the central area of ​​the silicon rod is less than the growth rate of the edge area. It should be noted that during the crystal pulling process, after the seed crystal is pulled up, the doped silicon liquid crystallizes on the seed crystal and gradually grows into a silicon rod, and the interface between the formed solid silicon rod and the doped silicon liquid is the interface of the silicon rod growth referred to herein in the present invention. In some embodiments, the surface of the central area in the cross-sectional direction of the silicon rod is circular, and the center of the circle is the center point of the cross section of the silicon rod. In some embodiments, the surface of the edge area in the cross-sectional direction of the silicon rod is annular, and the center of the circle is the center point of the cross section of the silicon rod.

[0058] Furthermore, the concentration of the N-type dopant in the central region is higher than that of the P-type dopant, and the concentration of the P-type dopant in the edge region is higher than that of the N-type dopant; or, the concentration of the P-type dopant in the central region is higher than that of the N-type dopant, and the concentration of the N-type dopant in the edge region is higher than that of the P-type dopant. It should be noted that when the P-type and N-type are co-doped, the conductivity type of a point in the crystal depends on the impurity concentration of this point. If the concentration of the N-type dopant is higher than that of the P-type dopant, this point shows N-type, and if the concentration of the P-type dopant is higher than that of the N-type dopant, this point shows P-type. In the present invention, in some embodiments, the concentration of the N-type dopant in the central region is higher than that of the P-type dopant, and the concentration of the P-type dopant in the edge region is higher than that of the N-type dopant; in this case, the concentration of the N-type dopant in the central region is higher than that of the P-type dopant, and the central region is N-type, and the concentration of the P-type dopant in the edge region is higher than that of the N-type dopant, and the edge region is P-type; or, in other embodiments, the concentration of the P-type dopant in the central region is higher than that of the N-type dopant, and the central region is P-type, and the concentration of the N-type dopant in the edge region is higher than that of the P-type dopant, and the edge region is N-type.

[0059] Furthermore, in order to achieve the above definition, the present invention defines the initial doping concentrations of the P-type dopant and the N-type dopant.

[0060] In some embodiments, the first concentration and the second concentration satisfy:

[0061] The effective segregation coefficient of the N-type dopant at the minimum growth rate of the crystalline silicon / the effective segregation coefficient of the P-type dopant at the minimum growth rate of the crystalline silicon < the second concentration / the first concentration < the effective segregation coefficient of the N-type dopant at the maximum growth rate of the crystalline silicon / the effective segregation coefficient of the P-type dopant at the maximum growth rate of the crystalline silicon.

[0062] Here, the first concentration is the impurity concentration of the N-type dopant in the silicon liquid, and the second concentration is the impurity concentration of the P-type dopant in the silicon liquid. During the crystal pulling process, the doped silicon liquid solidifies into a crystal. Due to the segregation effect, the impurity concentration of the N-type dopant at a certain point in the formed semi-finished silicon rod is the effective segregation coefficient k of the N-type dopant here. e,N The product of the first concentration and the P-type dopant impurity concentration at a certain point in the semi-finished silicon rod is the effective segregation coefficient k of the P-type dopant at this point. e,P The product of the first concentration. e,P and k e,N Calculated according to the following formula:

[0063] k e,N =1 / [1+(1-1 / k 0,N )exp(-Vδ / DN )]

[0064] k e,P =1 / [1+(1-1 / k 0,P )exp(-Vδ / D P )]

[0065] Among them, k 0,N and k 0,P are the equilibrium segregation coefficients of N-type dopants and P-type dopants, respectively. V is the growth rate, D N and D P is the diffusion coefficient of N-type dopant and P-type dopant. δ is the solute boundary layer thickness, δ = 1.61D 1 / 3 ν 1 / 6 ω -1 / 2

[0066] Among them, ν is the viscosity coefficient of molten silicon and ω is the crystal rotation speed.

[0067] The growth rate of crystalline silicon is controlled by temperature field design so that the crystalline silicon grows according to the following specific interface shape to form a silicon rod with both P-type and N-type properties.

[0068] In some embodiments, during the growth of crystalline silicon, the growth rate of the central region is greater than the growth rate of the edge region, the interface shape of the silicon rod growth is convex, the conductivity type of the central region is N-type, and the conductivity type of the edge region is P-type. In the above embodiment, the growth rate of the central region is greater than the growth rate of the edge region, then according to "effective segregation coefficient of N-type dopant at the minimum growth rate of crystalline silicon / effective segregation coefficient of P-type dopant at the minimum growth rate of crystalline silicon < second concentration / first concentration <effective segregation coefficient of N-type dopant at the maximum growth rate of crystalline silicon / effective segregation coefficient of P-type dopant at the maximum growth rate of crystalline silicon", it can be known that the concentration of N-type dopant in the central region is higher, then the conductivity type of the central region is N-type, and the concentration of P-type dopant in the edge region is higher, then the conductivity type of the edge region is P-type.

[0069] In some embodiments, during the growth of crystalline silicon, the growth rate of the central region is lower than the growth rate of the edge region, the interface shape of the silicon rod growth is concave, the conductivity type of the central region is P-type, and the conductivity type of the edge region is N-type. In the above embodiment, the growth rate of the central region is lower than the growth rate of the edge region. According to "effective segregation coefficient of N-type dopant at the minimum growth rate of crystalline silicon / effective segregation coefficient of P-type dopant at the minimum growth rate of crystalline silicon < second concentration / first concentration <effective segregation coefficient of N-type dopant at the maximum growth rate of crystalline silicon / effective segregation coefficient of P-type dopant at the maximum growth rate of crystalline silicon", the concentration of P-type dopant in the central region is higher, and the conductivity type of the central region is P-type. The concentration of N-type dopant in the edge region is higher, and the conductivity type of the edge region is N-type.

[0070] Furthermore, the boundary position between the P-type and N-type regions in the silicon rod can be changed by controlling the ratio of the second concentration to the first concentration. The larger the ratio of the second concentration to the first concentration, the closer the boundary line is to the center of the crystal rod, and vice versa.

[0071] Similarly, in some embodiments, the first concentration and the second concentration satisfy:

[0072] The effective segregation coefficient of the P-type dopant at the minimum growth rate of the crystalline silicon / the effective segregation coefficient of the N-type dopant at the minimum growth rate of the crystalline silicon < the first concentration / the second concentration < the effective segregation coefficient of the P-type dopant at the maximum growth rate of the crystalline silicon / the effective segregation coefficient of the N-type dopant at the maximum growth rate of the crystalline silicon.

[0073] Here, the first concentration is the impurity concentration of the N-type dopant in the silicon liquid, and the second concentration is the impurity concentration of the P-type dopant in the silicon liquid. During the crystal pulling process, the doped silicon liquid solidifies into a crystal. Due to the segregation effect, the impurity concentration of the N-type dopant at a certain point in the formed semi-finished silicon rod is the effective segregation coefficient k of the N-type dopant here. e,N The product of the first concentration and the P-type dopant impurity concentration at a certain point in the semi-finished silicon rod is the effective segregation coefficient k of the P-type dopant at this point. e,P The product of the first concentration. e,P and k e N Calculated according to the following formula:

[0074] k e,N =1 / [1+(1-1 / k 0,N )exp(-Vδ / D N )]

[0075] k e,P =1 / [1+(1-1 / k 0,P)exp(-Vδ / D P )]

[0076] Among them, k 0,N and k 0,P are the equilibrium segregation coefficients of N-type dopants and P-type dopants, respectively. V is the growth rate, D N and D P is the diffusion coefficient of N-type dopant and P-type dopant. δ is the solute boundary layer thickness, δ = 1.61D 1 / 3 ν 1 / 6 ω -1 / 2

[0077] Among them, ν is the viscosity coefficient of molten silicon and ω is the crystal rotation speed.

[0078] The growth rate of crystalline silicon is controlled by temperature field design so that the crystalline silicon grows according to the following specific interface shape to form a silicon rod with both P-type and N-type properties.

[0079] In some embodiments, during the growth of crystalline silicon, the growth rate of the central region is greater than the growth rate of the edge region, the interface shape of the silicon rod growth is convex, the conductivity type of the central region is P-type, and the conductivity type of the edge region is N-type. In the above embodiment, the growth rate of the central region is greater than the growth rate of the edge region, then according to "effective segregation coefficient of P-type dopant at the minimum growth rate of crystalline silicon / effective segregation coefficient of N-type dopant at the minimum growth rate of crystalline silicon < first concentration / second concentration <effective segregation coefficient of P-type dopant at the maximum growth rate of crystalline silicon / effective segregation coefficient of N-type dopant at the maximum growth rate of crystalline silicon", it can be known that the concentration of P-type dopant in the central region is higher, then the conductivity type of the central region is P-type, and the concentration of N-type dopant in the edge region is higher, then the conductivity type of the edge region is N-type.

[0080] In some embodiments, during the growth of crystalline silicon, the growth rate of the central region is lower than the growth rate of the edge region, the interface shape of the silicon rod growth is concave, the conductivity type of the central region is N-type, and the conductivity type of the edge region is P-type. In the above embodiment, the growth rate of the central region is lower than the growth rate of the edge region. According to "effective segregation coefficient of P-type dopant at the minimum growth rate of crystalline silicon / effective segregation coefficient of N-type dopant at the minimum growth rate of crystalline silicon < first concentration / second concentration <effective segregation coefficient of P-type dopant at the maximum growth rate of crystalline silicon / effective segregation coefficient of N-type dopant at the maximum growth rate of crystalline silicon", it can be known that the concentration of N-type dopant in the central region is higher, and the conductivity type of the central region is N-type, and the concentration of P-type dopant in the edge region is higher, and the conductivity type of the edge region is P-type.

[0081] Correspondingly, the present invention provides a silicon wafer, which is cut from the above-mentioned silicon rod; or, which is cut from the silicon rod prepared by the above-mentioned silicon rod preparation method.

[0082] Furthermore, the present invention provides a solar cell, which is made based on the above silicon wafer.

[0083] Furthermore, the present invention provides a battery assembly, including the above-mentioned solar cell.

[0084] Furthermore, the present invention provides a photovoltaic system, comprising the above-mentioned battery assembly.

[0085] The present invention is further described below with reference to specific embodiments.

[0086] Example 1

[0087] This embodiment provides a silicon rod and a method for preparing the same, comprising the following steps:

[0088] melting silicon raw materials to obtain silicon liquid;

[0089] Adding a first concentration of an N-type dopant and a second concentration of a P-type dopant into the silicon liquid to obtain a doped silicon liquid;

[0090] Placing a seed crystal on the doped silicon liquid, pulling up the seed crystal to allow the doped silicon liquid to crystallize on the seed crystal, and obtaining a silicon rod after the crystalline silicon is grown;

[0091] The effective segregation coefficient of the N-type dopant at the minimum growth rate of the crystalline silicon / the effective segregation coefficient of the P-type dopant at the minimum growth rate of the crystalline silicon < the second concentration / the first concentration < the effective segregation coefficient of the N-type dopant at the maximum growth rate of the crystalline silicon / the effective segregation coefficient of the P-type dopant at the maximum growth rate of the crystalline silicon, the growth rate of the central area is greater than the growth rate of the edge area, the interface shape of the silicon rod growth is convex, the conductivity type of the central area is N-type, and the conductivity type of the edge area is P-type.

[0092] Specifically, the second concentration is 1.27×10 16 atoms / cm 3 , the first concentration is 4.88×10 17 atoms / cm 3 , second concentration / first concentration=0.026.

[0093] The effective segregation coefficient of the N-type dopant at the minimum growth rate of the crystalline silicon = 0.0080, the effective segregation coefficient of the P-type dopant at the minimum growth rate of the crystalline silicon = 0.32, the effective segregation coefficient of the N-type dopant at the minimum growth rate of the crystalline silicon / the effective segregation coefficient of the P-type dopant at the minimum growth rate of the crystalline silicon = 0.025.

[0094] The effective segregation coefficient of the N-type dopant at the maximum growth rate of the crystalline silicon = 0.0095, the effective segregation coefficient of the P-type dopant at the maximum growth rate of the crystalline silicon = 0.35, the effective segregation coefficient of the N-type dopant at the maximum growth rate of the crystalline silicon / the effective segregation coefficient of the P-type dopant at the maximum growth rate of the crystalline silicon = 0.027.

[0095] Finally, a silicon rod is obtained in which the conductivity type of the central region is N-type and the conductivity type of the edge region is P-type.

[0096] Example 2

[0097] This embodiment provides a silicon rod and a method for preparing the same, comprising the following steps:

[0098] melting silicon raw materials to obtain silicon liquid;

[0099] Adding a first concentration of an N-type dopant and a second concentration of a P-type dopant into the silicon liquid to obtain a doped silicon liquid;

[0100] Placing a seed crystal on the doped silicon liquid, pulling up the seed crystal to allow the doped silicon liquid to crystallize on the seed crystal, and obtaining a silicon rod after the crystalline silicon is grown;

[0101] The effective segregation coefficient of the N-type dopant at the minimum growth rate of the crystalline silicon / the effective segregation coefficient of the P-type dopant at the minimum growth rate of the crystalline silicon < the second concentration / the first concentration < the effective segregation coefficient of the N-type dopant at the maximum growth rate of the crystalline silicon / the effective segregation coefficient of the P-type dopant at the maximum growth rate of the crystalline silicon. During the growth of crystalline silicon, the growth rate of the central area is lower than the growth rate of the edge area, the interface shape of the silicon rod growth is concave, the conductivity type of the central area is P type, and the conductivity type of the edge area is N type.

[0102] Specifically, the second concentration is 1.25×10 15 atoms / cm 3 , the first concentration is 5×10 16 atoms / cm 3 , second concentration / first concentration=0.025.

[0103] The effective segregation coefficient of the N-type dopant at the minimum growth rate of the crystalline silicon = 0.0079, the effective segregation coefficient of the P-type dopant at the minimum growth rate of the crystalline silicon = 0.33, the effective segregation coefficient of the N-type dopant at the minimum growth rate of the crystalline silicon / the effective segregation coefficient of the P-type dopant at the minimum growth rate of the crystalline silicon = 0.024.

[0104] The effective segregation coefficient of the N-type dopant at the maximum growth rate of the crystalline silicon = 0.0093, the effective segregation coefficient of the P-type dopant at the maximum growth rate of the crystalline silicon = 0.36, the effective segregation coefficient of the N-type dopant at the maximum growth rate of the crystalline silicon / the effective segregation coefficient of the P-type dopant at the maximum growth rate of the crystalline silicon = 0.0258.

[0105] Finally, a silicon rod is obtained in which the conductivity type of the central region is P type and the conductivity type of the edge region is N type.

[0106] Example 3

[0107] This embodiment provides a silicon rod and a method for preparing the same, comprising the following steps:

[0108] melting silicon raw materials to obtain silicon liquid;

[0109] Adding a first concentration of an N-type dopant and a second concentration of a P-type dopant into the silicon liquid to obtain a doped silicon liquid;

[0110] Placing a seed crystal on the doped silicon liquid, pulling up the seed crystal to allow the doped silicon liquid to crystallize on the seed crystal, and obtaining a silicon rod after the crystalline silicon is grown;

[0111] The effective segregation coefficient of the P-type dopant at the minimum growth rate of the crystalline silicon / the effective segregation coefficient of the N-type dopant at the minimum growth rate of the crystalline silicon < the first concentration / the second concentration < the effective segregation coefficient of the P-type dopant at the maximum growth rate of the crystalline silicon / the effective segregation coefficient of the N-type dopant at the maximum growth rate of the crystalline silicon. During the growth of crystalline silicon, the growth rate of the central area is greater than the growth rate of the edge area, the interface shape of the silicon rod growth is convex, the conductivity type of the central area is P type, and the conductivity type of the edge area is N type.

[0112] Example 4

[0113] This embodiment provides a silicon rod and a method for preparing the same, comprising the following steps:

[0114] melting silicon raw materials to obtain silicon liquid;

[0115] Adding a first concentration of an N-type dopant and a second concentration of a P-type dopant into the silicon liquid to obtain a doped silicon liquid;

[0116] Placing a seed crystal on the doped silicon liquid, pulling up the seed crystal to allow the doped silicon liquid to crystallize on the seed crystal, and obtaining a silicon rod after the crystalline silicon is grown;

[0117] The effective segregation coefficient of the P-type dopant at the minimum growth rate of the crystalline silicon / the effective segregation coefficient of the N-type dopant at the minimum growth rate of the crystalline silicon < the first concentration / the second concentration < the effective segregation coefficient of the P-type dopant at the maximum growth rate of the crystalline silicon / the effective segregation coefficient of the N-type dopant at the maximum growth rate of the crystalline silicon. During the growth of crystalline silicon, the growth rate of the central area is lower than the growth rate of the edge area, the interface shape of the silicon rod growth is concave, the conductivity type of the central area is N-type, and the conductivity type of the edge area is P-type.

[0118] Example 5

[0119] This embodiment provides a silicon wafer, which is cut from the silicon rod obtained in embodiment 1.

[0120] Example 6

[0121] This embodiment provides a solar cell, which is made based on the silicon wafer of Embodiment 5.

[0122] Example 7

[0123] This embodiment provides a battery assembly, including the solar cell described in Embodiment 6.

[0124] Example 8

[0125] This embodiment provides a photovoltaic system, including the battery assembly described in Embodiment 7.

[0126] In the description of this specification, the description with reference to the terms "some embodiments", "illustrative embodiments", "examples", "specific examples", or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiments or examples are included in at least one embodiment or example of the present application. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0127] In addition, the above are only preferred embodiments of the present application and are not intended to limit the present application. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present application should be included in the protection scope of the present application.

Claims

1. A silicon rod, characterized in that: Includes central and peripheral areas; The conductivity type of the central region is N-type, and the conductivity type of the edge region is P-type; Alternatively, the conductivity type of the central region is P type, and the conductivity type of the edge region is N type.

2. The silicon rod according to claim 1, characterized in that: The surface of the central area in the cross-sectional direction of the silicon rod is circular, and the center of the circle is the center point of the cross-sectional direction of the silicon rod; The surface of the edge region in the cross-sectional direction of the silicon rod is in the shape of a circular ring, and the center of the circle is the central point of the cross-sectional area of ​​the silicon rod.

3. The silicon rod according to claim 1, characterized in that: The P-type doping concentration is ≤9×10 18 atoms / cm 3 ; The N-type doping concentration is ≤5×10 17 atoms / cm 3 .

4. A method for preparing a silicon rod according to any one of claims 1 to 3, characterized in that: The following steps are involved: melting silicon raw materials to obtain silicon liquid; Adding a first concentration of an N-type dopant and a second concentration of a P-type dopant into the silicon liquid to obtain a doped silicon liquid; Placing a seed crystal on the doped silicon liquid, pulling up the seed crystal to allow the doped silicon liquid to crystallize on the seed crystal, and obtaining a silicon rod after the crystalline silicon is grown; During the growth of crystalline silicon, the growth rate of the central area of ​​the silicon rod is greater or less than the growth rate of the edge area; The concentration of the N-type dopant in the central region is higher than that of the P-type dopant, and the concentration of the P-type dopant in the edge region is higher than that of the N-type dopant; Alternatively, the concentration of the P-type dopant in the central region is higher than that of the N-type dopant, and the concentration of the N-type dopant in the edge region is higher than that of the P-type dopant.

5. The method for preparing a silicon rod according to claim 4, characterized in that: During the growth of crystalline silicon, the interface shape of the growing silicon rod is convex or concave.

6. The method for preparing a silicon rod according to claim 4, characterized in that: The first concentration and the second concentration satisfy: The effective segregation coefficient of the N-type dopant at the minimum growth rate of the crystalline silicon / the effective segregation coefficient of the P-type dopant at the minimum growth rate of the crystalline silicon < the second concentration / the first concentration < the effective segregation coefficient of the N-type dopant at the maximum growth rate of the crystalline silicon / the effective segregation coefficient of the P-type dopant at the maximum growth rate of the crystalline silicon.

7. The method for preparing a silicon rod according to claim 6, characterized in that: During the growth of crystalline silicon, the growth rate of the central region is greater than that of the edge region, the interface shape of silicon rod growth is convex, the conductivity type of the central region is N-type, and the conductivity type of the edge region is P-type.

8. The method for preparing a silicon rod according to claim 6, characterized in that: During the growth of crystalline silicon, the growth rate of the central region is lower than that of the edge region, the interface shape of silicon rod growth is concave, the conductivity type of the central region is P type, and the conductivity type of the edge region is N type.

9. The method for preparing a silicon rod according to claim 4, characterized in that: The first concentration and the second concentration satisfy: The effective segregation coefficient of the P-type dopant at the minimum growth rate of the crystalline silicon / the effective segregation coefficient of the N-type dopant at the minimum growth rate of the crystalline silicon < the first concentration / the second concentration < the effective segregation coefficient of the P-type dopant at the maximum growth rate of the crystalline silicon / the effective segregation coefficient of the N-type dopant at the maximum growth rate of the crystalline silicon.

10. The method for preparing a silicon rod according to claim 9, characterized in that: During the growth of crystalline silicon, the growth rate of the central region is greater than that of the edge region, the interface shape of the silicon rod growth is convex, the conductivity type of the central region is P type, and the conductivity type of the edge region is N type.

11. The method for preparing a silicon rod according to claim 9, characterized in that: During the growth of crystalline silicon, the growth rate of the central region is lower than that of the edge region, the interface shape of silicon rod growth is concave, the conductivity type of the central region is N-type, and the conductivity type of the edge region is P-type.

12. The method for preparing a silicon rod according to claim 4, characterized in that: The surface of the central area in the cross-sectional direction of the silicon rod is circular, and the center of the circle is the central point of the cross-sectional direction of the silicon rod.

13. The method for preparing a silicon rod according to claim 4, characterized in that: The surface of the edge region in the cross-sectional direction of the silicon rod is in the shape of a circular ring, and the center of the circle is the central point of the cross-sectional direction of the silicon rod.

14. The method for preparing a silicon rod according to claim 4, characterized in that: The N-type dopant includes at least one of a fifth main group element and a sixth main group element.

15. The method for preparing a silicon rod according to claim 4, characterized in that: The P-type dopant includes at least one of the third main group elements.

16. A silicon wafer, characterized in that: Cut from the silicon rod according to any one of claims 1 to 3; Alternatively, the silicon rod is cut from the silicon rod prepared by the method for preparing the silicon rod according to any one of claims 4 to 15.

17. A solar cell, characterized in that: Made based on the silicon wafer described in claim 16.

18. A battery assembly, characterized in that: Comprising the solar cell according to claim 17.

19. A photovoltaic system, characterized in that: A battery assembly comprising the battery assembly of claim 18.

Images