CN112071929A - Solar cell and preparation method of phosphorus-hydrogen doped monocrystalline silicon - Google Patents

Solar cell and preparation method of phosphorus-hydrogen doped monocrystalline silicon Download PDF

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CN112071929A
CN112071929A CN202010969731.2A CN202010969731A CN112071929A CN 112071929 A CN112071929 A CN 112071929A CN 202010969731 A CN202010969731 A CN 202010969731A CN 112071929 A CN112071929 A CN 112071929A
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hydrogen
phosphorus
silicon
layer
doped
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肖贵云
白枭龙
尚伟泽
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Xinjiang Jinko Energy Co ltd
Jinko Solar Co Ltd
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Xinjiang Jinko Energy Co ltd
Jinko Solar Co Ltd
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    • C30B15/00—Single-crystal growth by pulling from a melt, e.g. Czochralski method
    • C30B15/02—Single-crystal growth by pulling from a melt, e.g. Czochralski method adding crystallising materials or reactants forming it in situ to the melt
    • C30B15/04—Single-crystal growth by pulling from a melt, e.g. Czochralski method adding crystallising materials or reactants forming it in situ to the melt adding doping materials, e.g. for n-p-junction
    • C—CHEMISTRY; METALLURGY
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Abstract

The application provides a solar cell and a preparation method of phosphorus-hydrogen doped monocrystalline silicon, wherein the solar cell comprises a semiconductor substrate, a doping layer positioned on the front surface of the semiconductor substrate, a front passivation layer and/or antireflection layer positioned on the upper surface of the doping layer, a front electrode positioned on the upper surface of the front passivation layer and/or antireflection layer, a tunneling oxide layer positioned on the back surface of the semiconductor substrate, a doped polycrystalline silicon layer positioned on the back surface of the tunneling oxide layer, a back passivation layer positioned on the back surface of the doped polycrystalline silicon layer and a doped polycrystalline silicon layer positioned on the back surface ofA back electrode on the back of the back passivation layer, wherein the semiconductor substrate comprises phosphorus-hydrogen doped monocrystalline silicon with hydrogen doping concentration of 1 × 105～1×1016atoms/cm3Phosphorus doping concentration of 1X 1015～5×1017atoms/cm3The resistivity of the phosphorus-hydrogen doped monocrystalline silicon is 0.1-10 omega cm. The solar cell can effectively prolong the minority carrier lifetime in monocrystalline silicon, is favorable for improving the passivation effect of the cell, and improves the conversion efficiency of the solar cell.

Description

Solar cell and preparation method of phosphorus-hydrogen doped monocrystalline silicon
Technical Field
The application relates to the technical field of photovoltaic cells, in particular to a solar cell and a preparation method of phosphorus-hydrogen doped monocrystalline silicon.
Background
Currently, as one of the fastest growing fields in solar photovoltaic utilization, the technical development of crystalline silicon cells is attracting attention, and the improvement of the conversion efficiency of solar cells is a problem to be solved. In the existing monocrystalline silicon production process, the czochralski silicon is easy to have midpoint defects, dislocation defects, metal defects and the like, and the existence of the defects is easy to reduce the minority carrier lifetime of the monocrystalline silicon and reduce the conversion efficiency of the solar cell.
Disclosure of Invention
In view of this, embodiments of the present application provide a solar cell and a method for preparing a phosphorus-and-hydrogen-doped monocrystalline silicon, which can effectively improve minority carrier lifetime in the monocrystalline silicon, and is beneficial to improving a cell passivation effect and improving conversion efficiency of the solar cell.
The application provides a solar cell, the solar cell comprises a semiconductor substrate, a doping layer located on the front side of the semiconductor substrate, a front passivation layer and/or a reflection reducing layer located on the upper surface of the doping layer, a front electrode located on the upper surface of the front passivation layer and/or the reflection reducing layer, a tunneling oxidation layer located on the back side of the semiconductor substrate, a doped polycrystalline silicon layer located on the back side of the tunneling oxidation layer, a back passivation layer located on the back side of the doped polycrystalline silicon layer and a back electrode located on the back side of the back passivation layer,
wherein the semiconductor substrate comprises phosphorus-hydrogen doped monocrystalline silicon, and the hydrogen doping concentration in the phosphorus-hydrogen doped monocrystalline silicon is 1 × 105～1×1016atoms/cm3Phosphorus doping concentration of 1X 1015～5×1017atoms/cm3(ii) a The resistivity of the phosphorus-hydrogen doped monocrystalline silicon is 0.1-10 omega cm.
In a possible embodiment, the hydrogen content of the central region of the semiconductor substrate is greater than the hydrogen content of the edge region.
The application also provides a preparation method of the phosphorus-hydrogen doped monocrystalline silicon, which comprises the following steps:
putting a polycrystalline silicon raw material and a phosphorus dopant into a quartz crucible;
placing the quartz crucible in a single crystal furnace, vacuumizing, and melting a polycrystalline silicon raw material under the protection of inert gas to obtain a silicon melt;
after the temperature of the silicon melt is stable, adding a hydrogen source into the single crystal furnace, and immersing a seed crystal into the silicon melt to start seeding;
after seeding is finished, shouldering is started to enable the diameter of the crystal to be gradually increased to a preset width, and then equal-diameter growth is carried out;
after the isodiametric growth is finished, entering a final stage, and gradually reducing the diameter of the crystal until the crystal is separated from the silicon melt;
and cooling the grown crystal to room temperature and taking out to obtain the phosphorus and hydrogen doped monocrystalline silicon.
In a feasible embodiment, during seeding, the water-cooling heat shield is lifted to a direction away from the surface of the silicon melt, so that the distance between the bottom of the water-cooling heat shield and the surface of the silicon melt is adjusted to a first preset distance;
in the process of isometric growth, the water-cooling heat shield is descended towards the direction close to the surface of the silicon melt, so that the distance between the bottom of the water-cooling heat shield and the surface of the silicon melt is adjusted to a second preset distance;
the height difference between the first preset distance and the second preset distance is 15-50 mm.
In one possible embodiment, the hydrogen source is a hydrogen-containing gas, and the step of adding the hydrogen source into the single crystal furnace comprises:
and mixing the hydrogen-containing gas with the inert gas to form mixed gas, and introducing the mixed gas into the single crystal furnace, wherein the volume of the hydrogen-containing gas in the mixed gas is 0.1-10%.
In one possible embodiment, the hydrogen-containing gas comprises at least one of hydrogen, silane, ammonia; the inert gas comprises at least one of nitrogen, argon and helium.
In one possible embodiment, the flow rate of the mixed gas is 50slpm to 200 slpm.
In one possible embodiment, the hydrogen source is a polysilicon feedstock rich in hydrogen, and the step of adding the hydrogen source to the single crystal furnace comprises:
adding the hydrogen-rich polycrystalline silicon feedstock to the silicon melt.
In one possible embodiment, the hydrogen content of the hydrogen-rich polysilicon feedstock is greater than 6 x 1016atoms/cm3。
In one possible embodiment, the phosphorous dopant comprises at least one of phosphorous-doped master alloy, phosphorous, and phosphorous oxide.
The technical scheme of the application has at least the following beneficial effects:
according to the solar cell, the semiconductor substrate is made of phosphorus and hydrogen doped monocrystalline silicon, hydrogen atoms can form a complex or precipitate with other impurities and point defects in silicon, the electrical activity of the impurities is removed, and the passivation effect is achieved, so that the activity of the point defects, the dislocation defects and the metal defects of the semiconductor substrate can be greatly reduced, the minority carrier lifetime is effectively prolonged, and the conversion efficiency of the solar cell is improved. When the phosphorus and hydrogen doped single crystal silicon is prepared, a proper amount of phosphorus dopant and hydrogen source are added, so that trace hydrogen atoms are fused into the silicon melt to realize the doping of hydrogen and phosphorus elements.
Drawings
For a clearer explanation of the embodiments or technical solutions of the prior art of the present application, the drawings needed for the description of the embodiments or prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present application, and for those skilled in the art, other drawings can be obtained according to these drawings without creative efforts.
Fig. 1 is a schematic structural diagram of a solar cell provided in this embodiment.
FIG. 2a is a schematic structural diagram of a single crystal furnace according to the present embodiment;
FIG. 2b is a schematic view of another structure of a single crystal furnace according to this embodiment;
fig. 3 is a schematic flow chart of a method for preparing phosphorus-hydrogen doped monocrystalline silicon according to this embodiment.
Detailed Description
For better understanding of the technical solutions of the present application, the following detailed descriptions of the embodiments of the present application are provided with reference to the accompanying drawings.
It should be understood that the embodiments described are only a few embodiments of the present application, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present application.
The terminology used in the embodiments of the present application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. As used in the examples of this application and the appended claims, the singular forms "a", "an", and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise.
It should be understood that the term "and/or" as used herein is merely one type of association that describes an associated object, meaning that three relationships may exist, e.g., a and/or B may mean: a exists alone, A and B exist simultaneously, and B exists alone. In addition, the character "/" herein generally indicates that the former and latter related objects are in an "or" relationship.
An embodiment of the present application provides a solar cell, the solar cell includes a semiconductor substrate, is located the doping layer of semiconductor substrate front, is located the front passivation layer and/or the antireflection layer of doping layer upper surface, is located the front electrode of front passivation layer and/or antireflection layer upper surface, is located the tunneling oxide layer of semiconductor substrate back, is located the doping polycrystalline silicon layer at the tunneling oxide layer back, is located the back passivation layer at the doping polycrystalline silicon layer back and is located the back electrode at the back passivation layer back.
Fig. 1 is a schematic structural diagram of a solar cell provided in an embodiment of the present application, and as shown in fig. 1, the solar cell is a solar cell having a Topcon structure, and the structure includes:
the semiconductor substrate 100, the semiconductor substrate 100 comprises phosphorus-hydrogen doped monocrystalline silicon, wherein the hydrogen doping concentration in the phosphorus-hydrogen doped monocrystalline silicon is 1 × 105～1×1016atoms/cm3Phosphorus doping concentration of 1X 1015～5×1017atoms/cm3The resistivity of the phosphorus-hydrogen doped monocrystalline silicon is 0.1-10 omega cm.
In a specific embodiment, the hydrogen doping concentration in the phosphorus-hydrogen doped monocrystalline silicon may be, for example, 1 × 105atoms/cm3、1×106atoms/cm3、1×107atoms/cm3、1×108atoms/cm3、1×109atoms/cm3、1×1010atoms/cm3、1×1012atoms/cm3、1×1013atoms/cm3、1×1014atoms/cm3、1×1015atoms/cm3Or 1X 1016atoms/cm3And the like, and other values within this range are also possible, and are not limited herein.
The phosphorus-doped concentration in the phosphorus-and hydrogen-doped single crystal silicon may be, for example, 1 × 1015atoms/cm3、5×1015atoms/cm3、1×1016atoms/cm3、2×1016atoms/cm3、4×1016atoms/cm3、5×1016atoms/cm3、1×1017atoms/cm3、2×1017atoms/cm3Or 5X 1017atoms/cm3And the like, and other values within this range are also possible, and are not limited herein.
The resistivity of the phosphorus-and hydrogen-doped single crystal silicon is 0.1 to 10 Ω · cm, and may be, for example, 0.1 Ω · cm, 0.5 Ω · cm, 1.4 Ω · cm, 3.7 Ω · cm, 5.2 Ω · cm, 8.5 Ω · cm, or 10 Ω · cm, or the like, and may be any other value within this range, and is not limited thereto.
The doping concentration of phosphorus and hydrogen is controlled within the range, so that the semiconductor substrate can meet the performance requirement of the solar cell, and the monocrystalline silicon substrate doped with phosphorus and hydrogen can greatly reduce the activity of point defects, dislocation defects and metal defects in the monocrystalline silicon crystal, is beneficial to controlling the dislocation defects, can effectively prolong the minority carrier lifetime, and improves the conversion efficiency of the solar cell.
During the preparation process of the cell, a silicon wafer (including a semiconductor substrate, such as a silicon substrate) is subjected to a high temperature treatment (e.g., a high temperature annealing treatment), and hydrogen atoms in the silicon wafer can escape at a high temperature, and in some embodiments, hydrogen in an edge region of the silicon wafer is easier to escape than hydrogen in a central region of the silicon wafer, so that the hydrogen content in the central region of the semiconductor substrate is greater than that in the edge region. To some extent, the escaped hydrogen atoms contribute to defect passivation of the semiconductor substrate, thereby improving the conversion efficiency of the cell.
In some embodiments, during the fabrication of the solar cell, H-P bonds may be formed inside the semiconductor substrate 100 to fix the hydrogen atoms from excessive escape.
In the present embodiment, the semiconductor substrate 100 is an N-type semiconductor, the semiconductor substrate 100 includes a front surface and a back surface which are oppositely disposed, and the hydrogen content in the semiconductor substrate 100 is unevenly distributed, for example, the hydrogen content in the center region of the semiconductor substrate 100 is greater than that in the edge region thereof. It is understood that the edge region may refer to a region located at a depth, e.g., within 10nm, within the surface (e.g., front, back, and/or side) of the substrate. The central region may refer to a specific partial region or the entire region other than the edge region.
A doped layer 13 on the front side of the semiconductor substrate 100. The doping layer 13 may form a PN junction structure with the semiconductor substrate 100. Specifically, the P-type doped layer may be formed on the surface of the semiconductor substrate by one or more methods of high-temperature diffusion, slurry doping, or ion implantation. Illustratively, the surface of the semiconductor substrate 100 may be doped by boron diffusion, and a boron diffusion process is performed by using a boron source, for example, boron tribromide may be used as the boron source to form the boron diffusion layer.
Note that the doping layer 13 may be formed by doping an element in the surface layer of the semiconductor substrate 100; a doped layer 13 may be deposited on the surface of the semiconductor substrate 100, i.e. the semiconductor substrate 100 and the doped layer 13 are provided separately.
A front passivation and/or antireflective layer 12 on the top surface of doped layer 13;
a front electrode 111 on the upper surface of the front passivation layer and/or the antireflective layer 12, the front electrode 111 making electrical contact with the doped layer 13 through the front passivation layer 12 and/or the antireflective layer 12;
a tunnel oxide layer 14 located on the back surface of the semiconductor substrate 100, wherein the tunnel oxide layer 14 may be, for example, a silicon oxide layer;
a doped polysilicon layer 15 located on the back of the tunneling oxide layer 14;
a back passivation layer 16 located on the back of the doped polysilicon layer 15.
And a back electrode 112 located on the back of the back passivation layer 16, wherein the back electrode 112 penetrates through the back passivation layer 16 to form an electrical contact with the doped polysilicon layer 15, and the doped polysilicon layer 15 and the tunnel oxide layer 14 form a TopCon structure.
In other embodiments, an oxide layer may be formed on the back surface of the doped polysilicon layer 15, and then a back passivation layer 16 is formed on the back surface of the oxide layer, so as to further improve the passivation effect and the conversion rate of the solar cell. It should be noted that the back electrode 112 needs to pass through the back passivation layer 16 and the oxide layer to make electrical contact with the doped polysilicon layer 15.
In the embodiment of the present invention, the specific types of the front passivation layer 12 and the back passivation layer 16 are not limited, and for example, the front passivation layer and the back passivation layer may be any one or a combination of multiple silicon nitride layers, silicon oxynitride layers, and aluminum oxide/silicon nitride stacked structures, which can generate a good passivation effect on a silicon substrate, and is helpful for improving the conversion efficiency of a battery.
In the embodiment of the invention, the specific material of the front electrode 111 and the back electrode 112 is not limited. For example, the front electrode 111 is a silver electrode or a silver/aluminum electrode, and the back electrode 112 is a silver electrode.
In the embodiment of the invention, the conductive paste can be printed on the surface of the semiconductor substrate by adopting a screen printing technology, and the conductive paste is sintered and dried to form the grid-line-shaped electrode structure. And the formed grid line electrode is electrically connected with the semiconductor substrate through the heavily doped region of the doped layer. The conductive paste includes, but is not limited to, silver paste and/or aluminum paste, etc.
In other embodiments, both the front side and/or the back side of the semiconductor substrate may form an electrode structure.
It should be noted that, in the embodiment of the present invention, the thickness of each layer structure in the solar cell is not limited, and can be adjusted and controlled by a person skilled in the art according to actual situations.
The embodiment of the application also provides a preparation method of phosphorus and hydrogen doped monocrystalline silicon, the monocrystalline silicon is prepared by adopting a monocrystalline furnace based on a czochralski method (such as CZ, CCZ, MCZ, RCZ, OCZ and the like), partial structure of the monocrystalline furnace is shown in figures 2 a-2 b, and the monocrystalline furnace comprises a furnace body 1, a quartz crucible 2, a heater 3, a water-cooling heat shield 4, a heat-preserving cylinder 5, a guide cylinder 6, a crystal pulling device 7 and a crystal 8. The crystal pulling apparatus 7 is used for pulling the crystal 8.
The single crystal furnace also comprises a connecting piece 10 and a water-cooling heat shield lifting rod 11, wherein the connecting piece 10 is used for connecting the water-cooling heat shield lifting rod 11 with the guide cylinder 6, and the water-cooling heat shield lifting rod 11 is used for lifting the water-cooling heat shield 4.
In one embodiment, the connector 10 includes a lift stop 101, a support rod 102, and a lift buckle 103. Two ends of the supporting rod 102 are respectively connected with the lifting limiting part 101 and the guide cylinder 6, one end of the lifting buckle 103 is fixedly connected with the water-cooling heat shield lifting rod 11, and the other end is clamped on the supporting rod 102. The heater 3 is used to heat the polysilicon raw material and the phosphorus dopant in the quartz crucible 2, so that the polysilicon raw material is melted to form the silicon melt 9. The water-cooling heat shield 4 can reduce the temperature of the surface of the crystal 8, increase the temperature gradient inside the crystal 8 and improve the growth speed of the crystal.
Fig. 3 is a flowchart of a method for preparing phosphorus-and-hydrogen-doped single crystal silicon according to an embodiment of the present application, and as shown in fig. 3, the method includes the following steps:
putting a polycrystalline silicon raw material and a phosphorus dopant into a quartz crucible;
placing the quartz crucible in a single crystal furnace, vacuumizing, and melting a polycrystalline silicon raw material under the protection of inert gas to obtain a silicon melt;
after the temperature of the silicon melt is stable, adding a hydrogen source into the single crystal furnace, and immersing a seed crystal into the silicon melt to start seeding;
after seeding is finished, shouldering is started to enable the diameter of the crystal to be gradually increased to a preset width, and then equal-diameter growth is carried out;
after the isodiametric growth is finished, entering a final stage, and gradually reducing the diameter of the crystal until the crystal is separated from the silicon melt;
and cooling the grown crystal to room temperature and taking out to obtain the phosphorus and hydrogen doped monocrystalline silicon.
In the scheme, in the seeding process, a hydrogen source is added, so that trace hydrogen atoms are fused into silicon melt to realize hydrogen element doping, and the doped hydrogen atoms can greatly reduce the activity of point defects, dislocation defects and metal defects in the phosphorus-doped single crystal silicon crystal, effectively prolong the minority carrier lifetime of the phosphorus-doped single crystal and improve the quality of the single crystal silicon.
In the following, the technical solutions in the embodiments of the present invention will be clearly and completely described with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments of the present invention without making any creative effort, shall fall within the protection scope of the present invention.
And (1) putting a polycrystalline silicon raw material and a phosphorus dopant into a quartz crucible.
In one embodiment, the polysilicon feedstock may be a virgin polysilicon charge and the phosphorus dopant includes at least one of a phosphorus-doped master alloy, phosphorus, and an oxide of phosphorus. The resistivity of the phosphorus-doped master alloy is 0.001-0.05 omega cm. It should be noted that the phosphorus-doped master alloy is an alloy of phosphorus and silicon. The phosphorus doping concentration in the phosphorus-doped master alloy is 1 multiplied by 1016～5×1018atoms/cm3And the phosphorus-doped master alloy is adopted as a doping agent, so that the doping amount can be controlled more easily and more accurately.
In other embodiments, a phosphorus doped polysilicon feedstock may also be used.
In the actual preparation process, a layer of polycrystalline silicon raw material is firstly filled in a quartz crucible, then a phosphorus dopant is added, and finally a layer of polycrystalline silicon raw material is filled on the phosphorus dopant, so that the phosphorus dopant is placed in the polycrystalline silicon raw material, and is uniformly dispersed in silicon melt as much as possible during melting, and the resistivity of each part of the growing crystalline silicon is more uniform.
Step (2), placing the quartz crucible in a single crystal furnace for vacuumizing, and melting a polycrystalline silicon raw material under the protection of inert gas to obtain silicon melt;
specifically, the inert gas may be at least one of argon gas and helium gas, for example.
In the process of melting, the temperature in the single crystal furnace is controlled to be 1420-1570 ℃. For example, 1450 ℃, 1480 ℃, 1500 ℃, 1520 ℃, 1540 ℃, 1560 ℃, preferably 1520 ℃, in the single crystal furnace to obtain molten liquid silicon.
And (3) when the temperature of the silicon melt is stable, adding a hydrogen source into the single crystal furnace, and immersing a seed crystal into the silicon melt to start seeding.
The stable temperature of the silicon melt is 1420-1480 ℃, at the moment, the temperature of the silicon melt in the quartz crucible is stable, and a hydrogen source can be added into the inert gas, so that hydrogen atoms are doped into the silicon melt.
In one embodiment, the hydrogen source is a hydrogen-containing gas, and the step of adding the hydrogen source into the single crystal furnace comprises:
and mixing the hydrogen-containing gas with the inert gas to form mixed gas, and introducing the mixed gas into the single crystal furnace.
Specifically, the hydrogen-containing gas includes at least one of hydrogen, silane, and ammonia. The inert gas comprises at least one of nitrogen, argon and helium.
The volume ratio of the hydrogen-containing gas in the mixed gas is controlled to be 0.1% to 10% from the start of the seeding stage, and may be, for example, 0.1%, 1.5%, 2.8%, 3.4%, 4.0%, 5.5%, 6.7%, 8.0%, or 10%, or may be other values within this range, which is not limited herein.
In a specific embodiment, the hydrogen-containing gas is combined with the inert gas in the same pipeline before being introduced into the furnace body, and preferably, a gas mixing valve can be arranged on the pipeline, so that the gas mixing is more uniform.
In this embodiment, the flow rate of the mixed gas is 50 to 200slpm, which may be, for example, 50slpm, 80slpm, 100slpm, 120slpm, 150slpm, 180slpm or 200slpm, or may be other values within this range, which is not limited herein. The mixed gas in the flow range can effectively ensure the doping of hydrogen atoms, is favorable for controlling the temperature in a preparation device and is favorable for improving the seeding success rate.
In another embodiment, the hydrogen source is a polysilicon feedstock rich in hydrogen, and the specific step of adding the hydrogen source to the single crystal furnace comprises:
adding the hydrogen-rich polycrystalline silicon feedstock to the silicon melt.
The hydrogen content in the polysilicon raw material rich in hydrogen is more than 6 x 1016atoms/cm3. When the hydrogen-rich polysilicon raw material is adopted, the subsequent seeding, shouldering and equal diameter are carried outDuring the growth and the ending process, no hydrogen-containing gas is needed to be added.
In the seeding process, the water flow of the water-cooling heat shield is controlled to be 40-160 slpm, the rotating speed of the quartz crucible is 4-10 r/min, the temperature in the single crystal furnace is 1420-1480 ℃, the pressure in the single crystal furnace is 1000-3000 Pa, and the seeding speed is 40-400 mm/h.
Alternatively, the water flow rate of the water-cooled heat shield may be, for example, 40slpm, 60slpm, 80slpm, 100slpm, 120slpm, 140slpm or 160slpm, but may be other values within this range, which is not limited herein.
Alternatively, the rotation speed of the quartz crucible can be, for example, 4r/min, 5r/min, 6r/min, 7r/min, 8r/min, 9r/min or 10r/min, or other values within the range, which is not limited herein.
Alternatively, the temperature in the single crystal furnace may be, for example, 1420 ℃, 1440 ℃, 1460 ℃ or 1480 ℃, but may be other values within this range, and is not limited thereto.
Alternatively, the pressure inside the single crystal furnace may be, for example, 1000Pa, 1500Pa, 2000Pa, 2500Pa, or 3000Pa, but may be other values within this range, and is not limited herein.
Alternatively, the seeding rate may be, for example, 40mm/h, 80mm/h, 100mm/h, 150mm/h, 200mm/h, 250mm/h, 300mm/h, 350mm/h, or 400mm/h, without limitation.
In addition, the temperature and pressure in the furnace, the water flow of the water-cooling heat shield, the rotating speed of the quartz crucible and the seeding speed range are in the range, so that the seeding success rate is improved.
In this embodiment, as shown in fig. 2a, in the seeding process, the water-cooling heat shield lifting rod 11 lifts the water-cooling heat shield 4 away from the surface of the silicon melt, and the guide cylinder 6 rises along with the water-cooling heat shield lifting rod 11 under the action of the connecting piece 10, so that the distance h between the bottom of the water-cooling heat shield and the surface 91 of the silicon melt is adjusted to a first preset distance. Optionally, the first preset distance is 25-60 mm. The first preset distance is set so that the water-cooling heat shield is far away from the high-temperature silicon melt in the seeding stage, temperature fluctuation is avoided, the temperature of a growth interface is stable, and the seeding success rate is high.
Step (4), after seeding is finished, shouldering is started to enable the diameter of the crystal to be gradually increased to a preset width, and then equal-diameter growth is carried out;
in the shouldering process, the water flow of the water-cooling heat shield is controlled to be 40-160 slpm, the rotating speed of the quartz crucible is 4-10 r/min, the temperature in the single crystal furnace is 1420-1460 ℃, the pressure in the single crystal furnace is 1000-3000 Pa, and the flow of the mixed gas is 50-200 slpm.
The first pulling speed of the crystal is 40-80mm/h, so that the diameter of the crystal is gradually increased to 10-305 mm. Alternatively, the first pulling speed may be, for example, 40mm/h, 55mm/h, 65mm/h, 80mm/h, etc., and the diameter of the crystal is gradually increased to 40mm, 100mm, 150mm, 225mm, 245mm, 285mm, 295mm, 305mm, etc., without limitation. Understandably, the temperature gradient in the crystal is small in the shouldering process, and the growth speed and the pulling speed of the crystal are slow in order to ensure the stability of crystal pulling. In addition, in the whole shouldering process, the temperature in the single crystal furnace can be gradually reduced, and cannot be increased.
The diameter range of the crystal can be designed and controlled according to the size requirement of the cell piece on the silicon wafer, and is not limited herein.
In the shouldering process, the distance h between the bottom of the water-cooling heat shield and the surface of the silicon melt can be reduced, and the heat absorption capacity of the water-cooling heat shield on the crystal rod is improved.
Optionally, in the process of constant-diameter growth, the water flow of the water-cooling heat shield is controlled to be 40-160 slpm, the rotating speed of the quartz crucible is 4-10 r/min, the temperature in the single crystal furnace is 1420-1460 ℃, the pressure in the single crystal furnace is 1000-3000 Pa, and the flow of the mixed gas is 50-200 slpm.
The second pulling speed of the crystal is 70-140 mm/h, for example, 70mm/h, 80mm/h, 90mm/h, 100mm/h, 110mm/h, 120mm/h, 130mm/h or 140mm/h, etc., which is not limited herein. Understandably, in the equal-diameter growth stage, the crystal begins to enter the water-cooling heat shield area or completely enters the water-cooling heat shield area, the water-cooling heat shield can quickly absorb the heat of the crystal, so that the temperature gradient of the crystal bar is increased, and in the stage, in order to ensure the growth efficiency, the crystal growth speed is increased, and the crystal pulling speed can be increased.
As shown in fig. 2b, in the process of isodiametric growth, the water-cooling heat shield lifting rod 11 descends towards the direction close to the surface of the silicon melt to the water-cooling heat shield 4, the guide cylinder 6 also descends along with the water-cooling heat shield lifting rod until the flanging of the guide cylinder 6 is abutted to the heat-insulating cylinder 5, and the water-cooling heat shield 4 continues to descend towards the direction close to the surface of the silicon melt, so that the distance h between the bottom of the water-cooling heat shield 4 and the surface 91 of the silicon melt is adjusted to a second preset distance. Optionally, the second preset distance is 10-40 mm. At the moment, the water-cooling heat shield 4 descends relative to the guide cylinder 6, so that the distance between the bottom of the water-cooling heat shield 4 and the surface of the silicon melt is further reduced, the heat absorption capacity of the water-cooling heat shield on the crystal rod is improved, and the variable-temperature gradient crystal pulling is realized.
In this embodiment, a height difference between the first preset distance and the second preset distance is 15-50 mm, and the height difference may be, for example, 15mm, 20mm, 25mm, 30mm, 35mm, 40mm, 45mm, or 50 mm.
And (5) after the equal-diameter growth is finished, entering a final stage, and gradually reducing the diameter of the crystal until the crystal is separated from the silicon melt.
In the process, the water flow of the water-cooling heat shield is controlled to be 40-160 slpm, the rotating speed of the quartz crucible is 4-10 r/min, the temperature in the single crystal furnace is 1420-1460 ℃, the pressure in the single crystal furnace is 1000-3000 Pa, and the flow of the mixed gas is 50-200 slpm.
The third pulling speed of the crystals is 70 to 130mm/h, and may be, for example, 75mm/h, 85mm/h, 95mm/h, 100mm/h, 115mm/h or 120 mm/h; in the final stage, the temperature in the single crystal furnace is rapidly raised.
And (6) cooling the grown crystal to room temperature and taking out the crystal to obtain the phosphorus and hydrogen doped monocrystalline silicon.
The hydrogen doping concentration in the phosphorus and hydrogen doped monocrystalline silicon is 1 multiplied by 105～1×1016atoms/cm3Phosphorus doping concentration of 1X 1015～5×1017atoms/cm3The resistivity of the phosphorus-hydrogen doped monocrystalline silicon is 0.1-10 omega cm.
The above description is only a preferred embodiment of the present application and is not intended to limit the present application, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, improvement and the like made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims (10)

1. A solar cell is characterized by comprising a semiconductor substrate, a doping layer positioned on the front surface of the semiconductor substrate, a front passivation layer and/or an antireflection layer positioned on the upper surface of the doping layer, a front electrode positioned on the upper surface of the front passivation layer and/or the antireflection layer, a tunneling oxide layer positioned on the back surface of the semiconductor substrate, a doped polycrystalline silicon layer positioned on the back surface of the tunneling oxide layer, a back passivation layer positioned on the back surface of the doped polycrystalline silicon layer and a back electrode positioned on the back surface of the back passivation layer,
wherein the semiconductor substrate comprises phosphorus-hydrogen doped monocrystalline silicon, and the hydrogen doping concentration in the phosphorus-hydrogen doped monocrystalline silicon is 1 × 105～1×1016atoms/cm3Phosphorus doping concentration of 1X 1015～5×1017atoms/cm3(ii) a The resistivity of the phosphorus-hydrogen doped monocrystalline silicon is 0.1-10 omega cm.
2. The solar cell according to claim 1, wherein a hydrogen content of the central region of the semiconductor substrate is greater than a hydrogen content of the edge region.
3. A method of preparing phosphorus-hydrogen doped single crystal silicon as claimed in claim 1, comprising the steps of:
putting a polycrystalline silicon raw material and a phosphorus dopant into a quartz crucible;
placing the quartz crucible in a single crystal furnace, vacuumizing, and melting a polycrystalline silicon raw material under the protection of inert gas to obtain a silicon melt;
after the temperature of the silicon melt is stable, adding a hydrogen source into the single crystal furnace, and immersing a seed crystal into the silicon melt to start seeding;
after seeding is finished, shouldering is started to enable the diameter of the crystal to be gradually increased to a preset width, and then equal-diameter growth is carried out;
after the isodiametric growth is finished, entering a final stage, and gradually reducing the diameter of the crystal until the crystal is separated from the silicon melt;
and cooling the grown crystal to room temperature and taking out to obtain the phosphorus and hydrogen doped monocrystalline silicon.
4. The method of claim 3, wherein during seeding, the water-cooled heat shield is lifted away from the surface of the silicon melt such that the distance between the bottom of the water-cooled heat shield and the surface of the silicon melt is adjusted to a first predetermined distance;
in the process of isometric growth, the water-cooling heat shield is descended towards the direction close to the surface of the silicon melt, so that the distance between the bottom of the water-cooling heat shield and the surface of the silicon melt is adjusted to a second preset distance;
the height difference between the first preset distance and the second preset distance is 15-50 mm.
5. The method of claim 3, wherein the hydrogen source is a hydrogen-containing gas, and the step of adding the hydrogen source into the single crystal furnace comprises:
and mixing the hydrogen-containing gas with the inert gas to form mixed gas, and introducing the mixed gas into the single crystal furnace, wherein the volume of the hydrogen-containing gas in the mixed gas is 0.1-10%.
6. The method of claim 5, wherein the hydrogen-containing gas comprises at least one of hydrogen, silane, ammonia; the inert gas comprises at least one of nitrogen, argon and helium.
7. The method of claim 5, wherein the flow rate of the mixed gas is 50slpm to 200 slpm.
8. The method of claim 4, wherein the hydrogen source is a hydrogen-rich polysilicon feedstock, and the step of adding the hydrogen source to the single crystal furnace comprises:
adding the hydrogen-rich polycrystalline silicon feedstock to the silicon melt.
9. The method of claim 8 wherein the hydrogen content of the hydrogen rich polysilicon feedstock is greater than 6 x 1016atoms/cm3。
10. The method of claim 4, wherein the phosphorous dopant comprises at least one of phosphorous-doped master alloy, phosphorous, and oxides of phosphorous.
CN202010969731.2A 2020-09-15 2020-09-15 Solar cell and preparation method of phosphorus-hydrogen doped monocrystalline silicon Pending CN112071929A (en)

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Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0656149A1 (en) * 1992-08-24 1995-06-07 Midwest Research Institute Improved back-side hydrogenation technique for defect passivation in silicon solar cells
CN105474364A (en) * 2013-07-26 2016-04-06 新南创新私人有限公司 High concentration doping in silicon
CN107863417A (en) * 2017-10-31 2018-03-30 泰州隆基乐叶光伏科技有限公司 The preparation method of n-type solar cell
CN111647940A (en) * 2020-08-04 2020-09-11 浙江晶科能源有限公司 Monocrystalline silicon preparation method and device

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0656149A1 (en) * 1992-08-24 1995-06-07 Midwest Research Institute Improved back-side hydrogenation technique for defect passivation in silicon solar cells
CN105474364A (en) * 2013-07-26 2016-04-06 新南创新私人有限公司 High concentration doping in silicon
CN107863417A (en) * 2017-10-31 2018-03-30 泰州隆基乐叶光伏科技有限公司 The preparation method of n-type solar cell
CN111647940A (en) * 2020-08-04 2020-09-11 浙江晶科能源有限公司 Monocrystalline silicon preparation method and device

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