Solar cell and preparation method thereof

Abstract

The invention relates to the technical field of solar cells, and discloses a solar cell piece and a preparation method thereof.The solar cell piece comprises a pyramid suede silicon wafer, an antireflection film arranged on the pyramid suede silicon wafer and conductive grid lines arranged on the antireflection film; the antireflection film comprises a bottom film arranged on the silicon wafer, a middle film arranged on the bottom film and an outer film arranged on the middle film; the conductive grid lines are arranged on the surface of the outer film, and phosphorus doping is arranged on the surface of the pyramid suede silicon wafer; according to the battery piece, by adjusting the deposition thickness of the middle film and the outer film, the technical effects that the reflectivity is not obviously reduced and the current is obviously reduced are achieved, so that the power of the battery piece is not obviously changed and the current of the battery piece is obviously reduced; the battery piece is small in current, high in photoelectric conversion efficiency, high in safety and high in battery power when being applied to a low-short-circuit current area, and the power of a solar battery is remarkably improved while the safety is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of solar cells, and in particular to a solar cell wafer and a preparation method thereof. Background Art

[0002] With the continuous update and iteration of photovoltaic cell technology, the photoelectric conversion efficiency of PERC solar cells (passivated emitter and rear cell) is getting higher and higher. According to the photoelectric efficiency calculation formula: photoelectric conversion efficiency = open circuit voltage * current * fill factor / area / light intensity, it can be seen that the photoelectric efficiency is positively correlated with the current. Therefore, the higher the photoelectric conversion efficiency, the higher the current. At present, the circuits in some solar energy application areas are severely aged and the short-circuit current is low. Therefore, when applying PERC solar cells with high current and high conversion rate to these areas, safety problems such as short circuit and fire are likely to occur. Therefore, for safety reasons, low-current PERC solar cells are often used in these areas.

[0003] The battery efficiency of low-current PERC solar cells is low. Therefore, in order to improve the photoelectric conversion efficiency of low-current PERC solar cells, related technical solutions have also been disclosed in the prior art. For example, a method for manufacturing a solar cell module disclosed in CN102185007A determines the photoelectric conversion efficiency range and current threshold that a solar cell can withstand by detecting the components of the battery, and assembles appropriate solar components according to the detection results to ensure that the solar cell selects a suitable photoelectric conversion efficiency solar cell within the optimal short-circuit current range, and improves the utilization rate of the photoelectric conversion efficiency battery on the premise of ensuring safety. Another example is a high-power and low-hot-spot photovoltaic module disclosed in CN209071342U. This technical solution increases the light intensity of the battery through a high-transmittance film and a high-reflection material, and then combines multiple low-current segments to significantly reduce the current and significantly increase the light intensity, so that the photoelectric conversion efficiency of the battery remains basically unchanged, ensuring that the battery has a high photoelectric conversion efficiency while having a low current.

[0004] In the above prior art, mainly low-current PERC solar cell wafers are used and the high photoelectric conversion efficiency of low-current PERC solar cells is improved by adjusting other battery components. However, since low-current PERC solar cells are used, the upper limit of their photoelectric conversion efficiency is low. Therefore, in some areas with low short-circuit current, the photoelectric conversion efficiency of the solar cell is still at a low level. Summary of the Invention

[0005] In view of the problem that the upper limit of the photoelectric conversion efficiency of low-current PERC solar cells is low while ensuring the battery safety in the prior art, the present invention provides a solar cell and a preparation method thereof. The solar cell comprises a silicon wafer, an antireflection film and conductive grid lines. The antireflection film comprises a three-layer film structure of a bottom film, a middle film and an outer film. By adjusting the deposition thicknesses of the middle film and the outer film, the technical effect of significantly reducing the current while not significantly reducing the reflectivity is achieved, so that the power of the solar cell is not significantly changed while the current of the solar cell is significantly reduced.

[0006] The specific technical solution of the present invention is as follows: A solar cell, comprising a pyramidal-textured silicon wafer, an antireflection film provided on the pyramidal-textured silicon wafer, and conductive grid lines provided on the antireflection film. The antireflection film comprises a bottom film provided on the silicon wafer, a middle film provided on the bottom film, and an outer film provided on the middle film; the conductive grid lines are provided on the surface of the outer film, and phosphorus doping is provided on the surface of the pyramidal-textured silicon wafer.

[0007] Preferably, the reflectivity of the pyramidal-textured silicon wafer is 5-15%.

[0008] Preferably, the thickness ratio of the bottom film, the middle film and the outer film is 1:1.6-4:1.5-3.

[0009] Preferably, the width of the conductive grid lines is 10-100 μm, and the height is 5-25 μm.

[0010] The present invention provides a solar cell, which has the characteristics of small current and high photoelectric conversion efficiency. When the solar cell is applied in a low short-circuit current region, it has high safety and high battery power, and significantly improves the power of the solar cell while improving the safety.

[0011] A preparation method of the above-mentioned solar cell comprises the following steps: performing an alkaline wet etching texturing treatment on the silicon wafer to make a pyramidal-textured silicon wafer, then performing a high-temperature diffusion treatment on the pyramidal-textured silicon wafer to make a phosphorus-doped silicon wafer, then performing a chemical vapor deposition treatment on the phosphorus-doped silicon wafer to make an antireflection film silicon wafer, and then performing a screen printing treatment on the antireflection film silicon wafer to make a solar cell.

[0012] Preferably, the conditions of the alkaline wet etching texturing treatment include: the thinning amount is 0.2-0.9 mg / pcs.

[0013] Preferably, the conditions of the high-temperature diffusion treatment include a first deposition, a second deposition and a third deposition.

[0014] Preferably, the conditions of the first deposition are: the time is 100-500 s, and the nitrogen phosphorus source flow rate is 1000-3000 sccm.

[0015] Preferably, the conditions for the secondary deposition are as follows: time 100 - 500 s, nitrogen phosphorus source flow rate 1000 - 3000 sccm.

[0016] Preferably, the conditions for the tertiary deposition are as follows: time 50 - 200 s, nitrogen phosphorus source flow rate 500 - 1500 sccm.

[0017] Preferably, the conditions for the high - temperature diffusion treatment include: 750 - 850 °C, pressure 10 - 100 mbar, nitrogen phosphorus source is POCL3, oxygen flow rate 50 - 2000 sccm.

[0018] Preferably, the conditions for the chemical deposition treatment include bottom film deposition, middle film deposition and outer film deposition.

[0019] Preferably, the conditions for the bottom film deposition include: time 10 - 100 s, NH3 flow rate 2000 - 8000 sccm.

[0020] Preferably, the conditions for the middle film deposition include: time 100 - 500 s, NH3 flow rate 5000 - 10000 sccm.

[0021] Preferably, the conditions for the outer film deposition include: time 100 - 200 s, NH3 flow rate 5000 - 10000 sccm.

[0022] Preferably, the conditions for the chemical deposition treatment further include: pressure 100 - 500 mbar, temperature 400 - 600 °C, SiH4 flow rate 500 - 2000 sccm, power 10000 - 20000 W, effective pulse width 0 - 10, ineffective pulse width 0 - 200.

[0023] Preferably, the conditions for the wire electro - printing treatment include: time 100 - 600 s, applied current 0 - 12 A, upper temperature 100 - 400 °C, middle temperature 100 - 400 °C, lower temperature 100 - 450 °C.

[0024] The present invention also provides a method for preparing the above-mentioned solar cell. Firstly, the main method for reducing the current of the solar cell is to reduce the amount of light entering the silicon. When the number of photons entering the silicon decreases, the carriers in the silicon wafer will decrease, thereby reducing the current of the silicon wafer. The methods for reducing the light entering the silicon wafer include reducing the intensity of light in the external environment, such as setting a glass encapsulation film with low light transmittance on the cell. However, using this method will significantly reduce the photoelectric conversion efficiency of the solar cell, resulting in a very low upper limit of the solar cell. In addition, the current of the battery can also be reduced by increasing the reflectivity of the silicon wafer. After further research on the process of increasing the reflectivity of the silicon wafer, the present invention finds that by changing the chemical deposition method, it is possible to achieve the effect of significantly reducing the current of the silicon wafer without significantly increasing the reflectivity of the silicon wafer. The chemical deposition process of the present invention adopts the methods of bottom film deposition, middle film deposition and outer film deposition. The bottom film deposition is the same as the existing process. By changing the ammonia flow rate and deposition time of the middle film deposition and outer film deposition, the thickness of the middle film and outer film can be changed, so as to achieve the technical effect of significantly reducing the current of the silicon wafer without significantly reducing the reflectivity of the silicon wafer.

[0025] In addition, in order to ensure that the photoelectric conversion efficiency of the solar cell is not significantly changed, the present invention also optimizes the high-temperature diffusion process and the wire electroprinting process, and improves the open-circuit voltage and fill factor of the solar cell by optimizing the high-temperature diffusion process and the wire electroprinting process.

[0026] Compared with the prior art, the present application has the following technical effects: (1) The present invention provides a solar cell, which has the characteristics of small current and high photoelectric conversion efficiency. When the cell is applied in a low short-circuit current region, it has high safety and high cell power, significantly improving the power of the solar cell while improving safety; (2) The present invention also provides a method for preparing the above-mentioned solar cell. By changing the ammonia flow rate and deposition time of the middle film deposition and outer film deposition, the thickness of the middle film and outer film can be changed, so as to achieve the technical effect of significantly reducing the current of the silicon wafer without significantly reducing the reflectivity of the silicon wafer. By optimizing the high-temperature diffusion process and the wire electroprinting process, the open-circuit voltage and fill factor of the solar cell are improved, and the current is significantly reduced while the photoelectric conversion efficiency of the cell has no significant change. Specific Embodiments

[0027] The following further describes the present invention in conjunction with embodiments.

[0028] Embodiment 1: A method for preparing a solar cell includes the following steps: Front-side alkaline wet etching texturing treatment: The front side of the silicon wafer is subjected to alkaline wet etching texturing treatment to produce a pyramidal-textured silicon wafer. The conditions for the alkaline etching texturing treatment are as follows: sodium hydroxide alkaline solution (concentration 2.5%), automatic additional amount of alkaline solution 1500 ml / batch, additive, automatic additional amount 250 ml / batch, reflectivity controlled at 10%; High-temperature diffusion treatment: The pyramidal-textured silicon wafer is subjected to high-temperature diffusion treatment to produce a phosphorus-doped silicon wafer. The conditions for the high-temperature diffusion treatment are as follows: primary deposition time 300 s, primary deposition nitrogen phosphorus source flow rate 2000 sccm, primary deposition temperature 800 °C, primary deposition pressure 50 mbar, nitrogen phosphorus source is POCL3, primary deposition oxygen flow rate 1000 sccm; secondary deposition time 300 s, secondary deposition nitrogen phosphorus source flow rate 2000 sccm, secondary deposition temperature 800 °C, secondary deposition pressure 50 mbar, nitrogen phosphorus source is POCL3, secondary deposition oxygen flow rate 1000 sccm; tertiary deposition time 100 s, tertiary deposition nitrogen phosphorus source flow rate 1000 sccm, tertiary deposition temperature 800 °C, tertiary deposition pressure 50 mbar, nitrogen phosphorus source is POCL3, tertiary deposition oxygen flow rate 1000 sccm; SE treatment: The phosphorus-doped silicon wafer is subjected to local enhanced phosphorus doping by laser with instantaneous high temperature to form a uniform high-low junction and reduce the sintering window of the silver paste. High-temperature oxidation treatment: The phosphorus-doped silicon wafer is then subjected to a high-temperature oxidation process to form an oxide layer on the surface of the phosphorus-doped silicon wafer. The conditions for the high-temperature oxidation are as follows: oxygen flow rate 2000 sccm, time 1500 s, temperature 650 °C, pressure 200 mbar; PSG treatment: The phosphorus-doped silicon wafer is then subjected to PSG treatment to remove the phosphorus-containing oxide layer. The PSG treatment uses hydrofluoric acid; Back-side alkaline polishing treatment: The back side of the phosphorus-doped silicon wafer is subjected to alkaline polishing treatment to form a high-reflectivity surface on the back side of the phosphorus-doped silicon wafer; Annealing treatment: The phosphorus-doped silicon wafer after the back-side alkaline polishing treatment is then subjected to oxidation treatment to form an oxide layer. Oxygen flow rate 5500 sccm, time 2000 s, temperature 700 °C, pressure 200 mbar; ALD treatment: AL2O3 is deposited on the surface of the phosphorus-doped silicon wafer by high-temperature decomposition of AL(CH3)3. AL(CH3)3 pressure 1000 m Torr, time 2000 s, temperature 200 °C; Chemical deposition treatment: The phosphorus-doped silicon wafer is subjected to chemical deposition treatment using a PECVD device to produce an anti-reflection film silicon wafer. The chemical deposition includes bottom film deposition, middle film deposition, and outer film deposition in sequence, The conditions for bottom film deposition are as follows: time 50 s, NH3 flow rate 5000 sccm, pressure 300 mbar, temperature 500 °C, SiH4 flow rate 1000 sccm, power 15000 W, effective pulse width 0 - 10, ineffective pulse width 0 - 200; The conditions for middle film deposition are as follows: time 200 s, NH3 flow rate 7500 sccm, pressure 300 mbar, temperature 500 °C, SiH4 flow rate 1000 sccm, power 15000 W, effective pulse width 0 - 10, ineffective pulse width 0 - 200; The conditions for outer film deposition are as follows: time 150 s, NH3 flow rate 7500 sccm, pressure 300 mbar, temperature 500 °C, SiH4 flow rate 1000 sccm, power 15000 W, effective pulse width 0 - 10, ineffective pulse width 0 - 200; The thickness ratio of the bottom film, middle film and outer film is 1:1.8:1.6, and the refractive index of the antireflection film is 1%; Back laser treatment: Use a laser to perform local window opening on the back of the antireflection film silicon wafer, laser power 35 W, spot size 30 μm; Screen printing treatment: Arrange the conductive paste on the front and back of the antireflection film silicon wafer according to the design, and then sinter it at a temperature of 650 - 900 °C for 200 s, line width 20 μm, line height 15 μm. Then, perform an electro-injection process on the silicon wafer. By applying a current, hydrogen atoms in the back film layer are promoted to enter the silicon substrate to form internal passivation to make a solar cell wafer. The electro-injection conditions are: time 350 s, applied current 6 A, upper temperature 300 °C.

[0029] Example 2: A method for preparing a solar cell wafer, comprising the following steps: Front side alkaline wet etching texturing treatment: Perform alkaline wet etching texturing treatment on the front side of the silicon wafer to make a pyramid-textured silicon wafer. The conditions for the alkaline wet etching texturing treatment are: sodium hydroxide alkaline solution (concentration 5%), automatic alkali addition amount 2000 ml / batch, additive, automatic addition amount 500 ml / batch, reflectivity controlled at 15%; High-temperature diffusion treatment: The pyramid-textured silicon wafers are subjected to high-temperature diffusion treatment to produce phosphorus-doped silicon wafers. The conditions for high-temperature diffusion treatment are as follows: The first deposition time is 500 s, the nitrogen-phosphorus source flow rate for the first deposition is 3000 sccm, the first deposition temperature is 850 °C, the first deposition pressure is 100 mbar, the nitrogen-phosphorus source is POCL3, the oxygen flow rate for the first deposition is 2000 sccm, the second deposition time is 500 s, the nitrogen-phosphorus source flow rate for the second deposition is 3000 sccm, the second deposition temperature is 850 °C, the second deposition pressure is 100 mbar, the nitrogen-phosphorus source is POCL3, the oxygen flow rate for the second deposition is 2000 sccm, the third deposition time is 200 s, the nitrogen-phosphorus source flow rate for the third deposition is 1500 sccm, the third deposition temperature is 850 °C, the third deposition pressure is 100 mbar, the nitrogen-phosphorus source is POCL3, and the oxygen flow rate for the third deposition is 2000 sccm; SE treatment: The phosphorus-doped silicon wafers are subjected to local transient high-temperature phosphorus doping by laser to form a uniform high-low junction and reduce the sintering window of the wire-bonding paste; High-temperature oxidation treatment: The phosphorus-doped silicon wafers are then subjected to a high-temperature oxidation process to form an oxide layer on the surface of the phosphorus-doped silicon wafers. The conditions for high-temperature oxidation are an oxygen flow rate of 3000 sccm, a time of 2000 s, a temperature of 750 °C, and a pressure of 300 mbar; PSG treatment: The phosphorus-doped silicon wafers are then subjected to PSG treatment to remove the phosphorus-containing oxide layer. The PSG treatment uses hydrofluoric acid; Backside alkaline polishing treatment: The backside of the phosphorus-doped silicon wafers is subjected to alkaline polishing treatment to form a high-reflectivity surface on the backside of the phosphorus-doped silicon wafers; Annealing treatment: The phosphorus-doped silicon wafers after backside alkaline polishing treatment are then subjected to oxidation treatment to form an oxide layer. The oxygen flow rate is 8000 sccm, the time is 3000 s, the temperature is 800 °C, and the pressure is 300 mbar; ALD treatment: AL2O3 is deposited on the surface of the phosphorus-doped silicon wafers by high-temperature decomposition of AL(CH3)3. The pressure of AL(CH3)3 is 2000 m Torr, the time is 3000 s, and the temperature is 350 °C; Chemical deposition treatment: The phosphorus-doped silicon wafers are subjected to chemical deposition treatment using a PECVD apparatus to produce anti-reflection film silicon wafers. The chemical deposition includes bottom film deposition, middle film deposition, and outer film deposition in sequence. The conditions for bottom film deposition are as follows: The time is 100 s, the NH3 flow rate is 8000 sccm, the pressure is 500 mbar, the temperature is 600 °C, the SiH4 flow rate is 2000 sccm, the power is 20000 W, the effective pulse width is 10, and the ineffective pulse width is 200; The conditions for middle film deposition are as follows: The time is 500 s, the NH3 flow rate is 10000 sccm, the pressure is 500 mbar, the temperature is 600 °C, the SiH4 flow rate is 2000 sccm, the power is 20000 W, the effective pulse width is 0 to 10, and the ineffective pulse width is 0 to 200; The conditions for outer film deposition are as follows: time 200 s, NH3 flow rate 10000 sccm, pressure 100 - 500 mbar, temperature 600 °C, SiH4 flow rate 2000 sccm, power 20000 W, effective pulse width 0 - 10, ineffective pulse width 0 - 200; The thickness ratio of the bottom film, middle film and outer film is 1:4:3, and the refractive index of the antireflection film is 3%; Back laser treatment: Use a laser to perform local windowing on the back of the antireflection film silicon wafer, with a laser power of 50 W and a spot size of 40 μm; Wire electroprinting treatment: Arrange the conductive paste on the front and back of the antireflection film silicon wafer according to the design, and then sinter it at 900 °C for 300 s. The line width is 30 μm and the line height is 25 μm. Then, perform an electro-injection process on the silicon wafer. By applying a current, hydrogen atoms in the back film layer are pushed into the silicon substrate to form internal passivation to make a solar cell wafer. The electro-injection conditions are: time 600 s, applied current 12 A, upper temperature 500 °C.

[0030] Example 3: A method for preparing a solar cell wafer, comprising the following steps: Front side alkaline wet etching texturing treatment: Perform alkaline wet etching texturing treatment on the front side of the silicon wafer to make a pyramid-textured silicon wafer. The conditions for the alkaline wet etching texturing treatment are: sodium hydroxide alkaline solution (concentration 0.5%), automatic alkali addition amount ml / batch, additive, automatic addition amount ml / batch, and the reflectivity is controlled at 5%; High-temperature diffusion treatment: Perform high-temperature diffusion treatment on the pyramid-textured silicon wafer to make a phosphorus-doped silicon wafer. The conditions for the high-temperature diffusion treatment are: primary deposition time 100 s, primary deposition nitrogen phosphorus source flow rate 1000 sccm, primary deposition temperature 750 °C, primary deposition pressure 10 mbar, nitrogen phosphorus source is POCL3, and primary deposition oxygen flow rate 50 sccm; Secondary deposition time 100 s, secondary deposition nitrogen phosphorus source flow rate 1000 sccm, secondary deposition temperature 750 °C, secondary deposition pressure 10 mbar, nitrogen phosphorus source is POCL3, and secondary deposition oxygen flow rate 50 sccm; Tertiary deposition time 50 s, tertiary deposition nitrogen phosphorus source flow rate 500 sccm, tertiary deposition temperature 750 °C, tertiary deposition pressure 10 mbar, nitrogen phosphorus source is POCL3, and tertiary deposition oxygen flow rate 50 sccm; SE treatment: Use a laser to perform local promotion of phosphorus doping at high temperature on the phosphorus-doped silicon wafer to form a uniform high-low junction and reduce the sintering window of the wire electropaste; High-temperature oxidation treatment: Then perform a high-temperature oxidation process on the phosphorus-doped silicon wafer to form an oxide layer on the surface of the phosphorus-doped silicon wafer. The conditions for the high-temperature oxidation are: oxygen flow rate 1000 sccm, time 500 s, temperature 550 °C, pressure 50 mbar; PSG treatment: Then, perform PSG treatment on the phosphorus-doped silicon wafer to remove the phosphorus-containing oxide layer. The PSG treatment uses hydrofluoric acid; Back surface alkaline polishing treatment: Perform alkaline polishing treatment on the back surface of the phosphorus-doped silicon wafer to form a high-reflection surface on the back surface of the phosphorus-doped silicon wafer; Annealing treatment: Then, perform oxidation treatment on the phosphorus-doped silicon wafer after the back surface alkaline polishing treatment to form an oxide layer. The oxygen flow rate is 30000 sccm, the time is 1000 s, the temperature is 650 °C, and the pressure is 50 mbar; ALD treatment: Deposit Al2O3 on the surface layer of the phosphorus-doped silicon wafer by high-temperature decomposition of Al(CH3)3. The pressure of Al(CH3)3 is 100 mTorr, the time is 1000 s, and the temperature is 150 °C; Chemical deposition treatment: Use a PECVD device to perform chemical deposition treatment on the phosphorus-doped silicon wafer to make an antireflection film silicon wafer. The chemical deposition is in turn bottom film deposition, middle film deposition, and outer film deposition. The conditions for bottom film deposition are: time 10 s, NH3 flow rate 2000 sccm, pressure 100 mbar, temperature 400 °C, SiH4 flow rate 500 sccm, power 10000 - 20000 W, effective pulse width 0 - 10, ineffective pulse width 0 - 200; The conditions for middle film deposition are: time 100 s, NH3 flow rate 5000 sccm, pressure 100 mbar, temperature 400 °C, SiH4 flow rate 500 sccm, power 10000 W, effective pulse width 0 - 10, ineffective pulse width 0 - 200; The conditions for outer film deposition are: time 100 s, NH3 flow rate 5000 sccm, pressure 100 mbar, temperature 400 °C, SiH4 flow rate 500 sccm, power 10000 W, effective pulse width 0 - 10, ineffective pulse width 0 - 200; The thickness ratio of the bottom film, middle film, and outer film is 1:2:2, and the refractive index of the antireflection film is 2%; Back laser treatment: Use a laser to perform local windowing on the back surface of the antireflection film silicon wafer. The laser power is 20 W, and the spot size is 20 μm; Wire electroprinting treatment: Arrange the conductive paste according to the design on the front and back surfaces of the antireflection film silicon wafer, and then sinter it at a temperature of 650 °C for 10 s. The line width is 10 μm, and the line height is 5 μm. Then, perform an electro-injection process on the silicon wafer. By applying a current, the hydrogen atoms in the back surface film layer are pushed into the silicon substrate to form internal passivation to make a solar cell wafer. The electro-injection conditions are: time 100 s, applied current 0 A, upper temperature 100 °C.

[0031] Example 4: A method for preparing a solar cell wafer, comprising the following steps: Front-side alkaline wet chemical texturing treatment: The front side of the silicon wafer is subjected to alkaline wet chemical texturing treatment to produce a pyramid-textured silicon wafer. The conditions for the alkaline texturing treatment are as follows: sodium hydroxide alkaline solution (concentration 2.5%), automatic additional amount of alkaline solution 1500 ml / batch, additive, automatic additional amount 250 ml / batch, reflectivity controlled at 10%; High-temperature diffusion treatment: The pyramid-textured silicon wafer is subjected to high-temperature diffusion treatment to produce a phosphorus-doped silicon wafer. The conditions for the high-temperature diffusion treatment are as follows: primary deposition time 300 s, primary deposition nitrogen phosphorus source flow rate 2000 sccm, primary deposition temperature 800 °C, primary deposition pressure 50 mbar, nitrogen phosphorus source is POCL3, primary deposition oxygen flow rate 1000 sccm; secondary deposition time 300 s, secondary deposition nitrogen phosphorus source flow rate 2000 sccm, secondary deposition temperature 800 °C, secondary deposition pressure 50 mbar, nitrogen phosphorus source is POCL3, secondary deposition oxygen flow rate 1000 sccm; tertiary deposition time 100 s, tertiary deposition nitrogen phosphorus source flow rate 1000 sccm, tertiary deposition temperature 800 °C, tertiary deposition pressure 50 mbar, nitrogen phosphorus source is POCL3, tertiary deposition oxygen flow rate 1000 sccm; SE treatment: The phosphorus-doped silicon wafer is subjected to local transient high-temperature phosphorus doping by laser to form a uniform high-low junction and reduce the sintering window of the wire electrode paste; High-temperature oxidation treatment: The phosphorus-doped silicon wafer is then subjected to a high-temperature oxidation process to form an oxide layer on the surface of the phosphorus-doped silicon wafer. The conditions for the high-temperature oxidation are as follows: oxygen flow rate 2000 sccm, time 1500 s, temperature 650 °C, pressure 200 mbar; PSG treatment: The phosphorus-doped silicon wafer is then subjected to PSG treatment to remove the phosphorus-containing oxide layer. The PSG treatment uses hydrofluoric acid; Back-side alkaline polishing treatment: The back side of the phosphorus-doped silicon wafer is subjected to alkaline polishing treatment to form a high-reflectivity surface on the back side of the phosphorus-doped silicon wafer; Annealing treatment: The phosphorus-doped silicon wafer after the back-side alkaline polishing treatment is then subjected to oxidation treatment to form an oxide layer. Oxygen flow rate 5500 sccm, time 2000 s, temperature 700 °C, pressure 200 mbar; ALD treatment: AL2O3 is deposited on the surface layer of the phosphorus-doped silicon wafer by high-temperature decomposition of AL(CH3)3. AL(CH3)3 pressure 1000 m Torr, time 2000 s, temperature 200 °C; Chemical deposition treatment: A phosphorus-doped silicon wafer is processed by chemical deposition using a PECVD device to produce an antireflection film silicon wafer. The refractive index of the antireflection film silicon wafer increases by 0.25%. The chemical deposition is carried out in sequence as bottom film deposition, middle film deposition, and outer film deposition. The conditions for bottom film deposition are: time 50 s, NH3 flow rate 5000 sccm, pressure 300 mbar, temperature 500 °C, SiH4 flow rate 1000 sccm, power 15000 W, effective pulse width 0 - 10, ineffective pulse width 0 - 200; The conditions for middle film deposition are: time 200 s, NH3 flow rate 7500 sccm, pressure 300 mbar, temperature 500 °C, SiH4 flow rate 1000 sccm, power 15000 W, effective pulse width 0 - 10, ineffective pulse width 0 - 200; The conditions for outer film deposition are: time 250 s, NH3 flow rate 7500 sccm, pressure 300 mbar, temperature 500 °C, SiH4 flow rate 1000 sccm, power 15000 W, effective pulse width 0 - 10, ineffective pulse width 0 - 200; The thickness ratio of the bottom film, middle film, and outer film is 1:1.6:1.8, and the refractive index of the antireflection film is 1.2%. Back laser treatment: The back of the antireflection film silicon wafer is locally windowed using a laser with a laser power of 35 W and a spot size of 30 μm; Wire electroprinting treatment: The conductive paste is arranged on the front and back of the antireflection film silicon wafer according to the design, and then sintered at a temperature of 650 - 900 °C for 200 s. The line width is 20 μm and the line height is 15 μm. Then, an electro-injection process is carried out on the silicon wafer. By applying a current, hydrogen atoms in the back film layer are pushed into the silicon substrate to form internal passivation to produce a solar cell wafer. The electro-injection conditions are: time 350 s, applied current 6 A, upper temperature 300 °C.

[0032] Example 5: A method for preparing a solar cell wafer, comprising the following steps: Front side alkaline wet etching texturing treatment: The front side of the silicon wafer is subjected to alkaline wet etching texturing treatment to produce a pyramid-textured silicon wafer. The conditions for the alkaline wet etching texturing treatment are: sodium hydroxide alkaline solution (concentration 2.5%), automatic alkali addition amount 1500 ml / batch, additive, automatic addition amount 250 ml / batch, and the reflectivity is controlled at 10%; High-temperature diffusion treatment: The pyramid-textured silicon wafers are subjected to high-temperature diffusion treatment to produce phosphorus-doped silicon wafers. The conditions for high-temperature diffusion treatment are as follows: The primary deposition time is 300 s, the primary deposition nitrogen-phosphorus source flow rate is 2000 sccm, the primary deposition temperature is 800 °C, the primary deposition pressure is 50 mbar, the nitrogen-phosphorus source is POCL3, and the primary deposition oxygen flow rate is 1000 sccm; The secondary deposition time is 300 s, the secondary deposition nitrogen-phosphorus source flow rate is 2000 sccm, the secondary deposition temperature is 800 °C, the secondary deposition pressure is 50 mbar, the nitrogen-phosphorus source is POCL3, and the secondary deposition oxygen flow rate is 1000 sccm; The tertiary deposition time is 100 s, the tertiary deposition nitrogen-phosphorus source flow rate is 1000 sccm, the tertiary deposition temperature is 800 °C, the tertiary deposition pressure is 50 mbar, the nitrogen-phosphorus source is POCL3, and the tertiary deposition oxygen flow rate is 1000 sccm; SE treatment: The phosphorus-doped silicon wafers are subjected to local transient high-temperature phosphorus doping by laser to form a uniform high-low junction and reduce the sintering window of the wire-bonding paste; High-temperature oxidation treatment: The phosphorus-doped silicon wafers are then subjected to a high-temperature oxidation process to form an oxide layer on the surface of the phosphorus-doped silicon wafers. The conditions for high-temperature oxidation are an oxygen flow rate of 2000 sccm, a time of 1500 s, a temperature of 650 °C, and a pressure of 200 mbar; PSG treatment: The phosphorus-doped silicon wafers are then subjected to PSG treatment to remove the phosphorus-containing oxide layer, and hydrofluoric acid is used for PSG treatment; Backside alkaline polishing treatment: The backside of the phosphorus-doped silicon wafers is subjected to alkaline polishing treatment to form a high-reflectivity surface on the backside of the phosphorus-doped silicon wafers; Annealing treatment: The phosphorus-doped silicon wafers after backside alkaline polishing treatment are then subjected to oxidation treatment to form an oxide layer. The oxygen flow rate is 5500 sccm, the time is 2000 s, the temperature is 700 °C, and the pressure is 200 mbar; ALD treatment: AL2O3 is deposited on the surface of the phosphorus-doped silicon wafers by high-temperature decomposition of AL(CH3)3. The pressure of AL(CH3)3 is 1000 m Torr, the time is 2000 s, and the temperature is 200 °C; Chemical deposition treatment: The phosphorus-doped silicon wafers are subjected to chemical deposition treatment using a PECVD device to produce anti-reflection film silicon wafers. The refractive index of the anti-reflection film silicon wafers increases by 0.15%. The chemical deposition includes bottom film deposition, middle film deposition, and outer film deposition in sequence. The conditions for bottom film deposition are as follows: The time is 50 s, the NH3 flow rate is 5000 sccm, the pressure is 300 mbar, the temperature is 500 °C, the SiH4 flow rate is 1000 sccm, the power is 15000 W, the effective pulse width is 0 - 10, and the ineffective pulse width is 0 - 200; The conditions for middle film deposition are as follows: The time is 200 s, the NH3 flow rate is 7500 sccm, the pressure is 300 mbar, the temperature is 500 °C, the SiH4 flow rate is 1000 sccm, the power is 15000 W, the effective pulse width is 0 - 10, and the ineffective pulse width is 0 - 200; The conditions for outer film deposition are as follows: time 100 s, NH3 flow rate 7500 sccm, pressure 300 mbar, temperature 500 °C, SiH4 flow rate 1000 sccm, power 15000 W, effective pulse width 0 - 10, ineffective pulse width 0 - 200; The thickness ratio of the bottom film, middle film and outer film is 1:2:1.5, and the refractive index of the antireflection film is 1.5%; Back laser treatment: The back of the antireflection film silicon wafer is locally windowed using a laser, with a laser power of 35 W and a spot size of 30 μm; Screen printing treatment: The conductive paste is arranged on the front and back of the antireflection film silicon wafer according to the design layout, and then sintered at a temperature of 650 - 900 °C for 200 s. The line width is 20 μm and the line height is 15 μm. Then, an electro-injection process is carried out on the silicon wafer. By applying a current, hydrogen atoms in the back film layer are pushed into the silicon substrate to form internal passivation to make a solar cell wafer. The electro-injection conditions are as follows: time 350 s, applied current 6 A, upper temperature 300 °C.

[0033] Comparative Example 1: Compared with Example 1, in Comparative Example 1, the preparation method of a high-current PERC solar cell in the prior art was adopted.

[0034] Comparative Example 2: Compared with Example 1, in Comparative Example 2, the conditions for film deposition are the same as those for bottom film deposition, and the remaining conditions are the same as those in Example 1.

[0035] Comparative Example 3: Compared with Example 1, in Comparative Example 3, the conditions for outer film deposition are the same as those for bottom film deposition, and the remaining conditions are the same as those in Example 1.

[0036] Comparative Example 4: Compared with Example 1, in Comparative Example 5, the conditions for primary deposition, secondary deposition and tertiary deposition are the same, and the remaining conditions are the same as those in Example 1.

[0037] Comparative Example 5: Compared with Example 1, in Comparative Example 5, the grid line height is reduced, and the grid line height is 5 μm, and the remaining conditions are the same as those in Example 1.

[0038] Comparative Example 6: Compared with Example 1, in Comparative Example 6, the conditions for high-temperature diffusion are changed, increasing the sheet resistance of the silicon wafer, and the remaining conditions are the same as those in Example 1.

[0039] Detection Example: The photoelectric conversion efficiency and current of the solar cell wafers prepared in Examples 1 to 5 and Comparative Examples 1 to are tested: Test method: Assemble 10 solar cells into a solar battery. Use a xenon lamp to simulate sunlight and irradiate for 30 ms. Measure the current, power generation, and calculate the photoelectric conversion efficiency. The photoelectric conversion efficiency = electric power / (illumination area * illumination intensity). The test results are shown in Table 1.

[0040] Table 1 Test Results Current (A) Fill factor (%) Power generation (W) Photoelectric conversion efficiency (%) Example 1 9.42 78.12 301.46 22.41 Example 2 9.50 77.82 298.43 21.36 Example 3 9.49 77.61 299.69 21.47 Example 4 9.52 78.12 300.74 22.21 Example 5 9.49 77.70 298.65 22.35 Comparative example 1 9.85 78.66 314.65 22.50 Comparative example 2 9.69 78.12 304.95 21.58 Comparative example 3 9.72 78.12 305.21 21.63 Comparative example 4 9.78 78.12 308.94 21.89 Comparative example 5 9.42 77.61 300.54 21.93 As shown in Table 1, the current of the solar cells prepared in Examples 1 to 5 can reach 9.42 - 9.52 A, and the photoelectric conversion efficiency is 21.36 - 22.41%. Compared with high-current solar cells (Comparative Example 1), the photoelectric conversion efficiency has not decreased significantly, but the current value has decreased significantly, which can be reduced by 430 - 330 mA. The above results show that the solar cells provided by the present invention can significantly reduce the current of the cells while ensuring the conversion efficiency.

[0041] In Comparative Example 2, Comparative Example 3, and Comparative Example 4, the deposition conditions of the middle film and the outer film were adjusted respectively. It was found that the current of the adjusted solar cells could not be significantly reduced. The above results show that the deposition conditions will change the thickness of the middle film and the outer film, and the middle film and the outer film with different film thicknesses will produce a special refraction effect on light, so as to achieve the technical effect of not significantly changing the reflectivity but significantly reducing the current.

[0042] In Comparative Example 5, the height of the grid line was reduced. It was found that reducing the grid line would lead to a decrease in filling and a decrease in the final photoelectric conversion efficiency. The above results show that it is necessary to increase the filling factor by adjusting the grid line height so that the photoelectric conversion efficiency can not change significantly.

[0043] In Comparative Example 6, the high-temperature diffusion conditions were changed, and the sheet resistance of the silicon wafer was increased. It was found that the photoelectric conversion efficiency also decreased significantly after the sheet resistance increased. The above results show that it is necessary to adjust the high-temperature diffusion conditions to reduce the sheet resistance of the silicon wafer so that the photoelectric conversion efficiency can not change significantly.

[0044] The above are only the preferred embodiments of the present invention, and do not limit the present invention in any way. Any simple modifications, changes, and equivalent transformations made to the above embodiments according to the technical essence of the present invention still belong to the protection scope of the technical solution of the present invention.

Claims

1. A solar cell, characterized in that, It includes a pyramid-textured silicon wafer, an antireflection film disposed on the pyramid-textured silicon wafer, and a conductive grid line disposed on the antireflection film. The antireflection film includes a bottom film disposed on the silicon wafer, a middle film disposed on the bottom film, and an outer film disposed on the middle film; the conductive grid line is disposed on the surface of the outer film, and the surface of the pyramid-textured silicon wafer is doped with phosphorus.

2. The solar cell according to claim 1, characterized in that, The reflectivity of the pyramid-textured silicon wafer is 5-15%.

3. The solar cell according to claim 1, characterized in that, The width of the conductive grid line is 10-100 μm.

4. The solar cell according to claim 1, wherein The height of the conductive grid line is 5-25 μm.

5. A method for preparing a solar cell according to any one of claims 1 to 4, characterized in that, It includes the following steps: The silicon wafer is subjected to alkaline wet chemical texturing treatment to form a pyramid-textured silicon wafer, then the pyramid-textured silicon wafer is subjected to high-temperature diffusion treatment to form a phosphorus-doped silicon wafer, then the phosphorus-doped silicon wafer is subjected to chemical vapor deposition treatment to form an antireflection film silicon wafer, and then the antireflection film silicon wafer is subjected to screen printing treatment to form a solar cell.

6. The preparation method according to claim 5, characterized in that, The conditions of the alkaline wet chemical texturing treatment include: the thinning amount is 0.2-0.9 mg / pcs.

7. The preparation method according to claim 5, characterized in that, The conditions of the high-temperature diffusion treatment include primary deposition, secondary deposition, and tertiary deposition; The conditions of the primary deposition are: time 100-500 s, nitrogen phosphorus source flow rate 1000-3000 sccm; The conditions of the secondary deposition are: time 100-500 s, nitrogen phosphorus source flow rate 1000-3000 sccm; The conditions of the tertiary deposition are: time 50-200 s, nitrogen phosphorus source flow rate 500-1500 sccm; The conditions of the high-temperature diffusion treatment include: 750-850 °C, pressure 10-100 mbar, nitrogen phosphorus source is POCL3, oxygen flow rate 50-2000 sccm.

8. The preparation method according to claim 5, characterized in that, The conditions of the chemical deposition treatment include bottom film deposition, middle film deposition, and outer film deposition; The conditions of the bottom film deposition include: time 10-100 s, NH3 flow rate 2000-8000 sccm; The conditions of the middle film deposition include: time 100-500 s, NH3 flow rate 5000-10000 sccm; The conditions of the outer film deposition include: time 100-200 s, NH3 flow rate 5000-10000 sccm.

9. The preparation method according to claim 5 or 8, characterized in that, The conditions of the chemical deposition treatment also include: pressure 100-500 mbar, temperature 400-600 °C, SiH4 flow rate 500-2000 sccm, power 10000-20000 W, effective pulse width 0-10, ineffective pulse width 0-200.

10. The preparation method according to claim 5, characterized in that, The conditions of the screen printing treatment include: time 100-600 s, applied current 0-12 A, upper temperature 100-400 °C, middle temperature 100-400 °C, lower temperature 100-450 °C.