P-type TOPCon solar cell and preparation method thereof

Abstract

The invention discloses a P-type TOPCon solar cell and a preparation method thereof, and belongs to the technical field of solar cell manufacturing. The invention discloses a preparation method of a P-type TOPCon solar cell. The preparation method comprises the following steps: depositing a SiO2 film on an N-type silicon wafer; polycrystalline silicon is deposited on the SiO2 thin film; carrying out B thermal doping on the deposited polycrystalline silicon; and carrying out activation treatment on the region thermally doped with the B. According to the preparation method of the P-type TOPCon solar cell, through the combined action of annealing, B deposition and laser doping, high-doped P-type polycrystalline silicon and high-passivation-performance TOPCon contact are obtained, and the preparation method can be used for manufacturing and producing a high-performance TBC structure solar cell.

Description

Technical Field

[0001] The present invention relates to the technical field of solar cell manufacturing, and in particular to a P-type TOPCon solar cell and a preparation method thereof. Background Art

[0002] In the traditional TOPCon contact preparation method for TBC (TOPCon Back Contact) solar cells, the doping of polysilicon is achieved by thermal doping. For N-type P doping, the activation concentration can reach 10 21 cm -3 However, for P-type B doping, the doping concentration can only reach 10 due to its solid solubility. 19 -10 20 cm -3 Low B-doped polysilicon concentration will lead to high contact resistance during the metallization process. In addition, high B-doped polysilicon can theoretically improve the passivation contact effect, thereby improving efficiency, and can also provide an etch stop layer for a lower-cost maskless TBC solar cell preparation solution.

[0003] Currently, the P-type TOPCon contact fabrication method used in TBC cells results in a low boron doping concentration, hindering further improvement in cell performance. Therefore, a P-type TOPCon contact fabrication method for TBC solar cells is urgently needed to address the low boron doping concentration issue. Summary of the Invention

[0004] The purpose of the present invention is to provide a P-type TOPCon solar cell and a preparation method thereof, which is used to solve the technical problem of low B doping concentration in the P-type TOPCon contact preparation method for TBC solar cells in the prior art.

[0005] To achieve the above object, one embodiment of the present invention provides a method for preparing a P-type TOPCon solar cell, comprising the following steps:

[0006] Depositing SiO2 thin film on N-type silicon wafer;

[0007] Depositing polysilicon on the SiO2 film;

[0008] Thermally doping the deposited polysilicon with B;

[0009] The thermally doped B region is activated.

[0010] In one preferred embodiment of the present invention, the thickness of the N-type silicon wafer is 100 μm-200 μm, and the doping concentration range is 10 14 cm -3 -10 16cm -3 .

[0011] In one of the preferred solutions of the present invention, the thickness of the SiO2 film is 1nm-5nm.

[0012] In one preferred solution of the present invention, the N-type silicon wafer is pretreated before depositing the SiO2 thin film on the N-type silicon wafer.

[0013] In one of the preferred embodiments of the present invention, the pretreatment includes cleaning and polishing.

[0014] In one preferred embodiment of the present invention, the thickness of the deposited polysilicon is greater than 100 nm.

[0015] One of the preferred solutions of the present invention is to perform thermal doping of B on the deposited polysilicon, including: the gases used for thermal doping are BBr3 and O2, and the temperature range of thermal doping is 300°C-1000°C.

[0016] In one preferred solution of the present invention, before thermally doping the deposited polysilicon with B, the TOPCon structure after the polysilicon deposition is subjected to an annealing treatment.

[0017] In one of the preferred solutions of the present invention, the gas used for annealing is N2, and the annealing temperature range is 600°C-1300°C.

[0018] In one preferred solution of the present invention, the thermally doped TOPCon structure is pickled before the activation treatment is performed on the thermally doped B region.

[0019] One of the preferred solutions of the present invention is to activate the thermally doped B region, including: performing laser activation on the thermally doped B region, with a laser pulse bandwidth ranging from 1μs to 4μs and a laser energy density of 0.5J / cm -2 -5J / cm -2 .

[0020] In one preferred solution of the present invention, after the activation treatment of the thermally doped B region is completed, the laser-activated sample is annealed and repaired.

[0021] The present invention also discloses a P-type TOPCon solar cell, which is prepared by adopting the above-mentioned preparation method.

[0022] In summary, the beneficial effects of the present invention are:

[0023] 1. The preparation method of the P-type TOPCon solar cell of the present invention can obtain a polycrystalline silicon TOPCon contact with a higher B doping concentration, thereby improving the passivation performance of the TBC solar cell and reducing the contact resistance with the metal, thereby obtaining a TBC solar cell with better performance.

[0024] 2. The method for preparing a P-type TOPCon solar cell of the present invention can utilize the etching stop layer provided by highly B-doped polysilicon, thereby providing a preparation solution for a maskless TBC solar cell with lower cost and simpler process.

[0025] 3. The preparation method of the P-type TOPCon solar cell of the present invention obtains highly doped P-type polysilicon and high passivation performance TOPCon contact through the combined action of annealing, B deposition and laser doping, which can be used for the preparation and production of high-performance TBC structure solar cells.

[0026] Other features and advantages of the present invention will be described in the following description, and part of them will become obvious from the description, or they can be understood by practicing the present invention. The purpose and other advantages of the present invention can be described by the effects described in the description and the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 Schematic diagram of the process of preparing a P-type TOPCon solar cell according to an embodiment of the present invention;

[0028] Figure 2 Graph showing the distribution of doping concentration of highly B-doped polysilicon with depth under activation with different laser power densities in Example 1 of the present invention;

[0029] Figure 3 This is a comparison diagram of the square resistance of highly B-doped polysilicon activated at different laser power densities in Example 1 of the present invention. DETAILED DESCRIPTION

[0030] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts shall fall within the scope of protection of the present invention.

[0031] The endpoints of the ranges and any values disclosed herein are not limited to the precise ranges or values, and these ranges or values should be understood to include values close to these ranges or values. For numerical ranges, the endpoints of each range, the endpoints of each range and individual point values, and the individual point values can be combined with each other to form one or more new numerical ranges, and these numerical ranges should be considered to be specifically disclosed in the present invention.

[0032] The present invention provides a method for preparing a P-type TOPCon solar cell, such as Figure 1 As shown, the following steps are included:

[0033] Step (1): depositing a SiO2 film on an N-type silicon wafer; specifically, depositing a layer of SiO2 film on the surface of the N-type silicon wafer by thermal oxidation, the thickness of the SiO2 film is in the range of 1nm-5nm, and the process temperature is in the range of 300℃-1000℃; wherein, the thickness of the N-type silicon wafer is in the range of 100μm-200μm, and the doping concentration is in the range of 10 14 cm -3 -10 16 cm -3 ;

[0034] Before depositing SiO2 thin film on N-type silicon wafer, the N-type silicon wafer is pretreated. The pretreatment includes cleaning and polishing. Specifically, it includes:

[0035] 1) Pre-clean with low concentration of alkali solution and hydrogen peroxide for at least 3 minutes;

[0036] 2) Soaking the silicon wafer rinsed in step 1) in a high-concentration alkaline solution for at least 5 minutes, and then rinsing with deionized water at least three times;

[0037] 3) Soaking the silicon wafer soaked in the high concentration alkali solution in step 2) in a dilute hydrofluoric acid solution for at least 5 minutes;

[0038] 4) washing the silicon wafer soaked in the diluted hydrofluoric acid in step 3) with deionized water at least three times, and then drying;

[0039] Step (2): depositing polysilicon on the SiO2 film; specifically, depositing a layer of polysilicon on the SiO2 film by chemical vapor deposition or physical vapor deposition, wherein the thickness of the deposited polysilicon is in the range of 100 nm or more, and the process temperature is in the range of 300° C. to 1000° C.;

[0040] Step (3): thermally doping the deposited polysilicon with B; specifically, thermally doping the deposited polysilicon with B, using BBr3 and O2 as the gases, and a temperature range of 300°C to 1000°C for thermal doping;

[0041] Before the deposited polysilicon is thermally doped with B, the TOPCon structure after the polysilicon is deposited is annealed and then cooled. The gas used for annealing is N2, and the annealing temperature range is 600℃-1300℃. Note: This step can also be omitted and the following step (3) i.e. thermal doping with B can be directly performed. The purpose of annealing in this step is to strengthen the polysilicon and silicon dioxide film to make it stronger and reduce the damage of the laser to the TOPCon structure.

[0042] Step (4): Activate the region of thermally doped B. Specifically, perform laser activation on the region of thermally doped B. The laser pulse bandwidth range is 1μs-4μs, and the laser energy density is 0.5J / cm -2 -5J / cm -2 , preferably, the wavelength of the laser is 532nm;

[0043] Before activating the thermally doped B region, the thermally doped TOPCon structure is pickled. Specifically, the thermally doped TOPCon structure is immersed in a dilute hydrofluoric acid solution for at least 3 minutes, and then rinsed with deionized water for at least 3 times.

[0044] After the activation treatment of the thermally doped B area is completed, the laser-activated sample is annealed and repaired. The gas used for annealing is N2, and the annealing temperature range is 600℃-1300℃. The purpose of annealing in this step is to release stress and restore the damage to TOPCon caused by the laser.

[0045] In the preparation method of P-type TOPCon solar cells, annealing will affect the performance of the prepared P-type TOPCon solar cells. It is recommended to perform annealing at least once, preferably twice, to ensure better results. If annealing is not performed, the process window of the product will be very small, which will affect the product performance.

[0046] The present invention also discloses a P-type TOPCon solar cell, which is prepared by adopting the above-mentioned preparation method.

[0047] Example 1

[0048] A method for preparing a P-type TOPCon solar cell comprises the following steps:

[0049] Step (1): Cleaning the N-type silicon wafer, specifically, including:

[0050] Step (101): pre-cleaning for 3 minutes using low concentration alkali solution and hydrogen peroxide;

[0051] Step (102): Soaking the rinsed silicon wafer in a high concentration alkali solution for at least 5 minutes, and then rinsing with deionized water for at least three times;

[0052] Step (103): soaking the silicon wafer soaked in the high concentration alkali solution in a dilute hydrofluoric acid solution for at least 5 minutes;

[0053] Step (104): washing the silicon wafer soaked in the diluted hydrofluoric acid with deionized water at least three times, and then drying;

[0054] Step (2): growing a SiO2 film on the surface of the silicon wafer by thermal oxidation with a thickness of 1-5 nm and a process temperature range of 300-1000°C;

[0055] Step (3): depositing a layer of polysilicon on the SiO2 film by low-pressure chemical vapor deposition, wherein the thickness of the polysilicon is in the range of 100 nm or more and the process temperature is in the range of 300-1000°C;

[0056] Step (4): annealing the TOPCon structure after depositing polysilicon and then cooling it, the annealing gas is N2, and the annealing temperature is 950°C;

[0057] Step (5): thermally doping the polysilicon deposited after annealing in step (4) with B, using BBr3 and O2 as the gas, and at a doping temperature range of 300-1000°C;

[0058] Step (6): Soak the sample in step (5) in a diluted hydrofluoric acid solution for 3 minutes, and then rinse with deionized water three times;

[0059] Step (7): Laser activation of the polysilicon in step (6) with a power density ranging from 0.8 to 3.2 J / cm 2 ;

[0060] Step (8): Annealing and repairing the polysilicon in step (7) using N2 as the gas and an annealing temperature range of 600-1300° C. to form a TOPCon contact structure and obtain a P-type TOPCon solar cell.

[0061] Example 2

[0062] A method for preparing a P-type TOPCon solar cell is similar to that of Example 1 and includes the following steps:

[0063] Step (1): On the cleaned silicon wafer, a layer of SiO2 film with a thickness of 1-5 nm is grown by thermal oxidation at a process temperature range of 300-1000°C to ensure film quality and uniformity;

[0064] Step (2): depositing a layer of polysilicon with a thickness of more than 100 nm on the SiO2 film by low-pressure chemical vapor deposition, with a process temperature range of 300-1000°C;

[0065] Step (3): annealing the TOPCon structure prepared in step (2) above and then cooling it, the annealing gas is N2, and the annealing temperature range is 600-1300°C;

[0066] Step (4): thermally doping the deposited polysilicon with B using BBr3 and O2 gases at a doping temperature ranging from 300 to 1000°C.

[0067] Step (5): Soak the sample in a diluted hydrofluoric acid solution for 3 min, and then rinse with deionized water three times;

[0068] Step (6): Laser activation of polysilicon with a power density range of 0.8-3.2 J / cm 2 ; No annealing treatment is performed afterwards to form a TOPCon contact structure.

[0069] Example 3

[0070] A method for preparing a P-type TOPCon solar cell is similar to that of Example 1 and includes the following steps:

[0071] Step (1): On the cleaned silicon wafer, a layer of SiO2 film with a thickness of 1-5 nm is grown by thermal oxidation at a process temperature range of 300-1000°C to ensure film quality and uniformity;

[0072] Step (2): depositing a layer of polysilicon with a thickness of more than 100 nm on the SiO2 film by low-pressure chemical vapor deposition, with a process temperature range of 300-1000°C;

[0073] Step (3): thermally doping the deposited polysilicon with B using BBr3 and O2 gases at a doping temperature ranging from 300°C to 1000°C;

[0074] Step (4): Soak the sample in a diluted hydrofluoric acid solution for 3 min, and then rinse with deionized water three times;

[0075] Step (5): Laser activation of polysilicon with a power density ranging from 0.8 to 3.2 J / cm 2 ;

[0076] Step (6): annealing the TOPCon structure prepared in the above step (5) and then cooling it, the annealing gas is N2, the annealing temperature range is 600-1300°C, and a TOPCon contact structure is formed.

[0077] Test Example 1

[0078] The P-type TOPCon solar cell prepared in Example 1 was subjected to ECV testing. The capacitance-voltage test was performed while etching the polysilicon activated by lasers of different power densities. The doping concentration of the polysilicon was calculated based on the capacitance-voltage test, thereby obtaining the distribution of the doping concentration with respect to the depth of the polysilicon. The results are shown in FIG. Figure 2 As shown;

[0079] from Figure 2 It can be found that the power density of the laser is 1.6-2.8J / cm 2The polysilicon doping concentration of the sample is significantly higher than that of the sample without laser activation; the laser power density is lower than 1.6J / cm 2 Due to the low laser power, the doping concentration of the sample is not as good as that of the sample with higher laser power density. The laser power density is higher than 2.8J / cm 2 Due to the high laser power, the tunneling oxide layer of the sample was destroyed, and the B atoms diffused into the crystalline silicon, resulting in a decrease in the surface doping concentration.

[0080] The P-type TOPCon solar cell prepared in Example 1 was subjected to a four-probe test. The sheet resistance of the sample was calculated by current-voltage test to evaluate the effect of laser activation on resistance reduction. The results are as follows: Figure 3 As shown;

[0081] from Figure 3 It can be found that the sheet resistance of the sample after laser activation is significantly lower than that of the sample without laser activation, and for laser power density higher than 2.8J / cm 2 In the sample, due to the high laser power, the tunneling oxide layer was destroyed and the B atoms diffused into the crystalline silicon, resulting in an increase in the square resistance.

[0082] In summary, the preparation method of the P-type TOPCon solar cell of the present invention can obtain a polycrystalline silicon TOPCon contact with a higher B doping concentration, thereby improving the passivation performance of the TBC solar cell and reducing the contact resistance with the metal, thereby obtaining a TBC solar cell with better performance.

[0083] The embodiments described above are merely descriptions of preferred implementations of the present invention and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary engineering technicians in this field should fall within the scope of protection determined by the claims of the present invention.

Claims

1. A method for preparing a P-type TOPCon solar cell, characterized in that: The following steps are involved: Depositing SiO2 thin film on N-type silicon wafer; Depositing polysilicon on the SiO2 film; Thermally doping the deposited polysilicon with B; The thermally doped B region is activated.

2. The method for preparing a P-type TOPCon solar cell according to claim 1, wherein: The thickness of the N-type silicon wafer is 100 μm-200 μm, and the doping concentration range is 10 14 cm -3 -10 16 cm -3 .

3. The method for preparing a P-type TOPCon solar cell according to claim 1, wherein: The thickness of the SiO2 film is 1nm-5nm.

4. The method for preparing a P-type TOPCon solar cell according to claim 1, wherein: Before depositing the SiO2 film on the N-type silicon wafer, the N-type silicon wafer is pretreated.

5. The method for preparing a P-type TOPCon solar cell according to claim 4, wherein: The pretreatment includes cleaning and polishing.

6. The method for preparing a P-type TOPCon solar cell according to claim 1, wherein: The thickness of the deposited polysilicon is greater than 100 nm.

7. The method for preparing a P-type TOPCon solar cell according to claim 1, wherein: The deposited polysilicon is subjected to thermal doping with B, including: the gases used for thermal doping are BBr3 and O2, and the temperature range of the thermal doping is 300°C-1000°C.

8. The method for preparing a P-type TOPCon solar cell according to claim 1, wherein: Before the deposited polysilicon is thermally doped with B, the TOPCon structure after the polysilicon is deposited is annealed.

9. The method for preparing a P-type TOPCon solar cell according to claim 8, wherein: The gas used for annealing is N2, and the annealing temperature range is 600℃-1300℃.

10. The method for preparing a P-type TOPCon solar cell according to claim 1, wherein: Before the activation treatment is performed on the thermally doped B region, the thermally doped TOPCon structure is pickled.

11. The method for preparing a P-type TOPCon solar cell according to claim 1, wherein: The activation treatment of the thermally doped B region includes: performing laser activation treatment on the thermally doped B region, wherein the laser pulse bandwidth range is 1μs-4μs, and the laser energy density is 0.5J / cm -2 -5J / cm -2 .

12. The method for preparing a P-type TOPCon solar cell according to claim 1, wherein: After the activation treatment of the thermally doped B region is completed, the laser-activated sample is annealed and repaired.

13. A P-type TOPCon solar cell, characterized in that: The preparation method is described in any one of claims 1 to 12.

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