Method for preparing local passivation contact structure of topcon cell

Abstract

The present application relates to the technical field of photovoltaic cells, and particularly relates to a preparation method of a local passivation contact structure of a TOPCon cell. The preparation method comprises the following steps: preparing a hydrogen-containing passivation contact structure on a silicon surface, and then performing local pattern processing on the passivation contact structure by using a laser, so that the hydrogen content of the pattern area is reduced and the pattern area has alkali resistance. The preparation method of the local passivation contact structure utilizes the mechanism of the difference in etching resistance of alkali solution caused by the different hydrogen contents of the thin film structure, and solves the technical problems of the prior art, such as complex mask preparation and removal process, poor pattern accuracy, difficult alignment of later metallization printing, inability to mass production or high cost of mass production, and poor etching effect.

Description

Technical Field

[0001] This invention relates to the field of photovoltaic cell technology, and in particular to a method for preparing a localized passivated contact structure for TOPCon cells. Background Technology

[0002] With continuous improvements in passivation technology for solar photovoltaic cells, recombination in non-metallic regions is no longer a bottleneck for efficiency improvement; however, recombination in metallic regions has become the primary bottleneck. While passivation contact structures can significantly reduce metallic recombination, the light-absorbing properties of the poly layer lead to substantial absorption of sunlight, resulting in a decrease in cell current density. Therefore, there is a need to develop patterned localized passivation contact technology. Localized passivation contacts exist only in metallic regions, with no passivation contacts in other areas. This can resolve the contradiction between the high light absorption of the poly layer and the high rate of metallic recombination. Thus, the localized passivation contact structure (poly finger) has become a very promising technological approach.

[0003] Although various research institutions have adopted different methods for technology development, a mass-producible solution has yet to be developed. The technical challenge of this structure lies in the preparation of the mask and the precise control of the mask feature dimensions. Existing polyfinger technology involves the following steps: First, a TOPCon passivation contact layer is prepared; second, patterned wax grid lines resistant to alkaline corrosion are printed onto the passivation contact layer using inkjet printing; third, using these wax grid lines as a mask, the non-grid line areas are etched away in an alkaline solution of a certain concentration, forming a grid-shaped passivation contact layer; fourth, the mask wax grid line layer is cleaned away with an acid solution; and fifth, grid lines are printed onto the patterned passivation contact layer. The problems with this method are: low precision of the inkjet-printed pattern and large line width, which is detrimental to subsequent metallization printing alignment; and the excessively wide polyfin also leads to severe optical absorption.

[0004] Existing technologies offer several solutions to this problem. For example, CN201921593120.1 uses silicon nitride as the mask. However, this requires additional silicon nitride mask deposition and removal steps, and the patterning process for silicon nitride deposition is practically impossible to mass-produce. Another example is CN202210099446.9, which uses PVD to prepare a passivation contact layer by applying a metal shielding layer during the preparation process, utilizing the shielding effect to form localized passivation contacts. While this method is simple, the actual grid line distance of the battery is <1mm, making it impossible to achieve the required precision using the metal shielding method. CN202110749345.7 uses inkjet printing of paraffin wax as a mask. This method can now produce batteries, but inkjet printing has low precision, subsequent screen printing is difficult, paraffin wax has a low melting point, requiring low-temperature storage of the sample, and as an organic substance, it needs to be washed away, easily causing contamination of the wet processing tank. In the battery fabrication process described in CN201910805305.2, grid lines are directly printed after passivation of the contacts. Then, the self-masking effect of the silver grid lines is used to etch other areas of the passivation contact layer. However, during the etching process, metal ions such as Ag are still etched away, contaminating the battery. Furthermore, because the coating affects the outward displacement of charge carriers from the grid lines, this method involves two metal printing and sintering processes, resulting in high mass production costs. In addition, CN202110163667.3 describes a method that uses laser or other thermal treatments on the target portion of the amorphous silicon layer to form a doped polycrystalline silicon region. Then, the amorphous silicon region is removed to obtain a locally passivated contact structure on the front side of the silicon substrate. However, in practical applications, the etching rate of alkali on amorphous silicon is lower than that on polycrystalline silicon. This results in the alkali etching removing the laser-treated area while leaving the untreated area. This method cannot achieve the ideal processing effect of removing the untreated area and leaving the treated area. Summary of the Invention

[0005] In view of this, the present invention found that when heat treatment is performed by laser, the amorphous silicon in the target area is easily completely transformed into polycrystalline silicon, resulting in insufficient difference in hydrogen ion content between the amorphous silicon area and the polycrystalline silicon area. Consequently, the difference in etching rate is small during subsequent etching, which affects the etching effect.

[0006] This invention provides a method for preparing a localized passivated contact structure, which solves the technical problems in the prior art, such as complex mask preparation and removal processes, poor pattern accuracy, difficulty in subsequent metallization printing alignment, inability to mass produce or high mass production costs, and poor etching effect.

[0007] First, this invention provides a method for preparing a locally passivated contact structure, comprising:

[0008] A hydrogen-containing passivated contact structure is prepared on the silicon surface, and then patterned locally using a laser to reduce the hydrogen content in the patterned area, thereby giving it alkali resistance.

[0009] Preferably, the difference in hydrogen content in the patterned area before and after laser-based localized patterning is more than 5%.

[0010] In a preferred embodiment of the present invention, the passivation contact structure is a SiOx-doped amorphous silicon (Si) structure.

[0011] As a preferred embodiment of the present invention, patterned local processing is performed at a laser wavelength of 500-550 nanometers and an energy density of 4-15 joules per square centimeter.

[0012] As a preferred embodiment of the present invention, a laser is used for patterned local processing at a laser wavelength of 530-550 nanometers and an energy density of 10-15 joules per square centimeter.

[0013] As a preferred embodiment of the present invention, when using laser for patterned local processing, the pulse width is 3 to 50 nanoseconds; and / or, the laser spot shape is square, with a side length of ≤70 micrometers; and / or, the center-to-center distance of the spot is ≤ the side length of the spot shape.

[0014] In a preferred embodiment of the present invention, the width of the laser is 50 to 100 micrometers, the width of the front metal grid line is 5 to 30 micrometers, and the width of the metal grid line is less than the width of the local passivation contact structure, and the laser-processed pattern is consistent with the screen-printed pattern.

[0015] As a preferred embodiment of the present invention, laser is used for patterned local processing in an atmosphere containing at least one of Ar, N2, O2, N2O, and O3.

[0016] In a preferred embodiment of the present invention, SiOx-doped amorphous silicon (Si) structures are prepared by PECVD in an argon or hydrogen atmosphere at 400–500°C. Preferably, the flow ratio of argon or hydrogen to silane is controlled to be 1–8:1 during the preparation of the doped amorphous silicon (Si) structures. More preferably, the flow ratio of argon or hydrogen to silane is controlled to be 1–4:1.

[0017] In a preferred embodiment of the present invention, the thickness of the SiOx is 1 to 2 nanometers;

[0018] And / or, the thickness of the doped amorphous silicon (Si) structure is 100 nanometers or more;

[0019] And / or, the doping element in the doped amorphous silicon Si structure is at least one of B, Al, Ga, and P;

[0020] And / or, in the doped amorphous silicon (Si) structure, the number of atoms of the doping element per cubic centimeter is ≥1×10⁻⁶. 18 indivual.

[0021] As a preferred embodiment of the present invention, after patterning local processing with laser, the preparation method further includes: etching the processed sample in an alkaline solution, then annealing, coating passivation treatment, overprinting metal paste and sintering to form a local passivation contact structure.

[0022] Alternatively, after patterning local processing using laser, the preparation method may further include: annealing the processed sample, then etching, coating and passivating in an alkaline solution, overprinting metal paste and sintering to form a local passivated contact structure.

[0023] In a preferred embodiment of the present invention, the alkaline solution contains at least one of KOH, NaOH, and TMAH;

[0024] And / or, the alkaline solution contains etching additives;

[0025] And / or, the passivation film is at least one of SiOx, SiNx, SiNOx, and AlOx;

[0026] And / or, the thickness of the passivation film is 50–90 nanometers;

[0027] And / or, the annealing temperature is 780–920 degrees Celsius.

[0028] Furthermore, the present invention provides a method for fabricating a solar cell, comprising: fabricating a localized passivation contact structure on the front surface of the cell using the method for fabricating a localized passivation contact structure in any of the above embodiments, and then performing hydrogen passivation treatment.

[0029] In a preferred embodiment of the present invention, the light intensity of the hydrogen passivation treatment is above 20,000 kilowatts per square meter, and the temperature is 200 to 700 degrees Celsius.

[0030] Furthermore, the present invention also provides a solar cell containing the locally passivated contact structure obtained by the above-described preparation method, or obtained by the above-described solar cell preparation method.

[0031] The beneficial effects of this invention are as follows:

[0032] The method for preparing the localized passivated contact structure of the present invention utilizes the mechanism of the difference in resistance to alkaline etching due to different hydrogen contents in the thin film structure, and solves the technical problems in the prior art, such as complex mask preparation and removal processes, poor pattern accuracy, difficulty in alignment of subsequent metallization printing, inability to mass produce or high mass production cost, and poor etching effect. Detailed Implementation

[0033] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of this invention, not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0034] As an embodiment of the present invention, this embodiment provides a method for preparing a localized passivated contact structure, comprising: preparing a hydrogen-containing passivated contact structure on a silicon surface, and then performing patterned local processing using a laser to reduce the hydrogen content in the patterned area and thereby provide alkali resistance.

[0035] This invention discovers that by first preparing a hydrogen-containing passivated contact structure on the surface of a silicon wafer, and then using laser patterning, a large amount of hydrogen in the target area can be excited and escape from the silicon film. The high hydrogen content amorphous silicon (7-15%) in the target area is transformed into low / zero (≤2%) hydrogen content amorphous silicon, which makes the silicon layer in the target area have strong etching resistance to alkaline solutions.

[0036] Specifically, the etching rate of the alkaline solution on the laser-treated silicon film is much lower than that on the untreated silicon film, resulting in a significant difference in etching rates between the laser-treated and untreated areas, thus significantly improving the etching effect. The laser-treated silicon layer can act as a mask, and then the non-laser-treated areas can be removed by alkaline etching, while the laser-treated areas are retained. After acid washing, a localized passivated contact structure can be obtained.

[0037] Meanwhile, the preparation method of this invention offers high precision, adjustable passivation contact area width, and a simple process. It possesses mass production capabilities and the ability to improve battery efficiency, solving problems such as complex mask preparation and removal processes, poor pattern accuracy, and difficulties in subsequent metallization printing alignment. The laser-based preparation process offers significantly higher precision than other thin film deposition processes, providing a window for accurate subsequent screen printing overprinting.

[0038] As an embodiment of the present invention, the difference in hydrogen content in the patterned area before and after laser patterning local processing is more than 5%.

[0039] The hydrogen-containing passivation contact structures of the present invention include, but are not limited to, alumina-polycrystalline silicon passivation contact structures and SiO2 passivation contact structures. x N y - Polycrystalline silicon passivated contact structures and SiOx-doped amorphous silicon (Si) structures. Other hydrogen-containing passivated contact structures capable of achieving passivation contact performance are also within the scope of this invention.

[0040] As an embodiment of the present invention, the passivated contact structure is a SiOx-doped amorphous silicon (Si) structure.

[0041] As an embodiment of the present invention, patterned local processing is performed at a laser wavelength of 500-550 nanometers and an energy density of 4-15 joules per square centimeter.

[0042] As an embodiment of the present invention, a laser is used for patterned local processing at a laser wavelength of 530-550 nanometers and an energy density of 10-15 joules per square centimeter.

[0043] Under the aforementioned laser parameters, patterned local processing results in better hydrogen escape in the patterned area, further increasing the hydrogen content in both the laser-processed and unprocessed areas, thus improving the subsequent etching effect.

[0044] As an embodiment of the present invention, when using laser for patterned local processing, the pulse width is 3 to 50 nanoseconds; and / or, the laser spot shape is square, with a side length of ≤70 micrometers; and / or, the center-to-center distance of the spot is ≤ the side length of the spot shape.

[0045] Under the aforementioned laser pulse width, laser power, and laser wavelength, a longer laser wavelength facilitates laser penetration through the entire silicon film for processing. Simultaneously, the high laser energy density provides sufficient energy to break the H bonds in the silicon film, releasing hydrogen. The wider pulse width increases the laser's interaction time with the silicon film, allowing sufficient time for hydrogen release. After processing, during alkaline etching, the alkaline etching rate in the target area can still be ≤5 nm / min, while the etching rate in the untreated area can be ≥50 nm / min.

[0046] In one embodiment of the present invention, the width of the laser is 50 to 100 micrometers, the width of the front metal grid line is 5 to 30 micrometers, and the width of the metal grid line is less than the width of the local passivation contact structure. The laser-processed pattern is consistent with the screen-printed pattern.

[0047] As an embodiment of the present invention, a laser is used for patterned local processing in an atmosphere containing at least one of Ar, N2, O2, N2O, and O3.

[0048] Laser treatment in the above atmosphere can assist in the modification of the silicon film and promote the further escape of hydrogen from the silicon layer, resulting in a greater difference in hydrogen content between the laser-treated area and the untreated area, which is beneficial to significantly improve the etching effect.

[0049] As an embodiment of the present invention, SiOx-doped amorphous silicon Si structures are prepared by PECVD in an argon or H2 atmosphere at 400-500°C.

[0050] The present invention also found that by using PECVD to prepare SiOx-doped amorphous silicon Si structures, the silicon layer is amorphous and has a high hydrogen content. After laser treatment with the above parameters, the difference in hydrogen content between the laser-treated and untreated areas can be made greater, thereby resulting in a greater difference in etching rate and further improving the etching effect.

[0051] In one embodiment of the present invention, in the preparation of doped amorphous silicon (Si) structures, the flow ratio of argon or hydrogen to silane in the PECVD process is controlled to be 1 to 8:1. More preferably, the flow ratio of argon or hydrogen to silane is controlled to be 1 to 4:1.

[0052] In one embodiment of the present invention, the thickness of the SiOx is 1 to 2 nanometers;

[0053] And / or, the thickness of the doped amorphous silicon (Si) structure is 100 nanometers or more;

[0054] And / or, the doping element in the doped amorphous silicon Si structure is at least one of B, Al, Ga, and P;

[0055] And / or, in the doped amorphous silicon (Si) structure, the number of atoms of the doping element per cubic centimeter is ≥1×10⁻⁶. 18 indivual.

[0056] As an embodiment of the present invention, after patterning local processing using laser, the preparation method further includes: etching the processed sample in an alkaline solution, then annealing, coating passivation treatment, overprinting metal paste and sintering to form a local passivation contact structure.

[0057] Alternatively, after patterning local processing using laser, the preparation method may further include: annealing the processed sample, then etching, coating and passivating in an alkaline solution, overprinting metal paste and sintering to form a local passivated contact structure.

[0058] As an embodiment of the present invention, an n-type single crystal silicon wafer is used, and it is subjected to texturing, boron diffusion or phosphorus diffusion treatment and cleaning treatment. Then, a SiOx-doped amorphous silicon Si structure is prepared on the surface of the cleaned silicon wafer.

[0059] As an embodiment of the present invention, the alkaline solution contains at least one of KOH, NaOH, and TMAH;

[0060] And / or, the alkaline solution contains etching additives;

[0061] And / or, the passivation film is at least one of SiOx, SiNx, SiNOx, and AlOx;

[0062] And / or, the thickness of the passivation film is 50–90 nanometers;

[0063] And / or, the annealing temperature is 780–920 degrees Celsius.

[0064] Preferably, the annealing time is 20–50 min.

[0065] Annealing under the above conditions can further activate the doping elements in the localized SiOx-doped amorphous silicon Si structure and promote crystallization.

[0066] In any embodiment of the present invention, the alkaline content in the alkaline solution is 3-40 wt%.

[0067] As an embodiment of the present invention, this embodiment provides a method for fabricating a solar cell, comprising: fabricating a localized passivation contact structure on the front surface of the cell using the localized passivation contact structure fabrication method of any of the above embodiments, and then performing hydrogen passivation treatment.

[0068] In one embodiment of the present invention, the light intensity of the hydrogen passivation treatment is above 20,000 kilowatts per square meter, and the temperature is between 200 and 700 degrees Celsius. Preferably, the hydrogen passivation treatment time is above 5 minutes.

[0069] As a preferred embodiment of the present invention, the method for preparing a solar cell includes:

[0070] (1) Using an n-type single crystal silicon wafer, texturing, boron diffusion or phosphorus diffusion are performed on it. After removing the back-side diffusion layer area, acid washing is performed to obtain a clean silicon wafer.

[0071] (2) A SiOx-doped amorphous silicon Si structure is prepared on the front side of a cleaned silicon wafer, and then patterned local processing is performed using a laser at a wavelength of 500-550 nm and an energy density of 4-15 joules per square centimeter.

[0072] (3) The processed silicon wafer is subjected to alkaline etching;

[0073] (4) Prepare SiOx-phosphorus-doped amorphous silicon-Si structure on the back side of a silicon wafer;

[0074] (5) Anneal the processed sample and then perform passivation coating on the front side of the silicon wafer.

[0075] (6) Deposit a passivation film on the back side of the silicon wafer;

[0076] (7) Metal paste is printed on the front side of the silicon wafer and sintered to form a localized passivated contact structure; at the same time, silver metal grid lines are printed on the back side and sintered simultaneously with the silver aluminum grid lines on the front side.

[0077] (8) Perform hydrogen passivation treatment to obtain a solar cell.

[0078] As an embodiment of the present invention, this embodiment also provides a solar cell containing the locally passivated contact structure obtained by the above-described preparation method, or obtained by the above-described solar cell preparation method.

[0079] Because the solar cell uses the fabrication method of this invention to obtain a localized passivated contact structure, the etching rate of different regions varies greatly. This allows the passivated contact in the metallized region to be completely preserved, significantly reducing recombination in the metallized region of the photovoltaic cell. It also allows the passivated contact structure in the non-metallized region to be completely removed without generating the negative impact of related parasitic absorption. Ultimately, this results in a significant increase in open-circuit voltage without a decrease in short-circuit current, thereby achieving a significant improvement in cell performance.

[0080] Those skilled in the art can further combine the above embodiments to obtain other preferred embodiments of the method for preparing the localized passivated contact structure of the present invention.

[0081] The technical solution of the present invention will now be described in conjunction with more specific embodiments.

[0082] Unless otherwise specified, all methods used in the examples were conventional or performed according to techniques or conditions described in the literature in this field, or in accordance with the product instructions. Reagents and instruments used without specified manufacturers were all conventional products that could be purchased from legitimate channels.

[0083] Example 1

[0084] This embodiment provides a method for preparing a locally passivated contact structure, the specific steps of which are as follows:

[0085] (1) SiOx-doped amorphous silicon Si structure was prepared on the surface of a cleaned silicon wafer by PECVD. Specifically, the PECVD parameters were as follows: SiOx preparation parameters: time 95s, Ar gas flow rate 2000sccm, NO2 gas flow rate 8000sccm, power 13000W, duty cycle 1 / 60, temperature 470℃; Doped amorphous silicon layer preparation parameters: time 1300s, H2 gas flow rate 10000sccm, silane flow rate 2600sccm, hydrogen flow rate / silane flow rate 3.85, borane flow rate 1000sccm, power 14000W, duty cycle 6 / 60H2, deposition temperature 470℃.

[0086] (2) Patterned local processing is performed using laser; the laser wavelength is 532 nm, the energy density is 10 joules per square centimeter, the pulse width is 20 ns, the laser spot shape is square with a side length of 70 micrometers, and the center-to-center distance of the spot is less than or equal to the side length of the spot shape; the processing atmosphere is at atmospheric pressure with an oxygen volume ratio of 75%. The laser width is 70 micrometers, the width of the front metal grid line is 25 micrometers, and the width of the metal grid line is less than the width of the local passivation contact structure. The laser-processed pattern is consistent with the screen-printed pattern.

[0087] (3) The treated silicon wafer is immersed in a 30wt% KOH alkaline solution for etching for 300s at a solution temperature of 65℃.

[0088] (4) Anneal the sample at 920℃ for 50 min.

[0089] (5) Passivation treatment was performed on the sample surface by depositing an alumina / silicon nitride bilayer film. The alumina deposition temperature was 200℃, and the film thickness was 8nm. The silicon nitride deposition temperature was 500℃, the ammonia flow rate / silane flow rate was 11.5, the deposition time was 2800s, and the film thickness was 75nm.

[0090] (6) Silver and aluminum metal paste is overprinted in the local passivation area. The printing width of the metal paste is 25 micrometers, and it is sintered at 740°C to form a local passivation contact structure.

[0091] Furthermore, this embodiment provides a solar cell containing the above-described localized passivated contact structure, the fabrication method of which is as follows:

[0092] (7) The silicon wafer used is an n-type monocrystalline silicon wafer with a resistivity of 1.5 Ω·cm. The silicon wafer was texturized before step (1) above using a 2% wt KOH solution at a temperature of 80°C for 6 min.

[0093] (8) The texturized silicon wafer is subjected to boron diffusion treatment at a diffusion temperature of 1000℃ for 58 min, with a diffusion sheet resistance of 235Ω / □.

[0094] (9) The back surface and surrounding area of ​​the diffused silicon wafer are treated with 15% wt KOH solution at 82°C for 3 min to remove the area around the boron diffusion layer, and then HF acid cleaning is performed to obtain the cleaned silicon wafer required in step (1). Steps (1) to (3) are completed on the front surface of this silicon wafer.

[0095] (10) A SiOx-phosphorus-doped amorphous silicon Si structure was prepared on the back side of a cleaned silicon wafer using PECVD. Specifically, the PECVD parameters were as follows: SiOx preparation parameters: time 95s, Ar gas flow rate 2000sccm, NO2 gas flow rate 8000sccm, power 13000W, duty cycle 1 / 60, temperature 470℃; Phosphorus-doped amorphous silicon layer preparation parameters: time 1300s, H2 gas flow rate 10000sccm, silane flow rate 2600sccm, hydrogen flow rate / silane flow rate 3.85, phosphine flow rate 1000sccm, power 14000W, duty cycle 6 / 60H2, deposition temperature 470℃.

[0096] (11) Complete steps (4) to (5).

[0097] (12) A passivation film is deposited on the back surface of the battery. The passivation film layer is SiN. x / SiO2 stacked structure, with a total thickness of 75nm.

[0098] (13) Proceed to step (6), during which silver metal grid lines are printed on the other side of the battery and sintered simultaneously with the silver aluminum grid lines on the front side.

[0099] (14) Hydrogen passivation treatment is carried out, with a light intensity of 20,000 kilowatts per square meter and a temperature of 350 degrees Celsius, to produce solar cells.

[0100] Example 2

[0101] This embodiment provides a method for preparing a locally passivated contact structure, the only difference from that in Embodiment 1 being:

[0102] Steps (3) and (4) are reversed.

[0103] Furthermore, this embodiment provides a solar cell containing the above-mentioned localized passivated contact structure, and its preparation method is different from that of Embodiment 1 except for the order of steps (3) and (4).

[0104] Example 3

[0105] This embodiment provides a method for preparing a locally passivated contact structure, the only difference from that in Embodiment 1 being:

[0106] During the PECVD deposition process, the H2 gas flow rate in the H2 atmosphere during the deposition of amorphous silicon film is 20800 sccm, and the hydrogen flow rate / silane flow rate is 8.

[0107] Furthermore, this embodiment provides a solar cell containing the above-mentioned localized passivated contact structure, the preparation method of which differs from that of Embodiment 1 only in the deposition parameters of the amorphous silicon film layer.

[0108] Example 4

[0109] This embodiment provides a method for preparing a locally passivated contact structure, the only difference from that in Embodiment 1 being:

[0110] During the PECVD deposition process, an Ar atmosphere is used for the deposition of amorphous silicon films, with an Ar gas flow rate of 9000 sccm and an Ar gas flow rate / silane flow rate of 3.46.

[0111] Furthermore, this embodiment provides a solar cell containing the above-mentioned localized passivated contact structure, the preparation method of which differs from that of Embodiment 1 only in the deposition parameters of the amorphous silicon film layer.

[0112] Example 5

[0113] This embodiment provides a method for preparing a locally passivated contact structure, the only difference from that in Embodiment 1 being:

[0114] The laser wavelength is 550 nanometers and the energy density is 15 joules per square centimeter.

[0115] Furthermore, this embodiment provides a solar cell containing the above-described localized passivated contact structure, the preparation method of which differs from that of Embodiment 1 only in the laser wavelength and energy density.

[0116] Example 6

[0117] This embodiment provides a method for preparing a locally passivated contact structure, the only difference from that in Embodiment 1 being:

[0118] The laser wavelength is 500 nanometers and the energy density is 4 joules per square centimeter.

[0119] Furthermore, this embodiment provides a solar cell containing the above-described localized passivated contact structure, the preparation method of which differs from that of Embodiment 1 only in the laser wavelength and energy density.

[0120] Comparative Example

[0121] This comparative example provides a method for preparing a locally passivated contact structure, the only difference from Example 1 being the following steps:

[0122] (1) Preparation of SiOx-doped amorphous silicon Si layer: SiOx-doped amorphous silicon Si layer was prepared by in-situ doping. Specifically, the LPCVD parameters were: oxidation deposition temperature 605℃, deposition time 600s, and oxygen flow rate 3.6×10⁻⁶. 5 sccm; deposition temperature of doped amorphous silicon layer: 610℃, silane flow rate: 2240sccm, small nitrogen (carrying BCl3) flow rate: 970scm, time: 1900s.

[0123] (2) Laser treatment: The laser wavelength is 532 nanometers, the energy density is 0.5 joules per square centimeter, the treatment atmosphere is water vapor, and the water vapor flow rate is 200 sccm.

[0124] Furthermore, this embodiment provides a solar cell containing the above-mentioned localized passivated contact structure, the preparation method of which differs from that of Embodiment 1 only in the preparation of the SiOx-doped amorphous silicon Si layer and the laser processing steps.

[0125] Test case

[0126] Alkali etching resistance tests were performed on the laser-treated target areas prepared in the above embodiments and comparative examples.

[0127] The specific testing method is as follows: SiOx-doped silicon thin films are prepared on the surface of polished silicon wafers according to the above preparation method, and the thickness d0 of the silicon thin film is tested; regional laser treatment is performed with corresponding laser parameters; the treated sample is immersed in 30wt% KOH solution for 5 minutes, and the thickness d1 of the remaining silicon thin film in the laser-treated target area and the thickness d2 of the non-laser-treated area are tested; the alkaline etching rate S1 of the silicon thin film in the laser-treated target area and the alkaline etching rate S2 of the silicon thin film in the non-laser-treated area are calculated; the etching rate ratio S2 / S1 is used as the evaluation index, and the larger the ratio, the stronger the selective etching and the better the technical solution.

[0128] The test results are shown in Table 1.

[0129] Table 1. Experimental results of different embodiments

[0130]

[0131]

[0132] The solar cells prepared in the above embodiments and comparative examples were tested. 200 cells were tested for each embodiment, and the results were averaged.

[0133] Specifically, the IV curve was tested, and the battery open-circuit voltage Voc, short-circuit current density Jsc, fill factor FF, and battery photoelectric conversion efficiency Eff were determined.

[0134] The results are shown in Table 2.

[0135] Table 2. Test results of Experiment IV for different embodiments

[0136] Eff(%) Voc(mV) <![CDATA[Jsc(mA / cm 2 )]]> FF (%) Example 1 25.33 725 41.6 84 Example 2 25.20 723 41.5 84 Example 3 25.15 725 41.3 84 Example 4 25.21 725 41.4 84 Example 5 25.15 725 41.3 84 Example 6 24.99 722 41.2 84 Comparative Example 24.92 720 41.2 84

[0137] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a locally passivated contact structure, characterized in that, include: A hydrogen-containing passivated contact structure was prepared on the silicon surface, and then patterned local processing was performed using a laser at a wavelength of 500-550 nm and an energy density of 4-15 joules per square centimeter. This reduced the hydrogen content in the patterned area and gave it alkali resistance. The difference in hydrogen content in the patterned area before and after laser patterning was more than 5%. When using lasers for patterned local processing, the pulse width is 3~50 nanoseconds; the laser spot shape is square, with a side length ≤70 micrometers; the center-to-center distance of the spot is ≤the side length of the spot shape; After patterning local processing using laser, the preparation method further includes: etching the processed sample in an alkaline solution, followed by annealing, film passivation treatment, overprinting of metal paste, and sintering to form a local passivated contact structure. Alternatively, after patterning local processing using laser, the preparation method may further include: annealing the processed sample, then etching, coating and passivating in an alkaline solution, overprinting metal paste and sintering to form a local passivated contact structure.

2. The method for preparing the locally passivated contact structure according to claim 1, characterized in that, The passivated contact structure is a SiOx-doped amorphous silicon (Si) structure.

3. The method for preparing the locally passivated contact structure according to claim 1, characterized in that, The laser has a width of 50-100 micrometers, the front metal grid line has a width of 5-30 micrometers, and the width of the metal grid line is less than the width of the local passivation contact structure. The laser-processed pattern is consistent with the screen-printed pattern.

4. The method for preparing the locally passivated contact structure according to any one of claims 1 to 3, characterized in that, Graphical local processing is performed using lasers in an atmosphere containing at least one of Ar, N2, O2, N2O, and O3.

5. The method for preparing the locally passivated contact structure according to claim 2, characterized in that, The thickness of the SiOx is 1~2 nanometers; And / or, the thickness of the doped amorphous silicon (Si) structure is 100 nanometers or more; And / or, the doping element in the doped amorphous silicon Si structure is at least one of B, Al, Ga, and P; And / or, in the doped amorphous silicon (Si) structure, the number of atoms of the doping element per cubic centimeter is ≥1×10⁻⁶. 18 indivual.

6. The method for preparing the locally passivated contact structure according to claim 2, characterized in that, SiOx-doped amorphous silicon (Si) structures were prepared by PECVD in an argon or hydrogen atmosphere at 400–500 degrees Celsius.

7. The method for preparing the locally passivated contact structure according to claim 6, characterized in that, In the preparation of SiOx-doped amorphous silicon (Si) structures, the flow ratio of argon or hydrogen to silane is controlled to be (1~8):

1.

8. The method for preparing the locally passivated contact structure according to claim 1, characterized in that, The alkaline solution contains at least one of KOH, NaOH, and TMAH; And / or, the alkaline solution contains etching additives; And / or, the passivation film is at least one of SiOx, SiNx, SiNOx, and AlOx; And / or, the thickness of the passivation film is 50~90 nanometers; And / or, the annealing temperature is 780~920 degrees Celsius.

9. A method for preparing a solar cell, characterized in that, include: The local passivated contact structure is prepared on the positive surface of the battery using the method described in any one of claims 1 to 8, and then subjected to hydrogen passivation treatment. The light intensity of the hydrogen passivation treatment is above 20,000 kilowatts per square meter, and the temperature is 200~700 degrees Celsius.

10. A solar cell, characterized in that, It contains the locally passivated contact structure prepared by any one of claims 1 to 8, or prepared by the solar cell preparation method of claim 9.

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