Method for preparing local passivation contact structure of topcon cell

Abstract

The application relates to the technical field of photovoltaic cells, in particular to a preparation method of a local passivation contact structure of a TOPCon cell. The preparation method comprises the following steps: preparing a passivation contact structure containing polycrystalline doped silicon on a silicon surface, and then performing local pattern processing on the passivation contact structure by using a laser to amorphize the pattern area. The preparation method of the local passivation contact structure 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. Additionally, 202110163667.3 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 finds that existing technologies, through laser thermal treatment, transform amorphous silicon in the target region into polycrystalline silicon, resulting in a higher alkaline etching rate in the target region than in the non-target treated region. Furthermore, the parameters of its laser thermal treatment make the difference in etching rates between the amorphous silicon and polycrystalline silicon regions insufficiently significant. Additionally, the introduction of water vapor during the laser treatment process introduces hydrogen doping into the target region, which further increases the alkaline etching rate. The selective etching effect of its patented design is poor, and the improvement in battery efficiency is not significant, leaving room for further improvement.

[0006] The present invention provides a method for preparing a localized passivated contact structure, which solves the technical problems of 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 of the prior art.

[0007] First, the present invention provides a method for preparing a localized passivated contact structure, comprising: preparing a passivated contact structure containing polycrystalline doped silicon on a silicon surface, and then performing patterned local processing using a laser to make the patterned region amorphous.

[0008] In a preferred embodiment of the present invention, the passivation contact structure containing polycrystalline doped silicon is a SiOx-polycrystalline doped silicon Si structure.

[0009] As a preferred embodiment of the present invention, a laser wavelength of 350–360 nanometers and a density of 1–6 × 10⁻⁶ nanometers per square centimeter are used. -4 The graphical local processing is performed at the energy density of the joule.

[0010] As a preferred embodiment of the present invention, when using laser for patterned local processing, the pulse width is ≤15 picoseconds; 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.

[0011] 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.

[0012] 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.

[0013] In a preferred embodiment of the present invention, the thickness of the SiOx is 1 to 2 nanometers;

[0014] And / or, the thickness of the polycrystalline doped silicon (Si) structure is 100 nanometers or more;

[0015] And / or, the doping element in the polycrystalline doped silicon (Si) structure is at least one of B, Al, Ga, and P;

[0016] And / or, in the polycrystalline doped silicon (Si) structure, the number of atoms of the doping element per cubic centimeter is ≥1×10⁻⁶. 18 indivual.

[0017] As a preferred embodiment of the present invention, SiOx-intrinsic amorphous silicon Si structure is prepared by LPCVD, and then SiOx-polycrystalline doped silicon Si structure is obtained by diffusion.

[0018] Preferably, the SiOx-polycrystalline doped silicon (Si) structure is prepared by boron diffusion or phosphorus diffusion; more preferably, the deposition temperature of LPCVD is 550-700 degrees Celsius, or the temperature of boron diffusion is 850-1050 degrees Celsius, or the temperature of phosphorus diffusion is 700-820 degrees Celsius.

[0019] Alternatively, SiOx-polycrystalline doped silicon-Si structures can be fabricated using LPCVD in-situ doping.

[0020] As a preferred embodiment of the present invention, after the patterned region is amorphized by laser patterning, the preparation method further includes: etching the processed sample in an alkaline solution, then performing a passivation coating treatment, overprinting a metal paste, and sintering to form a localized passivated contact structure.

[0021] In a preferred embodiment of the present invention, the alkaline solution contains at least one of KOH, NaOH, and TMAH;

[0022] And / or, the alkaline solution contains etching additives;

[0023] And / or, the passivation film is at least one of SiOx, SiNx, SiNOx, and AlOx;

[0024] And / or, the thickness of the passivation coating is 50–90 nanometers.

[0025] Furthermore, the present invention provides a method for fabricating a solar cell, comprising fabricating a localized passivation contact structure on the front surface using any of the above-described methods for fabricating localized passivation contact structures, and then performing hydrogen passivation treatment.

[0026] 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.

[0027] 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.

[0028] The beneficial effects of this invention are as follows:

[0029] The method for preparing the localized passivated contact structure of the present invention solves the technical problems of 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 in the prior art. Detailed Implementation

[0030] 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.

[0031] As an embodiment of the present invention, this embodiment provides a method for preparing a localized passivated contact structure, comprising: preparing a passivated contact structure containing polycrystalline doped silicon on a silicon surface, and then performing patterned local processing using a laser to make the patterned region amorphous.

[0032] This invention discovers that when using laser treatment to passivated contact structures containing polycrystalline doped silicon, the gate line portion on the polycrystalline silicon can be amorphized, and an amorphous silicon layer can be induced to form on the polycrystalline silicon film. This amorphous silicon layer has higher etching resistance to alkaline solutions compared to monocrystalline or polycrystalline silicon layers, thereby creating a differential etching rate between the polycrystalline region (non-gate line region) and the amorphous region (gate line region), achieving excellent etching results.

[0033] 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.

[0034] 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.

[0035] The passivation contact structure containing polycrystalline doped silicon described in this invention includes, but is not limited to, alumina-polycrystalline silicon passivation contact structures and SiO2 passivation contact structures. x N y - Polycrystalline silicon passivated contact structures and SiOx-polycrystalline doped silicon (Si) structures. Other passivated contact structures containing polycrystalline doped silicon that can achieve passivated contact performance are also within the scope of this invention.

[0036] As an embodiment of the present invention, the passivation contact structure containing polycrystalline doped silicon is a SiOx-polycrystalline doped silicon Si structure.

[0037] When using the above-mentioned SiOx-polycrystalline doped silicon (Si) structure for laser patterning local processing, the difference in etching rates between the laser-processed and unprocessed regions can be further improved.

[0038] As an embodiment of the present invention, a laser wavelength of 350–360 nanometers and a density of 1–6 × 10⁻⁶ per square centimeter are used. -4 The graphical local processing is performed at the energy density of the joule.

[0039] At the aforementioned laser wavelengths and energy densities, the graphical local processing effect is even better.

[0040] As an embodiment of the present invention, when using laser for patterned local processing, the pulse width is ≤15 picoseconds; 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.

[0041] With the aforementioned laser pulse width and the assistance of an oxygen atmosphere, it is beneficial for the molten silicon to solidify and form amorphous silicon within a very short time after melting, before it can complete the crystallization process. Simultaneously, the oxygen incorporation expands the laser window and promotes the formation of silicon oxide, which is resistant to alkali. Under alkali etching conditions of 50-80℃ and a concentration ≥30wt%, an alkali etching rate ≤6nm / min can still be obtained for the target area, while the etching rate for the untreated area can be ≥40nm / min.

[0042] 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.

[0043] 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.

[0044] Laser treatment in the above atmosphere can assist in the modification of silicon film layers and generate silicon oxide of a certain thickness in the laser treatment area.

[0045] Preferably, the patterned local processing is performed using a laser in an oxygen-containing atmosphere, and more preferably, the volume percentage of oxygen is 70-80%.

[0046] In one embodiment of the present invention, the thickness of the SiOx is 1 to 2 nanometers;

[0047] And / or, the thickness of the polycrystalline doped silicon (Si) structure is 100 nanometers or more;

[0048] And / or, the doping element in the polycrystalline doped silicon (Si) structure is at least one of B, Al, Ga, and P;

[0049] And / or, in the polycrystalline doped silicon (Si) structure, the number of atoms of the doping element per cubic centimeter is ≥1×10⁻⁶. 18 indivual.

[0050] As an embodiment of the present invention, SiOx-intrinsic amorphous silicon Si structure is prepared by LPCVD, and then SiOx-polycrystalline doped silicon Si structure is obtained by diffusion.

[0051] Preferably, the SiOx-polycrystalline doped silicon (Si) structure is prepared by boron diffusion or phosphorus diffusion; more preferably, the deposition temperature of LPCVD is 550-700 degrees Celsius, or the temperature of boron diffusion is 850-1050 degrees Celsius, or the temperature of phosphorus diffusion is 700-820 degrees Celsius.

[0052] Alternatively, SiOx-polycrystalline doped silicon-Si structures can be fabricated using LPCVD in-situ doping.

[0053] This invention discovers that when SiOx-intrinsic amorphous silicon (Si) structures are deposited by LPCVD at 550–700 degrees Celsius, and then SiOx-polycrystalline doped silicon (Si) structures are prepared by diffusion, and the target area is then treated by laser as described above, a greater difference in etching rates between the laser-treated and untreated areas can be achieved, thereby further improving the etching effect.

[0054] In addition, SiOx-polycrystalline doped silicon-Si structures can also be prepared by in-situ doping using LPCVD.

[0055] As an embodiment of the present invention, SiOx-intrinsic amorphous silicon (Si) structure is prepared by LPCVD, and then SiOx-polycrystalline doped silicon (Si) structure is prepared by boron diffusion; wherein, the deposition temperature of LPCVD is 550-700 degrees Celsius, the temperature of boron diffusion is 850-1050 degrees Celsius, and more preferably the temperature of boron diffusion is 850-900 degrees Celsius.

[0056] As an embodiment of the present invention, SiOx-intrinsic amorphous silicon (Si) structure is prepared by LPCVD, and then SiOx-polycrystalline doped silicon (Si) structure is prepared by phosphorus diffusion; wherein, the deposition temperature of LPCVD is 550-700 degrees Celsius, the temperature of phosphorus diffusion is 700-820 degrees Celsius, and more preferably the temperature of phosphorus diffusion is 720-780 degrees Celsius.

[0057] The present invention further discovers that by controlling the maximum heat treatment temperature of deposition in the LPCVD process and the subsequent diffusion process to be <800°C, the silicon thin film layer can maintain a low crystallinity.

[0058] As an embodiment of the present invention, after patterning and localizing the patterned area using laser to make the patterned area amorphous, the processed sample is etched in an alkaline solution, and then subjected to film passivation treatment, overprinting of metal paste and sintering to form a localized passivated contact structure.

[0059] 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-polycrystalline doped silicon Si structure is prepared on the surface of the cleaned silicon wafer.

[0060] As an embodiment of the present invention, the alkaline solution contains at least one of KOH, NaOH, and TMAH;

[0061] And / or, the alkaline solution contains etching additives;

[0062] And / or, the passivation film is at least one of SiOx, SiNx, SiNOx, and AlOx;

[0063] And / or, the thickness of the passivation coating is 50–90 nanometers.

[0064] In any embodiment of the present invention, the alkaline content in the alkaline solution is 3-40 wt%.

[0065] As an embodiment of the present invention, this embodiment provides a method for fabricating a solar cell, including fabricating a localized passivation contact structure on the front surface using any of the above-described methods for fabricating localized passivation contact structures, and then performing hydrogen passivation treatment.

[0066] 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.

[0067] As a preferred embodiment of the present invention, the method for preparing a solar cell includes:

[0068] (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.

[0069] (2) A SiOx-polycrystalline doped silicon (Si) structure was fabricated on the front side of a cleaned silicon wafer, and then a laser was used at a wavelength of 350–360 nm and a density of 1–6 × 10⁻⁶ m² / cm². -4 Graphical local processing is performed at the energy density of joules;

[0070] (3) Prepare SiOx-phosphorus-doped amorphous silicon-Si structure on the back side of a silicon wafer;

[0071] (4) The processed sample is etched in an alkaline solution, and then the front side of the silicon wafer is coated and passivated.

[0072] (5) Deposit a passivation film on the back side of the silicon wafer;

[0073] (6) Metal paste is overprinted 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 of the silicon wafer and sintered simultaneously with the silver aluminum grid lines on the front side.

[0074] (7) Perform hydrogen passivation treatment to obtain a solar cell.

[0075] 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.

[0076] 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, and ultimately a significant improvement in performance.

[0077] 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.

[0078] The technical solution of the present invention will now be described in conjunction with more specific embodiments.

[0079] 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.

[0080] Example 1

[0081] This embodiment provides a method for preparing a locally passivated contact structure, the specific steps of which are as follows:

[0082] (1) SiOx-intrinsic amorphous silicon (Si) structures were prepared on a clean silicon wafer surface using LPCVD. Specifically, the LPCVD parameters were: oxidation deposition temperature 605℃, deposition time 600s, and oxygen flow rate 3.6×10⁻⁶. 5 sccm; amorphous silicon layer deposition temperature 610℃, silane flow rate 2240sccm, time 1900s.

[0083] (2) A SiOx-polycrystalline doped silicon Si structure was prepared on the surface of the SiOx-intrinsic amorphous silicon Si structure by boron diffusion. Specifically, the deposition conditions were: boron source BSG deposition temperature 790℃, deposition time 1200s, and small nitrogen flow rate 1400sccm; the propagation conditions were: boron diffusion was carried out at 850℃ for 900s.

[0084] (3) Graphical local processing is performed using laser; the laser wavelength is 355 nm ultraviolet laser, and the energy density is 4.5 × 10⁻⁶ per square centimeter. -4 The laser beam has a pulse width of 9 ps, a square spot shape with a side length of 70 micrometers, and a center-to-center distance between spots less than the side length of the spot shape. The processing atmosphere is at atmospheric pressure with an oxygen volume ratio of 75%. The laser beam width is 70 micrometers, the front-side metal grid line width is 25 micrometers, and the metal grid line width is less than the width of the local passivation contact structure. The laser-processed pattern is consistent with the screen-printed pattern.

[0085] (4) The treated silicon wafer is immersed in a 15wt% KOH alkaline solution for etching at a solution temperature of 70℃ for 300s.

[0086] (5) The sample was subjected to passivation treatment 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.

[0087] (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.

[0088] Furthermore, this embodiment provides a solar cell containing the above-described localized passivated contact structure, the fabrication method of which is as follows:

[0089] (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.

[0090] (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 / □.

[0091] (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.

[0092] (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℃.

[0093] (11) Complete steps (4) to (5).

[0094] (12) A passivation film is deposited on the back of the battery. The passivation film layer is SiN. x / SiO2 stacked structure, with a total thickness of 75nm.

[0095] (13) Proceed to step (6), during which silver metal grid lines are printed on the back of the battery and silver aluminum grid lines are sintered simultaneously on the front.

[0096] (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.

[0097] Example 2

[0098] This embodiment provides a method for preparing a locally passivated contact structure, the only difference from that in Embodiment 1 being:

[0099] In step (2), specifically in the phosphorus diffusion step, the deposition conditions are: phosphorus source PSG deposition temperature 790℃, deposition time 1200s, and small nitrogen flow rate 1400sccm; the propagation conditions are: phosphorus diffusion is carried out at 745℃ for 1200s.

[0100] 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 step (2) above.

[0101] Example 3

[0102] This embodiment provides a method for preparing a locally passivated contact structure, the only difference from that in Embodiment 1 being:

[0103] In step (3), a laser is used for localized graphic processing; the processing atmosphere is a pure nitrogen atmosphere at atmospheric pressure.

[0104] 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 step (3) above.

[0105] Example 4

[0106] This embodiment provides a method for preparing a locally passivated contact structure, the only difference from that in Embodiment 1 being:

[0107] In step (2), a SiOx-polycrystalline doped silicon Si structure is prepared on the surface of the SiOx-intrinsic amorphous silicon Si structure by boron diffusion. Specifically, the deposition conditions are: boron source BSG deposition temperature 810℃, deposition time 600s, and small nitrogen (carrying BCl3) flow rate 300sccm; the propagation conditions are: boron diffusion is carried out at 1050℃ for 3500s.

[0108] 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 step (2) above.

[0109] Example 5

[0110] This embodiment provides a method for preparing a locally passivated contact structure, the only difference from that in Embodiment 1 being:

[0111] The laser wavelength is 350 nanometers, and the energy density is 6 × 10⁻⁶ per square centimeter. -4 Jiao.

[0112] 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.

[0113] Example 6

[0114] This embodiment provides a method for preparing a locally passivated contact structure, the only difference from that in Embodiment 1 being:

[0115] The laser wavelength is 360 nanometers, and the energy density is 1 × 10⁻⁶ per square centimeter. -4 Jiao.

[0116] 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.

[0117] Comparative Example

[0118] This comparative example provides a method for preparing a locally passivated contact structure, the only difference from Example 1 being the following steps:

[0119] (1) Preparation of SiOx-amorphous silicon Si layer: SiOx-amorphous silicon Si layer was prepared by in-situ doping. Specifically, the parameters of LPCVD were: oxidation deposition temperature 605℃, deposition time 600s, oxygen flow rate 3.6×105sccm; doped amorphous silicon layer deposition temperature 610℃, silane flow rate 2240sccm, small nitrogen (carrying POCl3) flow rate 970scm, and time 1900s.

[0120] (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.

[0121] Furthermore, this comparative example provides a solar cell containing the above-mentioned localized passivated contact structure, the preparation method of which differs from that of Example 1 only in the preparation of the SiOx-amorphous silicon Si layer and the laser processing steps.

[0122] Test case

[0123] Alkali etching resistance tests were performed on the laser-treated target areas prepared in the above embodiments and comparative examples.

[0124] 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 a 15wt% 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.

[0125] The results are shown in Table 1.

[0126] Table 1. Experimental results of different embodiments

[0127] Example 1 3 52 17.3 Example 2 4 35 8.8 Example 3 6 52 8.7 Example 4 4 55 13.8 Example 5 4 52 13.0 Example 6 4 52 13.0 Comparative Example 25 13 0.5

[0128] The solar cells prepared in the above embodiments and comparative examples were tested, with 200 cells in each group, and the average value of the test results was taken.

[0129] 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.

[0130] The results are shown in Table 2.

[0131] Table 2. Test results of Experiment IV for different embodiments

[0132] Example 1 25.30 724 41.6 84 Example 2 25.20 723 41.5 84 Example 3 25.14 723 41.4 84 Example 4 25.30 724 41.6 84 Example 5 25.27 725 41.5 84 Example 6 25.27 725 41.5 84 Comparative Example 24.92 720 41.2 84

[0133] 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 passivated contact structure containing polycrystalline doped silicon is prepared on the silicon surface, and then patterned local processing is performed using laser to make the patterned region amorphous. After using laser to perform patterned local processing to make the patterned area amorphous, the preparation method further includes: etching the processed sample in an alkaline solution, then performing a film passivation treatment, overprinting a metal paste and sintering to form a local passivation contact structure. Laser wavelengths of 350-360 nanometers, 1-6 × 10⁻⁶ per square centimeter -4 The graphical local processing is performed at the energy density of the foil. When using lasers for patterned local processing, the pulse width is ≤15 picoseconds; and / or, the laser spot shape is square, with a side length of ≤70 micrometers; and / or, the center-to-center spacing of the spot is ≤the side length of the spot shape. 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.

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

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

4. 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 polycrystalline doped silicon Si is 100 nanometers or more; And / or, the doping element in the polycrystalline doped silicon Si is at least one of B, Al, Ga, and P; And / or, in the polycrystalline doped silicon Si, the number of atoms of the doping element per cubic centimeter is ≥1×10⁻⁶. 18 indivual.

5. The method for preparing the locally passivated contact structure according to claim 2 or 3, characterized in that, SiOx-intrinsic amorphous silicon (Si) structures were prepared by LPCVD, and then SiOx-polycrystalline doped silicon (Si) structures were prepared by diffusion. Alternatively, SiOx-polycrystalline doped silicon-Si structures can be fabricated using LPCVD in-situ doping.

6. The method for preparing the locally passivated contact structure according to claim 5, characterized in that, SiOx-polycrystalline doped silicon (Si) structures were prepared by boron diffusion or phosphorus diffusion.

7. The method for preparing the locally passivated contact structure according to claim 6, characterized in that, The deposition temperature of LPCVD is 550~700 degrees Celsius, or the temperature of boron diffusion is 850~1050 degrees Celsius, or the temperature of phosphorus diffusion is 700~820 degrees Celsius.

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 coating is 50~90 nanometers.

9. A method for preparing a solar cell, characterized in that, include: The localized passivated contact structure is prepared on the positive surface using the preparation method of 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 to 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.