Preparation process of photovoltaic cell and photovoltaic cell

Abstract

The invention relates to a preparation process of a photovoltaic cell and the photovoltaic cell, and the preparation process comprises the steps: providing a silicon substrate, and preparing a passivation layer on the surface of the silicon substrate; conducting paste is transferred on the passivation layer; transferring the silicon substrate with the conductive slurry to a drying device, and drying and shaping the conductive slurry; and sintering and curing the dried and shaped conductive slurry to form a grid line. The drying device can volatilize a part of solvent in the conductive slurry, dry and plasticize the conductive slurry and reduce the possibility of diffusion of the conductive slurry along the width direction, so that the width of the sintered and cured grid line can be limited, the shielding of the grid line on the light receiving surface of the photovoltaic cell can be reduced, the surface flatness of the grid line can be improved, and the conductivity of the grid line can be improved. And the power generation efficiency of the photovoltaic cell is improved. The solvent in the conductive slurry is partially evaporated in the drying process, so that the time required for sintering and curing can be shortened, and the production efficiency of the photovoltaic cell is improved.

Description

Technical Field

[0001] The embodiments of the present application relate to the technical field of photovoltaic power generation, and in particular, to a preparation process of a photovoltaic cell and a photovoltaic cell. Background Art

[0002] With the increasing shortage of conventional energy supply and the increasingly prominent environmental pollution problems in the world, humans have realized the crisis of energy and environment and began to seek renewable clean energy to replace conventional energy. Photovoltaic cells have become an emerging industry that has attracted widespread attention and key development in various countries in the world due to their characteristics such as cleanliness, safety, convenience, and high efficiency. Grid lines are provided on both the light-receiving surface and the backlight surface of the photovoltaic cell to conduct the electric energy generated in the photovoltaic cell. At present, the grid lines are generally prepared by screen printing technology. Limited by the mesh size, paste viscosity, and curing process, the width of the grid lines is relatively large, and the area of the light-receiving surface blocked is relatively large, resulting in low power generation efficiency of the photovoltaic cell. Summary of the Invention

[0003] The present application relates to a preparation method of a photovoltaic cell and a photovoltaic cell to solve the problem of low power generation efficiency of the photovoltaic cell.

[0004] In a first aspect, the present application provides a preparation process of a photovoltaic cell, and the preparation process includes:

[0005] Providing a silicon substrate and preparing a passivation layer on the surface of the silicon substrate;

[0006] Transferring conductive paste on the passivation layer;

[0007] Transporting the silicon substrate with the conductive paste to a drying device to dry and shape the conductive paste;

[0008] Sintering and curing the dried and shaped conductive paste to form grid lines.

[0009] In a possible embodiment, the drying device includes a plurality of nozzles, the plurality of nozzles are arranged in an array, the distance between adjacent nozzles is less than or equal to 2 mm, and is located on the side of the silicon substrate where the conductive paste is provided. When drying and shaping the conductive paste, the preparation process includes:

[0010] The nozzles blow out air flow, the temperature of the air flow is 20°C to 30°C, and the wind speed is 2 m / s to 4 m / s;

[0011] The purging time of the air flow is 3 s to 5 s.

[0012] In a possible embodiment, the drying device includes a heating table. When drying and shaping the conductive paste, the preparation process includes:

[0013] Transfer the silicon substrate with the conductive paste to the heating stage;

[0014] Raise the temperature of the heating stage to 40°C to 60°C;

[0015] The heating time is 2 s to 4 s.

[0016] In a possible embodiment, the temperature uniformity error at each position in the heating stage is within ±0.5°C.

[0017] In a possible embodiment, the drying device includes a light structure, and the light emitted by the light structure irradiates the conductive paste transferred onto the passivation layer. When drying and shaping the conductive paste, the preparation process includes:

[0018] The wavelength of the light is 365 nm to 450 nm, and the intensity is 100 mW / cm² to 300 mW / cm²;

[0019] The light irradiation time is 1 s to 3 s.

[0020] In a possible embodiment, the drying device includes a detector located on one side of the silicon substrate to detect the temperature and humidity of the environment around the silicon substrate.

[0021] In a possible embodiment, the conductive paste includes a solvent, and the content of the solvent in the conductive paste is 4% to 7%.

[0022] In a possible embodiment, when drying and shaping the conductive paste, the evaporation amount of the solvent is less than or equal to 30% of the total amount of the solvent.

[0023] In a possible embodiment, the transfer device of the conductive paste includes a transfer film, and the transfer film includes a receiving groove. When transferring the conductive paste onto the passivation layer, the preparation process includes:

[0024] Fill the conductive paste into the receiving groove;

[0025] Invert the transfer film onto the surface of the silicon substrate so that the opening of the receiving groove faces the silicon substrate;

[0026] The laser emission device emits a first laser, and the first laser sweeps the transfer film to make the conductive paste come out and fall onto the passivation layer.

[0027] In a possible embodiment, the sintering and curing device for sintering and curing the conductive paste includes a carrier table and a plurality of probes. When sintering and curing the dried and shaped conductive paste, the preparation process includes:

[0028] Place the silicon substrate on the carrier stage, and bring the probe into contact with the end of the conductive paste.

[0029] The laser emission device emits a second laser, which sweeps the conductive paste, and at the same time, the probe applies a deflection voltage to the silicon substrate.

[0030] In a possible embodiment, the power of the second laser is different from the power of the first laser.

[0031] In a second aspect, the present application also provides a photovoltaic cell, which includes a silicon substrate, a passivation layer is provided on the surface of the silicon substrate, a plurality of grid lines are arranged at intervals on the passivation layer, and the width of the grid lines is 3 μm to 10 μm.

[0032] In a possible embodiment, the aspect ratio of the grid lines is 60% to 100%.

[0033] The present application relates to a preparation process and a photovoltaic cell of a photovoltaic cell. The preparation process includes: providing a silicon substrate, preparing a passivation layer on the surface of the silicon substrate; transferring a conductive paste onto the passivation layer; transporting the silicon substrate with the conductive paste to a drying device to dry and shape the conductive paste; sintering and curing the dried and shaped conductive paste to form grid lines. The drying device can volatilize some solvents in the conductive paste, dry and plastify the conductive paste, reduce the possibility of the conductive paste spreading in the width direction, and thus can limit the width of the grid lines after sintering and curing, reduce the occlusion of the light-receiving surface of the photovoltaic cell by the grid lines, and can also improve the surface flatness of the grid lines and the conductivity of the grid lines, which is beneficial to improving the power generation efficiency of the photovoltaic cell. The drying process evaporates some solvents in the conductive paste, can shorten the time required for sintering and curing, and improve the production efficiency of the photovoltaic cell. Description of the Drawings

[0034] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following will briefly introduce the drawings required for the embodiments. Obviously, the drawings in the following description are only some embodiments of the present application. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained according to these drawings.

[0035] Figure 1 It is a schematic structural diagram of the photovoltaic cell provided by the embodiment of the present application;

[0036] Figure 2 It is a flowchart of the preparation process of the photovoltaic cell provided by the embodiment of the present application;

[0037] Figure 3 It is a schematic structural diagram of the transfer film provided by the embodiment of the present application;

[0038] Figure 4Schematic diagram during the transfer of the conductive paste in the embodiment of the present application;

[0039] Figure 5 Schematic diagram of one embodiment during the drying of the conductive paste in the embodiment of the present application;

[0040] Figure 6 Schematic diagram of another embodiment during the drying of the conductive paste in the embodiment of the present application;

[0041] Figure 7 Schematic diagram of another embodiment during the drying of the conductive paste in the embodiment of the present application;

[0042] Figure 8 Schematic diagram during the sintering of the conductive paste in the embodiment of the present application.

[0043] Reference numerals:

[0044] 1 - Photovoltaic cell;

[0045] 11 - Silicon substrate;

[0046] 12 - Passivation layer;

[0047] 13 - Conductive paste;

[0048] 14 - Grid line;

[0049] 15 - Doped layer;

[0050] 2 - Drying device;

[0051] 21 - Nozzle;

[0052] 22 - Heating table;

[0053] 23 - Lighting structure;

[0054] 24 - Detection part;

[0055] 3 - Transfer film;

[0056] 31 - Accommodating groove;

[0057] 4 - Sintering and curing equipment;

[0058] 41 - Carrying platform;

[0059] 42 - Probe. Detailed implementation manners

[0060] For a better understanding of the technical solutions of the present application, the embodiments of the present application will be described in detail below with reference to the accompanying drawings.

[0061] It should be clear that the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in the field without creative work are within the scope of protection of the present application.

[0062] The terms used in the embodiments of the present application are only for the purpose of describing specific embodiments, and are not intended to limit the present application. The singular forms "a", "said" and "the" used in the embodiments of the present application and the appended claims are also intended to include plural forms, unless the context clearly indicates other meanings.

[0063] It should be understood that the term "and / or" used in this article is only a description of the association relationship of associated objects, indicating that there can be three relationships. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. In addition, the character " / " in this article generally indicates that the associated objects before and after are in an "or" relationship.

[0064] like Figure 1 As shown, the embodiment of the present application provides a photovoltaic cell 1, which includes a silicon substrate 11, on which a doping layer 15 is arranged, and the doping layer 15 forms a PN junction on the silicon substrate 11, so that electrical energy can be generated in the photovoltaic cell 1. A passivation layer 12 is arranged on the doping layer 15, which can reduce surface recombination and improve the passivation effect of the photovoltaic cell 1, so as to improve the power generation efficiency of the photovoltaic cell 1. A plurality of gate lines 14 are arranged at intervals on the passivation layer 12, and the gate lines 14 are electrically connected to the doping layer 15, so that electrical energy can be extracted through the gate lines 14.

[0065] The present application does not limit the structure of the battery cell. The types of battery cells include but are not limited to Passivated Emitter Rear Cell (PERC), Tunnel Oxide Passivated Contact (TOPCon), Heterojunction with Intrinsic Thin-film (HJT), etc.

[0066] For PERC cells, along the thickness direction, PERC cells include front surface metal silver electrode, front surface silicon nitride passivation layer, phosphorus layer emitter, P-type silicon substrate, local aluminum back field, metal aluminum back electrode, back passivation layer (Al2O3 / SiNx). PERC cells use a passivation film to passivate the back, replacing the full aluminum back field, enhancing the internal back reflection of light in the silicon base, reducing the recombination rate on the back, and increasing the efficiency of the cell by 0.5%-1%.

[0067] For a TOPCon cell, along its thickness direction, the TOPCon cell sequentially includes a metallic silver electrode, a front surface silicon nitride passivation layer, a boron-doped emitter, an N-type silicon substrate, a diffusion doping layer, an ultrathin silicon oxide, doped polysilicon, silicon nitride, and a metallic silver electrode. The back surface of the cell is composed of an ultrathin silicon oxide (1 nm - 2 nm) and a phosphorus-doped microcrystalline amorphous hybrid Si film, and the two together form a passivated contact structure. This structure can block the recombination of minority carriers (holes), improving the open-circuit voltage and short-circuit current of the cell. The ultrathin oxide layer allows majority carriers (electrons) to tunnel into the polysilicon layer while blocking the recombination of minority carriers (holes). The good passivation effect of the ultrathin silicon oxide and the heavily doped silicon film causes the energy band on the silicon wafer surface to bend, thus forming a field passivation effect, significantly increasing the probability of electron tunneling, decreasing the contact resistance, improving the open-circuit voltage and short-circuit current of the cell, and thus improving the conversion efficiency of the cell.

[0068] For an HJT cell, along its thickness direction, the HJT cell sequentially includes a front-side low-temperature silver electrode, a front-side conductive film, an N-type amorphous silicon film, an intrinsic amorphous silicon film, an N-type substrate silicon layer, an intrinsic amorphous silicon film, a P-type amorphous silicon film, a back-side conductive film, and a back-side low-temperature silver electrode.

[0069] As Figure 1 shown, the grid line 14 is disposed on the light-receiving surface of the photovoltaic cell 1, and the width of the grid line 14 is 3 μm to 10 μm.

[0070] Sunlight enters the PN junction from the light-receiving surface of the photovoltaic cell 1. In the PN junction, holes in the N-type semiconductor move towards the P-type region, and electrons in the P-type region move towards the N-type region, thereby forming a current from the N-type region to the P-type region and forming a potential difference in the PN junction, constituting a power source. The grid line 14 is located on the light-receiving surface of the photovoltaic cell 1, and the width of the grid line 14 is less than or equal to 10 μm, so that the shielding area of the grid line 14 on the light-receiving surface is small, which can improve the light absorption efficiency of the photovoltaic cell 1 and is beneficial to improving the power generation efficiency of the photovoltaic cell 1. The grid line 14 collects carriers in the silicon substrate 11 and conducts the current generated in the photovoltaic cell 1. The width of the grid line 14 is greater than or equal to 3 μm, which can increase the cross-sectional area of the grid line 14, thereby reducing the resistance of the grid line 14 itself, reducing the power consumption of the grid line 14, and at the same time increasing the contact area between the grid line 14 and the silicon substrate 11, facilitating the collection of carriers in the silicon substrate 11 and being beneficial to improving the power generation efficiency of the photovoltaic cell 1. Therefore, the width of the grid line 14 can be 3 μm, 6 μm, 10 μm, etc., so that the grid line 14 can have good electrical conductivity and reduce the shielding of the grid line 14 on the light-receiving surface to improve the power generation efficiency of the photovoltaic cell 1.

[0071] As Figure 1 shown, the height of the grid line 14 is h, the width is w, and the aspect ratio of the grid line 14 is 60% to 100%.

[0072] To reduce the shielding of the light-receiving surface of the photovoltaic cell 1 by the grid line 14, in the embodiments of the present application, the width of the grid line 14 is limited so that the width of the grid line 14 is 3 μm to 10 μm. Increasing the aspect ratio of the grid line 14 can increase the cross-sectional area of the grid line 14 and improve the conductive effect of the grid line 14. If the aspect ratio of the grid line 14 is less than 60%, the cross-sectional area of the grid line 14 is small, resulting in an increase in the resistance of the grid line 14 itself, an increase in the consumed electrical energy, and thus a reduction in the power generation efficiency of the photovoltaic cell 1. If the aspect ratio of the grid line 14 is greater than 100%, the height of the grid line 14 is relatively high, which will lead to a small contact area between the grid line 14 and the silicon substrate 11, an increase in the contact resistance, and an increase in the manufacturing difficulty of the photovoltaic cell 1. Therefore, the aspect ratio of the grid line 14 can be 60%, 80%, 100%, etc., to reduce the resistance of the grid line 14 and improve the power generation efficiency of the photovoltaic cell 1.

[0073] As Figures 2 to 8 shown, the embodiments of the present application also provide a preparation process for the photovoltaic cell 1 for preparing the above-mentioned photovoltaic cell 1. The preparation process includes:

[0074] S1. Provide the silicon substrate 11 and prepare a passivation layer 12 on the surface of the silicon substrate 11;

[0075] S2. Transfer the conductive paste 13 onto the passivation layer 12;

[0076] S3. Transfer the silicon substrate 11 with the conductive paste 13 to the drying device 2 to dry and shape the conductive paste 13;

[0077] S4. Sinter and solidify the dried and shaped conductive paste 13 to form the grid line 14.

[0078] After the conductive paste 13 is transferred onto the passivation layer 12, part of the solvent in the conductive paste 13 is volatilized by the drying device 2, and the conductive paste 13 is dried and shaped, which can reduce the possibility of the conductive paste 13 spreading in the width direction, facilitate restricting the width of the grid line 14, reduce the shielding of the light-receiving surface of the photovoltaic cell 1 by the grid line 14, improve the power generation efficiency of the photovoltaic cell 1, and can also improve the flatness of the surface of the grid line 14. After sintering and solidifying, the bonding force and conductive efficiency between the grid line 14 and the silicon substrate 11 can be improved. The drying process evaporates part of the solvent in the conductive paste 13, which can shorten the time required for sintering and solidifying and improve the production efficiency of the photovoltaic cell 1.

[0079] As Figure 3 and Figure 4 shown, in a possible embodiment, the conductive paste 13 can be transferred onto the passivation layer 12 by laser transfer technology. The transfer device includes a transfer film 3, and a receiving groove 31 is provided on the transfer film 3 to receive the conductive paste 13. When transferring the conductive paste 13 onto the passivation layer 12, the preparation process includes:

[0080] S21. Fill the conductive paste 13 into the receiving groove 31;

[0081] S22. Invert the transfer film 3 onto the surface of the silicon substrate 11, with the opening of the receiving groove 31 facing the silicon substrate 11;

[0082] S23. The laser emitting device emits the first laser, causing the first laser to sweep the transfer film 3, so that the conductive paste 13 escapes and falls onto the passivation layer 12.

[0083] The conductive paste 13 can be filled into the receiving groove 31 by a squeegee, which is convenient for restricting the size and shape of the conductive paste 13, and can also improve the consistency of the height and width of multiple grid lines 14 in the photovoltaic cell 1. Multiple receiving grooves 31 are arranged at intervals on the transfer film 3, and the distance between adjacent receiving grooves 31 can be determined according to the distance between the required grid lines 14 in the photovoltaic cell 1. The conductive paste 13 is filled into the receiving groove 31, enabling the transfer film 3 to control the distance between adjacent conductive pastes 13 transferred onto the passivation layer 12, thereby controlling the distance between adjacent grid lines 14 in the photovoltaic cell 1.

[0084] Invert the transfer film 3 on the surface of the silicon substrate 11, and align the opening of the receiving groove 31 with the position where the grid line 14 needs to be set, so that the conductive paste 13 can fall to the preset position after escaping from the receiving groove 31.

[0085] The transfer film 3 is made of a transparent material. When the first laser irradiates the transfer film 3, it can heat the transfer film 3 and the conductive paste 13. The conductive paste 13 expands due to heat, and the conductive paste 13 can escape from the receiving groove 31 under the action of steam pressure and fall onto the passivation layer 12.

[0086] In a possible embodiment, along the direction from the opening to the bottom wall of the receiving groove 31, the cross-sectional area of the receiving groove 31 gradually decreases, making the cross-section of the receiving groove 31 trapezoidal, which is convenient for filling the conductive paste 13 into the receiving groove 31. After inverting the transfer film 3 onto the surface of the silicon substrate 11, it is convenient for the conductive paste 13 in the receiving groove 31 to escape, which is beneficial to reducing the preparation difficulty of the photovoltaic cell 1.

[0087] In a possible embodiment, the conductive paste 13 includes a solvent, and the solvent content is 4% to 7%.

[0088] The conductive paste 13 includes silver powder, glass oxide, organic resin, solvent, etc. The solvent acts as a carrier, enabling the other components in the conductive paste 13 to be uniformly mixed, and can also adjust the fluidity of the conductive paste 13, facilitating the transfer of the conductive paste 13. The content of the solvent in the conductive paste 13 is greater than or equal to 4%, enabling the components in the conductive paste 13 to be more uniformly fused, and can also improve the fluidity of the conductive paste 13, facilitating the filling of the conductive paste 13 into the receiving groove 31 of the transfer film 3 and also facilitating the transfer of the conductive paste 13 to the passivation layer 12. The solvent content in the conductive paste 13 is less than or equal to 7%, which can limit the fluidity of the conductive paste 13. After the conductive paste 13 is transferred to the passivation layer 12, it can reduce the possibility of the conductive paste 13 spreading to both sides, facilitating the control of the width of the gate line 14. Therefore, the solvent content in the conductive paste 13 can be 4%, 5%, 6%, 7%, etc.

[0089] In a possible embodiment, the solvent of the conductive paste 13 includes a release agent, which facilitates the removal of the conductive paste 13 from the receiving groove 31 of the transfer film 3, is beneficial to improving the production efficiency of the photovoltaic cell 1, and is also beneficial to improving the flatness of the surface of the conductive paste 13 transferred to the passivation layer 12.

[0090] In a possible embodiment, when drying and shaping the conductive paste 13, the evaporation amount of the solvent in the conductive paste 13 is less than or equal to 30% of the total amount of the solvent.

[0091] During the sintering and curing process of the conductive paste 13 to form the gate line 14, the glass oxide in the conductive paste 13 melts and corrodes the passivation layer 12 on the surface of the silicon substrate 11, enabling the silver powder to form an ohmic contact with the silicon substrate 11, reducing the resistance between the silicon substrate 11 and the gate line 14, so as to improve the power generation efficiency of the photovoltaic cell 1. During the drying and shaping stage, if the evaporation amount of the solvent in the conductive paste 13 is less than or equal to 30% of the total amount of the solvent, it can reduce the possibility of the solvent completely evaporating prematurely during the sintering process, and can reduce the possibility of the organic resin in the conductive paste 13 carbonizing to form impurities. Furthermore, it can reduce the resistance between the gate line 14 and the silicon substrate 11, which is beneficial to improving the power generation efficiency of the photovoltaic cell 1. It can also reduce the problems of collapse and uneven width at the edge of the gate line 14 after sintering and curing, reducing the resistance of the gate line 14 itself, which is beneficial to improving the power generation efficiency of the photovoltaic cell 1. Therefore, during the drying and shaping, the evaporation amount of the solvent can be 30%, 20%, 10%, etc. of the total amount of the solvent.

[0092] Such as Figure 5As shown, in a possible embodiment, the conductive paste 13 can be dried by blowing air. The drying device 2 includes a plurality of nozzles 21. When drying and shaping the conductive paste 13, the plurality of nozzles 21 are located on the side of the silicon substrate 11 where the conductive paste 13 is provided, and the air flow ejected from the nozzles 21 blows towards the silicon substrate 11. The plurality of nozzles 21 are arranged in an array, and the distance d between adjacent nozzles 21 is less than or equal to 2 mm, which can improve the uniformity of the air flow blowing towards the silicon substrate 11, is beneficial to improving the drying uniformity of different positions of the conductive paste 13, and improves the surface flatness of the conductive paste 13.

[0093] When drying and shaping the conductive paste 13, the preparation process includes:

[0094] S31. The nozzles 21 eject an air flow, the temperature of the air flow is 20°C to 30°C, the wind speed is 2 m / s to 4 m / s, and the purging time of the air flow is 3 s to 5 s.

[0095] When the nozzles 21 move to the surface of the silicon substrate 11, the air outlet ends of the nozzles 21 are located between adjacent conductive pastes 13, so that the air flow ejected from the nozzles 21 can purge the side walls of the conductive paste 13, which is convenient for reducing the possibility of the conductive paste 13 diffusing along the width direction, and at the same time can also avoid the air flow directly blowing towards the conductive paste 13 and affecting the conductive paste 13.

[0096] The temperature, wind speed, and purging time of the air flow will affect the evaporation amount of the solvent in the conductive paste 13. The temperature of the air flow can be 20°C, 25°C, 30°C, etc., the wind speed can be 2 m / s, 3 m / s, 4 m / s, etc., and the purging time of the air flow can be 3 s, 4 s, 5 s, etc., which can cause the solvent in the conductive paste 13 to evaporate, reduce the possibility of the conductive paste 13 diffusing to both sides, and can also control the evaporation amount of the solvent in the conductive paste 13, so that the evaporation amount of the solvent is less than or equal to 30% of the total amount of the solvent, reduce the possibility of damage to the grid line 14 after sintering and curing, and is beneficial to improving the power generation efficiency of the photovoltaic cell 1.

[0097] To reduce the possibility of the conductive paste 13 diffusing along the width direction, and to enable the evaporation amount of the solvent in the conductive paste 13 to be less than 30% of the total amount.

[0098] As Figure 6 As shown, in a possible embodiment, the conductive paste 13 can be dried by heating. The drying equipment includes a heating table 22, which can heat the silicon substrate 11 placed on the heating table 22. When drying and shaping the conductive paste 13, the preparation process includes:

[0099] S32. Transfer the silicon substrate 11 with the conductive paste 13 to the heating table 22;

[0100] S33. Raise the temperature of the heating stage 22 to 40°C to 60°C, and the heating time is 2 s to 4 s.

[0101] After the silicon substrate 11 with the conductive paste 13 is transferred to the heating stage 22, the side without the conductive paste 13 contacts the heating stage 22. The temperature of the heating stage 22 can be conducted to the conductive paste 13 through the silicon substrate 11, causing the solvent in the conductive paste 13 to volatilize, thereby reducing the possibility of the conductive paste 13 spreading in the width direction. The temperature and heating time of the heating stage 22 affect the amount of solvent volatilized in the conductive paste 13. The temperature of the heating stage 22 can be 40°C, 50°C, 60°C, etc., and the heating time can be 2 s, 3 s, 4 s, etc., so that the solvent in the conductive paste 13 volatilizes, reducing the possibility of the conductive solvent spreading to both sides in the width direction. Furthermore, the width of the grid line 14 can be controlled, reducing the possibility that the grid line 14 blocks a large area of the light-receiving surface of the photovoltaic cell 1. It can also limit the amount of solvent volatilized so that the amount of solvent volatilized is less than or equal to 30% of the total amount of solvent, reducing the possibility of damage to the grid line 14 after sintering and curing, which is beneficial to improving the power generation efficiency of the photovoltaic cell 1.

[0102] In a possible embodiment, the temperature uniformity error at each position in the heating stage 22 is within ±0.5°C.

[0103] Place the silicon substrate 11 with the conductive paste 13 on the heating stage 22. By heating, the solvent in the conductive paste 13 volatilizes. The temperature uniformity error at each position in the heating stage 22 is within ±0.5°C, which can reduce the heating degree of the conductive paste 13 at different positions, reduce the amount of solvent volatilized from the conductive paste 13 at different positions. After sintering and curing, it can improve the uniformity of the morphology of the grid line 14, reduce the resistance of the grid line 14 itself, and also improve the uniformity of the bonding strength between each position in the grid line 14 and the silicon substrate 11, which is beneficial to improving the power generation efficiency of the photovoltaic cell 1.

[0104] As Figure 7 shown, in a possible embodiment, the conductive paste 13 can be dried by light irradiation. The drying device 2 includes a light irradiation structure 23, and the light irradiation structure 23 can be a high-power LED light source or an ultraviolet lamp. The light emitted by the light irradiation structure 23 irradiates the conductive paste 13, which can cause partial solvent in the conductive paste 13 to volatilize. When drying and shaping the conductive paste 13, the preparation process includes:

[0105] S34. The wavelength of the light is 365 nm to 450 nm, the light intensity is 100 mW / cm 2 to 300 mW / cm 2 , and the light irradiation time is 1 s to 3 s.

[0106] To facilitate the removal of the conductive paste 13 from the transfer film 3, the solvent of the conductive paste 13 includes a release agent, and the release agent is a photosensitive material. The wavelength of the light emitted by the light illumination structure 23 is between 365 nm and 450 nm, and the light intensity is between 100 mW / cm 2 and 300 mW / cm 2 which can volatilize the release agent in the solvent to reduce the fluidity of the conductive paste 13. If the light illumination time is less than 1 s, the volatilization amount of the release agent is small, making it easy for the conductive paste 13 to diffuse along the width direction. When a high-power LED light source or ultraviolet lamp irradiates the conductive paste 13, the temperature of the conductive paste 13 will also increase. If the light illumination time is less than or equal to 3 s, it can reduce the possibility of the temperature of the conductive paste 13 being too high, reduce the volatilization amount of the solvent, make the volatilization amount of the solvent less than or equal to 30% of the total amount of the solvent, and reduce the possibility of damage to the sintered grid line 14, which is beneficial to improving the power generation efficiency of the photovoltaic cell 1.

[0107] Such as Figures 5 to 7 shown, in a possible embodiment, the drying device 2 includes a detector 24 for detecting the temperature and humidity of the environment around the silicon substrate 11. The detector 24 can be located on the side of the silicon substrate 11 or at the bottom of the silicon substrate 11, facilitating the detection of the temperature and humidity of the environment where the silicon substrate 11 is located.

[0108] The detector 24 can monitor the temperature and humidity of the environment around the silicon substrate 11 in real time, and control the drying method of the conductive paste 13 according to the data detected by the detector 24, so as to improve the drying efficiency of the conductive paste 13 and the production efficiency of the photovoltaic cell 1.

[0109] After the conductive paste 13 is transferred to the passivation layer 12, the silicon substrate 11 is transported to the heating table 22 of the drying device 2. The drying method of the conductive paste 13 can be any one or any combination of two or all three of blowing drying, heating drying, and light illumination drying. The detector 24 can be set on the surface of the heating table 22. After the silicon substrate 11 is transported to the heating table 22, it is located on the side of the detector 24. The detector 24 can also be set in the installation groove of the heating table 22. After the silicon substrate 11 is transported to the heating table 22, the detector 24 is located at the bottom of the silicon substrate 11, so as to facilitate the detection of the temperature and humidity of the environment around the silicon substrate 11.

[0110] According to the temperature and humidity detected by the detector 24, the drying parameters of the conductive paste 13 can be adjusted to improve the drying efficiency of the conductive paste 13. Taking the drying method of air blowing as an example, after the silicon substrate 11 is transferred to the heating table 22, the heating table 22 is not heated, and a plurality of nozzles 21 blow air flow to the conductive paste 13. If the detector 24 detects that the temperature of the environment around the silicon substrate 11 is lower than the preset value and the humidity is higher than the preset value, it is necessary to increase the temperature and / or wind speed of the air flow blown by the nozzles 21 to increase the drying rate of the conductive paste 13. If the detector 24 detects that the temperature of the environment around the silicon substrate 11 is higher than the preset value and the humidity is lower than the preset value, it is necessary to reduce the temperature and / or wind speed of the air flow blown by the nozzles 21 to reduce the possibility that the solvent evaporation amount in the conductive paste 13 is greater than 30%. Similarly, in the drying method of heating and drying, if the temperature detected by the detector 24 is lower than the preset value and the humidity is higher than the preset value, it is necessary to increase the heating temperature of the heating table 22. If the temperature detected by the detector 24 is higher than the preset value and the humidity is lower than the preset value, it is necessary to reduce the heating temperature of the heating table 22; in the drying method of light drying, if the temperature detected by the detector 24 is lower than the preset value and the humidity is higher than the preset value, it is necessary to increase the intensity and / or irradiation time of the light of the light structure 23. If the temperature detected by the detector 24 is higher than the preset value and the humidity is lower than the preset value, it is necessary to reduce the intensity and / or irradiation time of the light of the light structure 23. Through the above adjustment method, the humidity of the environment around the conductive paste 13 is kept below 5%, and the drying time of the conductive paste 13 is 3s to 5s.

[0111] According to the temperature and humidity detected by the detector 24, the drying method required when the conductive paste 13 is dried can be adjusted. Taking the drying method of air blowing as an example, after the silicon substrate 11 is transferred to the heating table 22, the heating table 22 is not heated, and a plurality of nozzles 21 blow air flow to the conductive paste 13. If the detector 24 detects that the temperature of the environment around the silicon substrate 11 is lower than the preset value and the humidity is higher than the preset value, the temperature of the heating table 22 can be increased to combine the air blowing drying method and the heating drying method. If at this time the detector 24 detects that the temperature of the environment around the silicon substrate 11 depends on the preset value and the humidity is higher than the preset value, the light structure 23 can also be turned on to combine the air blowing drying method, the heating drying method and the light drying method. Similarly, according to the temperature and humidity detected by the detector 24, any two drying methods can be combined, or three drying methods can be combined. Through the above adjustment method, the humidity of the environment around the conductive paste 13 is kept below 5%, and the drying time of the conductive paste 13 is 3s to 5s.

[0112] As Figure 8 shown, in a possible embodiment, the sintering and curing device 4 includes a carrier table 41 and a plurality of probes 42, and the dried and shaped conductive paste 13 is sintered and cured by laser enhanced contact optimization technology. When sintering and curing the dried and shaped conductive paste 13, the preparation process includes:

[0113] S41. Place the silicon substrate 11 on the carrier stage 41, and bring the probe 42 into contact with the end of the conductive paste 13.

[0114] S42. The laser emission device emits a second laser, causing the second laser to sweep across the conductive paste 13, and at the same time, the probe 42 applies a deflection voltage to the silicon substrate 11.

[0115] Utilizing the photoluminescence phenomenon, by irradiating the silicon substrate 11 with the second laser, the power of the second laser being 18 W to 25 W, charge carriers in the silicon substrate 11 are excited. At the same time, a deflection voltage of more than 10 V is applied through the probe 42, causing local current to initiate sintering, enabling the silver powder in the conductive paste 13 to diffuse with the silicon substrate 11, which can reduce the contact resistance between the gate line 14 and the silicon substrate 11, and is beneficial to improving the power generation efficiency of the photovoltaic cell 1. Sintering and curing the conductive paste 13 in the above manner can reduce the temperature during curing, reduce the damage to the passivation layer 12, and is beneficial to increasing the open-circuit voltage of the photovoltaic cell 1.

[0116] When the conductive paste 13 is transferred from the transfer film 3 to the passivation layer 12, it is necessary to sweep the transfer film 3 with the first laser. When the conductive paste 13 is sintered and cured, it is necessary to sweep the conductive paste 13 with the second laser. Since the functions of the first laser and the second laser are different, their powers are also different. The power of the first laser is 10 W to 50 W to transfer the conductive paste 13 to the passivation layer 12, and the power of the second laser is 18 W to 25 W to sinter and cure the conductive paste 13 into the gate line 14. The first laser and the second laser can be emitted by the same laser emission device, and the laser power emitted by the laser emission device can be adjusted according to different steps, which can simplify the production device of the photovoltaic cell 1.

[0117] This application relates to a preparation process of a photovoltaic cell 1 and the photovoltaic cell 1. The preparation process includes: providing a silicon substrate 11, preparing a passivation layer 12 on the surface of the silicon substrate 11; transferring a conductive paste 13 onto the passivation layer 12; transporting the silicon substrate 11 with the conductive paste 13 to the drying device 2 to dry and shape the conductive paste 13; sintering and curing the dried and shaped conductive paste 13 to form a gate line 14. The drying device 2 can volatilize some of the solvents in the conductive paste 13, dry and plasticize the conductive paste 13, which can reduce the possibility of the conductive paste 13 diffusing in the width direction, and thus can limit the width of the gate line 14 after sintering and curing, reduce the occlusion of the light-receiving surface of the photovoltaic cell 1 by the gate line 14, and can also improve the surface flatness of the gate line 14 and the conductivity of the gate line 14, which is beneficial to improving the power generation efficiency of the photovoltaic cell 1. The drying process evaporates some of the solvents in the conductive paste 13, which can shorten the time required for sintering and curing and improve the production efficiency of the photovoltaic cell 1.

Claims

1. A process for preparing a photovoltaic cell, characterized in that: The preparation process comprises: Providing a silicon substrate (11), and preparing a passivation layer (12) on the surface of the silicon substrate (11); Transferring a conductive paste (13) onto the passivation layer (12); The silicon substrate (11) carrying the conductive paste (13) is transported to a drying device (2) to dry and shape the conductive paste (13); The dried and shaped conductive paste (13) is sintered and solidified to form gate lines (14).

2. The process for preparing a photovoltaic cell according to claim 1, characterized in that: The drying device (2) comprises a plurality of nozzles (21), the plurality of nozzles (21) are arranged in an array, the spacing between adjacent nozzles (21) is less than or equal to 2 mm, and is located on a side of the silicon substrate (11) on which the conductive paste (13) is provided, and when the conductive paste (13) is dried and shaped, the preparation process comprises: The nozzle (21) blows out an airflow, wherein the temperature of the airflow is 20° C. to 30° C. and the wind speed is 2 m / s to 4 m / s; The purge time of the air flow is 3s to 5s.

3. The process for preparing a photovoltaic cell according to claim 1, characterized in that: The drying device (2) comprises a heating platform (22), and when the conductive paste (13) is dried and shaped, the preparation process comprises: Transferring the silicon substrate (11) with the conductive paste (13) to the heating stage (22); Raising the temperature of the heating stage (22) to 40°C to 60°C; The heating time is 2s to 4s.

4. The photovoltaic cell preparation process according to claim 3, characterized in that: The temperature uniformity error at each position in the heating stage (22) is within ±0.5°C.

5. The process for preparing a photovoltaic cell according to claim 1, characterized in that: The drying device (2) comprises an illumination structure (23), and the light emitted by the illumination structure (23) is irradiated onto the conductive paste (13) transferred onto the passivation layer (12). When the conductive paste (13) is dried and fixed, the preparation process comprises: The wavelength of the light is 365nm to 450nm, and the intensity is 100mW / cm 2 Up to 300mW / cm 2 ; The illumination time is 1s to 3s.

6. The process for preparing a photovoltaic cell according to claim 1, characterized in that: The drying device (2) comprises a detection component (24), wherein the detection component (24) is located on one side of the silicon substrate (11) to detect the temperature and humidity of the environment surrounding the silicon substrate (11).

7. The process for preparing a photovoltaic cell according to claim 1, characterized in that: The conductive paste (13) comprises a solvent, and the content of the solvent in the conductive paste (13) is 4% to 7%.

8. The process for preparing a photovoltaic cell according to claim 7, characterized in that: When the conductive paste (13) is dried and fixed, the volatilization amount of the solvent is less than or equal to 30% of the total amount of the solvent.

9. The process for preparing a photovoltaic cell according to claim 1, characterized in that: The transfer device for the conductive paste (13) comprises a transfer film (3), the transfer film (3) comprises a receiving groove (31), and when the conductive paste (13) is transferred onto the passivation layer (12), the preparation process comprises: Filling the conductive paste (13) into the containing groove (31); Placing the transfer film (3) upside down on the surface of the silicon substrate (11), so that the opening of the receiving groove (31) faces the silicon substrate (11); The laser emitting device emits a first laser, and the first laser scans the transfer film (3), causing the conductive paste (13) to come off and fall onto the passivation layer (12).

10. The process for preparing a photovoltaic cell according to claim 9, characterized in that: The sintering and curing device (4) for sintering and curing the conductive paste (13) comprises a carrier platform (41) and a plurality of probes (42). When the conductive paste (13) after drying and curing is sintered and cured, the preparation process comprises: Placing the silicon substrate (11) on the carrier platform (41), and the probe (42) in contact with the end of the conductive paste (13); The laser emitting device emits a second laser, which scans the conductive paste (13), while the probe (42) applies a deflection voltage to the silicon substrate (11).

11. The process for preparing a photovoltaic cell according to claim 10, characterized in that: The power of the second laser is different from the power of the first laser.

12. A photovoltaic cell, characterized in that: The photovoltaic cell (1) comprises a silicon substrate (11), a passivation layer (12) is provided on the surface of the silicon substrate (11), a plurality of gate lines (14) are arranged at intervals on the passivation layer (12), and the width of the gate lines (14) is 3 μm to 10 μm.

13. The photovoltaic cell according to claim 9, characterized in that: The height-to-width ratio of the gate line (14) is 60% to 100%.

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