Production method of photovoltaic cell

Abstract

The invention provides a production method of a photovoltaic cell. The production method comprises the following steps: printing an electrode on the surface of a cell piece; carrying out sintering treatment on the battery piece after the electrode is printed; the sintered battery piece is cut; passivating the side surface of the cut battery piece to form a passivation layer; and carrying out multiple times of optical auxiliary treatment on the battery piece, wherein the multiple times of optical auxiliary treatment comprises carrying out at least one time of laser auxiliary sintering treatment on the passivated battery piece. In the production method, multiple times of optical auxiliary treatment can meet different process requirements by setting process parameters step by step, defects generated in the sintering and cutting processes are fully repaired, carrier recombination is reduced, and the photoelectric conversion efficiency is improved.

Description

Technical Field

[0001] The present application relates to the technical field of photovoltaic cells, and in particular to a method for producing photovoltaic cells. Background Art

[0002] Photovoltaic cells, also known as solar cells, are devices that use light energy to generate electricity. They are typically made of semiconductor materials. When light strikes the cell's surface, photons excite electrons within the semiconductor material, generating an electric current. Therefore, photovoltaic cells are the core device for photoelectric conversion. Continuously improving the photoelectric conversion efficiency of photovoltaic cells is one of the core goals of the photovoltaic industry, and the efficiency of photovoltaic cells is highly dependent on the optimization of the production process.

[0003] In existing technology, photovoltaic cells are typically produced through a series of steps, including electrode printing, high-temperature sintering, cutting, edge passivation, and laser repair. However, after sintering or during cutting, numerous dangling bonds and lattice defects can form within the cell or along the cut edges. Due to the lack of effective in-situ repair mechanisms, these microscopic defects cannot be fully repaired in subsequent processes, leading to increased carrier recombination and a significant reduction in cell conversion efficiency. Summary of the Invention

[0004] In view of this, the present application provides a new method for producing photovoltaic cells, which can reduce carrier recombination and thus improve the photoelectric conversion efficiency of photovoltaic cells.

[0005] Specifically, the present application provides a method for producing photovoltaic cells, which includes: printing electrodes on the surface of the cell; sintering the cell after printing the electrodes; cutting the sintered cell; passivating the side of the cut cell to form a passivation layer; and performing multiple optical assisted treatments on the cell, wherein the multiple optical assisted treatments include at least one laser assisted sintering treatment on the passivated cell.

[0006] The production method provided in the present application performs multiple optical assisted treatments on the cell, which includes performing at least one laser assisted sintering treatment on the passivated cell. In the case of multiple optical assisted treatments, the multiple optical assisted treatments can meet different process requirements by setting process parameters in steps, fully repair the defects generated during sintering and cutting, reduce carrier recombination, and improve the photoelectric conversion efficiency. In addition, the second optical assisted treatment can adjust the process purpose according to the structural adaptability obtained after the first optical assisted treatment, expand the window of process adjustment, and can perform multiple lighter optical assisted treatments to avoid damage to the solar cell caused by excessive laser or bias voltage energy during a single treatment process. In the process of performing at least one laser assisted sintering treatment on the passivated cell, the laser can cover the electrode and the passivation layer at the same time. It ensures that the electrode can form a good ohmic contact with the cell, and the laser irradiation of the passivation layer can anneal the passivation layer to a certain extent, thereby improving the passivation degree of the passivation layer on the cut edge, reducing the damage to the cell at the cut edge, and thereby reducing the recombination of the produced cell at the cut edge, and improving the photoelectric conversion efficiency of the produced cell.

[0007] In some embodiments, the multiple optical auxiliary treatments further include: performing at least one optical repair on the cell, wherein the at least one optical repair is performed after the sintering treatment and / or after the passivation treatment.

[0008] In some embodiments, the multiple optically assisted processes include two laser-assisted sintering processes, which include: (1) synchronously applying a first laser and a first bias voltage to the passivated cell to perform a first laser-assisted sintering process; and (2) synchronously applying a second laser and a second bias voltage to the cell after the first laser-assisted sintering process to perform a second laser-assisted sintering process.

[0009] In some embodiments, the power of the first laser is less than or equal to the power of the second laser, and the first bias voltage is less than or equal to the second bias voltage.

[0010] In some embodiments, the power of the first laser is 25-45W, and the first bias voltage is 10-25V.

[0011] In some embodiments, the power of the second laser is 25-45W, and the second bias voltage is 10-25V.

[0012] In some embodiments, multiple optically assisted treatments include a laser-assisted sintering treatment and an optical repair, which include: (1) synchronously applying a third laser and a third bias voltage to the passivated cell to perform a laser-assisted sintering treatment; (2) applying a first light source to the cell after the laser-assisted sintering treatment to perform an optical repair; wherein the power of the third laser is less than the power of the first light source, and the wavelength of the first light source is in the ultraviolet band.

[0013] In some embodiments, the multiple optically assisted treatments include an optical repair and a laser-assisted sintering treatment, which include: (1) applying a second light source to the cell after the sintering treatment to perform an optical repair; (2) synchronously applying a third laser and a third bias voltage to the passivated cell to perform a laser-assisted sintering treatment; wherein the power of the third laser is less than the power of the second light source, and the wavelength of the second light source is in the ultraviolet band.

[0014] In some embodiments, the passivation process includes forming a passivation layer on both the cut surface and the non-cut surface of the side surface of the cell.

[0015] In some embodiments, the non-cut surface comprises the original side of the cell opposite the cut surface.

[0016] In some embodiments, the non-cut surface also includes one or two original side surfaces of the cell adjacent to the cut surface.

[0017] In some embodiments, the production method further comprises: performing a light-injection hydrogenation treatment on the cell after the sintering treatment.

[0018] In some embodiments, the light injection hydrogenation treatment includes: (1) heating the cell to 150-700°C; (2) applying a light intensity of 3-10 standard solar constants to the heated cell for 20-200 seconds to complete the light injection; and (3) cooling the cell after light injection to room temperature.

[0019] In some embodiments, the passivation treatment method is atomic layer deposition, wherein the deposition temperature is greater than 200°C. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the following is a brief introduction to the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other implementation plans can be obtained based on these drawings without paying any creative work.

[0021] Figure 1 A flow chart of a photovoltaic cell preparation process according to some embodiments of the present application is shown.

[0022] Figure 2 A top view of the structure of a battery cell produced by the production method provided in the present application according to some embodiments of the present application is shown.

[0023] Figure 3 A three-dimensional diagram showing the structure of a battery cell produced by the production method provided in this application according to some embodiments of the application is shown.

[0024] Among them, 1 is a battery cell, 11 is an electrode, 12 is a side surface, 121 is a cutting surface, 122 is a non-cutting surface, and 13 is a passivation layer. DETAILED DESCRIPTION

[0025] The present application will be described clearly and completely below in conjunction with the embodiments and drawings of the present application. Obviously, the embodiments described are only part of the embodiments of the present application, rather than all of the embodiments. All other embodiments that can be obtained by a person of ordinary skill in the art based on the embodiments in the present application are within the scope of protection of the present application.

[0026] In this application, the terms "first" and "second" are used solely to describe features for descriptive purposes and should not be understood to indicate or imply relative importance or implicitly specify the quantity of the technical features being described. Features specified as "first" or "second" may explicitly or implicitly include at least one of the specified features. It is understood that "at least one" includes one or more, and "plurality" generally means at least two, such as two, three, four, five, six, etc., unless otherwise specifically defined.

[0027] In this application, unless otherwise specified or limited, terms such as "mounted," "connected," "connect," and "fixed" should be interpreted broadly. For example, they can refer to fixed connections, removable connections, or integration; mechanical connections, electrical connections, direct connections, or indirect connections through an intermediary; and internal connections between two components or interactions between two components. Those skilled in the art will understand the specific meanings of these terms in this application based on the specific circumstances.

[0028] In this application, the terms "one embodiment", "some embodiments", "an example", "some examples", "examples", "specific examples" or "some examples" mean that the specific features, structures, materials or characteristics described in conjunction with the embodiment, example or example are included in at least one embodiment, example or example of the present application. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment, example or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments, examples or examples in a suitable manner. In addition, those skilled in the art may combine and combine different embodiments, examples or examples described in this specification and features of different embodiments, examples or examples, unless they are mutually inconsistent.

[0029] As mentioned above, in the production of photovoltaic cells, due to the lack of an effective in-situ repair mechanism, defects caused by high temperatures or physical damage such as sintering and cutting cannot be fully repaired in subsequent processes, resulting in intensified carrier recombination and ultimately a significant decrease in cell conversion efficiency.

[0030] Therefore, the present application provides a method for producing a photovoltaic cell ( Figure 1 ), the production method includes: printing an electrode 11 on the surface of a battery cell 1; sintering the battery cell 1 after printing the electrode 11; cutting the sintered battery cell 1; and passivating the side surface 12 of the cut battery cell to form a passivation layer 13.

[0031] Figure 1 The order of the steps in the production method shown is for illustrative purposes only and does not limit the production method. Those skilled in the art may adjust the order of the steps based on actual production needs or adjust the order of certain steps without affecting the technical effect. Such variations are within the scope of protection of the present invention.

[0032] In the above-described production method, during the step of printing electrodes 11, electrodes 11 are typically formed by screen printing a conductive paste on the surface of battery cell 1. The conductive paste typically contains metal particles such as silver and aluminum. Electrodes 11 are used to collect the current generated by battery cell 1 and conduct it to an external circuit.

[0033] After printing the electrode 11, the cell 1 needs to be sintered. This sintering process removes volatile organic solvents from the conductive paste while simultaneously melting and diffusing the metal particles, forming a stable ohmic contact (e.g., an Ag-Si eutectic) with the silicon substrate. This ensures low contact resistance and high adhesion between the electrode 11 and the silicon substrate, ensuring current collection and transmission. However, during the sintering process, uneven heating of the silicon wafer may occur locally, leading to microcracks or lattice distortions such as dislocations. Furthermore, during the sintering process, metal particles such as silver and aluminum in the conductive paste may diffuse into the silicon substrate or dope the conductive layer, replacing silicon atoms and forming metal impurity defects (e.g., Ag-Si or Al-Si complexes). Furthermore, high-temperature sintering can generate thermal stress, which can break silicon-silicon bonds and form dangling bonds, increasing the carrier recombination rate and reducing the photoelectric conversion efficiency.

[0034] After sintering, the sintered cell 1 can be cut to reduce current loss caused by large-sized cells 1. Cutting into smaller cells 1 can also improve module reliability and increase the flexibility of photovoltaic cell layout. The cell 1 can be cut by mechanical cutting methods such as diamond wire cutting or laser cutting. However, cutting breaks the covalent bonds (Si-Si) between silicon atoms, resulting in defects such as dangling bonds and impurity contamination on the cut surface 121 or surface. These defects can become carrier recombination centers, resulting in an increase in the carrier recombination rate, thereby reducing the photoelectric conversion efficiency.

[0035] After the cutting process, the side surface 12 of the cut cell 1 can be passivated to form a passivation layer 13. Specifically, the passivation layer 13 is formed by atomic layer deposition or chemical vapor deposition. In some embodiments, the material of the passivation layer 13 can be SiN x The passivation layer 13 can, for example, reduce defects in the cell 1, lower the surface recombination rate, and improve the photoelectric conversion efficiency by chemical bonding (such as forming saturated bonds Si-H and Si-O).

[0036] In some embodiments, the thickness of the passivation layer 13 is 10-200 nm, for example, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 110, 120, 130, 140, 150, 160, 170, 180, 190, or 200 nm. If the passivation layer 13 is too thin, the passivation effect of the passivation layer 13 will be poor, and carrier recombination will not be effectively suppressed, resulting in limited improvement in open circuit voltage and photoelectric conversion efficiency. If the passivation layer 13 is too thick, it will not only increase material consumption and process costs, but may also introduce additional optical losses and mechanical stress. Controlling the thickness of the passivation layer 13 within the above range can ensure sufficient passivation of the cell 1, especially the cut surface 121, while balancing cost-effectiveness, thereby maximizing the overall performance of the photovoltaic cell.

[0037] In some embodiments, the passivation process includes forming a passivation layer 13 on both the cut surface 121 and the non-cut surface 122 of the cell 1 . Figure 3 The illustration shows the passivation layer formed only on cut surface 121. In existing technologies, the passivation process only repairs the cut locations of the cell. However, the uncut surfaces 122 are also critical areas for charge recombination. Due to their small and exposed edges, they are more susceptible to defects and impurities, becoming recombination centers for electron-hole pairs, leading to an increased recombination rate and current loss. By simultaneously passivating both cut and uncut surfaces 121, 122 of the cell 1, defects in the cell 1 can be further reduced, the surface recombination rate can be lowered, and the photovoltaic conversion efficiency can be improved without significantly increasing process complexity.

[0038] In some embodiments, the non-cut surface 122 includes the original side surface of the cell 1 opposite the cut surface 121. It is understood that the original side surface refers to the side surface of the cell 1 before cutting, and the cell 1 generally has four sides. The passivation treatment of the cut surface 121 of the cell 1 and the original side surface opposite the cut surface 121 can be performed simultaneously in the same process step.

[0039] In some embodiments, the non-cut surface 122 also includes one or two original side surfaces of the cell 1 adjacent to the cut surface 121. Preferably, the non-cut surface 122 also includes two original side surfaces adjacent to the cut surface 121. Such a method can achieve full passivation of the side surfaces of the cell 1, minimize the recombination rate of the surface, and improve the photoelectric conversion efficiency. Passivation of one or two original side surfaces adjacent to the cut surface can be performed in the same process step as the cut surface, or an additional passivation layer deposition step can be added. This can be selected based on the actual process flow and tooling conditions and is not limited here.

[0040] In some embodiments, as Figure 2 and Figure 3As shown, the passivation layer 13 extends over the surface adjacent to the cut surface 121 of the cell 1. In some embodiments, the length L of the passivation layer 13 extending over the surface adjacent to the cut surface 121 of the cell 1 satisfies the following relationship: 1 mm ≤ L ≤ 3 mm. For example, the length L can be 1 mm, 1.3 mm, 1.5 mm, 1.8 mm, 2 mm, 2.3 mm, 2.5 mm, 3 mm, etc. The length L of the passivation layer 13 extending on the surface adjacent to the cut surface 121 of the cell 1 should not be too long or too short. If the length L of the passivation layer 13 extending on the surface adjacent to the cut surface 121 of the cell 1 is too short (for example, shorter than 1 mm), the passivation effect of the passivation layer 13 on the edge of the cut surface 121 may be poor. If the length L of the passivation layer 13 extending on the surface adjacent to the cut surface 121 of the cell 1 is too long (for example, longer than 3 mm), the passivation layer 13 may contact the auxiliary grid 112, affecting the connection between the auxiliary grid 112 and the cell 1. At the same time, the passivation layer 13 increases the shielding of the light-receiving surface of the cell 1, which may also reduce the photoelectric conversion efficiency of the cell 1. Therefore, the length L of the passivation layer 13 extending on the surface adjacent to the cut surface 121 of the cell 1 should be set within a reasonable range.

[0041] The above-mentioned production method also includes performing multiple optical-assisted treatments on the cell 1, wherein the multiple optical-assisted treatments include performing at least one laser-assisted sintering treatment on the passivated cell 1. The optical-assisted treatment performed in stages enables the appropriate process parameters to be adjusted separately during each optical-assisted treatment to meet the annealing function of the electrodes and the front, back and side passivation layers of the cell. In addition, the second optical-assisted treatment can adjust the process purpose according to the structural adaptability obtained after the first optical-assisted treatment, expand the window for process adjustment, and can perform multiple lighter optical-assisted treatments to avoid damage to the solar cell caused by excessive laser or bias voltage energy during a single treatment. Multiple optical-assisted treatments including performing at least one laser-assisted sintering treatment on the passivated cell 1 can ensure that the electrode can form a good ohmic contact with the cell, and have a certain annealing effect on the passivation layer of the cell, thereby improving the passivation performance of the passivation layer.

[0042] In some embodiments, the laser power and bias voltage applied in each of the at least one laser-assisted sintering process are smaller than the laser power and bias voltage applied in a single laser-assisted sintering process in the prior art.

[0043] In some embodiments, when multiple laser-assisted sintering treatments are performed, the laser power and bias voltage applied in the first laser-assisted sintering treatment are less than the laser power and bias voltage applied in the second laser-assisted sintering treatment, and the laser power and bias voltage applied in each subsequent laser-assisted sintering treatment (if any) are less than or equal to the laser power and bias voltage applied in the previous laser-assisted sintering treatment.

[0044] In some embodiments, the laser used in the laser-assisted sintering process can be green light or red light. For example, when the laser is green light, the wavelength of the laser is 532 nm; when the laser is red light, the wavelength of the laser is 1064 nm.

[0045] Laser is a high-energy excitation light source that can be applied to different processes in the preparation of solar cells. By applying laser and bias voltage to the solar cell, high-intensity laser is irradiated on the cell 1 to excite carriers, and bias voltage is applied at the same time to generate local current. By applying bias voltage to the solar cell, carriers can be guided to move in a directional manner, generating local Joule heat at the metal-semiconductor interface, which can trigger mutual diffusion of metal and silicon between the electrode and the solar cell, improve the ohmic contact between the electrode and the solar cell, and reduce the contact resistance between the electrode and the solar cell. Alternatively, by applying laser to the solar cell to anneal the passivation layer 13, the passivation degree of the passivation layer 13 on the cut edge can be improved, reducing damage to the solar cell at the cut edge, thereby reducing the recombination of the produced solar cell at the cut edge, and improving the photoelectric conversion efficiency of the produced solar cell.

[0046] In some embodiments, the multiple optically assisted treatments include two laser-assisted sintering treatments, which include: (1) synchronously applying a first laser and a first bias voltage to the passivated cell 1 to perform a first laser-assisted sintering treatment; (2) synchronously applying a second laser and a second bias voltage to the cell 1 after the first laser-assisted sintering treatment to perform a second laser-assisted sintering treatment.

[0047] Multiple laser-assisted sintering processes can result in a more uniform formation of metal particles (such as silver-silicon alloy particles, silver particles, aluminum-silicon alloy particles, or aluminum particles). The second or more laser-assisted sintering processes, on the one hand, generate localized high temperatures at locations below the electrode where metal particles have not formed after the first laser-assisted sintering process, promoting the formation of metal particles and resulting in a more uniform distribution of metal crystals below the electrode. On the other hand, they can prevent the continuous growth of metal particles from the same nucleation site during a single laser-assisted sintering process, which could lead to excessively large metal particles and damage the doped semiconductor layer (doped polycrystalline silicon layer, diffusion layer formed on the silicon substrate surface, or doped amorphous silicon layer), thereby further improving the photoelectric conversion efficiency. Multiple low-energy sintering processes promote the formation of more small, uniform metal particles, ensuring good conductivity while avoiding damage to the semiconductor layer. Furthermore, the laser in multiple laser-assisted sintering processes can repeatedly irradiate the passivation layer at the cut edge, enhancing the degree of improvement in the passivation performance of the passivation layer.

[0048] In some embodiments, the power of the first laser is less than or equal to the power of the second laser, and the first bias voltage is less than or equal to the second bias voltage.

[0049] In the above two laser-assisted sintering treatments, the first treatment is a pretreatment step, and its power (i.e., the power of the first laser) and bias voltage (i.e., the first bias voltage) are respectively smaller than the power (i.e., the power of the second laser) and bias voltage (i.e., the second bias voltage) of the second treatment. The relatively low laser power in the first treatment can avoid the formation of too many alloy sites, thereby effectively protecting the passivation layer 13, reducing the surface recombination velocity, and forming the characteristics of high opening voltage of the battery. In addition, the relatively low bias voltage can provide a weak electric field to assist the metal ions to move to the silicon surface, generating local Joule heat, but will not trigger a violent alloying reaction, thus avoiding Avoid forming too many alloy sites; on the basis of the first treatment, apply a second treatment that is equal to or higher but still within the appropriate process window, the second laser power and the second bias voltage can generate local high temperature at the position where metal particles are not formed under the electrode cover after the first treatment, and promote the formation of metal particles, so that the metal crystals under the electrode 11 are more evenly distributed, and can also steadily widen the alloy contact points generated by the first treatment, such as silver-silicon alloy contact points, to ensure good ohmic contact with the silicon substrate, but without excessive diffusion, promote the directional migration and local alloying of metal ions, and further reduce the contact resistance. Multiple low-energy sintering can promote the formation of more small and uniform metal particles, which not only ensures good conductivity but also avoids damage to the semiconductor layer. In addition, the laser in the multiple laser-assisted sintering treatments can irradiate the passivation layer 13 at the cutting edge position multiple times, and the thermal effect of the laser can enhance the passivation performance of the passivation layer 13.

[0050] It should be noted that the electric field directions of the first bias voltage and the second bias voltage applied to the solar cell are the same and opposite to the electric field direction of the PN junction on the solar cell.

[0051] In some embodiments, the power of the first laser is 25-45 W, such as 25, 27, 30, 33, 35, 38, 40, 42, 45 W, and the first bias voltage is 10-25 V, such as 10, 12, 15, 17, 20, 22, 25 V.

[0052] In some embodiments, the power of the second laser is 25-50W, such as 25, 27, 30, 33, 35, 38, 40, 42, 45, 47, 50W, and the second bias voltage is 10-25V, such as 10, 12, 15, 17, 20, 22, 25V.

[0053] In some embodiments, the multiple optically assisted treatments include two laser-assisted sintering treatments, which include: (1) synchronously applying a first laser and a first bias voltage to the sintered cell 1 to perform a first laser-assisted sintering treatment; (2) synchronously applying a second laser and a second bias voltage to the cell 1 after the first laser-assisted sintering treatment and the passivation treatment to perform a second laser-assisted sintering treatment. In the above two laser-assisted sintering treatments, the first laser-assisted sintering treatment after sintering the electrode can improve the ohmic contact between the electrode 11 and the silicon substrate, and the second laser-assisted sintering treatment after the slice passivation can further reduce the contact resistance between the electrode and the silicon substrate. In addition, the laser in the second laser-assisted sintering treatment can repair the damage and defects caused to the cell by the high-temperature treatment during the passivation process, and irradiate the passivation layer 13 at the cutting edge. The thermal effect of the laser can enhance the passivation performance of the passivation layer 13.

[0054] In some embodiments, multiple optically assisted treatments further include: performing N laser-assisted sintering treatments on the cell 1 after the second laser-assisted sintering treatment, wherein each laser-assisted sintering treatment includes synchronously applying a laser and a bias voltage, and wherein the power and bias voltage of the laser applied in the Nth laser-assisted sintering treatment are both less than or equal to the power and bias voltage of the laser applied in the N-1th laser-assisted sintering treatment, and wherein N ≥ 3. For example, when N = 3, the laser power of the third laser-assisted sintering treatment is ≤ the laser power of the second laser-assisted sintering treatment, and the bias voltage of the third laser-assisted sintering treatment is ≤ the bias voltage of the second laser-assisted sintering treatment, and so on, which will not be repeated here. By at least one treatment, the contact performance can be further optimized, defects can be repaired, the fault tolerance of the production method can be improved, and the contact resistance can be reduced. In the present application, N is an integer greater than or equal to 3, such as 3, 4, 5, 6, 7, 8, 9, 10.

[0055] In some embodiments, the multiple optical auxiliary treatments further include: performing at least one optical repair on the cell 1 , wherein the at least one optical repair is performed after the sintering treatment and / or after the passivation treatment.

[0056] In some embodiments, the at least one optical repair is two optical repairs.

[0057] It can be understood that in the present application, multiple optically assisted treatments must include at least one laser-assisted sintering treatment performed directly on the passivated cell 1 after the passivation treatment, and may also include at least one optical repair. The at least one optical repair can be performed directly on the sintered cell 1 after the sintering treatment, or can be performed directly on the passivated cell 1 after the passivation treatment, and / or can be performed on the cell 1 after at least one laser-assisted sintering treatment after the passivation treatment.

[0058] In some embodiments, optical repair includes ultraviolet light repair, which includes applying a light source with a wavelength in the ultraviolet band to the photovoltaic cell 1. In some embodiments, ultraviolet light repair is performed by irradiating the photovoltaic cell surface directly above the photovoltaic cell at a distance of 5 to 10 cm from the photovoltaic cell for an irradiation time of 0.5 to 3 seconds.

[0059] In some embodiments, the wavelength of the light source in the ultraviolet band is 280-400 nm, for example, 280, 300, 320, 340, 360, 380, 400 nm. In some embodiments, the power of the light source applied for ultraviolet light repair is 20-60 W, for example, 20, 25, 30, 35, 40, 45, 50, 55, 60 W.

[0060] It can be understood that UV repair uses high-power, high-energy UV light to irradiate solar cells. The UV light energy will excite a large number of electron-hole pairs, and the local carrier concentration will increase significantly, which helps to reduce the recombination loss of carriers inside the battery. In addition, the defect states caused by overall or local high-temperature treatment inside the battery are excited to jump to higher energy levels, changing the electronic structure of the defects and reducing the recombination effect of the defects on carriers, thereby improving the photoelectric conversion efficiency of the produced battery cell 1 to a certain extent.

[0061] In some embodiments, multiple optically assisted treatments include a laser-assisted sintering treatment and an optical repair, which include: (1) synchronously applying a third laser and a third bias voltage to the passivated cell 1 to perform a laser-assisted sintering treatment; (2) applying a first light source to the cell 1 after the laser-assisted sintering treatment to perform an optical repair; wherein the power of the third laser is less than the power of the first light source, and the wavelength of the first light source is in the ultraviolet band.

[0062] In some embodiments, the power of the third laser is 25-45 W, for example, 25, 27, 30, 33, 35, 38, 40, 42, or 45 W, and the third bias voltage is 10-25 V, for example, 10, 12, 15, 17, 20, 22, or 25 V. In some embodiments, the power of the first light source is 20-60 W, for example, 20, 25, 30, 35, 40, 45, 50, 55, or 60 W.

[0063] During the multiple optically assisted treatments described above, a laser-assisted sintering treatment is performed by applying a bias voltage and laser light, thereby increasing the temperature of the electrode-covered area, causing a large number of metal particles, such as Ag and Si, to melt and form an alloy, thereby enhancing the ohmic contact between the electrode 11 and the cell 1. Then, an optical repair process is performed, which utilizes a high-power, high-energy ultraviolet light source to irradiate the solar cell. The energy of the ultraviolet light source excites a large number of electron-hole pairs, significantly increasing the local carrier concentration, which helps to reduce carrier recombination losses within the cell. Furthermore, defect states within the cell caused by the overall or local high-temperature treatment are excited to transition to higher energy levels, changing the electronic structure of the defects and reducing the effect of the defects on carrier recombination. This, to a certain extent, repairs the damage to the solar cell caused by the local high temperature during the first laser-assisted sintering process, and improves the passivation degree of the passivation layer 13 on the cut edge, thereby reducing damage to the cell 1 at the cut edge. This, in turn, reduces recombination at the cut edge of the produced cell 1, thereby improving the photoelectric conversion efficiency of the produced cell 1.

[0064] In some embodiments, the multiple optically assisted treatments include an optical repair and a laser-assisted sintering treatment, which include: (1) applying a second light source to the cell 1 after sintering to perform an optical repair; (2) synchronously applying a fourth laser and a fourth bias voltage to the passivated cell 1 to perform a laser-assisted sintering treatment; wherein the power of the second light source is greater than the power of the fourth laser, and the wavelength of the second light source is in the ultraviolet band.

[0065] In some embodiments, the power of the fourth laser is 25-45 W, for example, 25, 27, 30, 33, 35, 38, 40, 42, or 45 W, and the fourth bias voltage is 10-25 V, for example, 10, 12, 15, 17, 20, 22, or 25 V. In some embodiments, the power of the second light source is 20-60 W, for example, 20, 25, 30, 35, 40, 45, 50, 55, or 60 W.

[0066] It should be noted that the laser-assisted sintering process in the above technical solution can also be performed more times according to the actual battery process and battery status, for example, two laser-assisted sintering processes can be performed before or after optical repair.

[0067] Furthermore, regarding the arrangement of the laser or other light source, it is understandable that the surface of the solar cell can be irradiated by surface scanning or line scanning, wherein the surface scanning method can directly and simultaneously irradiate the front and side surfaces of the solar cell, covering the gate lines and the passivation layer at the edge; the line scanning method can first irradiate the electrode 11 and then the passivation layer 13, or can first irradiate the passivation layer 13 and then the electrode 11. In addition, when two sets of laser or light source emitting devices are provided, the two sets of laser or light source emitting devices can irradiate the electrode 11 and the passivation layer 13 with lasers at the same time. More specifically, the laser emitting device is capable of emitting laser light to irradiate the electrode 11 or the passivation layer 13. The laser emitted by the laser emitting device forms light spots arranged in the same direction on the cell 1. When the electrode 11 is irradiated with laser, multiple light spots of the laser are arranged along the length direction of the electrode 11, and the multiple light spots of the laser are tangent to or intersect with the electrode 11.

[0068] In some embodiments, the above production method further comprises: after the sintering process, performing a light injection hydrogenation process on the cell 1. It is understood that light injection hydrogenation refers to activating hydrogen atoms in the passivation layer on the front and back sides of the cell 1 by increasing the temperature. Under high temperature conditions, the high energy of light injection causes the activated H ions to migrate from the passivation layer to the doped semiconductor layer or silicon substrate, so that dangling bonds or defect states on the surface of the doped semiconductor layer or silicon substrate can be saturated with the activated H ions, thereby completing interface passivation.

[0069] It should be noted that the passivation layers on the front and back of the cell 1 include a single layer or a stacked layer structure of one or more of aluminum oxide, silicon nitride, silicon oxynitride, etc. The passivation layer structures on the front and back can be the same or different and are not specifically limited here.

[0070] In some embodiments, the light injection hydrogenation treatment includes: (1) heating the cell 1 to 150-700°C; (2) applying a light intensity of 3-10 standard solar constants to the heated cell 1 for 20-200 seconds to complete the light injection; and (3) cooling the cell 1 after light injection to room temperature.

[0071] During the light injection hydrogenation process, the cell 1 is heated to 150-700° C., for example, 150, 200, 300, 400, 500, 600, or 700° C. The temperature increase can activate hydrogen atoms in the passivation layer 13 , such as a silicon nitride layer, formed during the passivation process of the cell 1 .

[0072] During the light injection hydrogenation process, the heated cell 1 is exposed to light at an intensity of 3-10, for example, 3, 4, 5, 6, 7, 8, 9, or 10, standard solar constants for 20-200 seconds, for example, 20, 30, 40, 50, 60, 70, 80, 90, 100, 110, 120, 130, 140, 150, 160, 170, 180, 190, or 200 seconds, to complete the light injection. Light irradiation can be used to manipulate the atomic valence state, causing H atoms to combine with recombination centers (defects) in the emitter and substrate to form non-recombination centers, thereby reducing carrier recombination.

[0073] In some embodiments, the light source for light injection hydroprocessing is an LED.

[0074] In the present application, the light-injection hydrogenation treatment can be performed after any step after the sintering process, such as after the sintering process, after the cutting process, after the passivation process, after the optical repair process, and / or after the laser-assisted sintering process, to further repair any unrepaired defects that may exist, reduce carrier recombination, and improve the photoelectric conversion efficiency. Preferably, the light-injection hydrogenation treatment is performed after the sintering process and before the cutting process, as the improvement in the photoelectric conversion efficiency is more significant when the light-injection hydrogenation treatment is performed at this time.

[0075] In some embodiments, the production method further comprises: printing glue dots on the front and / or back of the photovoltaic cell before the photovoltaic cell is passivated. It is understood that in order to improve production efficiency, multiple cells 1 are usually stacked together for passivation treatment. When the photovoltaic cell is a back-contact cell, since the front surface is a smooth surface, when stacked together in this way, the front surface of the lower cell 1 will be scratched by the electrode 11 on the back surface of the upper cell 1. Therefore, before the photovoltaic cell is passivated, glue dots are printed on the front and / or back of the photovoltaic cell to avoid direct contact between the electrode 11 on the back surface of the cell 1 and the front surface of the cell 1, thereby improving the reliability of the production method.

[0076] In some embodiments, the glue dots may be UV glue, light-curing glue, etc. Of course, other glue commonly used in the art may also be used, and this application does not limit this. Those skilled in the art may select as needed, as long as the purpose of this application can be achieved.

[0077] In some embodiments, the photovoltaic cell is a TOPCon cell, in which the passivation treatment is performed by atomic layer deposition. The deposition temperature is above 200°C. Furthermore, the temperature of the atomic layer deposition is 200-400°C, for example, 200, 220, 240, 260, 280, 300, 320, 340, 360, 380, 400°C. The manufacturing process of the TOPCon cell is compatible with high-temperature processes, so atomic layer deposition at a high temperature of more than 200°C can be used to deposit the passivation layer 13 for passivation treatment. Applying multiple optical auxiliary treatments to the TOPCon cell after high-temperature treatment can better repair the damage caused to the cell at high temperature and improve cell efficiency.

[0078] Atomic layer deposition (ALD) is a thin film growth technology based on self-limiting surface chemical reactions. It deposits materials layer by layer (with atomic-level precision) on the substrate surface by alternating the introduction of precursor gases. High-temperature atomic layer deposition above 200°C can promote the full reaction of the precursor gases, reduce defects in the deposited passivation layer 13, and form a denser passivation layer 13. Under high temperature conditions, ALD precursor byproducts (such as CH4) or subsequently deposited passivation layers 13, such as SiN x The hydrogen (H) in the H passivation layer 13 diffuses more easily into defects, saturating dangling bonds, reducing recombination centers, and improving photoelectric conversion efficiency. Furthermore, in the above-described production method, laser-assisted sintering is also required after the passivation process. The high-temperature deposited passivation layer 13 can prevent failure at the high temperatures of the subsequent laser-assisted sintering process.

[0079] The above is only a preferred implementation scheme of the present application and is not intended to limit the present application. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present application should be included in the scope of protection of the present application.

Claims

1. A method for producing a photovoltaic cell, characterized in that: The production method comprises: Printing electrodes on the surface of the battery cell; Sintering the battery cells after printing electrodes; Cutting the sintered battery cells; Passivating the sides of the cut cells to form a passivation layer; and The cell is subjected to multiple optical auxiliary treatments, wherein the multiple optical auxiliary treatments include at least one laser-assisted sintering treatment on the passivated cell. The multiple optical auxiliary treatments further include: performing at least one optical repair on the cell, wherein the at least one optical repair is performed after the sintering treatment and / or after the passivation treatment.

2. The production method according to claim 1, characterized in that The multiple optically assisted processes include two laser-assisted sintering processes, which include: (1) synchronously applying a first laser and a first bias voltage to the passivated cell to perform a first laser-assisted sintering process; (2) A second laser and a second bias voltage are synchronously applied to the cell after the first laser-assisted sintering process to perform a second laser-assisted sintering process.

3. The production method according to claim 2, characterized in that The power of the first laser is less than or equal to the power of the second laser, and the first bias voltage is less than or equal to the second bias voltage.

4. The production method according to claim 2, characterized in that The power of the first laser is 25-45W, and the first bias voltage is 10-25V; And / or the power of the second laser is 25-45W, and the second bias voltage is 10-25V.

5. The production method according to claim 1, characterized in that The multiple optically assisted processes include a laser-assisted sintering process and an optical repair process, which include: (1) synchronously applying a third laser and a third bias voltage to the passivated cell to perform a laser-assisted sintering process; (2) Applying a first light source to the cell after the laser-assisted sintering process to perform an optical repair; The power of the third laser is less than the power of the first light source, and the wavelength of the first light source is in the ultraviolet band.

6. The production method according to claim 1, characterized in that The multiple optically assisted processes include one optical repair process and one laser-assisted sintering process, which include: (1) Applying a second light source to the sintered cell to perform an optical repair; (2) synchronously applying a fourth laser and a fourth bias voltage to the passivated cell to perform a laser-assisted sintering process; The power of the second light source is greater than the power of the fourth laser, and the wavelength of the second light source is in the ultraviolet band.

7. The production method according to claim 1, characterized in that The passivation treatment includes forming a passivation layer on both the cut surface and the non-cut surface of the side surface of the battery cell.

8. The production method according to claim 7, characterized in that The non-cutting surface includes the original side surface of the battery cell opposite to the cutting surface; And / or, the non-cutting surface further includes one or two original side surfaces of the battery cell adjacent to the cutting surface.

9. The production method according to claim 1, characterized in that The production method further comprises: after the sintering process, performing a light injection hydrogenation process on the cell; the light injection hydrogenation process comprises: (1) Heating the cell to 150-700°C; (2) Apply a light intensity of 3-10 standard solar constants to the heated cell for 20-200 seconds to complete light injection; (3) Cool the cell to room temperature after light injection.

10. The production method according to claim 1, characterized in that The passivation treatment method is atomic layer deposition, wherein the deposition temperature is greater than 200°C.

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