Cell string fabrication method, cell string, and photovoltaic module

Abstract

The present application relates to a cell string fabrication method, a cell string, and a photovoltaic module. The cell string fabrication method comprises the following steps: providing a semiconductor substrate; performing metallization on the semiconductor substrate, so as to obtain cells; connecting the cells to a connecting member, so as to obtain a cell string precursor; and performing an illumination treatment on the cell string precursor and simultaneously applying a reverse bias voltage to the cell string precursor. By adding a target photoelectric treatment step, electric current conduction paths can be increased, and the contact between a metal and a semiconductor substrate can be improved, thereby reducing the series resistance of cells, increasing a fill factor of the cells, and improving the photoelectric conversion efficiency.

Description

Preparation method of battery string, battery string and photovoltaic module

[0001] Related applications

[0002] This application claims priority to Chinese patent application No. 202410104307X, filed on January 23, 2024, entitled “Method for preparing battery strings, battery strings and photovoltaic modules,” the entire text of which is hereby incorporated by reference. Technical Field

[0003] The present application relates to the technical field of photovoltaic modules, and in particular to a method for preparing a battery string, a battery string, and a photovoltaic module. Background Art

[0004] Single solar cells need to be connected to form a cell string. The connection process can easily lead to an increase in the series resistance of the cell and a decrease in the fill factor, causing the photoelectric conversion efficiency of the solar cell to decline. Summary of the Invention

[0005] In a first aspect, a method for preparing a battery string comprises the following steps:

[0006] providing a semiconductor substrate;

[0007] Metallization treatment: performing metallization treatment on the semiconductor substrate to obtain a battery cell;

[0008] Cell connection processing: connecting the cell to a connector to obtain a cell string precursor;

[0009] Target photoelectric treatment: performing light treatment on the cell string precursor and simultaneously applying a reverse bias voltage on the cell string precursor.

[0010] In one embodiment, in the target photoelectric processing step, the cell string precursor includes at least one cell; wherein,

[0011] Lighting treatment: setting a light source to illuminate the battery cells in sequence, or setting multiple light sources to illuminate each battery cell respectively;

[0012] Applying a reverse bias voltage: providing a plurality of voltage sources to apply a reverse bias voltage to at least one of the battery cells in the battery string precursor.

[0013] In one embodiment, the spectral wavelength of the light source is 500 nm to 1200 nm.

[0014] In one embodiment, the energy density of the light source is 10 kW / m2 to 10000 kW / m2.

[0015] In one embodiment, the scanning rate of the light source is 26 m / s to 65 m / s.

[0016] In one embodiment, the reverse bias voltage value loaded by the voltage source is equal to the product of the number of the battery cells connected in series with it and the reverse bias voltage value loaded on a single battery cell, wherein the reverse bias voltage loaded on a single battery cell is 10V to 50V.

[0017] In one embodiment, in the metallization step, a conductive material is applied on the semiconductor substrate and sintered and solidified at a low temperature to obtain the cell.

[0018] In one embodiment, the peak temperature of the low temperature sintering ranges from 550°C to 720°C.

[0019] In one embodiment, after the metallization step and before the cell connection step, the following steps are further included:

[0020] Photoelectric pretreatment: the cell is subjected to light treatment and a reverse bias voltage is applied to the cell at the same time.

[0021] In one embodiment, in the photoelectric pretreatment step, the reverse bias voltage is 10V to 50V.

[0022] In one embodiment, the spectral wavelength of the light in the light treatment is 500 nm to 1200 nm.

[0023] In one embodiment, the energy density of light in the light treatment is 10 kW / m2 to 10,000 kW / m2.

[0024] In one embodiment, the scanning rate of the light in the light irradiation treatment is 26 m / s to 65 m / s.

[0025] In one embodiment, after the metallization process step and before the cell connection process step, the method further includes: light injection process on the cell.

[0026] In one embodiment, in the metallization step, a conductive material is applied on the semiconductor substrate and sintered and solidified at a high temperature to obtain a cell.

[0027] In one embodiment, the peak temperature of the high temperature sintering ranges from 780°C to 850°C.

[0028] In one embodiment, after the metallization process step and before the cell connection process step, the method further includes: light injection process on the cell.

[0029] In one embodiment, the light injection processing step of the cell comprises the following steps:

[0030] heating the battery cell once;

[0031] secondary heating the battery cell while irradiating the battery cell with light;

[0032] The peak temperature of the primary heating is 400°C to 600°C, the peak temperature of the secondary heating is 100°C to 300°C, and the energy density of the light is 10kW / m2 to 100kW / m2.

[0033] In one embodiment, the step of providing a semiconductor substrate further comprises the following steps:

[0034] Providing a textured silicon substrate, wherein the silicon substrate is an N-type silicon substrate or a P-type silicon substrate;

[0035] Preparing a functional layer: Preparing a functional layer on the silicon substrate to obtain the semiconductor matrix, wherein the functional layer includes one or more of a doping layer, a passivation layer, a conductive layer, an anti-reflection layer, and a dielectric layer.

[0036] In one embodiment, in the cell connection processing step, the area size of the cell accounts for one or more combinations of 100%, 50%, 25%, 12.5% ​​and 6.25% of the area size of the full cell.

[0037] In one embodiment, in the cell connection processing step, the cell includes a passivated contact solar cell, a heterojunction solar cell, an emitter and back passivated solar cell, a back contact solar cell or a tandem solar cell.

[0038] In a second aspect, a battery string is provided. The battery string is prepared by the method for preparing a battery string according to the first aspect, and the battery string includes a plurality of battery cells connected in at least one of series and parallel.

[0039] In a third aspect, a photovoltaic module comprises a plurality of battery strings connected in at least one of series and parallel, wherein the battery strings are prepared by the preparation method of the battery string in the first aspect. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the conventional technology, the following briefly introduces the drawings required for use in the embodiments or the conventional technology descriptions. Obviously, the drawings described below are merely embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on the disclosed drawings without any creative work.

[0041] FIG1 is a schematic flow chart of a method for preparing a battery string according to one or more embodiments.

[0042] FIG. 2 is a schematic diagram illustrating a processing method of a target light processing step in one or more embodiments.

[0043] FIG. 3 is a schematic diagram illustrating another processing method of the target light processing step in one or more embodiments.

[0044] FIG. 4 is a schematic diagram illustrating another processing method of the target light processing step in one or more embodiments.

[0045] FIG. 5 is a schematic diagram illustrating another processing method of the target light processing step in one or more embodiments.

[0046] Explanation of reference numerals: 10, single-cell battery string; 20, multi-cell battery string; 100, battery cell; 1, light source; 2, voltage source; 3, connector. DETAILED DESCRIPTION

[0047] The following will be combined with the drawings in the embodiments of this application to clearly and completely describe the technical solutions in the embodiments of this application. Obviously, the embodiments described are only part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0048] To make the above-mentioned objects, features, and advantages of the present application more clearly understood, the specific embodiments of the present application are described in detail below with reference to the accompanying drawings. The following description sets forth many specific details to facilitate a full understanding of the present application. However, the present application can be implemented in many other ways than those described herein, and those skilled in the art can make similar improvements without violating the scope of the present application. Therefore, the present application is not limited to the specific embodiments disclosed below.

[0049] In the description of this application, it should be understood that if the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc. appear, the orientation or position relationship indicated by these terms is based on the orientation or position relationship shown in the accompanying drawings, which is only for the convenience of describing this application and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on this application.

[0050] In addition, if the terms "first" or "second" appear, these terms are used for descriptive purposes only and should not be understood to indicate or imply relative importance or implicitly specify the number of technical features indicated. Therefore, a feature specified as "first" or "second" may explicitly or implicitly include at least one of such features. In the description of this application, if the term "plurality" appears, "plurality" means at least two, for example, two, three, etc., unless otherwise specifically defined.

[0051] In this application, unless otherwise specified or limited, the terms "mounted," "connected," "connected," "fixed," etc., should be interpreted broadly. For example, these terms may refer to fixed connections, removable connections, or integration; mechanical connections or electrical connections; direct connections or indirect connections through an intermediary; and internal communication between two components or interaction between two components, unless otherwise specified. Those skilled in the art will understand the specific meanings of these terms in this application based on the specific circumstances.

[0052] In a first aspect, an embodiment of the present application provides a method for preparing a battery string, as shown in FIG1 , comprising the following steps: providing a semiconductor substrate, metallization processing, battery cell connection processing, and target photoelectric processing.

[0053] The metallization step involves metallizing the semiconductor substrate to produce a cell. Specifically, this involves forming metal electrodes on the semiconductor substrate to produce the cell. The cell connection step involves connecting the cell to connectors to produce a cell string precursor. The target photoelectric processing step involves irradiating the cell string precursor with light while simultaneously applying a reverse bias voltage.

[0054] Adding a target photoelectric processing step after the cell connection processing step can promote the broken molten conductive dendrites or conductive particles to re-contact the semiconductor substrate and restore the current conduction path, or make the conductive dendrites or conductive particles that originally had no contact come into contact with the semiconductor substrate to increase the current conduction path, thereby improving the contact between the metal electrode and the semiconductor substrate, thereby reducing the series resistance of the cell, increasing the fill factor of the cell, and alleviating the problem of photoelectric conversion efficiency attenuation caused by the cell connection processing step.

[0055] The following will describe in detail the various steps of the preparation method according to the preparation sequence of the battery string.

[0056] In some embodiments, providing a semiconductor substrate includes the following steps: providing a textured silicon substrate and preparing a functional layer. In the embodiments of the present application, the semiconductor substrate refers to a semi-finished cell without electrodes. The semiconductor substrate includes a silicon substrate and a functional layer provided on the silicon substrate. The silicon substrate is an N-type silicon substrate or a P-type silicon substrate. The functional layer includes one or more of a doping layer, a passivation layer, a conductive layer, an anti-reflection layer, and a dielectric layer. The silicon substrate includes a relative light incident surface and a backlight surface along its own thickness direction, and the functional layer can be provided on at least one of the light incident surface and the backlight surface.

[0057] For example, the doped layer may be lightly doped or heavily doped, and may include lightly doped polysilicon or heavily doped polysilicon. The passivation layer may include polysilicon, silicon oxide, aluminum oxide, etc. The conductive layer may include an indium tin oxide layer, tin oxide, etc.

[0058] In some embodiments, the dielectric layer acts as a barrier to electrons and holes, combining with the polysilicon to prevent minority carriers from passing through. The dielectric layer can also function as a pinhole channel, allowing carriers within the solar cell to move freely. The heavily doped polysilicon selectively channels majority carriers, thus reducing minority carrier recombination losses. Furthermore, the dielectric layer can act as a diffusion barrier to prevent dopants from the doped polysilicon layer from diffusing into the semiconductor substrate.

[0059] The dielectric layer can be made of a variety of dielectric materials, such as at least one of silicon oxide, magnesium fluoride, amorphous silicon, polycrystalline silicon, silicon carbide, silicon nitride, silicon oxynitride, aluminum oxide, or titanium oxide. The dielectric layer can be made of silicon oxide. This is because silicon oxide has excellent passivation properties, minimizing recombination losses of minority carriers on the semiconductor substrate surface, and is a film with excellent durability against subsequent high-temperature processes.

[0060] In order to better provide interface passivation for the substrate, the thickness of the dielectric layer can be 0.1 nm to 5 nm. For example, the thickness of the dielectric layer can be 0.1 nm, 0.5 nm, 1 nm, 1.5 nm, 2 nm, 3 nm, 4 nm, etc. However, the present invention is not limited thereto, and the thickness of the dielectric layer can have various values.

[0061] In the deposition step, for example, a conductive layer and an anti-reflection layer may be deposited on the light incident side of an N-type silicon substrate, while a passivation layer and a conductive layer may be deposited on the backlight side of the N-type silicon substrate. Alternatively, a conductive layer and an anti-reflection layer may be deposited on the light incident side of a P-type silicon substrate, while a passivation layer and a conductive layer may be deposited on the backlight side of the P-type silicon substrate.

[0062] Furthermore, the deposition method may be a combination of one or more of plasma enhanced chemical vapor deposition, atomic layer deposition, or low pressure chemical vapor deposition.

[0063] After the semiconductor substrate is fabricated, metallization is performed to create metal electrodes on the light-incident or backlight-reflecting sides of the semiconductor substrate to form a complete solar cell. For example, in some embodiments, the cell includes a passivated contact solar cell, a heterojunction solar cell, an emitter and back-passivated solar cell, a back-contact solar cell, or a tandem solar cell.

[0064] Exemplarily, the metallization treatment may be performed by screen printing a conductive material and sintering and curing. Screen printing and sintering and curing is the process of printing a conductive material onto a semiconductor substrate to form metal electrodes on the light incident surface and the backlight surface of the semiconductor substrate. The metal electrodes on the light incident surface include main grid lines and auxiliary grid lines, and then the conductive material is sintered and cured to form electrodes. Exemplarily, the conductive material may be silver paste, aluminum paste, or silver-aluminum paste. Sintering and curing may be high-temperature sintering or low-temperature sintering.

[0065] In some embodiments, the peak temperature of the high-temperature sintering is in the range of 780° C. to 850° C. For example, the peak temperature of the high-temperature sintering can be any point within the above range, for example, 780° C., 790° C., 800° C., 810° C., 820° C., 830° C., 840° C., 850° C., etc.

[0066] In some other embodiments, the peak temperature of the low-temperature sintering is in the range of 550° C. to 720° C. For example, the peak temperature of the low-temperature sintering may be any point within the above range, for example, 550° C., 560° C., 570° C., 580° C., 590° C., 600° C., 610° C., 620° C., 630° C., 640° C., 650° C., 660° C., 670° C., 680° C., 690° C., 700° C., 710° C., 720° C., etc.

[0067] In other words, the preparation method of the battery string of the present application can solve the problem of attenuation of photoelectric conversion efficiency caused by increase in series resistance and decrease in fill factor of the battery cells after the battery cell connection processing step, regardless of whether it is for battery cells prepared by high-temperature sintering or low-temperature sintering.

[0068] In some embodiments, after the metallization step and before the cell connection step, a light injection step is performed on the cell. The light injection step is applicable to both high-temperature sintering processes and low-temperature sintering processes.

[0069] In some embodiments, the light injection treatment of the cell includes the following steps: primary heating of the cell; secondary heating of the cell and simultaneous exposure to light. The peak temperature of the primary heating is 400°C to 600°C, the peak temperature of the secondary heating is 100°C to 300°C, and the energy density of the light is 10kW / m² to 100kW / m².

[0070] For example, the peak temperature of the primary heating may be any value within the above range, for example, 400°C, 420°C, 440°C, 460°C, 480°C, 500°C, 520°C, 540°C, 560°C, 580°C, 600°C, etc. The peak temperature of the secondary heating may be any value within the above range, for example, 100°C, 120°C, 140°C, 160°C, 180°C, 200°C, 220°C, 240°C, 260°C, 280°C, 300°C, etc. The energy density of the light may be any value within the above range, for example, 10 kW / m2, 20 kW / m2, 30 kW / m2, 40 kW / m2, 50 kW / m2, 60 kW / m2, 70 kW / m2, 80 kW / m2, 90 kW / m2, 100 kW / m2, etc.

[0071] It should be noted that in the process of screen printing and sintering and curing to make electrodes, both the low-temperature sintering process and the high-temperature sintering process will cause certain metal corrosion damage to the battery cell, which will lead to an increase in the contact resistance between the battery cell and the metal electrode, reduce the open-circuit voltage of the battery cell, and affect the stability of the battery cell and the photoelectric conversion efficiency.

[0072] Based on this problem, in some embodiments, after the electrodes are manufactured by low-temperature sintering and curing, and before the cell connection processing step, a photoelectric pretreatment step is also included: treating the cell with light and simultaneously loading a reverse bias voltage on the cell.

[0073] Photoelectric pretreatment has two functions: first, it mitigates metal corrosion damage caused by low-temperature sintering; second, it allows for efficiency sorting of cells after low-temperature sintering before the cell connection process. For cells with electrodes made by low-temperature sintering, adding a photoelectric pretreatment step can create better contact between the metal electrode and the semiconductor substrate, reducing the series resistance of the cell to a level that satisfies efficiency sorting before the cell connection process.

[0074] During the photoelectric pretreatment step, the built-in electric field of the PN junction is significantly enhanced under the action of reverse bias, and the light causes a large number of electron-hole pairs to be generated inside the semiconductor substrate. A large number of electrons and holes are quickly separated under the action of the electric field, and then accumulate and recombine in the contact interface area between the metal and the semiconductor substrate to generate high heat. Under high heat conditions, local metal and interface silicon are rapidly remelted and crystallized to form metal-silicon alloys (such as silver-silicon alloys), conductive dendrites and conductive particles, which alleviate large-area metal corrosion damage, thereby improving contact performance, helping to reduce contact resistance, increase open circuit voltage and fill factor, and improve the stability of the battery cell and the photoelectric conversion efficiency.

[0075] The present embodiments do not limit the order in which the photovoltaic pretreatment step and the light injection step are performed on cells manufactured by low-temperature sintering and curing. In other words, the photovoltaic pretreatment step can be performed after the metallization step and before the light injection step. Alternatively, the photovoltaic pretreatment step can be performed after the light injection step and before the cell connection step.

[0076] It should be noted that because high-temperature sintering and curing use excessively high temperatures, irreversible metal corrosion damage is caused to the cells. Therefore, the photovoltaic pretreatment step cannot mitigate the metal corrosion damage caused by high-temperature sintering and curing. Cells manufactured through high-temperature sintering and curing are not suitable for photovoltaic pretreatment prior to the cell connection step.

[0077] In some embodiments, during the photoelectric pretreatment step, the reverse bias voltage is 10V to 50V. A voltage within this range can ensure the built-in electric field strength of the cell, providing sufficient energy for carrier sorting. Exemplarily, the reverse bias voltage can be any value within the above range, such as 10V, 20V, 30V, 40V, 50V, etc.

[0078] In some embodiments, the spectral wavelength of the light used in the illumination treatment is between 500 nm and 1200 nm. Spectral wavelengths below or above this range do not match the band gap of the silicon substrate and cannot excite electron-hole pairs within the cell. Exemplarily, the spectral wavelength may be 500 nm, 532 nm, 635 nm, 650 nm, 808 nm, 980 nm, 1064 nm, 1200 nm, etc. In some embodiments, the energy density of the light used in the illumination treatment is between 10 kW / m² and 10,000 kW / m². Exemplarily, the energy density of the light may be any value within the above range, such as 10 kW / m², 100 kW / m², 1,000 kW / m², 2,000 kW / m², 5,000 kW / m², 10,000 kW / m², etc. In some embodiments, the scanning rate of the light used in the illumination treatment is between 26 m / s and 65 m / s. For example, it can be 26m / s, 30m / s, 35m / s, 40m / s, 45m / s, 50m / s, 55m / s, 60m / s, 65m / s, etc.

[0079] Furthermore, in the photoelectric pretreatment step, the illumination treatment can be performed by scanning the cell with a small light spot parallel to the secondary grid lines, or by scanning the cell with a large light spot perpendicular to the secondary grid lines. When scanning with a small light spot, the corresponding reverse bias voltage applied to the cell can be 10V to 20V. When scanning with a large light spot, the corresponding reverse bias voltage applied to the cell can be 15V to 30V. In some cases, those skilled in the art can set a reasonable reverse bias voltage range based on the specific usage scenario.

[0080] After the metallization step, a cell connection step is performed to obtain a cell string precursor. The cell string precursor includes at least one cell that has undergone metallization.

[0081] The cell connection process includes the following optional embodiments, but is not limited to: Referring to FIG2 , when the cell string precursor includes only one cell 100, the cell 100 is connected to the connector 3 to form a single-cell cell string 10. Referring to FIG3 to FIG5 , when the cell string precursor includes multiple cells 100, the connector 3 can be simultaneously connected to multiple cells 100 to form a multi-cell cell string 20; or, after connecting one cell 100 to the connector 3 to form a single-cell cell string 10, multiple single-cell cell strings 10 are then connected to form a multi-cell cell string 20. Optionally, the connector can be a soldering ribbon or conductive adhesive, etc.

[0082] In some embodiments, in the cell connection processing step, the cell includes at least one of a passivated contact solar cell, an emitter back passivated solar cell, and a heterojunction solar cell. The cell may also include a solar cell with a PN junction and a metal electrode arranged on the backlight side of the semiconductor substrate.

[0083] Furthermore, in some embodiments, during the cell connection process, the cell area size accounts for one or more of 100%, 50%, 25%, 12.5%, and 6.25% of the area size of the full cell. In other words, the cell subjected to the cell connection process may be a full cell, a half cell, a quarter cell, a eighth cell, or a sixteenth cell.

[0084] After the cell connection process, target photoelectric processing is performed. Target photoelectric processing refers to irradiating the cell string precursor with light and simultaneously applying a reverse bias voltage to the cell string precursor.

[0085] In some embodiments, in the target photoelectric processing step, the cell string precursor includes at least one cell; wherein the illumination treatment comprises providing a single light source to illuminate the cells sequentially, or providing multiple light sources to illuminate each cell separately. The reverse bias voltage application comprises providing multiple voltage sources to apply a reverse bias voltage to at least one cell in the cell string precursor.

[0086] The plurality of voltage sources may include one or more. When only one voltage source is provided, a reverse bias voltage is applied to both ends of the precursor of the entire string of cells. Alternatively, when multiple voltage sources are provided, each voltage source may apply a reverse bias voltage to each cell. Alternatively, when multiple voltage sources are provided, each voltage source may apply a reverse bias voltage to a portion of the cells.

[0087] The target photoelectric processing steps are specifically described in conjunction with illumination processing and reverse bias voltage application. The following processing methods are provided, but not limited to: Referring to FIG2 , when the cell string precursor includes only one cell 100, the cell string precursor is a single cell string 10. A voltage source 2 and a light source 1 are provided at both ends of the single cell string 10. When the cell string precursor includes multiple cells 100, the cell string precursor is a multi-cell string 20. Referring to FIG3 , a light source 1 can be provided to sequentially illuminate the multiple cells 100, and multiple voltage sources can be provided to apply a reverse bias voltage to each cell 100. Referring to FIG4 , multiple light sources 1 can be provided to illuminate each cell 100 separately, and multiple voltage sources 2 can be provided to apply a reverse bias voltage to each cell 100 separately. Referring to FIG5 , multiple light sources 1 can be provided to illuminate each cell 100 separately, and a voltage source 1 can be provided at both ends of the multi-cell string 20 to apply a reverse bias voltage.

[0088] In some embodiments, the spectral wavelength of the light source is 500 nm to 1200 nm, the energy density of the light source is 10 kW / m² to 10,000 kW / m², and the scanning rate of the light source is 26 m / s to 65 m / s. The spectral wavelength can be any value within the above range. For example, it can be 500 nm, 532 nm, 635 nm, 650 nm, 808 nm, 980 nm, 1064 nm, 1200 nm, etc. The energy density of the light source can be any value within the above range, for example, it can be 10 kW / m², 1000 kW / m², 2000 kW / m², 5000 kW / m², 10,000 kW / m², etc. The scanning rate of the light source is 26 m / s to 65 m / s. For example, it can be 26m / s, 30m / s, 35m / s, 40m / s, 45m / s, 50m / s, 55m / s, 60m / s, 65m / s, etc.

[0089] In some embodiments, the reverse bias voltage value loaded by the voltage source is equal to the product of the number of battery cells connected in series with it and the reverse bias voltage value loaded on a single battery cell, wherein the reverse bias voltage loaded on a single battery cell is 10V to 50V.

[0090] Exemplarily, when multiple voltage sources are set, the multiple voltage sources load a reverse bias voltage on each battery cell respectively, and the reverse bias voltage loaded by each voltage source is 10V to 50V, for example, 10V, 20V, 30V, 40V, 50V, etc.

[0091] In other exemplary embodiments, when multiple voltage sources are provided, each voltage source applies a reverse bias voltage to a portion of the battery cells. The reverse bias voltage applied by each voltage source is equal to the product of the number of battery cells in the portion and the reverse bias voltage applied to a single battery cell, where the reverse bias voltage applied to a single battery cell is between 10V and 50V. The number of battery cells in the portion is less than the total number of battery cells. When the number of battery cells connected in series is two, the reverse bias voltage applied by the voltage source is between 20V and 100V. Furthermore, the reverse bias voltage applied to a single battery cell can be any value within the aforementioned range, for example, 10V, 20V, 30V, 40V, 50V, etc.

[0092] In some further embodiments, when a voltage source is provided, the reverse bias voltage applied by the voltage source is equal to the product of the total number of battery cells connected in series in the battery string precursor and the reverse bias voltage applied to a single battery cell, wherein the reverse bias voltage applied to a single battery cell is 10V to 50V. When the number of battery cells connected in series is 2, the reverse bias voltage applied by the voltage source is 20V to 100V. When the number of battery cells connected in series is 6, the reverse bias voltage applied by the voltage source is 60V to 300V, and so on. Exemplarily, the reverse bias voltage applied to a single battery cell can be any value within the above range, for example, 10V, 20V, 30V, 40V, 50V, etc.

[0093] Furthermore, in the target photoelectric processing step, the illumination treatment can be performed by scanning the cell with a small light spot parallel to the secondary grid lines, or by scanning the cell with a large light spot perpendicular to the secondary grid lines. When scanning with a small light spot, the corresponding reverse bias voltage applied to a cell can be 10V to 20V. When scanning with a large light spot, the corresponding reverse bias voltage applied to a cell can be 15V to 30V. In some cases, those skilled in the art can set a reasonable reverse bias voltage range based on the specific usage scenario.

[0094] It should be emphasized that the series resistance of the cell with metal electrodes made by the low-temperature sintering and curing process is greater than the series resistance after the photoelectric pretreatment, which means that even after the photoelectric pretreatment, the series resistance of the cell will still increase after the cell connection. In order to solve this problem, the applicant found that subjecting the cell to the target photoelectric treatment can not only reduce the series resistance of the cell, but even make the series resistance lower than before the cell connection treatment step. This is because the interface contact conductive dendrites formed during the photoelectric pretreatment are unstable. The conductive dendrites melt or break during the connection process, resulting in contact deterioration, making the metal electrode and the semiconductor substrate in indirect contact, and increasing the series resistance. During the target photoelectric treatment process, local high temperature will re-form contact between the metal electrode and the semiconductor substrate. The location of the re-formed contact may be the original location of the break or other new locations, thereby adding more current conduction paths, thereby further reducing the series resistance of the cell. Therefore, through photoelectric pretreatment, cell connection and target photoelectric treatment, the series resistance can be further reduced on the basis of photoelectric pretreatment, and the contact between the electrode and the silicon substrate can be effectively improved.

[0095] In summary, in some embodiments, the method for preparing a battery string includes at least the following practicable methods:

[0096] In the first embodiment, the following steps are performed in sequence: providing a semiconductor substrate; applying a conductive material and sintering and curing at a high temperature to obtain a cell; connecting the cell; and performing a target photoelectric process.

[0097] In the second embodiment, the following steps are performed in sequence: providing a semiconductor substrate; applying a conductive material and sintering and curing at a high temperature to obtain a cell; light injection processing; cell connection processing; and target photoelectric processing.

[0098] In the third embodiment, the following steps are performed in sequence: providing a semiconductor substrate; applying a conductive material and sintering and curing at a low temperature to obtain a cell; connecting the cell; and performing a target photoelectric process.

[0099] In a fourth embodiment, the following steps are performed in sequence: providing a semiconductor substrate; applying a conductive material and sintering and curing at a low temperature to obtain a cell; photoelectric pretreatment; cell connection treatment; and target photoelectric treatment.

[0100] In a fifth embodiment, the following steps are performed in sequence: providing a semiconductor substrate; applying a conductive material and sintering and curing at a low temperature to obtain a cell; light injection processing; cell connection processing; and target photoelectric processing.

[0101] In a sixth embodiment, the following steps are performed in sequence: providing a semiconductor substrate; applying a conductive material and sintering and curing at a low temperature to obtain a cell; light injection processing; photoelectric preprocessing; cell connection processing; and target photoelectric processing.

[0102] In a seventh embodiment, the following steps are performed in sequence: providing a semiconductor substrate; applying a conductive material and sintering and curing at a low temperature to obtain a cell; photoelectric pretreatment; light injection treatment; cell connection treatment; and target photoelectric treatment.

[0103] In summary, the method for preparing a battery string provided in an embodiment of the present application has at least the following technical effects: First, by setting a target photoelectric processing step after the battery cell connection processing step, the problem of increased series resistance, reduced fill factor, and attenuated photoelectric conversion efficiency caused by the battery cell connection processing is solved. Second, for battery cells with electrodes made by low-temperature sintering and curing, photoelectric pretreatment is performed before the battery cell connection processing, which can achieve efficiency sorting of the battery cells while alleviating metal corrosion damage. Third, for battery cells with electrodes made by low-temperature sintering and curing, through photoelectric pretreatment, battery cell connection processing and target photoelectric processing, the series resistance can be further reduced on the basis of reducing the series resistance by photoelectric pretreatment.

[0104] In a second aspect, embodiments of the present application further provide a battery string comprising a plurality of battery cells connected in series and / or in parallel. Because the battery string is produced using the battery string production method described in the first aspect, the battery string also has all the technical effects achievable by the production method described in the first aspect.

[0105] In a third aspect, embodiments of the present application further provide a photovoltaic module comprising a plurality of battery strings connected in series and / or in parallel. Because the battery strings are prepared using the battery string preparation method described in the first aspect, the photovoltaic module also has all the technical effects achievable by the preparation method described in the first aspect.

[0106] The solution of this application will be further illustrated below through specific examples, comparative examples and experimental data.

[0107] Example 1

[0108] Embodiment 1 provides a method for preparing a battery string, comprising the following steps: providing a semiconductor substrate; metallization processing; light injection processing; photoelectric preprocessing; battery cell connection processing and target photoelectric processing.

[0109] The step of providing a semiconductor substrate includes: providing a textured silicon substrate and depositing. The silicon substrate is an N-type silicon substrate; depositing a first conductive layer and an anti-reflection layer on the front surface of the N-type silicon substrate, and depositing a tunneling oxide layer, a second conductive layer, and a passivation layer on the back surface of the N-type silicon substrate to obtain a semiconductor substrate for a passivated contact solar cell.

[0110] The metallization treatment steps include: screen printing silver paste on the light incident surface of the anti-reflection layer and the backlight surface of the passivation layer, and low-temperature sintering and curing the silver paste to make positive and negative electrodes to obtain a passivated contact solar cell, wherein the peak temperature of the low-temperature sintering is 600°C.

[0111] The light injection treatment steps are: one heating passivation contact solar cell; two heating and simultaneous light irradiation passivation contact solar cell; wherein, the peak temperature of the first heating is 500 ℃, the peak temperature of the second heating is 200 ℃, and the energy density of light is 50kW / m2.

[0112] The photoelectric pretreatment steps are: treating the passivated contact solar cell with light and simultaneously loading a reverse bias voltage on the passivated contact solar cell; wherein the reverse bias voltage is 30V; the spectral wavelength of the light is 1064nm; the energy density of the light is 5000kW / m2; and the scanning rate of the light is 50m / s.

[0113] The cell connection processing step includes: welding the welding ribbon to 6 passivated contact solar cells at the same time to obtain a cell string, and the 6 passivated contact solar cells are half-cell cells.

[0114] The target photoelectric processing steps include: using a light source to illuminate the battery string and using a voltage source to load a reverse bias voltage on the battery string; wherein the spectral wavelength of the light source is 1064nm; the energy density of the light is 5000kW / m2; and the scanning rate of the light is 50m / s.

[0115] The first embodiment further provides a battery string, which is prepared by the above-mentioned battery string preparation method.

[0116] Example 2

[0117] The second embodiment provides a method for preparing a battery string and a battery string. The difference between the preparation method and the first embodiment is that the photoelectric pretreatment step is not provided.

[0118] Example 3

[0119] The third embodiment provides a method for preparing a battery string and a battery string. The difference between the preparation method and the first embodiment is that the photoelectric pretreatment step is performed first, and then the light injection treatment step is performed.

[0120] Example 4

[0121] The fourth embodiment provides a method for preparing a battery string and a battery string. The difference between the preparation method and the first embodiment is that the light injection processing step is not provided.

[0122] Example 5

[0123] The fifth embodiment provides a method for preparing a battery string and a battery string. The difference between the preparation method and the first embodiment is that the light injection processing step and the photoelectric pre-processing step are not provided.

[0124] Example 6

[0125] Example 6 provides a method for preparing a battery string and a battery string. The difference between the preparation method and Example 5 is that in the metallization treatment step, the silver paste is sintered and solidified at high temperature to produce the positive electrode and the negative electrode.

[0126] Example 7

[0127] The seventh embodiment provides a method for preparing a battery string and a battery string. The difference between the preparation method and the sixth embodiment is that a light injection process step is provided after the metallization process step and before the battery cell connection process step.

[0128] Comparative Example 1

[0129] Comparative Example 1 provides a method for preparing a battery string and a battery string. The difference between Comparative Example 1 and Example 1 is that the target photoelectric processing step is not provided.

[0130] Comparative Example 2

[0131] Comparative Example 2 provides a passivated contact solar cell. The difference between Comparative Example 2 and Example 1 is that the target photoelectric processing step and the cell connection processing step are not provided.

[0132] Comparative Example 3

[0133] Comparative Example 3 provides a method for preparing a battery string and a battery string. The difference between Comparative Example 3 and Example 2 is that the target photoelectric processing step is not provided.

[0134] Comparative Example 4

[0135] Comparative Example 4 provides a passivated contact solar cell. The difference between Comparative Example 4 and Example 2 is that no cell connection processing step and no target photoelectric processing step are provided.

[0136] Comparative Example 5

[0137] Comparative Example 5 provides a method for preparing a battery string and a battery string. The difference between Comparative Example 5 and Example 3 is that the target photoelectric processing step is not set.

[0138] Comparative Example 6

[0139] Comparative Example 6 provides a passivated contact solar cell. The difference between Comparative Example 6 and Example 3 is that the cell connection processing step and the target photoelectric processing step are not provided.

[0140] Comparative Example 7

[0141] Comparative Example 7 provides a passivated contact solar cell. The difference between Comparative Example 7 and Example 3 is that the light injection processing step, the cell connection processing step and the target photoelectric processing step are not provided.

[0142] Comparative Example 8

[0143] Comparative Example 8 provides a method for preparing a battery string and a battery string. The difference between Comparative Example 8 and Example 4 is that the target photoelectric processing step is not set.

[0144] Comparative Example 9

[0145] Comparative Example 9 provides a method for preparing a battery string and a battery string. The difference between Comparative Example 9 and Example 5 is that the target photoelectric processing step is not set.

[0146] Comparative Example 10

[0147] Comparative Example 10 provides a passivated contact solar cell. The difference between Comparative Example 10 and Example 5 is that the cell connection processing step and the target photoelectric processing step are not provided.

[0148] Comparative Example 11

[0149] Comparative Example 11 provides a method for preparing a battery string and a battery string. The difference between Comparative Example 11 and Example 6 is that the target photoelectric processing step is not provided.

[0150] Comparative Example 12

[0151] Comparative Example 12 provides a passivated contact solar cell. The difference between Comparative Example 12 and Example 6 is that the cell connection processing step and the target photoelectric processing step are not provided.

[0152] Comparative Example 13

[0153] Comparative Example 13 provides a method for preparing a battery string and a battery string. The difference between Comparative Example 13 and Example 7 is that the target photoelectric processing step is not set.

[0154] Comparative Example 14

[0155] Comparative Example 14 provides a passivated contact solar cell. The difference between Comparative Example 14 and Example 7 is that the cell connection processing step and the target photoelectric processing step are not provided.

[0156] Performance Testing

[0157] The cell strings or passivated contact solar cells in the aforementioned examples and comparative examples were tested for performance, including photoelectric conversion efficiency, open-circuit voltage, short-circuit current, fill factor, and series resistance, using a solar cell module tester. The test results are as follows, where Eff (%) represents photoelectric conversion efficiency, ISC (A) represents short-circuit current, VOC (mV) represents open-circuit voltage, FF (%) represents fill factor, and Rs (mΩ) represents series resistance. The test results are shown in Tables 1 to 7.

[0158] Table 1

[0159] Table 2

[0160] Table 3

[0161] Table 4

[0162] Table 5

[0163] Table 6

[0164] Table 7

[0165] Comparing the Examples and Comparative Examples in each table individually, each table shows that adding a target photovoltaic processing step after the cell connection processing step can reduce series resistance and / or improve fill factor.

[0166] From Examples 1 to 5, it can be seen that for low-temperature sintering processes, adding a targeted photoelectric treatment after cell connection can reduce the series resistance to between 1mΩ and 1.2mΩ. From Examples 6 and 7, it can be seen that for high-temperature sintering processes, adding a targeted photoelectric treatment after cell connection can reduce the series resistance to 2.97mΩ and 5.6mΩ.

[0167] In Example 1, Example 2, and Example 3, the light injection processing step of Example 1 is located before the photoelectric pretreatment step, Example 2 does not have a photoelectric pretreatment step, and the light injection processing step of Example 3 is located after the photoelectric pretreatment step. The photoelectric conversion efficiency, fill factor, and series resistance of Example 1 and Example 2 are relatively close, but because Example 1 has a photoelectric pretreatment step, it can significantly reduce the series resistance before the cell connection processing step (combined with Comparative Example 3), thereby enabling efficiency sorting. However, the series resistance of Example 2 before the cell connection processing step is too large, making efficiency sorting impossible. Comparison between Example 1 and Example 3 shows that the photoelectric pretreatment step located before the light injection step can more effectively improve the photoelectric conversion efficiency, short-circuit current, open-circuit voltage, and fill factor, and can reduce the series resistance.

[0168] It can be seen from Comparative Examples 6 and 7 in Table 3, and Comparative Examples 11 and 13 in Table 6 and Table 7 that adding the light injection step can increase the open circuit voltage and the short circuit current.

[0169] As can be seen from the data in Table 1, Comparative Example 1 adds a cell connection processing step on the basis of the solution of Comparative Example 2. The series resistance of Comparative Example 1 increases, the fill factor and the photoelectric conversion efficiency all decrease significantly, indicating that only setting the photoelectric pretreatment step cannot balance the impact caused by the cell connection. Example 1 further reduces the series resistance and improves the photoelectric conversion efficiency compared to the cell connection by adding the target photoelectric processing step after the cell connection step. This shows that the combination of the photoelectric pretreatment step + cell connection + target photoelectric processing step can further reduce the contact resistance and improve the photoelectric conversion efficiency on the basis of reducing the series resistance by the photoelectric pretreatment (combined with Comparative Example 4).

[0170] As can be seen from Tables 1 to 5, the metal electrode produced by low-temperature sintering has the best five performance indicators in Example 3. As can be seen from Tables 6 and 7, the metal electrode produced by high-temperature sintering has the best five performance indicators in Example 7.

[0171] In this application, unless otherwise expressly specified or limited, if a first feature is described as being "above" or "below" a second feature, or similar descriptions, this may mean that the first and second features are in direct contact, or that the first and second features are in indirect contact through an intermediate medium. Furthermore, when a first feature is described as being "above," "above," or "above" a second feature, it may mean that the first feature is directly above or diagonally above the second feature, or simply means that the first feature is at a higher level than the second feature. When a first feature is described as being "below," "below," or "below" a second feature, it may mean that the first feature is directly below or diagonally below the second feature, or simply means that the first feature is at a lower level than the second feature.

[0172] It should be noted that if an element is referred to as being "fixed to" or "disposed on" another element, it may be directly on the other element or there may be an intermediate element. If an element is considered to be "connected to" another element, it may be directly connected to the other element or there may be an intermediate element. If any, the terms "vertical", "horizontal", "upper", "lower", "left", "right" and similar expressions used in this application are for illustrative purposes only and do not represent the only embodiment.

[0173] The technical features of the above-mentioned embodiments can be combined arbitrarily. In order to make the description concise, not all possible combinations of the technical features in the above-mentioned embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0174] The above-described embodiments merely represent several implementation methods of the present application. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent application. It should be noted that a person of ordinary skill in the art may make various modifications and improvements without departing from the spirit of the present application, and these modifications and improvements fall within the scope of protection of the present application. Therefore, the scope of protection of the present patent application shall be determined by the appended claims.

Claims

1. A method for preparing a battery string, characterized in that, It includes the following steps: Provide a semiconductor substrate; Metallization treatment: Perform metallization treatment on the semiconductor substrate to obtain a cell; Cell connection treatment: Connect the cell with a connector to obtain a cell string precursor; Target optoelectronic treatment: Perform light treatment on the cell string precursor and simultaneously apply a reverse bias voltage to the cell string precursor.

2. The method for preparing a battery string according to claim 1, wherein In the step of the target optoelectronic treatment, at least one of the cells is included in the cell string precursor; wherein, Light treatment: Set a light source to sequentially perform light treatment on the cells, or set multiple light sources to respectively perform light treatment on each of the cells; Apply a reverse bias voltage: Set a plurality of voltage sources to apply a reverse bias voltage to at least one of the cells in the cell string precursor.

3. The preparation method of the battery string according to claim 2, wherein The spectral wavelength of the light source is 500nm - 1200nm.

4. The method for preparing a battery string according to claim 2 or 3, characterized in that, The energy density of the light source is 10kW / m2 - 10000kW / m2.

5. The method for preparing a battery string according to any one of claims 2 to 4, characterized in that, The scanning rate of the light source is 26m / s - 65m / s.

6. The method for preparing a battery string according to any one of claims 2 to 5, characterized in that, The value of the reverse bias voltage applied by the voltage source is equal to the product of the number of the cells connected in series therewith and the value of the reverse bias voltage applied to a single cell, wherein the reverse bias voltage applied to a single cell is 10V - 50V.

7. The method for preparing a battery string according to any one of claims 1 to 6, characterized in that, In the metallization treatment step, apply a conductive material on the semiconductor substrate and sinter and cure it at a low temperature to obtain the cell.

8. The method for preparing a battery string according to any one of claims 1 to 7, characterized in that, The range of the peak temperature of the low-temperature sintering is 550°C - 720°C.

9. The manufacturing method of the battery string according to any one of claims 1 to 7, characterized in that, After the metallization treatment step and before the cell connection treatment step, the following steps are further included: Optoelectronic pre-treatment: Perform light treatment on the cell and simultaneously apply a reverse bias voltage to the cell.

10. The method for preparing a battery string according to claim 9, wherein, In the optoelectronic pre-treatment step, the reverse bias voltage is 10V - 50V.

11. The method for preparing a battery string according to claim 9 or 10, characterized in that, The spectral wavelength of the light in the light treatment is 500nm - 1200nm.

12. The method for preparing a battery string according to any one of claims 9 to 11, characterized in that, The energy density of the light in the light treatment is 10kW / m2 - 10000kW / m2.

13. The method for preparing a battery string according to any one of claims 9 to 12, characterized in that, The scanning rate of the light in the light treatment is 26m / s - 65m / s.

14. The method for preparing a battery string according to claim 7, wherein After the metallization treatment step and before the cell connection treatment step, the following is further included: Light injection treatment of the cell.

15. The method for preparing a battery string according to any one of claims 1 to 14, characterized in that, In the metallization treatment step, apply a conductive material on the semiconductor substrate and sinter and cure it at a high temperature to obtain a cell.

16. The method for preparing a battery string according to claim 15, wherein The range of the peak temperature of the high-temperature sintering is 780°C - 850°C.

17. The method for preparing a battery string according to claim 15, wherein, After the metallization treatment step and before the cell connection treatment step, the following is further included: Light injection treatment of the cell.

18. The method for preparing a battery string according to claim 14 or 17, characterized in that, The step of the light injection treatment of the cell includes the following steps: Heat the cell once; Heat the cell a second time while illuminating the cell; Wherein, the peak temperature of the first heating is 400°C - 600°C, the peak temperature of the second heating is 100°C - 300°C, and the energy density of the light is 10kW / m2 - 100kW / m2.

19. The method for preparing a battery string according to any one of claims 1 to 18, characterized in that, The step of providing the semiconductor substrate further includes the following steps: Provide a textured silicon substrate, and the silicon substrate is an N-type silicon substrate or a P-type silicon substrate; Fabricating a functional layer: A functional layer is fabricated on the silicon substrate to obtain the semiconductor matrix, and the functional layer includes one or more of a doping layer, a passivation layer, a conductive layer, an antireflection layer, and a dielectric layer.

20. The method for preparing a battery string according to any one of claims 1 to 19, characterized in that, In the step of connecting the cell, the area size of the cell accounts for one or more combinations of 100%, 50%, 25%, 12.5%, and 6.25% of the area size of the whole cell.

21. The method for preparing a battery string according to any one of claims 1 to 20, characterized in that, In the step of connecting the cell, the cell includes a passivated contact solar cell, a heterojunction solar cell, an emitter and back surface passivated solar cell, a back contact solar cell, or a tandem solar cell.

22. A battery string, characterized in that, The battery string is prepared by the method for preparing a battery string according to any one of claims 1 to 21, and the battery string includes a plurality of battery cells connected in at least one of series and parallel.

23. A photovoltaic module, characterized in that, The photovoltaic module includes a plurality of battery strings connected in at least one of series and parallel, and the battery string is prepared by the method for preparing a battery string according to any one of claims 1 to 21.

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