Preparation method of battery string, battery string and photovoltaic module

Abstract

The invention relates to the technical field of photovoltaic modules, in particular to a preparation method of a battery string, the battery string and a photovoltaic module. The preparation method of the cell string comprises the following steps: providing a semiconductor substrate; carrying out metallization processing on the semiconductor substrate to obtain a battery piece; connecting the battery pieces with the connecting pieces to obtain a battery string precursor; and carrying out light treatment on the battery string precursor, and loading reverse bias voltage on the battery string precursor at the same time. The target photoelectric processing step is added, so that the current conduction path can be increased, the contact between the metal and the semiconductor substrate is improved, the series resistance of the battery piece is further reduced, the filling factor of the battery piece is improved, and the photoelectric conversion efficiency is improved.

Description

Technical Field

[0001] The present application relates to the technical field of photovoltaic modules, and particularly to a method for preparing a battery string, a battery string and a photovoltaic module. Background Art

[0002] Monolithic solar cells need to be interconnected to form a battery string. During the connection process, the series resistance of the solar cells is likely to increase and the fill factor is likely to decrease, resulting in attenuation of the photoelectric conversion efficiency of the solar cells. Summary of the Invention

[0003] Based on this, it is necessary to provide a method for preparing a battery string, a battery string and a photovoltaic module to solve the problem that monolithic solar cells need to be interconnected to form a battery string, and during the connection process, the temperature is likely to be too high, resulting in an increase in the series resistance of the solar cells and a decrease in the fill factor, thereby causing attenuation of the photoelectric conversion efficiency of the solar cells.

[0004] In a first aspect, a method for preparing a battery string includes the following steps:

[0005] Provide a semiconductor substrate;

[0006] Metallization treatment: perform metallization treatment on the semiconductor substrate to obtain a solar cell;

[0007] Solar cell connection treatment: connect the solar cell to a connector to obtain a battery string precursor;

[0008] Target optoelectronic treatment: perform light treatment on the battery string precursor and simultaneously apply a reverse bias voltage to the battery string precursor.

[0009] In one embodiment, in the step of the target optoelectronic treatment, at least one of the solar cells is included in the battery string precursor; wherein,

[0010] Light treatment: set a light source to sequentially irradiate the solar cells, or set multiple light sources to separately irradiate each of the solar cells;

[0011] Apply a reverse bias voltage: set a plurality of voltage sources to apply a reverse bias voltage to at least one of the solar cells in the battery string precursor.

[0012] In one embodiment, the spectral wavelength of the light source is 500 nm to 1200 nm;

[0013] and / or, the energy density of the light source is 10 kW / m 2 ~10000 kW / m 2 ;

[0014] and / or, the scanning rate of the light source is 26 m / s to 65 m / s;

[0015] And / or, 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 therewith 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.

[0016] In one embodiment, in the metallization treatment step, a conductive material is applied to the semiconductor substrate and sintered and cured at a low temperature to fabricate an electrode.

[0017] In one embodiment, the range of the temperature peak of the low-temperature sintering is 550°C to 720°C.

[0018] In one embodiment, after the metallization treatment step and before the battery cell connection treatment step, the following steps are further included:

[0019] Photoelectric pre-treatment: performing a light irradiation treatment on the battery cell and simultaneously loading a reverse bias voltage on the battery cell.

[0020] In one embodiment, in the photoelectric pre-treatment step, the reverse bias voltage is 10V to 50V;

[0021] And / or, the spectral wavelength of the light in the light irradiation treatment is 500nm to 1200nm;

[0022] And / or, the energy density of the light in the light irradiation treatment is 10kW / m 2 ~10000 kW / m 2 ;

[0023] And / or, the scanning rate of the light in the light irradiation treatment is 26m / s to 65 m / s.

[0024] In one embodiment, after the metallization treatment step and before the battery cell connection treatment step, it further includes: performing a light injection treatment on the battery cell.

[0025] In one embodiment, in the metallization treatment step, a conductive material is applied to the semiconductor substrate and sintered and cured at a high temperature to fabricate an electrode.

[0026] In one embodiment, the range of the temperature peak of the high-temperature sintering is 780°C to 850°C.

[0027] In one embodiment, after the metallization treatment step and before the battery cell connection treatment step, it further includes: performing a light injection treatment on the battery cell.

[0028] In one embodiment, the step of performing a light injection treatment on the battery cell further includes the following steps:

[0029] Heat the cell once.

[0030] Heat the cell a second time while illuminating the cell.

[0031] Among them, the peak temperature of the first heating is 400°C to 600°C, the peak temperature of the second heating is 100°C to 300°C, and the energy density of the light is 10 kW / m 2 ~100 kW / m 2 .

[0032] In one embodiment, the step of providing the semiconductor substrate further includes the following steps:

[0033] Provide a textured silicon substrate, and the silicon substrate is an N-type silicon substrate or a P-type silicon substrate;

[0034] Prepare a functional layer: Prepare a functional layer on the silicon substrate to obtain the semiconductor substrate, 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.

[0035] In one embodiment, in the step of connecting and processing 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 full-cell cell.

[0036] In one embodiment, in the step of connecting and processing the cell, 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.

[0037] In a second aspect, a battery string is obtained by the method for preparing a battery string according to the first aspect, and the battery string includes a plurality of serially and / or parallely connected cells.

[0038] In a third aspect, a photovoltaic module includes a plurality of serially and / or parallely connected battery strings, and the battery strings are obtained by the method for preparing a battery string according to the first aspect.

[0039] In the step of metallization treatment, conductive dendrites or conductive particles are formed between the metal and the semiconductor substrate. When the conductive dendrites or conductive particles form contacts with the semiconductor substrate, they can serve as current transmission paths. However, in the step of connecting and processing the cell, some of the conductive dendrites or conductive particles may be broken or melted, reducing the contact sites between the metal and the semiconductor substrate, resulting in an increase in the series resistance between the metal and the semiconductor substrate and a decrease in the fill factor, causing attenuation of the photoelectric conversion efficiency of the cell.

[0040] The key to solving the above problems in the method for preparing a battery string provided by this application is: adding a target light treatment step after the battery cell connection treatment step, performing light treatment on the battery string precursor while applying a reverse bias voltage, so as to generate a large number of electron-hole pairs inside the battery cell, and at the same time accelerating the movement speeds of the two carriers, namely electrons and holes. Under the action of the built-in electric field of the battery cell, the carriers are separated and quickly move to accumulate and recombine between the metal and the semiconductor to generate heat. The more the number of electron-hole pairs, the faster the speed, and the higher the heat generated by recombination. This process promotes the reformation of conductive dendrites or conductive particles that are broken or melted to form conductive contacts, restores the current conduction path, or enables the positions that were not in contact originally to be conducted. Thus, by adding the target optoelectronic treatment step, more electron transmission paths can be formed between the metal and the semiconductor matrix, significantly improving the contact performance of the battery cell, and further reducing the series resistance and increasing the fill factor, so as to improve the photoelectric conversion efficiency of the battery cell and alleviate the adverse effects on the battery cell during the battery cell connection treatment step. Description of the Drawings

[0041] Figure 1 It is a schematic flowchart of a method for preparing a battery string provided by an embodiment of this application.

[0042] Figure 2 It is a schematic diagram of the first treatment method of the target light treatment step in an embodiment of this application.

[0043] Figure 3 It is a schematic diagram of the second treatment method of the target light treatment step in an embodiment of this application.

[0044] Figure 4 It is a schematic diagram of the third treatment method of the target light treatment step in an embodiment of this application.

[0045] Figure 5 It is a schematic diagram of the fourth treatment method of the target light treatment step in an embodiment of this application.

[0046] Description of the reference numerals: 10, single-piece battery string; 20, multi-piece battery string; 100, battery cell; 1, light source; 2, voltage source; 3, connecting piece. Detailed Embodiments

[0047] To make the above objects, features, and advantages of this application more obvious and understandable, the following will describe the detailed embodiments of this application with reference to the drawings. Many specific details are set forth in the following description to facilitate a thorough understanding of this application. However, this application can be implemented in many other ways different from those described herein, and those skilled in the art can make similar improvements without departing from the connotation of this application. Therefore, this application is not limited by the specific embodiments disclosed below.

[0048] In the description of the present application, it should be understood that if there are terms such as "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc., the orientation or positional relationship indicated by these terms is based on the orientation or positional relationship shown in the drawings. These are only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, it should not be construed as a limitation to the present application.

[0049] In addition, if there are terms such as "first" and "second", these terms are only used for descriptive purposes and should not be construed as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, features defined with "first" and "second" may explicitly or implicitly include at least one of such features. In the description of the present application, if there is a term "plurality", the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise specifically defined.

[0050] In the present application, unless otherwise clearly specified and limited, if there are terms such as "installation", "connection", "connection", "fixation", etc., these terms should be understood in a broad sense. For example, it may be a fixed connection, a detachable connection, or integrated; it may be a mechanical connection or an electrical connection; it may be directly connected or indirectly connected through an intermediate medium, and it may be the communication inside two elements or the interaction relationship between two elements, unless otherwise clearly limited. For those of ordinary skill in the art, the specific meanings of the above terms in the present application can be understood according to specific circumstances.

[0051] In a first aspect, an embodiment of the present application provides a method for preparing a battery string. Please refer to Figure 1 , which includes the following steps: providing a semiconductor substrate, metallization treatment, battery cell connection treatment, and target optoelectronic treatment.

[0052] Among them, the metallization treatment step is to perform metallization treatment on the semiconductor substrate to obtain battery cells. Specifically, it means to fabricate metal electrodes on the semiconductor substrate to obtain battery cells. The battery cell connection treatment step is to connect the battery cells with connectors to obtain a battery string precursor. The target optoelectronic treatment step is to perform light irradiation treatment on the battery string precursor and simultaneously apply a reverse bias voltage to the battery string precursor.

[0053] Adding a target optoelectronic processing step after the cell connection processing step can promote the re - contact of fractured and molten conductive dendrites or conductive particles with the semiconductor substrate, restore the current conduction path, or enable the conductive dendrites or conductive particles that did not originally form contacts to contact the semiconductor substrate, so as to increase the current conduction path, thereby improving the contact between the metal electrode and the semiconductor substrate, reducing the series resistance of the cell, increasing the fill factor of the cell, and alleviating the problem of the attenuation of the optoelectronic conversion efficiency caused by the cell connection processing step.

[0054] Next, each step of the preparation method will be described in detail according to the preparation sequence of the cell string.

[0055] 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 antireflection layer, and a dielectric layer. The silicon substrate includes an opposite light - incident surface and a backlight surface along its thickness direction, and the functional layer can be provided on at least one of the light - incident surface and the backlight surface.

[0056] Exemplarily, the doping layer can be lightly doped or heavily doped, and the doping layer can include lightly doped polysilicon or heavily doped polysilicon. The passivation layer can include polysilicon, silicon oxide, aluminum oxide, etc. The conductive layer can be an indium tin oxide layer, tin oxide, etc.

[0057] In some embodiments, the dielectric layer, as a kind of barrier for electrons and holes, can combine with polysilicon to prevent minority carriers from passing through. The dielectric layer can also have the function of pinhole channels, enabling the carriers in the solar cell to move freely, and selectively passing the majority carriers through the heavily doped polysilicon, which is beneficial to reducing the recombination loss of minority carriers. In addition, the dielectric layer can be used as a diffusion barrier to prevent the dopant in the doped polysilicon layer from diffusing into the semiconductor substrate.

[0058] The material of the dielectric layer can include a variety of dielectric materials, such as at least one of silicon oxide, magnesium fluoride, amorphous silicon, polysilicon, silicon carbide, silicon nitride, silicon oxynitride, aluminum oxide, or titanium oxide. Specifically, the dielectric layer can be composed of silicon oxide. This is because the silicon oxide layer has excellent passivation performance, can minimize the recombination loss of minority carriers on the surface of the semiconductor substrate, and is a film with excellent durability for subsequent high - temperature processes.

[0059] To better provide interface passivation for the substrate, the thickness of the dielectric can be from 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.

[0060] In the deposition step, exemplarily, a conductive layer and an antireflection layer can be deposited on the light incident surface of the N-type silicon substrate, while a passivation layer and a conductive layer are deposited on the backlight surface of the N-type silicon substrate. Alternatively, a conductive layer and an antireflection layer can be deposited on the light incident surface of the P-type silicon substrate, while a passivation layer and a conductive layer are deposited on the backlight surface of the P-type silicon substrate.

[0061] Furthermore, the deposition method can be one or a combination of plasma enhanced chemical vapor deposition, atomic layer deposition, or low-pressure chemical vapor deposition.

[0062] After the semiconductor substrate is fabricated, metallization is required to fabricate metal electrodes on the light incident surface or the backlight surface of the semiconductor substrate to form a complete solar cell. Exemplarily, 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.

[0063] Exemplarily, the metallization process can adopt the method of screen printing a conductive material and sintering and curing it. Among them, screen printing and sintering and curing is to print the conductive material onto the semiconductor substrate to form metal electrodes on the light incident surface and the backlight surface of the semiconductor substrate. Among them, the metal electrodes on the light incident surface include main grid lines and sub-grid lines, and then the conductive material is sintered and cured to form electrodes. Exemplarily, the conductive material can be silver paste, aluminum paste, or silver-aluminum paste. Sintering and curing can be high-temperature sintering or low-temperature sintering.

[0064] In some embodiments, the peak temperature range of high-temperature sintering is 780 °C to 850 °C. Exemplarily, the peak temperature of high-temperature sintering can be any value within the above range, for example, it can be 780 °C, 790 °C, 800 °C, 810 °C, 820 °C, 830 °C, 840 °C, 850 °C, etc.

[0065] In some other embodiments, the peak temperature range of low-temperature sintering is 550 °C to 720 °C. Exemplarily, the peak temperature of low-temperature sintering can be any value within the above range, for example, it can be 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.

[0066] In other words, the method for preparing the battery string of the present application can solve the problem of the attenuation of the photoelectric conversion efficiency caused by the increase in the series resistance and the decrease in the fill factor of the battery cell after the battery cell connection processing step, regardless of whether the battery cell is prepared by high-temperature sintering or low-temperature sintering.

[0067] In some embodiments, after the metallization treatment step and before the battery cell connection processing step, the battery cell is subjected to light injection treatment. The step of light injection treatment of the battery cell is applicable to both the high-temperature sintering process and the low-temperature sintering process.

[0068] In some embodiments, the step of light injection treatment of the battery cell includes the following steps: heating the battery cell for the first time; heating the battery cell for the second time while irradiating the battery cell with light. Among them, the peak temperature of the first heating is 400°C to 600°C, the peak temperature of the second heating is 100°C to 300°C, and the energy density of the light is 10 kW / m 2 ~100 kW / m 2 .

[0069] Exemplarily, the peak temperature of the first heating can be any value within the above range, for example, it can be 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 second heating can be any value within the above range, for example, it can be 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 can be any value within the above range, for example, it can be 10 kW / m 2 、20 kW / m 2 、30 kW / m 2 、40 kW / m 2 、50 kW / m 2 、60 kW / m 2 、70 kW / m 2 、80 kW / m 2 、90 kW / m 2 、100 kW / m 2 etc.

[0070] It should be noted that in the process of screen printing and sintering and curing to make the electrode, 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 and photoelectric conversion efficiency of the battery cell.

[0071] Based on this problem, in some embodiments, after fabricating the electrodes by low-temperature sintering and curing, and before the cell connection processing step, an optoelectronic pretreatment step is further included: irradiating the cells with light and simultaneously applying a reverse bias voltage to the cells.

[0072] The optoelectronic pretreatment has two functions: on the one hand, it alleviates the metal corrosion damage caused by low-temperature sintering, and on the other hand, it enables efficiency sorting of the cells after low-temperature sintering before the cell connection processing step. Specifically, for the cells fabricated with electrodes by low-temperature sintering, adding the optoelectronic pretreatment step can form a better contact between the metal electrodes and the semiconductor substrate, and reduce the series resistance of the cells before the cell connection processing step to meet the requirements for efficiency sorting.

[0073] In the optoelectronic pretreatment step, the built-in electric field of the P-N junction is significantly enhanced under the action of the reverse bias voltage, and light irradiation 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 region between the metal and the semiconductor substrate to generate high heat. The local metal and the interfacial silicon are quickly remelted and crystallized under the condition of high heat to form a metal-silicon alloy (such as silver-silicon alloy), conductive dendrites, and conductive particles, alleviating the large-area metal corrosion damage, thereby improving the contact performance, helping to reduce the contact resistance, increasing the open-circuit voltage and the fill factor, and improving the stability and optoelectronic conversion efficiency of the cells.

[0074] The embodiments of the present application do not limit the sequence of the optoelectronic pretreatment step and the light injection treatment step for the cells fabricated by low-temperature sintering and curing. In other words, the optoelectronic pretreatment step can be located after the metallization treatment step and before the light injection treatment step. Or, the optoelectronic pretreatment step can be located after the light injection treatment step and before the cell connection processing step.

[0075] It should be noted that since the temperature used in high-temperature sintering and curing is too high, irreversible metal corrosion damage is caused to the cells, so the optoelectronic pretreatment step cannot alleviate the metal corrosion damage caused by high-temperature sintering and curing. The cells fabricated by high-temperature sintering and curing are not suitable for the optoelectronic pretreatment step before the cell connection processing step.

[0076] In some embodiments, in the optoelectronic pretreatment step, the reverse bias voltage is 10V to 50V. The voltage within this range can ensure the built-in electric field strength of the cells and provide sufficient energy for the sorting of carriers. Exemplarily, the reverse bias voltage can be any value within the above range, such as 10V, 20V, 30V, 40V, 50V, etc.

[0077] In some embodiments, the spectral wavelength of the light in the illumination treatment is 500nm~1200nm. Spectral wavelengths below or above this range do not match the band gap of the silicon substrate and cannot excite electron-hole pairs inside the cell. Exemplary spectral wavelengths may be 500nm, 532nm, 635nm, 650nm, 808nm, 980nm, 1064nm, 1200nm, etc. In some embodiments, the energy density of the light in the illumination treatment is 10kW / m 2 ~10000 kW / m 2 For example, the energy density of light can be any value within the above range, for example, 10 kW / m 2 , 100kW / m 2 , 1000kW / m 2 , 2000kW / m 2 5000kW / m 2 、10000 kW / m 2 In some embodiments, the scanning rate of the light during the light treatment is 26 m / s to 65 m / s. For example, it can be 26 m / s, 30 m / s, 35 m / s, 40 m / s, 45 m / s, 50 m / s, 55 m / s, 60 m / s, 65 m / s, etc.

[0078] Furthermore, during 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.

[0079] 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.

[0080] The battery cell connection process includes the following optional implementations but is not limited to: Figure 2 When the battery string precursor includes only one battery cell 100, the battery cell 100 is connected to the connector 3 to form a single battery string 10. Figures 3 to 5 When the battery string precursor includes multiple battery cells 100, the connector 3 can be connected to multiple battery cells 100 simultaneously to form a multi-cell battery string 20; or a single battery cell 100 can be connected to the connector 3 to form a single-cell battery string 10, and then multiple single-cell battery strings 10 can be connected to form a multi-cell battery string 20. Optionally, the connector can be a soldering ribbon or conductive adhesive.

[0081] In some embodiments, in the battery cell connection processing step, the battery cell includes at least one of a passivated contact solar cell, an emitter-back-passivated solar cell, and a heterojunction solar cell. The battery cell may further include a solar cell with a P-N junction and metal electrodes disposed on the backlight surface of the semiconductor substrate.

[0082] Furthermore, in some embodiments, in the battery cell connection processing step, the area size of the battery cell accounts for one or more combinations of 100%, 50%, 25%, 12.5%, and 6.25% of the area size of the entire battery cell. In other words, the battery cell for which the battery cell connection processing step is performed can be a full-sized battery cell, a half-sized battery cell, a 1 / 4 battery cell, a 1 / 8 battery cell, or a 1 / 16 battery cell.

[0083] After the battery cell connection processing step, target optoelectronic processing is performed. Target optoelectronic processing refers to irradiating the battery string precursor with light and simultaneously applying a reverse bias voltage to the battery string precursor.

[0084] In some embodiments, in the step of target optoelectronic processing, the battery string precursor includes at least one battery cell; wherein, for the light irradiation processing: one light source is set to irradiate the battery cells in sequence, or multiple light sources are set to irradiate each battery cell separately. For applying the reverse bias voltage: a number of voltage sources are set to apply a reverse bias voltage to at least one battery cell in the battery string precursor.

[0085] It can be understood that the number of voltage sources includes one or more. When only one voltage source is set, a reverse bias voltage is applied to both ends of the entire battery string precursor. Alternatively, when multiple voltage sources are set, each voltage source can apply a reverse bias voltage to each battery cell separately. Alternatively, when multiple voltage sources are set, each voltage source can apply a reverse bias voltage to some of the battery cells.

[0086] Combining the light irradiation processing and applying the reverse bias voltage, the target optoelectronic processing step is specifically described as follows, but not limited to: Please refer to Figure 2 , when the battery string precursor includes only one battery cell 100, the battery string precursor is a single-cell battery string 10. One voltage source 2 is set at both ends of the single-cell battery string 10, and one light source 1 is set. When the battery string precursor includes multiple battery cells 100, the battery string precursor is a multi-cell battery string 20. Please refer to Figure 3 , one light source 1 can be set to irradiate multiple battery cells 100 in sequence, and multiple voltage sources are set to apply a reverse bias voltage to each battery cell 100 separately. Please refer to Figure 4 , multiple light sources 1 can be set to irradiate each battery cell 100 separately, and multiple voltage sources 2 are set to apply a reverse bias voltage to each battery cell 100 separately. Please refer to Figure 5, multiple light sources 1 can be set to irradiate each cell 100 respectively, and a voltage source 1 is set at both ends of multiple cell strings 20 to apply a reverse bias voltage.

[0087] In some embodiments, the spectral wavelength of the light source is 500 nm to 1200 nm, and the energy density of the light source is 10 kW / m 2 ~10000 kW / m 2 , 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 / m 2 、100 kW / m 2 、1000 kW / m 2 、2000 kW / m 2 、5000 kW / m 2 、10000 kW / m 2 etc. The scanning rate of the light source is 26 m / s to 65 m / s. For example, it can be 26 m / s, 30 m / s, 35 m / s, 40 m / s, 45 m / s, 50 m / s, 55 m / s, 60 m / s, 65 m / s, etc.

[0088] In some embodiments, the value of the reverse bias voltage applied by the voltage source is equal to the product of the number of cells connected in series therewith and the value of the reverse bias voltage applied on a single cell, where the reverse bias voltage applied on a single cell is 10 V to 50 V.

[0089] Exemplarily, when multiple voltage sources are set, the multiple voltage sources apply reverse bias voltages on each cell respectively, and the reverse bias voltage applied by each voltage source is 10 V to 50 V. For example, it can be 10 V, 20 V, 30 V, 40 V, 50 V, etc.

[0090] In another example, when multiple voltage sources are set, each voltage source applies a reverse bias voltage on some cells, and the value of the reverse bias voltage applied by each voltage source is equal to the product of the number of some cells and the value of the reverse bias voltage applied on a single cell, where the value of the reverse bias voltage applied on a single cell is 10 V to 50 V. It can be understood that the number of some cells is less than the number of all cells. When the number of cells connected in series is 2, the reverse bias voltage applied by this voltage source is 20 V to 100 V. Further exemplarily, the reverse bias voltage applied on a single cell can be any value within the above range. For example, it can be 10 V, 20 V, 30 V, 40 V, 50 V, etc.

[0091] In some embodiments, when a voltage source is set, the value of the reverse bias voltage loaded by the voltage source is equal to the product of the total number of solar cells connected in series in the precursor of the solar cell string and the value of the reverse bias voltage loaded on a single solar cell, where the reverse bias voltage loaded on a single solar cell is 10V to 50V. It can be understood that when the number of series-connected solar cells is 2, the reverse bias voltage loaded by the voltage source is 20V to 100V. When the number of series-connected solar cells is 6, the reverse bias voltage loaded by the voltage source is 60V to 300V, and so on. Exemplarily, the reverse bias voltage loaded on a single solar cell can be any value within the above range, for example, it can be 10V, 20V, 30V, 40V, 50V, etc.

[0092] Furthermore, in the target optoelectronic processing step, the light treatment can be to scan the solar cell with a small spot parallel to the sub-grid lines or to scan the solar cell with a large spot perpendicular to the sub-grid lines. When scanning with a small spot, the reverse bias voltage loaded on a single solar cell can be 10V to 20V. When scanning with a large spot, the reverse bias voltage loaded on a single solar cell can be 15V to 30V. In some cases, those skilled in the art can set a reasonable range of reverse bias voltages according to specific usage scenarios.

[0093] It should be emphasized that for the solar cell with a metal electrode fabricated by a low-temperature sintering and curing process, after successively undergoing photo-injection treatment, optoelectronic pre-treatment, and solar cell connection treatment, the series resistance of the solar cell is greater than that after optoelectronic pre-treatment, indicating that even after optoelectronic pre-treatment, the series resistance of the solar cell will still increase after the solar cells are connected. To solve this problem, the applicant found that subjecting the solar cell to the target optoelectronic treatment can not only reduce the series resistance of the solar cell, but even make the series resistance lower than that before the solar cell connection treatment step. This is because the interfacial contact conductive dendrites formed in the optoelectronic pre-treatment are unstable, and the conductive dendrites melt or break during the connection process, resulting in deteriorated contact, making the contact between the metal electrode and the semiconductor substrate an indirect contact and increasing the series resistance. During the target optoelectronic treatment process, local high temperature will re-form contact between the metal electrode and the semiconductor substrate, and the position where the contact is re-formed may be the original position where the break occurred or other new positions, thereby increasing more current conduction paths, and thus further reducing the series resistance of the solar cell. Thus, through optoelectronic pre-treatment, solar cell connection, and target optoelectronic treatment, on the basis of optoelectronic pre-treatment, the series resistance can be further reduced, effectively improving the contact between the electrode and the silicon substrate.

[0094] In summary, in some embodiments, the method for preparing a solar cell string at least includes the following feasible ways:

[0095] In the first embodiment, the following steps are sequentially carried out: providing a semiconductor substrate; applying a conductive material and sintering and curing at a high temperature to obtain a cell; cell connection processing; target optoelectronic processing.

[0096] In the second embodiment, the following steps are sequentially carried out: providing a semiconductor substrate; applying a conductive material and sintering and curing at a high temperature to obtain a cell; photo-injection processing; cell connection processing; target optoelectronic processing.

[0097] In the third embodiment, the following steps are sequentially carried out: providing a semiconductor substrate; applying a conductive material and sintering and curing at a low temperature to obtain a cell; cell connection processing; target optoelectronic processing.

[0098] In the fourth embodiment, the following steps are sequentially carried out: providing a semiconductor substrate; applying a conductive material and sintering and curing at a low temperature to obtain a cell; optoelectronic preprocessing; cell connection processing; target optoelectronic processing.

[0099] In the fifth embodiment, the following steps are sequentially carried out: providing a semiconductor substrate; applying a conductive material and sintering and curing at a low temperature to obtain a cell; photo-injection processing; cell connection processing; target optoelectronic processing.

[0100] In the sixth embodiment, the following steps are sequentially carried out: providing a semiconductor substrate; applying a conductive material and sintering and curing at a low temperature to obtain a cell; photo-injection processing; optoelectronic preprocessing; cell connection processing; target optoelectronic processing.

[0101] In the seventh embodiment, the following steps are sequentially carried out: providing a semiconductor substrate; applying a conductive material and sintering and curing at a low temperature to obtain a cell; optoelectronic preprocessing; photo-injection processing; cell connection processing; target optoelectronic processing.

[0102] In summary, a method for preparing a battery string provided by the embodiments of the present application has at least the following technical effects: First, by setting a target optoelectronic processing step after the cell connection processing step, the problems of increased series resistance, reduced fill factor, and attenuation of optoelectronic conversion efficiency caused by cell connection processing are solved. Second, for the cells with electrodes made by low-temperature sintering and curing, optoelectronic preprocessing is carried out before cell connection processing, which can relieve metal corrosion damage and realize efficiency sorting of cells at the same time. Third, for the cells with electrodes made by low-temperature sintering and curing, through optoelectronic preprocessing, cell connection processing, and target optoelectronic processing, on the basis of reducing the series resistance by optoelectronic preprocessing, the series resistance can be further reduced.

[0103] Second aspect, an embodiment of the present application further provides a battery string, which includes a plurality of serially and / or parallely connected solar cells. Since this battery string is prepared by the preparation method of the battery string described in the first aspect, this battery string also has all the technical effects that can be achieved by the preparation method described in the first aspect.

[0104] Third aspect, an embodiment of the present application further provides a photovoltaic module, which includes a plurality of serially and / or parallely connected battery strings. Since this battery string is prepared by the preparation method of the battery string described in the first aspect, this photovoltaic module also has all the technical effects that can be achieved by the preparation method described in the first aspect.

[0105] Next, the solution of the present application will be further described through specific examples, comparative examples, and experimental data.

[0106] Example 1

[0107] Example 1 provides a preparation method of a battery string, including the following steps: providing a semiconductor substrate; metallization treatment; photo-injection treatment; optoelectronic pretreatment; solar cell connection treatment, and target optoelectronic treatment.

[0108] The step of providing a semiconductor substrate includes: providing a textured silicon substrate and deposition. The silicon substrate is an N-type silicon substrate; a first conductive layer and an antireflection layer are sequentially deposited on the front surface of the N-type silicon substrate, and a tunneling oxide layer, a second conductive layer, and a passivation layer are sequentially deposited on the back surface of the N-type silicon substrate to obtain a semiconductor substrate of a passivated contact solar cell.

[0109] The metallization treatment step includes: screen-printing silver paste on the light incident surface of the antireflection layer and the backlight surface of the passivation layer, and sintering and curing the silver paste at a low temperature to fabricate a positive electrode and a negative electrode, obtaining a passivated contact solar cell, wherein the peak temperature of the low-temperature sintering is 600 °C.

[0110] The photo-injection treatment step is: heating the passivated contact solar cell once; heating and simultaneously irradiating the passivated contact solar cell twice; wherein, the peak temperature of the first heating is 500 °C, the peak temperature of the second heating is 200 °C, and the energy density of the light is 50 kW / m 2 .

[0111] The optoelectronic pretreatment step is: irradiating the passivated contact solar cell and simultaneously applying a reverse bias voltage to the passivated contact solar cell; wherein, the reverse bias voltage is 30 V; the spectral wavelength of the light is 1064 nm; the energy density of the light is 5000 kW / m 2 ; the scanning rate of the light is 50 m / s.

[0112] The processing steps for connecting solar cells include: simultaneously welding a welding tape to 6 passivated contact solar cells to obtain a battery string, and these 6 passivated contact solar cells are half cells.

[0113] The target optoelectronic processing steps include: irradiating the battery string with a light source, and simultaneously applying a reverse bias voltage to the battery string using a voltage source; wherein, the spectral wavelength of the light source is 1064 nm; the energy density of the light is 5000 kW / m 2 ; the scanning rate of the light is 50 m / s.

[0114] Example 1 also provides a battery string, which is prepared by the preparation method of the above-mentioned battery string.

[0115] Example 2

[0116] Example 2 provides a preparation method of a battery string and a battery string. The difference between this preparation method and that of Example 1 is that no optoelectronic pretreatment step is set.

[0117] Example 3

[0118] Example 3 provides a preparation method of a battery string and a battery string. The difference between this preparation method and that of Example 1 is that the optoelectronic pretreatment step is carried out first, and then the light injection treatment step is carried out.

[0119] Example 4

[0120] Example 4 provides a preparation method of a battery string and a battery string. The difference between this preparation method and that of Example 1 is that no light injection treatment step is set.

[0121] Example 5

[0122] Example 5 provides a preparation method of a battery string and a battery string. The difference between this preparation method and that of Example 1 is that no light injection treatment step and optoelectronic pretreatment step are set.

[0123] Example 6

[0124] Example 6 provides a preparation method of a battery string and a battery string. The difference between this preparation method and that of Example 5 is that in the metallization treatment step, the silver paste is sintered at high temperature to form the positive electrode and the negative electrode.

[0125] Example 7

[0126] Example 7 provides a preparation method of a battery string and a battery string. The difference between this preparation method and that of Example 6 is that after the metallization treatment step and before the battery cell connection treatment step, a light injection treatment step is set.

[0127] Comparative Example 1

[0128] 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 optoelectronic processing step is not set.

[0129] Comparative Example 2

[0130] Comparative Example 2 provides a passivated contact solar cell. The difference between Comparative Example 2 and Example 1 is that the target optoelectronic processing step and the cell connection processing step are not set.

[0131] Comparative Example 3

[0132] 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 optoelectronic processing step is not set.

[0133] Comparative Example 4

[0134] Comparative Example 4 provides a passivated contact solar cell. The difference between Comparative Example 4 and Example 2 is that the cell connection processing step and the target optoelectronic processing step are not set.

[0135] Comparative Example 5

[0136] 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 optoelectronic processing step is not set.

[0137] Comparative Example 6

[0138] 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 optoelectronic processing step are not set.

[0139] Comparative Example 7

[0140] 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 optoelectronic processing step are not set.

[0141] Comparative Example 8

[0142] 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 optoelectronic processing step is not set.

[0143] Comparative Example 9

[0144] 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 optoelectronic processing step is not set.

[0145] Comparative Example 10

[0146] Comparative Example Ten provides a passivated contact solar cell. The difference between Comparative Example Ten and Example Five is that the cell connection processing step and the target optoelectronic processing step are not provided.

[0147] Comparative Example Eleven

[0148] Comparative Example Eleven provides a method for preparing a battery string and a battery string. The difference between Comparative Example Eleven and Example Six is that the target optoelectronic processing step is not provided.

[0149] Comparative Example Twelve

[0150] Comparative Example Twelve provides a passivated contact solar cell. The difference between Comparative Example Twelve and Example Six is that the cell connection processing step and the target optoelectronic processing step are not provided.

[0151] Comparative Example Thirteen

[0152] Comparative Example Thirteen provides a method for preparing a battery string and a battery string. The difference between Comparative Example Thirteen and Example Seven is that the target optoelectronic processing step is not provided.

[0153] Comparative Example Fourteen

[0154] Comparative Example Fourteen provides a passivated contact solar cell. The difference between Comparative Example Fourteen and Example Seven is that the cell connection processing step and the target optoelectronic processing step are not provided.

[0155] Performance Test

[0156] For the battery strings or passivated contact solar cells provided in the above examples and comparative examples, performance tests of photoelectric conversion efficiency, open-circuit voltage, short-circuit current, fill factor, and series resistance are carried out using a solar cell module tester. The experimental test results are as follows, where E ff (%) represents the photoelectric conversion efficiency, I SC (A) represents the short-circuit current, V OC (mV) represents the open-circuit voltage, FF (%) represents the fill factor, and Rs (mΩ) represents the series resistance. The test results are shown in Tables 1 to 7.

[0157] Table 1

[0158]

[0159] Table 2

[0160]

[0161] Table 3

[0162]

[0163] Table 4

[0164]

[0165] Table 5

[0166]

[0167] Table 6

[0168]

[0169] Table 7

[0170]

[0171] Comparing the examples and comparative examples in each table individually, each table shows that adding the target optoelectronic processing step after the cell connection processing step can reduce the series resistance and / or increase the fill factor.

[0172] It can be seen from Example 1 to Example 5 that for the low-temperature sintering process, adding the target optoelectronic processing after cell connection can reduce the series resistance to between 1 mΩ and 1.2 mΩ. It can be seen from Example 6 and Example 7 that for the high-temperature sintering process, adding the target optoelectronic processing after cell connection can reduce the series resistance of the cells to 2.97 mΩ and 5.6 mΩ.

[0173] In Example 1, Example 2, and Example 3, the light injection processing step in Example 1 is before the optoelectronic pretreatment step, Example 2 does not have an optoelectronic pretreatment step, and the light injection processing step in Example 3 is after the optoelectronic pretreatment step. The optoelectronic conversion efficiency, fill factor, and series resistance of Example 1 and Example 2 are relatively close. However, since Example 1 has an optoelectronic pretreatment step, it can significantly reduce the series resistance before the cell connection processing step (combining with Comparative Example 3), so efficiency sorting can be carried out. While the series resistance of Example 2 before the cell connection processing step is too large to carry out efficiency sorting. Comparing Example 1 and Example 3, when the optoelectronic pretreatment step is before the light injection step, it can more effectively improve the optoelectronic conversion efficiency, short-circuit current, open-circuit voltage, and fill factor, and can reduce the series resistance.

[0174] It can be seen from Comparative Example 6 and Comparative Example 7 in Table 3, and Comparative Example 11 and Comparative Example 13 in Table 6 and Table 7 that adding the light injection step can increase the open-circuit voltage and short-circuit current.

[0175] As can be seen from the data in Table 1, in Comparative Example 1, a cell connection treatment step was added based on the solution of Comparative Example 2. The series resistance of Comparative Example 1 increased, and both the fill factor and the photoelectric conversion efficiency decreased significantly, indicating that only setting the photoelectric pretreatment step could not balance the influence caused by cell connection. In Example 1, by adding a target photoelectric treatment step after the cell connection step, the series resistance was further reduced and the photoelectric conversion efficiency was improved compared with cell connection. This shows that the combination of the photoelectric pretreatment step + cell connection + target photoelectric treatment step can further reduce the contact resistance and improve the photoelectric conversion efficiency on the basis of the photoelectric pretreatment reducing the series resistance (in combination with Comparative Example 4).

[0176] Regarding the production of metal electrodes by low-temperature sintering, it can be seen from Tables 1 to 5 that the solution with the most excellent five performance indicators is Example 3. Regarding the production of metal electrodes by high-temperature sintering, it can be seen from Tables 6 and 7 that the most excellent one among the five performance indicators is Example 7.

[0177] In this application, unless otherwise clearly specified and limited, if there is a description such as a first feature being "on" or "under" a second feature, its meaning can be that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. Moreover, the first feature being "above", "over" and "on" the second feature can be that the first feature is directly above or obliquely above the second feature, or merely indicates that the first feature has a higher horizontal height than the second feature. The first feature being "under", "beneath" and "under" the second feature can be that the first feature is directly below or obliquely below the second feature, or merely indicates that the first feature has a lower horizontal height than the second feature.

[0178] It should be noted that if an element is referred to as "fixed to" or "disposed on" another element, it can be directly on the other element or there may also be an intermediate element. If an element is considered to be "connected" to another element, it can be directly connected to the other element or there may be an intermediate element at the same time. If so, the terms "vertical", "horizontal", "upper", "lower", "left", "right" and similar expressions used in this application are only for the purpose of illustration and do not represent the only implementation.

[0179] The technical features of the above-described embodiments can be combined arbitrarily. For the sake of brevity of description, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered as the scope described in this specification.

[0180] The above-described embodiments merely represent several implementation manners of the present application. The description thereof is relatively specific and detailed, but it should not be construed as a limitation on the scope of the patent application. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present application, several modifications and improvements can still be made, and these all fall within the protection scope of the present application. Therefore, the protection scope of the patent of the present application shall be subject to 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 to 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 separately 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 method for preparing a cell string according to claim 2, wherein The spectral wavelength of the light source is 500nm - 1200nm; and / or, the energy density of the light source is 10 kW / m 2 ~10000 kW / m 2 ; And / or, the scanning rate of the light source is 26m / s - 65 m / s; And / or, 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.

4. The manufacturing method of the battery string according to claim 1, wherein, In the metallization treatment step, apply a conductive material on the semiconductor substrate and sinter and cure it at a low temperature to obtain a cell.

5. The manufacturing method of the battery string according to claim 4, characterized in that, The range of the peak temperature of the low-temperature sintering is 550°C - 720°C.

6. The method for preparing a battery string according to claim 4, wherein 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.

7. The method for preparing a battery string according to claim 6, characterized in that, In the optoelectronic pre-treatment step, the reverse bias voltage is 10V - 50V; And / or, the spectral wavelength of the light in the light treatment is 500nm - 1200nm; and / or, the energy density of light in the light treatment is 10 kW / m 2 ~10000 kW / m 2 ; And / or, the scanning rate of the light in the light treatment is 26m / s - 65 m / s.

8. The method for preparing a battery string according to claim 4, wherein, After the metallization treatment step and before the cell connection treatment step, it further includes: performing light injection treatment on the cell.

9. The method for preparing a battery string according to claim 1, wherein, 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.

10. The manufacturing method of the battery string according to claim 9, characterized in that, The range of the peak temperature of the high-temperature sintering is 780°C - 850°C.

11. The method for preparing a battery string according to claim 9, characterized in that, After the metallization treatment step and before the cell connection treatment step, it further includes: performing light injection treatment on the cell.

12. The method for preparing a battery string according to claim 8 or 11, wherein The step of performing light injection treatment on the cell includes the following steps: Heat the cell once; Heat the cell a second time while irradiating the cell with light; Among them, the peak temperature of the first heating is 400°C to 600°C, the peak temperature of the second heating is 100°C to 300°C, and the energy density of light is 10 kW / m 2 ~100 kW / m 2 .

13. The method for preparing a battery string according to any one of claims 1 to 11, 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; Prepare a functional layer: Prepare a functional layer on the silicon substrate to obtain the semiconductor substrate, 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.

14. The method for preparing a battery string according to any one of claims 1 to 11, characterized in that, In the step of connecting and processing the cell, the area size of the cell accounts for one or a combination of 100%, 50%, 25%, 12.5%, and 6.25% of the area size of the full-sized cell.

15. The manufacturing method of the battery string according to any one of claims 1 to 11, characterized in that In the step of connecting and processing 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.

16. A battery string, characterized in that, The battery string is prepared by the method for preparing the battery string according to any one of claims 1 to 15, and the battery string includes a plurality of serially and / or parallely connected cells.

17. A photovoltaic module, characterized in that, The photovoltaic module includes a plurality of serially and / or parallely connected battery strings, and the battery strings are prepared by the method for preparing the battery string according to any one of claims 1 to 15.

Images