Back contact photovoltaic cell and method of making same, photovoltaic module

Abstract

The application relates to a back contact photovoltaic cell and a preparation method thereof and a photovoltaic module. The preparation method of the back contact photovoltaic cell comprises the following steps: providing a cell pre-product, the first surface of the cell pre-product is provided with positive grid lines and negative grid lines at intervals; applying a reverse voltage smaller than a breakdown voltage to the cell pre-product in a first preset area; and using a laser light source to scan and irradiate the cell pre-product in a second preset area, and the circuit current value of the second preset area is controlled to be 0.1 A-40 A; wherein the first preset area and the second preset area are located in different areas of the cell pre-product. The preparation method of the back contact photovoltaic cell can improve the passivation contact performance of the back contact photovoltaic cell, improve the open circuit voltage and the fill factor of the back contact photovoltaic cell, and further improve the conversion efficiency.

Description

[0001] Related applications

[0002] This application is a divisional application of the Chinese patent application filed by the applicant on May 29, 2025, with application number 202510716006.7 and entitled "Back contact photovoltaic cell and preparation method thereof, photovoltaic module". Technical Field

[0003] This application relates to the field of photovoltaic technology, and in particular to a back-contact photovoltaic cell and its preparation method, and a photovoltaic module. Background Technology

[0004] Silicon-based photovoltaic (PV) cells are currently the most widely used type of PV cell. In silicon-based PV cells, P-type and N-type silicon are formed through doping, with a PN junction formed at the interface, generating a built-in electric field. Under the influence of this built-in electric field, electrons move towards the N-region, and holes move towards the P-region, thus achieving carrier separation. When an external circuit is closed, the separated electrons and holes flow in the circuit, forming a current, thereby converting solar energy into electrical energy. Back-contact PV cells concentrate all the positive and negative grid lines on the back of the cell, avoiding light loss due to shading from the front grid lines, and achieving higher photoelectric conversion efficiency. Summary of the Invention

[0005] Therefore, it is necessary to provide a back-contact photovoltaic cell, its fabrication method, and a photovoltaic module. The fabrication method of the back-contact photovoltaic cell in this application can improve the passivation contact performance of the back-contact photovoltaic cell, increase the open-circuit voltage and fill factor of the back-contact photovoltaic cell, and thus improve the conversion efficiency.

[0006] In a first aspect, this application provides a method for preparing a back-contact photovoltaic cell, comprising:

[0007] A battery pre-product is provided, wherein a positive grid line and a negative grid line are spaced apart on a first surface of the battery pre-product;

[0008] A reverse voltage less than the breakdown voltage is applied to the battery pre-finished product in the first preset region;

[0009] The battery pre-product is scanned and irradiated in a second preset area using a laser light source, and the circuit current value of the second preset area is controlled to be 0.1A~40A; wherein the first preset area and the second preset area are located in different areas of the battery pre-product;

[0010] The scanning irradiation sequentially includes a first scanning period, a second scanning period, and a third scanning period;

[0011] During the first scanning period, the circuit current value of the second preset region is increased, and the voltage value of the second preset region is decreased.

[0012] During the third scan period, the circuit current value of the second preset region is reduced, and the voltage value of the second preset region is increased.

[0013] During the second scanning period, the fluctuation range of the circuit current value in the second preset region is less than or equal to the first preset value.

[0014] In some embodiments, the second scan period includes a first sub-scan period, a second sub-scan period, and a third sub-scan period in sequence;

[0015] The voltage value of the first sub-scan period is controlled to be greater than the voltage value of the second sub-scan period;

[0016] The voltage value of the first sub-scan period is controlled to be greater than the voltage value of the third sub-scan period.

[0017] In some embodiments, during the second sub-scan period, the initial voltage value of the second preset region is controlled to be greater than the final voltage value.

[0018] In some embodiments, during the second sub-scan period, the voltage fluctuation range of the second preset region is controlled to be less than or equal to a second preset value.

[0019] In some implementations, during the second sub-scan period, the voltage fluctuation of the second preset region is controlled to be larger in the initial stage.

[0020] In some implementations, during the second sub-scan period, the fluctuation range of the voltage value in the second preset region is controlled to be smaller at the end.

[0021] In some implementations, the first preset value is [-2A, +2A].

[0022] In some implementations, the second preset value is [-1V, +4V].

[0023] In some implementations, the voltage value of the third sub-scan period is controlled to be greater than the voltage value at the end of the second sub-scan period.

[0024] In some implementations, the voltage value of the third sub-scan period is controlled to be lower than the voltage value at the beginning of the second sub-scan period.

[0025] In some implementations, during the first sub-scan period, the fluctuation range of the voltage value in the second preset region is controlled to be less than or equal to a third preset value.

[0026] In some embodiments, during the third sub-scan period, the fluctuation range of the voltage value in the second preset region is controlled to be less than or equal to a third preset value.

[0027] In some implementations, the third preset value is [-0.5V, +0.5V].

[0028] In some implementations, the durations of the second sub-scan period, the first sub-scan period, and the third sub-scan period decrease sequentially.

[0029] In some embodiments, after applying a reverse voltage less than the breakdown voltage to the battery pre-product in a first preset region, before scanning and irradiating the battery pre-product in a second preset region using a laser light source, the circuit current value in the second preset region is less than 10A.

[0030] In some embodiments, the first preset region and the second preset region are located on the first surface.

[0031] In some embodiments, the first preset region is located on the first surface, the second preset region is located on the second surface, and the second surface and the first surface are disposed opposite to each other.

[0032] In some embodiments, the shape of the laser spot is controlled to be circular or rectangular.

[0033] In some embodiments, the wavelength of the laser source is 300nm to 1200nm.

[0034] In some embodiments, the scanning speed of the laser light source is controlled to be 0.5 m / s to 8 m / s.

[0035] In some embodiments, the scanning time of the laser light source is controlled to be 0.05s to 30s.

[0036] In some embodiments, the equivalent load of the detection circuit for the battery pre-product is less than 5Ω.

[0037] In some embodiments, the reverse voltage is 1V to 25V.

[0038] In some embodiments, during the scanning irradiation process, the surface temperature of the battery preform is controlled to be less than 300°C.

[0039] Secondly, this application provides a back-contact photovoltaic cell, which is prepared using the back-contact photovoltaic cell preparation method described in any one of the above-mentioned methods.

[0040] In some embodiments, the emitter sheet resistance of the photovoltaic cell is less than 1000 Ω / sq.

[0041] Thirdly, this application provides a photovoltaic module, comprising:

[0042] Cover plate;

[0043] At least one battery string, the battery string comprising a plurality of back-contact photovoltaic cells as described in any one of the preceding descriptions; and

[0044] An encapsulation layer is located between the cover plate and the battery string, and the cover plate is connected to the battery string through the encapsulation layer.

[0045] In the aforementioned method for fabricating a back-contact photovoltaic cell, a reverse voltage less than the breakdown voltage is applied to the pre-formed cell in a first preset region. A laser source is then used to scan and irradiate the pre-formed cell in a second preset region, different from the first preset region. This laser irradiation excites charge carriers, and the applied reverse voltage generates a local current in the second preset region. Under the influence of this current, sintering occurs at the laser irradiation site, initiating mutual diffusion between the grid paste and the silicon material, thereby significantly reducing the contact resistance between the metal and the semiconductor. Once the diffused contact is formed, the resistance decreases, the heat at the melting point disappears instantly, and the temperature drops, resulting in an ohmic contact with good contact effect and high contact quality. A reverse voltage less than the breakdown voltage is applied to the pre-finished battery in the first preset region. A laser light source is used to scan and irradiate the pre-finished battery in the second preset region. Based on controlling the circuit current value of the second preset region to be 0.1A~40A, the reverse voltage and the laser light source work together. In the first scanning period, the circuit current value of the second preset region is increased while the voltage value of the second preset region is decreased. In the second scanning period, the fluctuation range of the circuit current value of the second preset region is controlled to be less than or equal to the first preset value. In the third scanning period, the circuit current value of the second preset region is controlled to decrease while the voltage value of the second preset region is increased. This can improve the synchronization matching of laser and voltage, ensure that the laser-excited charge carriers achieve directional movement under the action of the electric field, reduce the decrease in current density caused by charge carrier recombination, improve sintering quality, facilitate the improvement of passivation contact performance of back contact photovoltaic cells, improve the open circuit voltage and fill factor of back contact photovoltaic cells, and thus improve conversion efficiency. Attached Figure Description

[0046] Figure 1 A schematic diagram illustrating the steps of a method for preparing a back-contact photovoltaic cell according to an embodiment of this application;

[0047] Figure 2A schematic diagram illustrating the application of a reverse voltage less than the breakdown voltage to a battery preform in a first predetermined region, as provided in one embodiment of this application.

[0048] Figure 3 This is a graph showing the changes in circuit current and voltage values ​​in a second preset area during the scanning and irradiation of the battery pre-finished product using a laser light source, as provided in one embodiment of this application. Detailed Implementation

[0049] To make the above-mentioned objectives, features, and advantages of this application more apparent and understandable, a detailed description of specific embodiments of this application is provided below. Many specific details are set forth in the following description to provide 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 modifications without departing from the spirit of this application. Therefore, this application is not limited to the specific embodiments disclosed below.

[0050] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0051] In the description of this application, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc., indicating the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application.

[0052] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this application, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0053] In this application, unless otherwise expressly specified and limited, the terms "installation," "connection," "joining," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise expressly limited. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0054] Reference Figure 1 , Figure 3 As shown, one embodiment of this application provides a method for fabricating a back-contact photovoltaic cell, comprising:

[0055] A battery pre-finished product is provided, wherein positive grid lines and negative grid lines are spaced apart on the first surface of the battery pre-finished product;

[0056] A reverse voltage less than the breakdown voltage is applied to the battery pre-finished product in the first preset region;

[0057] A laser light source is used to scan and irradiate the pre-finished battery in a second preset area, and the circuit current value of the second preset area is controlled to be 0.1A~40A; wherein, the first preset area and the second preset area are located in different areas of the pre-finished battery.

[0058] The scanning irradiation consists of the first scanning phase, the second scanning phase, and the third scanning phase, in sequence.

[0059] During the first scan period, the circuit current value of the second preset region is increased, and the voltage value of the second preset region is decreased.

[0060] During the third scan period, the circuit current value of the second preset region is reduced, and the voltage value of the second preset region is increased.

[0061] During the second scan period, the fluctuation range of the circuit current value controlling the second preset region is less than or equal to the first preset value.

[0062] It is understandable that before scanning and irradiating the pre-formed battery using a laser source in the second preset region, the positive and negative grid lines spaced apart on the first surface of the pre-formed battery are both grid line pastes. Through the above-described preparation method, good ohmic contact can be achieved between the positive and negative grid lines and the doped silicon layer in the pre-formed battery. In the above-described method for preparing a back-contact photovoltaic cell, a reverse voltage less than the breakdown voltage is applied to the pre-formed battery in the first preset region, and a laser source is used to scan and irradiate the pre-formed battery in a second preset region different from the first preset region. By scanning and irradiating the pre-formed battery with the laser source, charge carriers are excited, and the applied reverse voltage generates a local current in the second preset region. Under the influence of this current, sintering occurs at the laser irradiation site, inducing mutual diffusion between the grid line paste and the silicon material, thereby significantly reducing the contact resistance between the metal and the semiconductor. Once the diffused contact is formed, the resistance decreases, the heat at the melting point disappears instantly, and the temperature drops, thus forming an ohmic contact with good contact effect and high contact quality. A reverse voltage less than the breakdown voltage is applied to the pre-finished battery in the first preset region. A laser light source is used to scan and irradiate the pre-finished battery in the second preset region. Based on controlling the circuit current value of the second preset region to be 0.1A~40A, the reverse voltage and the laser light source work together. In the first scanning period, the circuit current value of the second preset region is increased while the voltage value of the second preset region is decreased. In the second scanning period, the fluctuation range of the circuit current value of the second preset region is controlled to be less than or equal to the first preset value. In the third scanning period, the circuit current value of the second preset region is controlled to decrease while the voltage value of the second preset region is increased. This can improve the synchronization matching of laser and voltage, ensure that the laser-excited charge carriers achieve directional movement under the action of the electric field, reduce the decrease in current density caused by charge carrier recombination, improve sintering quality, facilitate the improvement of passivation contact performance of back contact photovoltaic cells, improve the open circuit voltage and fill factor of back contact photovoltaic cells, and thus improve conversion efficiency.

[0063] Reference Figure 2As shown, it can be understood that the circuit current in the second preset region refers to the current value of the output signal of the back-contact photovoltaic cell, and the voltage value refers to the voltage value of the output signal of the back-contact photovoltaic cell. Changes in the circuit current and voltage values ​​can be monitored by setting voltage and current detection modules at both ends of the cell. For example, the reverse voltage can be connected to the grid lines of the back-contact photovoltaic cell via an external voltage source. The contact point between the voltage source and the photovoltaic cell can be a solder joint or a grid line. The contact point can be all grid lines and all solder joints in the first preset region, or it can be some grid lines and some solder joints in the first preset region. It can be understood that compared to existing technologies where the positive and negative grid lines are located on different sides of the cell, in a back-contact photovoltaic cell, both the positive and negative grid lines are located on the same surface of the photovoltaic cell. Applying a reverse voltage to the pre-finished cell in the first preset region is more difficult and requires precise control. For example, the contact between the voltage source and the photovoltaic cell can be achieved using a probe.

[0064] Controlling the circuit current value in the second preset region allows for control of the local heat generation efficiency within that region. Within the aforementioned circuit current value range, the instantaneous temperature in the second preset region is conducive to melting the grid paste and achieving co-diffusion with silicon, forming a highly conductive ohmic contact region upon cooling. Simultaneously, it avoids the risk of thermal damage to the pre-finished battery. Optionally, the circuit current value in the second preset region can be controlled to be 0.1A, 0.2A, 0.5A, 1A, 2A, 5A, 8A, 10A, 15A, 20A, 25A, 30A, 35A, or 40A. Alternatively, the circuit current value can be controlled within any two of the aforementioned circuit current values. Preferably, the circuit current value in the second preset region is controlled to be between 2A and 20A.

[0065] In some implementations, the voltage value of the second preset region is different from the value of the reverse voltage.

[0066] In some implementations, the first preset value is [-2A, +2A].

[0067] Optionally, the first preset value is -2A, -1.5A, -1A, -0.5A, 0A, +0.5A, +1A, +1.5A or +2A, or the first preset value may be within the range of any two of the above current values.

[0068] In some embodiments, the second scan period includes a first sub-scan period, a second sub-scan period, and a third sub-scan period in sequence;

[0069] The voltage value of the first sub-scan period is controlled to be greater than the voltage value of the second sub-scan period;

[0070] The voltage value of the first sub-scan period is controlled to be greater than the voltage value of the third sub-scan period.

[0071] Based on controlling the signals of the first, second, and third scan periods, the directional movement of charge carriers is driven by reverse voltage. By controlling the voltage value of the first sub-scan period to be greater than that of the second sub-scan period, and the voltage value of the first sub-scan period to be greater than that of the third sub-scan period, the reverse voltage and the scanning irradiation energy of the laser source can work together to promote the electric field to accelerate electron migration, generate Joule heat by colliding with the grid paste, promote the formation of ohmic contact regions, facilitate the improvement of the passivation contact performance of the back contact photovoltaic cell, increase the open circuit voltage and fill factor of the back contact photovoltaic cell, and thus improve the conversion efficiency.

[0072] In some implementations, during the second sub-scan period, the initial voltage value of the second preset region is controlled to be greater than the final voltage value.

[0073] It is understandable that in the second sub-scan period, the initial period refers to the first half of the time frame of the first sub-scan period, and the final period refers to the second half of the time frame of the third sub-scan period. Controlling the initial voltage value of the second preset region to be greater than the final voltage value during the second sub-scan period means that the voltage value of the second preset region in the first half of the second sub-scan period is greater than the voltage value in the second half. Controlling the initial voltage value of the second preset region to be greater than the final voltage value during the second sub-scan period helps improve the passivation contact performance of the back contact photovoltaic cells, increases the open-circuit voltage and fill factor of the back contact photovoltaic cells, and thus improves the conversion efficiency.

[0074] In some implementations, during the second sub-scan period, the voltage fluctuation range of the second preset region is controlled to be less than or equal to a second preset value.

[0075] In some implementations, the second preset value is [-1V, +4V].

[0076] Optionally, the second preset value is -1V, -0.5V, 0V, +0.5V, +1V, +1.5V, +2V, +2.5V, +3V, +3.5V, or +4V. Optionally, the second preset value can also be within the range of any two of the above voltage values.

[0077] It is understandable that in the above photovoltaic cell preparation method, controlling the fluctuation range of the voltage value has an important impact, specifically as follows: (1) Impact on contact resistance: Appropriate reverse voltage can promote the interdiffusion of conductive particles in the grid paste with silicon and reduce contact resistance. Excessive voltage fluctuation may cause the reverse voltage to be too high or too low instantaneously. When it is too high, it may cause reverse breakdown of the cell. Once reverse breakdown occurs, due to the current shunting effect, the local conductive current density in the illuminated area will be much lower than when it is not broken down, which increases the contact resistance between the metal and silicon. When the voltage is too low, it cannot provide sufficient driving force, so that the carriers do not move sufficiently and the silver-silicon interdiffusion is insufficient, which will also lead to an increase in contact resistance. (2) Impact on cell efficiency: When the voltage fluctuation is too large, it is easy to deviate from the optimal voltage value during sintering, which will reduce the cell efficiency. When the voltage is too high and exceeds the threshold, although the contact resistance may be further reduced, it will damage the passivation layer, increase the recombination current density, reduce the open circuit voltage, reduce the overall performance, and significantly reduce the efficiency. When the voltage is too low, the carrier concentration is insufficient, the contact optimization effect is poor, the fill factor is reduced, and the battery efficiency will also be reduced. (3) Effect on the passivation layer: A stable and appropriate voltage value helps to reduce damage to the passivation layer. If the voltage value fluctuates too much, the passivation layer will be subjected to too high electric field and energy, which will lead to increased damage to the passivation layer, affect its passivation effect on the battery, and increase the recombination of carriers inside the battery; while if the voltage value is too low, it is difficult to make full use of the synergistic effect of laser and reverse voltage to optimize the contact, and it may be necessary to compensate by increasing the sintering temperature, which will also cause some damage to the passivation layer.

[0078] During the second sub-scanning period, the voltage fluctuation range of the second preset region is controlled to be less than or equal to the second preset value. This facilitates keeping the voltage value within an optimal range during the scanning irradiation process. This reduces the contact resistance while minimizing the impact on cell efficiency and passivation layer, improving the passivation contact performance of the back contact photovoltaic cell, increasing the open-circuit voltage and fill factor of the back contact photovoltaic cell, and ultimately improving the conversion efficiency.

[0079] In some implementations, during the second sub-scan period, the voltage fluctuation of the second preset region is controlled to be larger in the initial stage.

[0080] In some implementations, during the second sub-scan period, the fluctuation range of the voltage value in the preset region is smaller at the end.

[0081] In some implementations, the voltage value of the third sub-scan period is controlled to be greater than the voltage value at the end of the second sub-scan period.

[0082] It is understandable that in the third sub-scan period, the initial stage refers to the first half of the period close to the second sub-scan period, and the final stage refers to the second half of the period close to the third sub-scan period. The voltage value in the third sub-scan period being greater than the voltage value at the end of the second sub-scan period means that the voltage value in the first half of the third sub-scan period is greater than the voltage value in the second half. Controlling the voltage value in the third sub-scan period to be greater than the voltage value at the end of the second sub-scan period helps improve the passivation contact performance of the back-contact photovoltaic cells, increases the open-circuit voltage and fill factor of the back-contact photovoltaic cells, and thus improves the conversion efficiency.

[0083] In some implementations, the voltage value of the third sub-scan period is controlled to be lower than the voltage value at the beginning of the second sub-scan period.

[0084] Controlling the voltage value of the third sub-scan period to be lower than the voltage value at the beginning of the second sub-scan period facilitates the improvement of the passivation contact performance of the back contact photovoltaic cell, increases the open circuit voltage and fill factor of the back contact photovoltaic cell, and thus improves the conversion efficiency.

[0085] In some implementations, during the first sub-scan period, the fluctuation range of the voltage value in the second preset region is controlled to be less than or equal to a third preset value.

[0086] In some implementations, during the third sub-scan period, the fluctuation range of the voltage value in the second preset region is controlled to be less than or equal to a third preset value.

[0087] In some implementations, the third preset value is [-0.5V, +0.5V].

[0088] Optionally, the third preset value is -0.5V, -0.4V, -0.3V, -0.2V, -0.1V, 0V, +0.1V, +0.2V, +0.3V, +0.4V, or +0.5V, or the third preset value may be within the range of any two of the above voltage values.

[0089] During the first sub-scanning period, the voltage fluctuation range of the second preset region is controlled to be less than or equal to the third preset value; during the third sub-scanning period, the voltage fluctuation range of the second preset region is controlled to be less than or equal to the third preset value. This facilitates controlling the voltage value within an optimal voltage range during the scanning irradiation process, thereby reducing contact resistance, minimizing the impact on cell efficiency and passivation layer, improving the passivation contact performance of the back contact photovoltaic cell, increasing the open-circuit voltage and fill factor of the back contact photovoltaic cell, and ultimately improving the conversion efficiency.

[0090] In some implementations, the durations of the second sub-scan period, the first sub-scan period, and the third sub-scan period decrease sequentially.

[0091] Refer again Figure 3As shown, in some embodiments, the scanning irradiation sequentially includes a first scanning period, a first sub-scanning period, a second sub-scanning period, a third sub-scanning period, and a third scanning period. During the first scanning period, the laser source begins to irradiate the pre-finished battery, the circuit current increases rapidly, and the voltage across the battery cell drops rapidly due to the influence of the external circuit resistance. During the first sub-scanning period, both the voltage and current values ​​across the pre-finished battery cell are relatively stable, with only minor fluctuations. During the second sub-scanning period, as the scanning irradiation progresses, the voltage value drops by 1V to 4V with significant fluctuations, while the circuit current remains essentially constant. During the third sub-scanning period, near the end of the scanning irradiation, the voltage value stabilizes again. During the third scanning period, the laser source leaves the pre-finished battery, the light emission ends, the circuit current drops rapidly, and the voltage value across the pre-finished battery cell returns to its pre-incident state.

[0092] In some embodiments, after applying a reverse voltage less than the breakdown voltage to the battery pre-product in the first preset region, before scanning and irradiating the battery pre-product in the second preset region using a laser light source, the circuit current value in the second preset region is less than 10A.

[0093] Optionally, before scanning and irradiating the pre-finished battery product in the second preset area using a laser light source, the circuit current value of the second preset area is greater than or equal to 0.0001A and less than 10A. Further optionally, before scanning and irradiating the pre-finished battery product in the second preset area using a laser light source, the circuit current value of the second preset area is 0.0001A, 0.001A, 0.01A, 0.1A, 1A, 2A, 3A, 4A, 5A, 6A, 7A, 8A, 9A, 9.9A, 9.99A, or 9.999A; or, before scanning and irradiating the pre-finished battery product in the second preset area using a laser light source, the circuit current value of the second preset area can also be within the range of any two of the above current values.

[0094] In some embodiments, the first preset region and the second preset region are located on the first surface.

[0095] In some embodiments, a first preset region is located on a first surface, a second preset region is located on a second surface, and the second surface and the first surface are arranged opposite to each other.

[0096] In some embodiments, the shape of the laser spot is controlled to be circular or rectangular.

[0097] In some embodiments, the wavelength of the laser source is 300nm to 1200nm.

[0098] Optionally, the wavelength of the laser source is 300nm, 400nm, 500nm, 600nm, 700nm, 800nm, 900nm, 1000nm, 1100nm, or 1200nm, or the wavelength of the laser source may be within the range of any two of the above wavelengths.

[0099] In some embodiments, the scanning speed of the laser light source is controlled to be 0.5 m / s to 8 m / s.

[0100] Optionally, the scanning speed of the laser source can be controlled to be 0.5m / s, 1m / s, 2m / s, 3m / s, 4m / s, 5m / s, 6m / s, 7m / s or 8m / s, or the scanning speed of the laser source can be controlled to be within the range of any two of the above speeds.

[0101] In some embodiments, the scanning time of the laser light source is controlled to be 0.05s to 30s.

[0102] Optionally, the scanning time of the laser source can be controlled to be 0.05s, 0.1s, 0.5s, 1s, 2s, 5s, 10s, 15s, 20s, 25s or 30s, or the scanning time of the laser source can be controlled to be within any two of the above times.

[0103] It is understandable that the energy input density per unit area can be controlled by adjusting the wavelength, scanning speed, and scanning time of the laser source. When the energy input density per unit area is too low, it may result in insufficient excitation of charge carriers or failure to achieve silver-silicon diffusion, leading to insufficient diffusion depth, poor passivation, and high contact resistance. When the energy input density per unit area is too high, it can lead to an expansion of the heat-affected zone, potentially causing localized overheating and melting of the silicon wafer, damage to the surrounding passivation layer, or destruction of the cell structure. Within the parameter ranges of the aforementioned laser sources, the effect of promoting eutectic formation between the grid lines and silicon material is better, which facilitates improved passivation contact performance of the back-contact photovoltaic cell, increases the open-circuit voltage and fill factor of the back-contact photovoltaic cell, and thus improves conversion efficiency.

[0104] In some embodiments, the equivalent load of the detection circuit for the battery pre-product is less than 5Ω.

[0105] Optionally, the equivalent load of the detection circuit for the battery pre-product is 0.001Ω to 4.999Ω. Further optionally, the equivalent load of the detection circuit for the battery pre-product is 0.001Ω, 0.01Ω, 0.1Ω, 0.5Ω, 1Ω, 2Ω, 3Ω, 4Ω, 4.5Ω, 4.9Ω, 4.99Ω, or 4.999Ω; alternatively, the equivalent load of the detection circuit for the battery pre-product can also be within the range of any two of the above resistors.

[0106] In some implementations, the reverse voltage is 1V to 25V.

[0107] The reverse voltage is used to establish an electric field in the laser-irradiated area, driving the directional movement of charge carriers and increasing the local current density. If the reverse voltage is too low, the local current may not generate sufficient Joule heating. If the reverse voltage is too high, it may trigger an arc discharge or break down the passivation layer. Optionally, the reverse voltage can be 1V, 2V, 5V, 8V, 10V, 12V, 15V, 18V, 20V, 22V, or 25V, or it can be within any two of the above voltage ranges.

[0108] In some embodiments, during the scanning irradiation process, the surface temperature of the battery preform is controlled to be less than 300°C.

[0109] Excessive surface temperature of the battery pre-product may affect battery performance. The surface temperature of the battery pre-product can be controlled by adjusting the reverse voltage or the parameters of the laser light source. Optionally, during scanning and irradiation, the surface temperature of the battery pre-product is controlled between 20°C and 299°C. More preferably, the surface temperature of the battery pre-product is controlled at 20°C, 30°C, 50°C, 80°C, 100°C, 120°C, 150°C, 180°C, 200°C, 220°C, 250°C, 290°C, or 299°C, or it can be controlled within any two of the above temperature ranges.

[0110] Within the range of parameters in the above-mentioned method for preparing back-contact photovoltaic cells, it is convenient to improve the passivation contact performance of back-contact photovoltaic cells, increase the open-circuit voltage and fill factor of back-contact photovoltaic cells, and thus improve the conversion efficiency.

[0111] Another embodiment of this application provides a back-contact photovoltaic cell, which is prepared using any of the back-contact photovoltaic cell preparation methods described above.

[0112] In some of these implementations, the emitter sheet resistance of the photovoltaic cell is less than 1000 Ω / sq.

[0113] Optionally, the emitter sheet resistance of the photovoltaic cell is 1Ω / sq to 999Ω / sq. More preferably, the emitter sheet resistance of the photovoltaic cell is 1Ω / sq, 2Ω / sq, 5Ω / sq, 1Ω / sq, 20Ω / sq, 50Ω / sq, 100Ω / sq, 200Ω / sq, 300Ω / sq, 500Ω / sq, 600Ω / sq, 800Ω / sq, 900Ω / sq, or 999Ω / sq; alternatively, the emitter sheet resistance of the photovoltaic cell may fall within the range of any two of the aforementioned sheet resistances.

[0114] Another embodiment of this application provides a photovoltaic module, including:

[0115] Cover plate;

[0116] At least one battery string, the battery string comprising a plurality of back-contact photovoltaic cells of any one of the above; and

[0117] The encapsulation layer is located between the cover plate and the battery string, and the cover plate is connected to the battery string through the encapsulation layer.

[0118] The technical features of the above embodiments can be combined in any way. For the sake of brevity, 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, they should be considered to be within the scope of this specification.

[0119] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims, and the specification and drawings can be used to interpret the content of the claims.

Claims

1. A method for preparing a back-contact photovoltaic cell, characterized in that, include: A battery pre-product is provided, wherein a positive grid line and a negative grid line are spaced apart on a first surface of the battery pre-product; A reverse voltage less than the breakdown voltage is applied to the pre-finished battery in a first preset region; the reverse voltage is provided by connecting an external voltage source to the back contact photovoltaic cell; the contact point between the external voltage source and the back contact photovoltaic cell is all or part of the solder joints in the first preset region, and / or, the contact point between the external voltage source and the back contact photovoltaic cell is all or part of the grid lines in the first preset region; The battery pre-product is scanned and irradiated using a laser light source in a second preset area; wherein the first preset area and the second preset area are located in different areas of the battery pre-product. The scanning irradiation sequentially includes a first scanning period, a second scanning period, and a third scanning period; During the first scanning period, the circuit current value of the second preset region is increased, and the voltage value of the second preset region is decreased. During the second scan period, the fluctuation range of the circuit current value in the second preset region is less than or equal to a first preset value, where the first preset value is [-2A, +2A]; the duration of the second scan period is greater than the duration of the first scan period and the third scan period. During the third scan period, the circuit current value of the second preset region is reduced, and the voltage value of the second preset region is increased.

2. The method for preparing a back-contact photovoltaic cell according to claim 1, characterized in that, The second scan period includes, in sequence, a first sub-scan period, a second sub-scan period, and a third sub-scan period; The voltage value of the first sub-scan period is controlled to be greater than the voltage value of the second sub-scan period; The voltage value of the first sub-scan period is controlled to be greater than the voltage value of the third sub-scan period.

3. The method for preparing a back-contact photovoltaic cell according to claim 2, characterized in that, During the second sub-scan period, the initial voltage value of the second preset region is controlled to be greater than the final voltage value.

4. The method for preparing a back-contact photovoltaic cell according to claim 2, characterized in that, During the second sub-scan period, the voltage fluctuation range of the second preset region is controlled to be less than or equal to the second preset value.

5. The method for preparing a back-contact photovoltaic cell according to claim 4, characterized in that, The second preset value is [-1V, +4V].

6. The method for preparing a back-contact photovoltaic cell according to claim 2, characterized in that, Controlling the voltage value of the third sub-scan period to be greater than the voltage value at the end of the second sub-scan period; and / or, The voltage value of the third sub-scan period is controlled to be lower than the voltage value at the beginning of the second sub-scan period.

7. The method for preparing a back-contact photovoltaic cell according to claim 2, characterized in that, During the first sub-scan period, the voltage fluctuation range of the second preset region is controlled to be less than or equal to a third preset value; and / or, During the third sub-scan period, the fluctuation range of the voltage value in the second preset region is controlled to be less than or equal to a third preset value.

8. The method for preparing a back-contact photovoltaic cell according to claim 7, characterized in that, The third preset value is [-0.5V, +0.5V].

9. The method for preparing a back-contact photovoltaic cell according to claim 2, characterized in that, The durations of the second sub-scan period, the first sub-scan period, and the third sub-scan period decrease sequentially.

10. The method for preparing a back-contact photovoltaic cell according to any one of claims 1 to 9, characterized in that, After applying a reverse voltage less than the breakdown voltage to the battery pre-product in the first preset region, before scanning and irradiating the battery pre-product in the second preset region using a laser light source, the circuit current value in the second preset region is less than 10A.

11. The method for preparing a back-contact photovoltaic cell according to any one of claims 1 to 9, characterized in that, The first preset region and the second preset region are located on the first surface; or, The first preset area is located on the first surface, and the second preset area is located on the second surface, with the second surface and the first surface being positioned opposite each other.

12. The method for preparing a back-contact photovoltaic cell according to any one of claims 1 to 9, characterized in that, The laser light source is controlled to have a circular or rectangular spot shape; and / or, The wavelength of the laser source is 300nm~1200nm; and / or, The scanning speed of the laser source is controlled to be 0.5 m / s to 8 m / s; and / or, The scanning time of the laser light source is controlled to be 0.05s~30s; and / or, The equivalent load of the detection circuit used for the battery pre-finished product is less than 5Ω; and / or, The reverse voltage is 1V~25V; and / or, During the scanning irradiation process, the surface temperature of the pre-finished battery is controlled to be less than 300°C.

13. A back-contact photovoltaic cell, characterized in that, The back-contact photovoltaic cell is prepared using any one of claims 1 to 12.

14. The photovoltaic cell according to claim 13, characterized in that, The emitter sheet resistance of the photovoltaic cell is less than 1000 Ω / sq.

15. A photovoltaic module, characterized in that, include: Cover plate; At least one battery string, the battery string comprising a plurality of back-contact photovoltaic cells as described in claim 13 or 14; as well as An encapsulation layer is located between the cover plate and the battery string, and the cover plate is connected to the battery string through the encapsulation layer.

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