Back contact photovoltaic cell, preparation method thereof and photovoltaic module

Abstract

The invention relates to a back contact photovoltaic cell, a preparation method thereof and a photovoltaic module. The preparation method of the back contact photovoltaic cell comprises the steps that a cell pre-finished product is provided, and a positive electrode grid line and a negative electrode grid line are arranged on the first surface of the cell pre-finished product at intervals; applying a reverse voltage smaller than the breakdown voltage to the battery pre-finished product in the first preset area; a laser light source is used for scanning and irradiating the battery pre-finished product in a second preset area, and the circuit current value of the second preset area is controlled to be 0.1-40A; wherein the first preset area and the second preset area are located in different areas of the battery pre-finished product. According to the preparation method of the back contact photovoltaic cell, the passivation contact performance of the back contact photovoltaic cell can be improved, the open-circuit voltage and the fill factor of the back contact photovoltaic cell are improved, and the conversion efficiency is further improved.

Description

Technical Field

[0001] The present application relates to the technical field of photovoltaic technology, and particularly relates to a back-contact photovoltaic cell, a preparation method thereof, and a photovoltaic module. Background Art

[0002] Silicon-based photovoltaic cells are currently the most widely used type of photovoltaic cells. In silicon-based photovoltaic cells, P-type silicon and N-type silicon are formed by doping, and a PN junction is formed at the junction of the two, generating a built-in electric field. Under the action of the built-in electric field, photo-generated carriers move, with electrons moving to the N region and holes moving to the P region, thereby achieving the separation of carriers. When the external circuit is closed, the separated electrons and holes flow in the circuit, forming an electric current, thus realizing the conversion of solar energy into electrical energy. Among them, in a back-contact photovoltaic cell, all the positive and negative grid lines of the photovoltaic cell are concentrated on the back of the cell, avoiding the shading loss of the front grid lines and enabling a relatively high photoelectric conversion efficiency. Summary of the Invention

[0003] Based on this, it is necessary to provide a back-contact photovoltaic cell, a preparation method thereof, and a photovoltaic module. The preparation method of the back-contact photovoltaic cell in the present 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.

[0004] In a first aspect, the present application provides a preparation method of a back-contact photovoltaic cell, including:

[0005] Providing a battery pre-product, on the first surface of which a positive grid line and a negative grid line are arranged at intervals;

[0006] Applying a reverse voltage less than the breakdown voltage to the battery pre-product in a first preset area;

[0007] Scanning and irradiating the battery pre-product in a second preset area using a laser light source, and controlling the circuit current value in the second preset area to be 0.1 A to 40 A; wherein, the first preset area and the second preset area are located in different areas of the battery pre-product;

[0008] The scanning and irradiation sequentially include a first scanning period, a second scanning period, and a third scanning period;

[0009] In the first scanning period, controlling the circuit current value in the second preset area to increase and controlling the voltage value in the second preset area to decrease;

[0010] In the third scanning period, controlling the circuit current value in the second preset area to decrease and controlling the voltage value in the second preset area to increase;

[0011] During the second scanning period, control the fluctuation amplitude of the circuit current value in the second preset area to be less than or equal to a first preset value.

[0012] In some embodiments, the second scanning period sequentially includes a first sub-scanning period, a second sub-scanning period, and a third sub-scanning period;

[0013] Control the voltage value in the first sub-scanning period to be greater than the voltage value in the second sub-scanning period;

[0014] Control the voltage value in the first sub-scanning period to be greater than the voltage value in the third sub-scanning period.

[0015] In some embodiments, during the second sub-scanning period, control the initial voltage value in the second preset area to be greater than the final voltage value.

[0016] In some embodiments, during the second sub-scanning period, control the fluctuation amplitude of the voltage value in the second preset area to be less than or equal to a second preset value.

[0017] In some embodiments, during the second sub-scanning period, control the fluctuation amplitude of the voltage value in the second preset area to be relatively large at the initial stage.

[0018] In some embodiments, during the second sub-scanning period, control the fluctuation amplitude of the voltage value in the second preset area to be relatively small at the final stage.

[0019] In some embodiments, the first preset value is [-2A, +2A].

[0020] In some embodiments, the second preset value is [-1V, +4V].

[0021] In some embodiments, control the voltage value in the third sub-scanning period to be greater than the final voltage value in the second sub-scanning period.

[0022] In some embodiments, control the voltage value in the third sub-scanning period to be less than the initial voltage value in the second sub-scanning period.

[0023] In some embodiments, during the first sub-scanning period, control the fluctuation amplitude of the voltage value in the second preset area to be less than or equal to a third preset value.

[0024] In some embodiments, during the third sub-scanning period, control the fluctuation amplitude of the voltage value in the second preset area to be less than or equal to a third preset value.

[0025] In some embodiments, the third preset value is [-0.5V, +0.5V].

[0026] In some of these embodiments, the durations of the second sub-scanning period, the first sub-scanning period, and the third sub-scanning period decrease in sequence.

[0027] In some of these embodiments, after applying a reverse voltage less than the breakdown voltage to the prefabricated battery in a first preset area, and before scanning and irradiating the prefabricated battery with a laser light source in a second preset area, the circuit current value of the second preset area is less than 10 A.

[0028] In some of these embodiments, the first preset area and the second preset area are located on the first surface.

[0029] In some of these embodiments, the first preset area is located on the first surface, and the second preset area is located on a second surface, and the second surface and the first surface are oppositely arranged.

[0030] In some of these embodiments, the spot shape of the laser light source is controlled to be circular or rectangular.

[0031] In some of these embodiments, the wavelength of the laser light source is 300 nm to 1200 nm.

[0032] In some of these embodiments, the scanning speed of the laser light source is controlled to be 0.5 m / s to 8 m / s.

[0033] In some of these embodiments, the scanning time of the laser light source is controlled to be 0.05 s to 30 s.

[0034] In some of these embodiments, the equivalent load of the detection circuit for the prefabricated battery is less than 5 Ω.

[0035] In some of these embodiments, the reverse voltage is 1 V to 25 V.

[0036] In some of these embodiments, during the scanning and irradiating process, the surface temperature of the prefabricated battery is controlled to be less than 300 °C.

[0037] In a second aspect, the present application provides a back-contact photovoltaic cell, which is prepared by using the preparation method of the back-contact photovoltaic cell described in any one of the above.

[0038] In some of these embodiments, the sheet resistance of the emitter of the photovoltaic cell is less than 1000 Ω / sq.

[0039] In a third aspect, the present application provides a photovoltaic module, including:

[0040] Cover plate;

[0041] At least one battery string, the battery string including a plurality of the back-contact photovoltaic cells described in any one of the above; and

[0042] An encapsulation layer, the encapsulation layer being located between the cover plate and the battery string, and the cover plate being connected to the battery string through the encapsulation layer.

[0043] In the method for preparing the above-mentioned back-contact photovoltaic cell, a reverse voltage less than the breakdown voltage is applied to the battery preform in a first preset area, and a laser light source is used to scan and irradiate the battery preform in a second preset area different from the first preset area. By scanning and irradiating the battery preform with the laser light source, charge carriers are excited, and at the same time, a reverse voltage is applied, so that a local current can be generated in the second preset area. Under the action of the current, sintering occurs at the irradiation position of the laser light source, triggering the mutual diffusion of the grid paste and the silicon material, thereby significantly reducing the contact resistance between the metal and the semiconductor. When the diffusion contact is formed, the resistance decreases, the heat at the melting point disappears instantly, and the temperature decreases, thereby forming an ohmic contact with better contact effect and higher contact quality. By applying a reverse voltage less than the breakdown voltage to the battery preform in the first preset area, using a laser light source to scan and irradiate the battery preform in the second preset area, and controlling the circuit current value in the second preset area to be 0.1A - 40A, through the cooperation of the reverse voltage and the laser light source, at the same time, in the first scanning period, controlling the circuit current value in the second preset area to increase and controlling the voltage value in the second preset area to decrease, in the second scanning period, controlling the fluctuation range of the circuit current value in the second preset area to be less than or equal to a first preset value, and in the third scanning period, controlling the circuit current value in the second preset area to decrease and controlling the voltage value in the second preset area to increase, the synchronous matching of the laser-voltage can be improved, ensuring that the carriers excited by the laser move directionally under the action of the electric field, reducing the decrease in current density caused by carrier recombination, improving the sintering quality, facilitating the improvement of 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 further improving the conversion efficiency. Description of the Drawings

[0044] Figure 1 It is a schematic diagram of the steps of the method for preparing the back-contact photovoltaic cell provided by an embodiment of the present application;

[0045] Figure 2 It is a schematic diagram of applying a reverse voltage less than the breakdown voltage to the battery preform in a first preset area provided by an embodiment of the present application;

[0046] Figure 3 It is a change curve graph of the circuit current value and voltage value in the second preset area during the process of using a laser light source to scan and irradiate the battery preform in the second preset area provided by an embodiment of the present application. Detailed Embodiments

[0047] To make the above objects, features, and advantages of the present application more apparent and understandable, the following provides a detailed description of the specific embodiments of the present application. Many specific details are set forth in the following description to facilitate a thorough understanding of the present application. However, the present 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 spirit of the present application. Therefore, the present application is not limited by the specific embodiments disclosed below.

[0048] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the technical field to which this application belongs. The terms used herein in the description of the present application are for the purpose of describing specific embodiments only and are not intended to limit the present application. The term "and / or" as used herein includes any and all combinations of one or more of the related listed items.

[0049] In the description of the present application, it should be understood that the orientation or positional relationship indicated by the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc. is based on the orientation or positional relationship shown in the drawings, and is 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, and thus should not be construed as limiting the present application.

[0050] In addition, 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 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, "a plurality" means at least two, such as two, three, etc., unless otherwise specifically defined.

[0051] In the present application, unless otherwise clearly specified and limited, the terms "mounted", "connected", "coupled", "fixed", etc. 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 internal communication of 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.

[0052] Refer to Figure 1 、Figure 3 As shown, an embodiment of the present application provides a method for manufacturing a back-contact photovoltaic cell, including:

[0053] Providing a battery pre-product, on the first surface of which positive grid lines and negative grid lines are arranged at intervals;

[0054] Applying a reverse voltage less than the breakdown voltage to the battery pre-product in a first preset area;

[0055] Scanning and irradiating the battery pre-product in a second preset area using a laser light source, and controlling the circuit current value in the second preset area to be 0.1 A to 40 A; wherein, the first preset area and the second preset area are located in different areas of the battery pre-product;

[0056] The scanning and irradiation sequentially include a first scanning period, a second scanning period, and a third scanning period;

[0057] In the first scanning period, controlling the circuit current value in the second preset area to increase and controlling the voltage value in the second preset area to decrease;

[0058] In the third scanning period, controlling the circuit current value in the second preset area to decrease and controlling the voltage value in the second preset area to increase;

[0059] In the second scanning period, controlling the fluctuation amplitude of the circuit current value in the second preset area to be less than or equal to a first preset value.

[0060] It can be understood that before the battery preform is scanned and irradiated with a laser light source in the second preset area, the positive grid lines and negative grid lines arranged at intervals on the first surface of the battery preform are both grid pastes. Through the above preparation method, good ohmic contact between the positive grid lines, negative grid lines and the doped silicon layer in the battery preform can be achieved. In the preparation method of the above back-contact photovoltaic cell, a reverse voltage less than the breakdown voltage is applied to the battery preform in the first preset area, and the battery preform is scanned and irradiated with a laser light source in a second preset area different from the first preset area. By scanning and irradiating the battery preform with the laser light source, charge carriers are excited, and at the same time, a reverse voltage is applied, so that a local current can be generated in the second preset area. Under the action of the current, sintering occurs at the irradiation position of the laser light source, triggering the mutual diffusion of the grid paste and the silicon material, thereby significantly reducing the contact resistance between the metal and the semiconductor. When the diffusion contact is formed, the resistance decreases, the heat at the melting point disappears instantly, and the temperature decreases, thus forming an ohmic contact with a better contact effect and higher contact quality. On the basis that a reverse voltage less than the breakdown voltage is applied to the battery preform in the first preset area, the battery preform is scanned and irradiated with a laser light source in the second preset area, and the circuit current value in the second preset area is controlled to be 0.1 A to 40 A. Through the cooperation of the reverse voltage and the laser light source, at the same time, in the first scanning period, the circuit current value in the second preset area is controlled to increase, and the voltage value in the second preset area is controlled to decrease. In the second scanning period, the fluctuation amplitude of the circuit current value in the second preset area is controlled to be less than or equal to the first preset value. In the third scanning period, the circuit current value in the second preset area is controlled to decrease, and the voltage value in the second preset area is controlled to increase, which can improve the synchronous matching of the laser-voltage, ensure the directional movement of the carriers excited by the laser under the action of the electric field, reduce the decrease of the current density caused by carrier recombination, improve the sintering quality, facilitate the improvement of the passivation contact performance of the back-contact photovoltaic cell, improve the open-circuit voltage and fill factor of the back-contact photovoltaic cell, and thus improve the conversion efficiency.

[0061] Refer to Figure 2As shown, it can be understood that the circuit current in the second preset area 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. The change of the circuit current and voltage value can be monitored by setting a voltage-current detection module at both ends of the cell. Exemplarily, the reverse voltage can be connected to the grid line of the back-contact photovoltaic cell through an external voltage source. Among them, 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 the grid lines and all the solder joints in the first preset area, or can also be part of the grid lines and part of the solder joints in the first preset area. It can be understood that, compared with the prior art where the positive grid line and the negative grid line are located on different sides of the cell, in the back-contact photovoltaic cell, both the positive grid line and the negative grid line are located on the same surface of the photovoltaic cell. When applying a reverse voltage to the prefabricated cell in the first preset area, the process difficulty is relatively large and precise control is required. Exemplarily, the contact between the voltage source and the photovoltaic cell can be achieved through a probe.

[0062] Controlling the circuit current value in the second preset area can control the local heat generation efficiency in the second preset area. Within the range of the above-mentioned circuit current value, it is beneficial to make the instantaneous temperature in the second preset area capable of melting the grid paste and realizing co-diffusion with silicon, and forming a highly conductive ohmic contact area after cooling, while also being able to avoid the risk of thermal damage to the prefabricated cell. Optionally, control the circuit current value in the second preset area to be 0.1A, 0.2A, 0.5A, 1A, 2A, 5A, 8A, 10A, 15A, 20A, 25A, 30A, 35A or 40A, or alternatively, the circuit current value in the second preset area can also be controlled within the range between any two of the above-mentioned circuit current values. Preferably, control the circuit current value in the second preset area to be 2A~20A.

[0063] In some embodiments, the voltage value in the second preset area is different from the value of the reverse voltage.

[0064] In some embodiments, the first preset value is [-2A, +2A].

[0065] Optionally, the first preset value is -2A, -1.5A, -1A, -0.5A, 0A, +0.5A, +1A, +1.5A or +2A, or alternatively, the first preset value can also be within the range between any two of the above-mentioned current values.

[0066] In some embodiments, the second scanning period sequentially includes a first sub-scanning period, a second sub-scanning period and a third sub-scanning period;

[0067] Control the voltage value in the first sub-scanning period to be greater than the voltage value in the second sub-scanning period;

[0068] The voltage value controlling the first sub-scanning period is greater than the voltage value of the third sub-scanning period.

[0069] Based on the signals controlling the first scanning period, the second scanning period, and the third scanning period, by driving the directional movement of charge carriers with a reverse voltage, controlling the voltage value of the first sub-scanning period to be greater than the voltage value of the second sub-scanning period, and controlling the voltage value of the first sub-scanning period to be greater than the voltage value of the third sub-scanning period, it is possible to synergistically combine the reverse voltage and the scanning irradiation energy of the laser light source, promote the acceleration of electron migration by the electric field, generate Joule heat by colliding with the grid line paste, promote the formation of the ohmic contact region, 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.

[0070] In some embodiments, during the second sub-scanning period, the initial voltage value of the second preset region is controlled to be greater than the final voltage value.

[0071] It can be understood that during the second sub-scanning period, the initial stage refers to the first half of the time period close to the first sub-scanning period, and the final stage refers to the second half of the time period close to the third sub-scanning period. Controlling the initial voltage value of the second preset region to be greater than the final voltage value during the second sub-scanning period means that the voltage value of the second preset region is greater in the first half of the time period than in the second half during the second sub-scanning period. Controlling the initial voltage value of the second preset region to be greater than the final voltage value during the second sub-scanning 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.

[0072] In some embodiments, during the second sub-scanning period, the voltage value fluctuation range of the second preset region is controlled to be less than or equal to the second preset value.

[0073] In some embodiments, the second preset value is [-1V, +4V].

[0074] 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 between any two of the above voltage values.

[0075] It can be understood that in the above method for preparing a photovoltaic cell, controlling the fluctuation range of the voltage value has an important impact, which is specifically as follows: (1) Impact on contact resistance: An appropriate reverse voltage can promote the interdiffusion of conductive particles in the grid paste and silicon, reducing the contact resistance. If the voltage fluctuation range is too large, the reverse voltage may be too high or too low instantaneously. When it is too high, it may cause reverse breakdown of the battery. Once reverse breakdown occurs, due to the current shunting effect, the local conductive current density in the illuminated area will be much lower than that before breakdown, increasing the contact resistance between the metal and silicon. When the voltage is too low, it cannot provide sufficient driving force, resulting in insufficient movement of carriers and insufficient silver-silicon interdiffusion, also leading to an increase in contact resistance. (2) Impact on battery efficiency: When the voltage fluctuation range is too large, it is easy to deviate from the optimal voltage value during the sintering process, resulting in a decrease in battery 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, and the overall performance will decline, with a significant reduction in efficiency. When the voltage is too low, the carrier concentration is insufficient, the contact optimization effect is poor, and the fill factor is reduced, also leading to a decrease in battery efficiency. (3) Impact on the passivation layer: A stable and appropriate voltage value helps to reduce the damage to the passivation layer. If the voltage value fluctuation range is too large, too high a voltage will cause the passivation layer to withstand too high an electric field and energy, resulting in increased damage to the passivation layer, affecting its passivation effect on the battery and increasing the carrier recombination inside the battery; while too low a voltage value is difficult to fully utilize the synergistic effect of laser and reverse voltage to optimize the contact, and may need to increase the sintering temperature to make up for it, which will also cause certain damage to the passivation layer.

[0076] In the second sub-scanning period, control the fluctuation range of the voltage value in the second preset area to be less than or equal to the second preset value, so as to control the voltage value within a better voltage value range during the scanning and irradiation process, while reducing the contact resistance, reducing the impact on battery efficiency and the 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 thus improving the conversion efficiency.

[0077] In some of these embodiments, in the second sub-scanning period, control the fluctuation range of the voltage value in the second preset area to be relatively large at the beginning.

[0078] In some of these embodiments, in the second sub-scanning period, control the fluctuation range of the voltage value in the preset area to be relatively small at the end.

[0079] In some of these embodiments, control the voltage value in the third sub-scanning period to be greater than the voltage value at the end of the second sub-scanning period.

[0080] It can be understood that in the third sub-scanning period, the initial stage refers to the first half of the time period close to the second sub-scanning period, and the final stage refers to the second half of the time period close to the third scanning period. That the voltage value in the third sub-scanning period is greater than the voltage value at the end of the second sub-scanning period means that the voltage value in the first half of the third sub-scanning period is greater than the voltage value in the second half. Controlling the voltage value in the third sub-scanning period to be greater than the voltage value at the end of the second sub-scanning period is conducive to 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 thus improving the conversion efficiency.

[0081] In some embodiments, the voltage value in the third sub-scanning period is controlled to be less than the voltage value at the initial stage of the second sub-scanning period.

[0082] Controlling the voltage value in the third sub-scanning period to be less than the voltage value at the initial stage of the second sub-scanning period is conducive to 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 thus improving the conversion efficiency.

[0083] In some embodiments, in the first sub-scanning period, the fluctuation amplitude of the voltage value in the second preset region is controlled to be less than or equal to a third preset value.

[0084] In some embodiments, in the third sub-scanning period, the fluctuation amplitude of the voltage value in the second preset region is controlled to be less than or equal to a third preset value.

[0085] In some embodiments, the third preset value is [-0.5V, +0.5V].

[0086] 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 can also be within the range between any two of the above voltage values.

[0087] In the first sub-scanning period, controlling the fluctuation amplitude of the voltage value in the second preset region to be less than or equal to the third preset value; in the third sub-scanning period, controlling the fluctuation amplitude of the voltage value in the second preset region to be less than or equal to the third preset value; is conducive to controlling the voltage value within a better voltage value range during the scanning and irradiation process, reducing the contact resistance while reducing the impact on the battery efficiency and the 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 thus improving the conversion efficiency.

[0088] In some embodiments, the durations of the second sub-scanning period, the first sub-scanning period, and the third sub-scanning period decrease in sequence.

[0089] Refer again to Figure 3As shown, it can be seen that in some of these 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. In the first scanning period, the laser light source starts to irradiate the battery preform, the circuit current increases rapidly, and affected by the external circuit resistance, the voltage across the battery chip drops rapidly. In the first sub-scanning period, both the voltage value and the current value across the battery preform are relatively stable, with only small fluctuations. In the second sub-scanning period, as the scanning irradiation progresses, the voltage value drops by 1V to 4V and fluctuates greatly, while the circuit current remains basically unchanged. In the third sub-scanning period, near the end of the scanning irradiation, the voltage value becomes stable again. In the third scanning period, the laser light source leaves the battery preform, the light output ends, the circuit current drops rapidly, and the voltage value across the battery preform returns to the state before incidence.

[0090] In some of these embodiments, after applying a reverse voltage less than the breakdown voltage to the battery preform in the first preset area, before using the laser light source to perform scanning irradiation on the battery preform in the second preset area, the circuit current value in the second preset area is less than 10A.

[0091] Optionally, before using the laser light source to perform scanning irradiation on the battery preform in the second preset area, the circuit current value in the second preset area is greater than or equal to 0.0001A and less than 10A. Further optionally, before using the laser light source to perform scanning irradiation on the battery preform in the second preset area, the circuit current value in 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 using the laser light source to perform scanning irradiation on the battery preform in the second preset area, the circuit current value in the second preset area can also be within the range between any two of the above current values.

[0092] In some of these embodiments, the first preset area and the second preset area are located on the first surface.

[0093] In some of these embodiments, the first preset area is located on the first surface, the second preset area is located on the second surface, and the second surface and the first surface are oppositely arranged.

[0094] In some of these embodiments, the spot shape of the laser light source is controlled to be circular or rectangular.

[0095] In some of these embodiments, the wavelength of the laser light source is 300nm to 1200nm.

[0096] Optionally, the wavelength of the laser light source is 300 nm, 400 nm, 500 nm, 600 nm, 700 nm, 800 nm, 900 nm, 1000 nm, 1100 nm or 1200 nm. Alternatively, the wavelength of the laser light source can also be within the range between any two of the above wavelengths.

[0097] In some of these embodiments, the scanning speed of the laser light source is controlled to be 0.5 m / s to 8 m / s.

[0098] Optionally, the scanning speed of the laser light source is controlled to be 0.5 m / s, 1 m / s, 2 m / s, 3 m / s, 4 m / s, 5 m / s, 6 m / s, 7 m / s or 8 m / s. Alternatively, the scanning speed of the laser light source can also be within the range between any two of the above speeds.

[0099] In some of these embodiments, the scanning time of the laser light source is controlled to be 0.05 s to 30 s.

[0100] Optionally, the scanning time of the laser light source is controlled to be 0.05 s, 0.1 s, 0.5 s, 1 s, 2 s, 5 s, 10 s, 15 s, 20 s, 25 s or 30 s. Alternatively, the scanning time of the laser light source can also be within the range between any two of the above times.

[0101] It can be understood that by controlling the wavelength, scanning speed and scanning time of the laser light source, the energy input density per unit area can be controlled. When the energy input density per unit area is too low, it may lead to ineffective excitation of charge carriers or failure to achieve silver-silicon diffusion, resulting in insufficient diffusion depth and poor passivation effect and high contact resistance. When the energy input density per unit area is too high, it will cause an increase in the thermally affected area, which may lead to local overheating and melting of the silicon wafer, damage to the surrounding passivation layer or destruction of the cell structure. Within the above parameter ranges of the laser light source, the effect of promoting the eutectic melting of the grid line and the silicon material is better, which is convenient for 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 thus improving the conversion efficiency.

[0102] In some of these embodiments, the equivalent load of the detection circuit for the battery pre-product is less than 5 Ω.

[0103] Optionally, the equivalent load of the detection circuit for the battery pre-product is 0.001 Ω to 4.999 Ω. Further optionally, the equivalent load of the detection circuit for the battery pre-product is 0.001 Ω, 0.01 Ω, 0.1 Ω, 0.5 Ω, 1 Ω, 2 Ω, 3 Ω, 4 Ω, 4.5 Ω, 4.9 Ω, 4.99 Ω or 4.999 Ω. Alternatively, the equivalent load of the detection circuit for the battery pre-product can also be within the range between any two of the above resistances.

[0104] In some of these embodiments, the reverse voltage is 1V to 25V.

[0105] The reverse voltage is used to establish an electric field in the laser-irradiated area, drive the directional movement of charge carriers, and enhance the local current density. When the reverse voltage is too low, it is difficult for the local current to generate sufficient Joule heat. When the reverse voltage is too high, it may cause arc discharge or breakdown of the passivation layer. Optionally, the reverse voltage is 1V, 2V, 5V, 8V, 10V, 12V, 15V, 18V, 20V, 22V, or 25V, or the reverse voltage can also be within the range between any two of the above voltages.

[0106] In some of these embodiments, during the scanning irradiation process, the surface temperature of the battery preform is controlled to be less than 300°C.

[0107] When the surface temperature of the battery preform is too high, it may affect the performance of the battery. The surface temperature of the battery preform can be controlled by adjusting the reverse voltage or the parameters of the laser light source. Optionally, during the scanning irradiation process, the surface temperature of the battery preform is controlled to be 20°C to 299°C. Further optionally, the surface temperature of the battery preform is controlled to be 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 the surface temperature of the battery preform can also be within the range between any two of the above temperatures.

[0108] Within the ranges of the parameters of the above method for preparing a back-contact photovoltaic cell, it is convenient to 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.

[0109] Another embodiment of the present application provides a back-contact photovoltaic cell prepared by using the method for preparing a back-contact photovoltaic cell according to any one of the above.

[0110] In some of these embodiments, the sheet resistance of the emitter of the photovoltaic cell is less than 1000 Ω / sq.

[0111] Optionally, the sheet resistance of the emitter of the photovoltaic cell is 1 Ω / sq to 999 Ω / sq. Further optionally, the sheet resistance of the emitter of the photovoltaic cell is 1 Ω / sq, 2 Ω / sq, 5 Ω / sq, 10 Ω / sq, 20 Ω / sq, 50 Ω / sq, 100 Ω / sq, 200 Ω / sq, 300 Ω / sq, 500 Ω / sq, 600 Ω / sq, 800 Ω / sq, 900 Ω / sq, or 999 Ω / sq, or the sheet resistance of the emitter of the photovoltaic cell can also be within the range between any two of the above sheet resistances.

[0112] Another embodiment of the present application provides a photovoltaic module, comprising:

[0113] Cover plate;

[0114] At least one battery string, the battery string including a plurality of back-contact photovoltaic cells according to any one of the above; and

[0115] Encapsulation layer, the encapsulation layer being located between the cover plate and the battery string, and the cover plate being connected to the battery string through the encapsulation layer.

[0116] 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 various technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered as falling within the scope described in this specification.

[0117] 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 invention patent. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present application, several deformations and improvements can still be made, and these all belong to 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, and the specification and the drawings can be used to explain the content of the claims.

Claims

1. A method for preparing a back-contact photovoltaic cell, characterized in that, Including: Providing a battery preform, on the first surface of which positive grid lines and negative grid lines are arranged at intervals; Applying a reverse voltage less than the breakdown voltage to the battery preform in a first preset area; Scanning and irradiating the battery preform in a second preset area with a laser light source, and controlling the circuit current value of the second preset area to be 0.1A - 40A; wherein, the first preset area and the second preset area are located in different areas of the battery preform; The scanning irradiation sequentially includes a first scanning period, a second scanning period, and a third scanning period; In the first scanning period, controlling the circuit current value of the second preset area to increase and controlling the voltage value of the second preset area to decrease; In the third scanning period, controlling the circuit current value of the second preset area to decrease and controlling the voltage value of the second preset area to increase; In the second scanning period, controlling the fluctuation amplitude of the circuit current value of the second preset area to be less than or equal to a first preset value.

2. The manufacturing method of the back contact photovoltaic cell according to claim 1, characterized in that, The second scanning period sequentially includes a first sub-scanning period, a second sub-scanning period, and a third sub-scanning period; Controlling the voltage value of the first sub-scanning period to be greater than the voltage value of the second sub-scanning period; Controlling the voltage value of the first sub-scanning period to be greater than the voltage value of the third sub-scanning period.

3. The manufacturing method of the back-contact photovoltaic cell according to claim 2, characterized in that, In the second sub-scanning period, controlling the initial voltage value of the second preset area to be greater than the final voltage value.

4. The manufacturing method of the back-contact photovoltaic cell according to claim 2, characterized in that, In the second sub-scanning period, controlling the fluctuation amplitude of the voltage value of the second preset area to be less than or equal to a second preset value.

5. The preparation method of the back-contact photovoltaic cell according to claim 4, characterized in that, In the second sub-scanning period, controlling the fluctuation amplitude of the voltage value of the second preset area to be larger in the initial stage; and / or, In the second sub-scanning period, controlling the fluctuation amplitude of the voltage value of the second preset area to be smaller in the final stage.

6. The preparation method of the back-contact photovoltaic cell according to claim 4, characterized in that, The first preset value is [-2A, +2A]; and / or, The second preset value is [-1V, +4V].

7. The method for preparing a back-contact photovoltaic cell according to claim 2, wherein Controlling the voltage value of the third sub-scanning period to be greater than the final voltage value of the second sub-scanning period; and / or, Controlling the voltage value of the third sub-scanning period to be less than the initial voltage value of the second sub-scanning period.

8. The manufacturing method of the back-contact photovoltaic cell according to claim 2, characterized in that, In the first sub-scanning period, controlling the fluctuation amplitude of the voltage value of the second preset area to be less than or equal to a third preset value; and / or, In the third sub-scanning period, controlling the fluctuation amplitude of the voltage value of the second preset area to be less than or equal to a third preset value.

9. The method for manufacturing a back-contact photovoltaic cell according to claim 8, wherein, The third preset value is [-0.5V, +0.5V].

10. The preparation method of the back-contact photovoltaic cell according to claim 2, wherein The durations of the second sub-scanning period, the first sub-scanning period, and the third sub-scanning period decrease in sequence.

11. The preparation method of the back-contact photovoltaic cell according to any one of claims 1 to 10, characterized in that, Before scanning and irradiating the battery preform in the second preset area with a laser light source after applying a reverse voltage less than the breakdown voltage to the battery preform in the first preset area, the circuit current value of the second preset area is less than 10A.

12. The preparation method of the back-contact photovoltaic cell according to any one of claims 1 to 10, characterized in that, The first preset area and the second preset area are located on the first surface; or, The first preset area is located on the first surface, the second preset area is located on the second surface, and the second surface and the first surface are oppositely arranged.

13. The preparation method of the back-contact photovoltaic cell according to any one of claims 1 to 10, characterized in that, Controlling the spot shape of the laser light source to be circular or rectangular; and / or, The wavelength of the laser light source is 300 nm to 1200 nm; and / or, control the scanning speed of the laser light source to be 0.5 m / s to 8 m / s; and / or, control the scanning time of the laser light source to be 0.05 s to 30 s; and / or, the equivalent load of the detection circuit for the battery preform is less than 5 Ω; and / or, the reverse voltage is 1 V to 25 V; and / or, during the scanning irradiation process, control the surface temperature of the battery preform to be less than 300 °C.

14. A back-contact photovoltaic cell, characterized in that, Prepared by using the preparation method of the back-contact photovoltaic cell according to any one of claims 1 to 13.

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

16. A photovoltaic module, characterized in that, Comprising: A cover plate; At least one battery string, the battery string comprising a plurality of back-contact photovoltaic cells according to claim 14 or 15; And An encapsulation layer, the encapsulation layer being located between the cover plate and the battery string, and the cover plate being connected to the battery string through the encapsulation layer.

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