Laser sintering method and laser sintering apparatus for solar cells

Abstract

The application discloses a laser sintering method and a laser sintering device for a solar cell. The laser sintering method comprises the following steps: transmitting the solar cell to a base so that the back surface of the solar cell is in contact with the base; contacting a probe with the front surface of the solar cell and applying a voltage to the solar cell through the probe so that a closed loop is formed among the probe, the solar cell and the base; irradiating the front surface of the solar cell by a laser to excite the silicon-based layer to generate carriers, and the carriers move directionally under the action of the voltage applied by the probe; and applying an electric field to the solar cell, wherein the direction of the electric field is perpendicular to the back surface of the solar cell and points from the back surface of the solar cell to the front surface of the solar cell. The above scheme can solve the problem that the voltage applied by the probe is too large in the laser sintering method for the solar cell in the related art and causes damage to the solar cell.

Description

Technical Field

[0001] This invention relates to the field of solar cell technology, and in particular to a laser sintering method and laser sintering equipment for solar cells. Background Technology

[0002] With the increasing demand for clean energy, the development of solar cell technology is particularly crucial. Laser sintering, as an advanced manufacturing process, is widely used in the fabrication of high-performance solar cells, especially in the fabrication of thin-film solar cells (such as copper indium gallium selenide (CIGS), cadmium telluride (CdTe), and perovskite).

[0003] In the sintering process of solar cells, a voltage needs to be applied to the solar cell using a probe. This causes laser-excited charge carriers inside the solar cell to move in a directional manner. When the charge carriers concentrate in the area where the grid lines contact the surface of the solar cell, a high temperature (800-1000℃) is generated, which melts the grid lines on the solar cell surface and fuses them with the solar cell surface, thus achieving the sintering process. However, to achieve better directional movement of charge carriers, a relatively large voltage needs to be applied by the probe. Excessive voltage can easily damage the solar cell. Therefore, the laser sintering method for solar cells in related technologies suffers from the problem of damage caused by excessively high probe voltage. Summary of the Invention

[0004] This invention discloses a laser sintering method and laser sintering equipment for solar cells, in order to solve the problem that the laser sintering method for solar cells in related technologies causes damage to the solar cells due to excessive voltage applied by the probe.

[0005] To solve the above-mentioned technical problems, the present invention is implemented as follows:

[0006] In a first aspect, this application discloses a laser sintering method for a solar cell, wherein the solar cell has a silicon substrate inside, and grid lines are present on both the front and back sides of the solar cell. The laser sintering method includes:

[0007] The solar cell is transferred to the base so that the back side of the solar cell contacts the base;

[0008] The probe is brought into contact with the front of the solar cell, and a voltage is applied to the solar cell through the probe to form a closed loop between the probe, the solar cell, and the base.

[0009] By irradiating the front side of the solar cell with a laser, charge carriers are generated in the silicon substrate. The charge carriers move directionally under the voltage applied by the probe, so that the electrons in the charge carriers are concentrated at the grid lines on the back side of the solar cell, and the holes in the charge carriers are concentrated at the grid lines on the front side of the solar cell.

[0010] An electric field is applied to the solar cell, wherein the direction of the electric field is perpendicular to the back of the solar cell and points from the back of the solar cell to the front of the solar cell.

[0011] Secondly, this application also discloses a laser sintering apparatus for performing the laser sintering method described in the first aspect. The laser sintering apparatus includes: a base, a probe, a laser emitter, a first electrode plate, and a second electrode plate. The laser emitter is disposed above the base. The probe is used to apply a voltage to the solar cell when the base supports the solar cell. The first electrode plate is located below the base, and the second electrode plate is located between the base and the laser emitter. An electric field is formed between the first electrode plate and the second electrode plate, with its direction perpendicular to the back surface of the solar cell and pointing from the back surface of the solar cell to the front surface of the solar cell.

[0012] The technical solution adopted in this invention can achieve the following technical effects:

[0013] The laser sintering method disclosed in this application applies an electric field perpendicular to the back surface of the solar cell and pointing from the back surface to the front surface. This allows for the directional movement of charge carriers when the front surface of the solar cell is irradiated with a laser to excite the silicon substrate and generate charge carriers. The directional movement of these charge carriers is achieved through the combined effect of the voltage and electric field applied by the probe to the solar cell. This concentrates electrons towards the grid lines on the back surface of the solar cell and holes towards the grid lines on the front surface. Under the premise of directional movement of charge carriers as required, compared to applying only a voltage to the solar cell through the probe, the laser sintering method disclosed in this application, due to the presence of an electric field, allows for the achievement of directional movement of charge carriers with a smaller voltage applied by the probe. Because the voltage applied by the probe to the solar cell is smaller, damage caused by the probe to the solar cell can be mitigated. Attached Figure Description

[0014] Figure 1 This is a flowchart of the laser sintering method for solar cells disclosed in an embodiment of the present invention;

[0015] Figure 2The laser sintering equipment disclosed in the embodiments of the present invention is shown in the figure, where the arrows indicate the direction of the electric field;

[0016] Figure 3 The distribution of contact resistance after using the laser sintering method disclosed in the embodiments of this application;

[0017] Figure 4 This shows the distribution of contact resistance when only a probe is used and no electric field is applied.

[0018] Explanation of reference numerals in the attached figures:

[0019] A-Solar cells,

[0020] 100 - Base, 200 - Probe, 310 - First electrode plate, 320 - Second electrode plate, 400 - Laser emitter. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below in conjunction with specific embodiments and corresponding drawings. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0022] The technical solutions disclosed in the various embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0023] Please refer to Figures 1 to 2 This invention discloses a laser sintering method for solar cells. Solar cell A has a silicon substrate inside, and grid lines are present on both the front and back sides of the solar cell. Grid lines are fine metallic structures used to collect and conduct current, collecting charge carriers (electrons and holes) generated by illumination and guiding these carriers to external circuitry.

[0024] The laser sintering method disclosed in this invention includes:

[0025] S101, transfer solar cell A to base 100 so that the back side of solar cell A contacts base 100.

[0026] It should be noted that solar cell A can be transmitted using a transmission device.

[0027] S102, the probe 200 is brought into contact with the front side of the solar cell A, and a voltage is applied to the solar cell A through the probe 200 so that a closed loop is formed between the probe 200, the solar cell A and the base 100.

[0028] It should be noted that the voltage applied by probe 200 to solar cell A is a reverse voltage. The reverse voltage can cause electrons in solar cell A to move toward the back of solar cell A, and holes in solar cell A to move toward the front of solar cell A.

[0029] S103, by irradiating the front side of solar cell A with a laser, the silicon substrate is excited to generate charge carriers. The charge carriers move directionally under the voltage applied by probe 200, so that the electrons in the charge carriers are concentrated at the grid lines on the back side of solar cell A, and the holes in the charge carriers are concentrated at the grid lines on the front side of solar cell A.

[0030] It should be noted that the principle of using laser to irradiate the front side of solar cell A to excite the silicon substrate to generate charge carriers is existing technology and will not be described again in the embodiments of this application.

[0031] When electrons are concentrated in large numbers at the grid lines on the back side of solar cell A, and holes are concentrated in large numbers at the grid lines on the front side of solar cell A, the temperature of the grid lines on both sides of solar cell A will rise rapidly to a certain level (e.g., 800-1000℃). This causes the grid lines to melt, and after the temperature drops and the grid lines solidify, they form a whole with the surface of solar cell A, thereby reducing the contact resistance between the grid lines and the silicon substrate.

[0032] S104, an electric field is applied to solar cell A, wherein the direction of the electric field is perpendicular to the back of the solar cell and points from the back of solar cell A to the front of solar cell A.

[0033] It should be noted that the front and back sides of solar cell A are parallel. Since the direction of the electric field is perpendicular to the back side of the solar cell and points from the back side to the front side, electrons will be further concentrated towards the grid lines on the back side of solar cell A under the influence of the electric field, while holes will be further concentrated towards the grid lines on the front side of solar cell A under the influence of the electric field.

[0034] It is necessary to further explain the laser sintering method disclosed in the embodiments of this application that the probe 200 is a relatively delicate component. If the directional movement of charge carriers is controlled only by the voltage applied by the probe 200, the contact area between the probe 200 and the front side of the solar cell A is small, which will result in uneven distribution of charge carriers in different areas of the solar cell A after directional movement. Moreover, when the directional movement of charge carriers is controlled only by the voltage applied by the probe 200, the voltage applied by the probe 200 to the solar cell A is very large, which can easily cause damage to the contact area between the solar cell A and the probe 200.

[0035] The laser sintering method disclosed in this application applies an electric field perpendicular to the back surface of solar cell A and pointing from the back surface to the front surface of solar cell A. This allows for the directional movement of charge carriers when the front surface of solar cell A is irradiated with a laser to excite the silicon substrate and generate charge carriers. This is achieved through the combined effect of the voltage and electric field applied by the probe 200 to solar cell A, causing electrons to concentrate towards the grid lines on the back surface of solar cell A and holes towards the grid lines on the front surface. Under the premise of directional movement of charge carriers as required, the laser sintering method disclosed in this application, compared to simply applying voltage to the solar cell using a probe, achieves the desired directional movement of charge carriers with a smaller voltage applied by the probe 200 because the electric field is perpendicular to the back surface of solar cell A and pointing from the back surface to the front surface. Since the voltage applied by the probe 200 to solar cell A is smaller, damage caused by the probe 200 to solar cell A can be mitigated.

[0036] Furthermore, because the electric field is relatively uniformly distributed across the entire solar cell A, the problem of uneven distribution of charge carriers in different regions of solar cell A during directional movement can be improved, resulting in a more uniform distribution of contact resistance between the grid lines and the silicon substrate. For details, please refer to... Figure 3 and Figure 4 , Figure 3 The distribution of contact resistance after using the laser sintering method disclosed in the embodiments of this application is disclosed. Figure 4 The present invention discloses the contact resistance distribution when only a probe 200 is used without setting an electric field perpendicular to the back of solar cell A and pointing from the back of solar cell A to the front of solar cell A. By comparison, it can be seen that the contact resistance distribution of various parts of the solar cell obtained by the laser sintering method disclosed in this application is relatively more concentrated.

[0037] Optionally, in the laser sintering method disclosed in this application embodiment, applying an electric field to solar cell A includes:

[0038] An electric field is formed between the first electrode plate 310 located below the base 100 and the second electrode plate 320 located above the base 100 by applying a voltage, wherein the first electrode plate 310 and the second electrode plate 320 are opposite to each other and arranged in parallel.

[0039] It should be noted that in the embodiments of this application, the first electrode plate 310 is a positive electrode plate and the second electrode plate 320 is a negative electrode plate.

[0040] The laser sintering method disclosed in this application employs a first electrode plate disposed below the base 100 and a second electrode plate 320 disposed above the base 100. By applying voltage to the first electrode plate 310 and the second electrode plate 320, a more uniform electric field is formed between the first electrode plate 310 and the second electrode plate 320. This facilitates the adjustment of the electric field intensity by controlling the first electrode plate 310 and the second electrode plate 320.

[0041] Of course, the laser sintering method disclosed in this application can also generate an electric field in other ways, such as by generating an electric field through a changing magnetic field. This application does not impose specific limitations on the way of generating an electric field.

[0042] Optionally, the potential difference of the electric field can be between 10V and 20V, and the voltage applied by the probe 200 to the solar cell A placed on the base 100 can be between 1V and 5V.

[0043] It should be noted that, referring to Table 1, in related technologies where only a probe is used to apply voltage to the solar cell, the voltage applied by the probe is typically around 20V. For example, when the voltage applied by the probe is 20V, the contact resistance is 2.831mΩ. However, in the laser sintering method disclosed in this application, after applying an electric field with a potential difference between 10V and 20V, the probe 200 only needs to apply a voltage between 1V and 5V to meet the contact resistance requirements, thereby reducing the voltage applied by the probe 200 to the solar cell A.

[0044] Table 1

[0045]

[0046] Optionally, the power of the laser irradiation of solar cell A can be between 50W and 120W.

[0047] In one alternative embodiment, the laser can be a circular spot with a diameter between 5000 μm and 2000 μm.

[0048] The laser sintering method disclosed in this application sets the shape of the laser to a circular spot with a diameter between 5000 μm and 2000 μm. This makes the diameter of the circular spot relatively large, so that during the laser scanning process, adjacent circular spots will have overlapping areas, which is equivalent to increasing the laser irradiation time and thus improving the ability to excite charge carriers.

[0049] Optionally, the wavelength of the laser is between 500 nm and 1100 nm.

[0050] In one optional embodiment, the laser can be a continuous laser, and the laser scanning speed is between 20 m / s and 70 m / s. By using a continuous laser, the irradiation uniformity of the solar cell is improved, which in turn is beneficial to the uniform distribution of charge carriers.

[0051] Optionally, the laser loading time is between 0.5s and 2.5s.

[0052] It should be noted that the laser loading time refers to the time required to complete scanning of a solar cell. By using a laser loading time between 0.5s and 2.5s, the laser loading time is relatively short, which helps to improve the efficiency of laser sintering.

[0053] This application also discloses a laser sintering apparatus for performing the laser sintering method disclosed in the above embodiments. The disclosed laser sintering apparatus includes: a base 100, a probe 200, a laser emitter 400, a first electrode plate 310, and a second electrode plate 320. The laser emitter 400 is disposed above the base 100. The probe 200 is used to apply a voltage to the solar cell A when the base 100 supports the solar cell A. The first electrode plate 310 is located below the base 100, and the second electrode plate 320 is located between the base 100 and the laser emitter 400. An electric field is formed between the first electrode plate 310 and the second electrode plate 320, with its direction perpendicular to the back surface of the solar cell A and pointing from the back surface of the solar cell A to the front surface of the solar cell A.

[0054] The laser sintering equipment disclosed in this application has a first electrode plate 310 disposed below the base 100 and a second electrode plate 320 disposed above the base 100. This creates an electric field between the first electrode plate 310 and the second electrode plate 320, perpendicular to the back surface of the solar cell A and pointing from the back surface of the solar cell A to the front surface. When the front surface of the solar cell A is irradiated with a laser to excite the silicon substrate to generate charge carriers, the directional movement of the charge carriers is achieved by the combined effect of the voltage and electric field applied to the solar cell A by the probe 200. This causes electrons to concentrate towards the grid lines on the back surface of the solar cell A, and holes to concentrate towards the grid lines on the front surface of the solar cell A. Under the premise that the charge carriers move in the same directional manner, compared to applying only voltage to the solar cell by the probe, the laser sintering method disclosed in this application has an electric field. Therefore, a smaller voltage applied by the probe 200 to the solar cell A is sufficient to achieve the effect of directional movement of charge carriers. Because the voltage applied by the probe 200 to the solar cell A is smaller, damage caused by the probe 200 to the solar cell A can be mitigated. Moreover, since the electric field is relatively uniformly distributed across the entire solar cell A, the problem of uneven distribution of charge carriers in different regions of solar cell A during directional movement can be improved.

[0055] Optionally, the projections of the first electrode plate 310 and the second electrode plate 320 in the direction perpendicular to the base 100 can both cover the base 100.

[0056] The laser sintering equipment disclosed in this application sets the first electrode plate 310 and the second electrode plate 320 to cover the base 100 in a direction perpendicular to the base 100, thereby making the electric field applied to the solar cell by the first electrode plate 310 and the second electrode plate 320 more uniform.

[0057] The above embodiments of the present invention focus on describing the differences between the various embodiments. As long as the different optimization features between the various embodiments are not contradictory, they can be combined to form a better embodiment. For the sake of brevity, they will not be described in detail here.

[0058] The embodiments of the present invention have been described above with reference to the accompanying drawings. However, the present invention is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art can make many other forms under the guidance of the present invention without departing from the spirit and scope of the claims, and all of these forms are within the protection scope of the present invention.

Claims

1. A laser sintering method for solar cells, characterized in that, The solar cell (A) has a silicon substrate inside, and grid lines are present on both the front and back sides of the solar cell. The laser sintering method includes: The solar cell (A) is transferred to the base (100) such that the back side of the solar cell (A) contacts the base (100); The probe (200) is brought into contact with the front of the solar cell (A), and a voltage is applied to the solar cell (A) through the probe (200) to form a closed loop between the probe (200), the solar cell (A) and the base (100); By irradiating the front side of the solar cell (A) with a laser, the silicon substrate is excited to generate charge carriers. The charge carriers move directionally under the voltage applied by the probe (200), so that the electrons in the charge carriers are concentrated at the grid lines on the back side of the solar cell (A), and the holes in the charge carriers are concentrated at the grid lines on the front side of the solar cell (A). A voltage is applied to a first electrode plate (310) located below the base (100) and a second electrode plate (320) located above the base (100) to form an electric field between the first electrode plate (310) and the second electrode plate (320), wherein the first electrode plate (310) and the second electrode plate (320) are opposite to each other and arranged in parallel, the projections of the first electrode plate (310) and the second electrode plate (320) in a direction perpendicular to the base (100) both cover the base (100), and the direction of the electric field is perpendicular to the back of the solar cell and points from the back of the solar cell (A) to the front of the solar cell (A); The potential difference of the electric field is between 10V and 20V, and the voltage applied by the probe (200) to the solar cell (A) placed on the base (100) is between 1V and 5V.

2. The laser sintering method according to claim 1, characterized in that, The power of the laser irradiating the solar cell (A) is between 50W and 120W.

3. The laser sintering method according to claim 1, characterized in that, The laser is a circular spot with a diameter between 5000 μm and 2000 μm.

4. The laser sintering method according to claim 1, characterized in that, The wavelength of the laser is between 500nm and 1100nm.

5. The laser sintering method according to claim 1, characterized in that, The laser is a continuous laser, and the scanning speed of the laser is between 20m / s and 70m / s.

6. The laser sintering method according to claim 1, characterized in that, The laser loading time is between 0.5s and 2.5s.

7. A laser sintering apparatus for performing the laser sintering method according to any one of claims 1 to 6, characterized in that, The laser sintering equipment includes: a base (100), a probe (200), a laser emitter (400), a first electrode plate (310), and a second electrode plate (320). The laser emitter (400) is located above the base (100). The probe (200) is used to apply voltage to the solar cell (A) when the base (100) supports the solar cell (A). The first electrode plate (310) is located below the base (100), and the second electrode plate (320) is located between the base (100) and the laser emitter (400). An electric field is formed between the first electrode plate (310) and the second electrode plate (320) with its direction perpendicular to the back of the solar cell (A) and pointing from the back of the solar cell (A) to the front of the solar cell (A).

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