Connection method of heterojunction silicon solar cell for space

Abstract

The invention discloses a connection method of a heterojunction silicon solar cell for space, the silicon solar cell is a p-type silicon solar cell, an interconnection sheet is a silver interconnection sheet with the thickness of 20-23 microns and the purity of 99.99%, a welding method between the interconnection sheet and a cell electrode adopts a two-step and multi-pulse parallel gap resistance welding method, and the method comprises the following steps of: 1, welding the interconnection sheet and the cell electrode by using a two-step and multi-pulse parallel gap resistance welding method; the method comprises the following steps: carrying out pulse pretreatment with the voltage of 1.2-1.5 V and the interval of 25-30ms, cleaning a to-be-welded surface, and removing an oxide film on the surface of an electrode; and secondly, the voltage is increased to 3.6 V to 4.0 V, pulse pressurization treatment with the single pulse being 5-8 ms and the loading voltage being 4.5 V to 4.8 V is carried out five times, and welding of the silver interconnection piece and the battery is completed. The welding firmness of the battery is improved, the surface temperature of the battery in the welding process is reduced, and damage of high temperature to the solar battery is avoided.

Description

Technical Field

[0001] The invention belongs to the field of space solar cell preparation, and in particular relates to a connection method for a space heterojunction silicon solar cell with the characteristics of light weight, low cost and flexibility. Background Art

[0002] The ground photovoltaic industry based on crystalline silicon solar cells has developed rapidly in recent years. How to adapt ground silicon solar cells and apply them to space by taking advantage of the industry is an important way to reduce the cost of space solar cells. In the 1990s, the structure of traditional silicon solar cells for space use was a p-type structure based on aluminum back field, with a thickness of more than 260 microns. The surface current collection electrode used Ag and Au system. Pure Ag foil with a thickness of 25 to 30 microns was used as the interconnection sheet between single cells. The parallel gap resistance welding method with higher reliability was used to connect the cells. The preparation of silicon solar cell arrays in this way was very expensive, generally hundreds of thousands of yuan per square meter.

[0003] At present, terrestrial silicon cells can be divided into multiple structures according to their structure, such as emitter and back passivation cells (PERC), oxide passivation contact cells (TopCon), intrinsic thin film heterojunction cells (HJT), and interdigitated back contact cells (IBC). Among them, HJT cells have become the best choice due to their higher operating voltage and lower power temperature coefficient. The preparation of the front and back electrodes of HJT cells adopts low-temperature screen printing, and the direct combination connection of cells and cells adopts low-temperature soldering, with a welding temperature of 310℃±20℃. The battery assembly using this connection method cannot withstand up to 10,000 times of temperature changes from -90℃ to +90℃ when used in space, and further exploration of the connection method between silicon cells is needed. When the one-step resistance welding method used for traditional space silicon cells and gallium arsenide solar cells (as shown in CN 109768119 B) is used to weld HJT structure silicon solar cells, the surface electrode is damaged due to the welding temperature exceeding 900℃, which seriously affects the performance of the battery after assembly. Summary of the invention

[0004] In view of the problems existing in the prior art, the present invention provides a method for connecting heterojunction silicon solar cells for space use, which improves the welding firmness of the cells, reduces the temperature of the cell surface during the welding process, and avoids damage to the solar cells caused by high temperature.

[0005] The present invention is implemented as follows: a method for connecting heterojunction silicon solar cells for space use, wherein the silicon solar cells are p-type silicon solar cells, the interconnection sheets are silver interconnection sheets with a thickness of 20-23 microns and a purity of 99.99%, and the welding method between the interconnection sheets and the battery electrodes adopts a two-step, multi-pulse parallel gap resistance welding method, comprising the following steps:

[0006] The first step is pulse pre-treatment with a voltage of 1.2V to 1.5V and an interval of 25ms to 30ms to clean the surface to be welded and remove the oxide film on the electrode surface;

[0007] In the second step, the voltage is increased to 3.6V~4.0V, and pulse pressure treatment is performed 5 times with a single pulse of 5m~8ms and a loading voltage of 4.5V~4.8V to complete the welding of the silver interconnect and the battery.

[0008] The thickness of the silicon solar cell is controlled to be between 80 microns and 100 microns.

[0009] The width of the silver interconnection sheet is 3mm-8mm.

[0010] The above-mentioned method for connecting heterojunction silicon solar cells for space use, the method for welding the interconnection sheet and the battery electrode comprises the following steps:

[0011] (1) The silicon solar cell is fixed on the welding platform, the surface of the interconnection sheet is cleaned with an alcohol cotton ball, the position of the interconnection sheet to be welded is aligned with the welding pad on the surface of the cell, and the welding head position of the resistance welding machine is adjusted to align with the area of ​​the interconnection sheet to be welded;

[0012] (2) Setting the welding parameters of the welding machine, after the pressure head descends to press the interconnection sheet, the welding head voltage rises to 1.2V~1.5V within 5m~8ms, lasts for 25ms~30ms, and the voltage drops to 0V within 5ms. After 20ms, the second pulse loading is performed. After the voltage rises to 3.6V~4.0V, the voltage is loaded five times with a single loading time of 5m~8ms. The loading voltage is 4.5V~4.8V, and the single loading interval time is 5m~8ms. After completing the five voltage loadings, the voltage is dropped to 0V within 25ms. After welding is completed, slowly lift the welding head, check the surface of the welding area and clean the welding area with an alcohol cotton ball.

[0013] The silicon solar cell is fixed on the welding platform by a lower suction cup.

[0014] The advantages and technical effects of the present invention are as follows: The preparation of HJT silicon solar cell substrate and each functional layer film adopts the large-scale production process of terrestrial photovoltaics, with low production cost and sufficient output. The welding between individual cells adopts the parallel gap resistance welding method with higher welding strength, and adopts the form of two steps and multiple pulses. First, it improves the welding firmness of the cell, and second, it reduces the temperature of the cell surface during the welding process to avoid high temperature damage to the solar cell. After testing and verification, this packaging form meets the three-year life assessment requirements of low-orbit satellites. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1The invention discloses a parallel gap resistance welding process for connecting heterojunction silicon solar cells for space use. DETAILED DESCRIPTION

[0016] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings. It should be understood that the specific implementation methods described herein are only used to explain the present invention and are not used to limit the present invention.

[0017] The connection method of the space heterojunction silicon solar cell of the present invention comprises the following steps: the silicon solar cell is a p-type silicon solar cell, the interconnection sheet is a silver interconnection sheet with a thickness of 20-23 microns and a purity of 99.99%, and the welding method between the interconnection sheet and the battery electrode adopts a two-step, multi-pulse parallel gap resistance welding method, comprising the following steps:

[0018] The first step is pulse pre-treatment with a voltage of 1.2V to 1.5V and an interval of 25ms to 30ms to clean the surface to be welded and remove the oxide film on the electrode surface;

[0019] In the second step, the voltage is increased to 3.6V~4.0V, and pulse pressure treatment is performed 5 times with a single pulse of 5m~8ms and a loading voltage of 4.5V~4.8V to complete the welding of the silver interconnect and the battery.

[0020] Preferably, the thickness of the silicon solar cell is controlled to be between 80 microns and 100 microns.

[0021] Preferably, the width of the silver interconnection sheet is 3 mm-8 mm.

[0022] The specific steps include:

[0023] (1) The silicon solar cell is fixed on the welding platform, the surface of the interconnection sheet is cleaned with an alcohol cotton ball, the position of the interconnection sheet to be welded is aligned with the welding pad on the surface of the cell, and the welding head position of the resistance welding machine is adjusted to align with the area of ​​the interconnection sheet to be welded;

[0024] (2) Setting the welding parameters of the welding machine, after the pressure head descends to press the interconnection sheet, the welding head voltage rises to 1.2V~1.5V within 5m~8ms, lasts for 25ms~30ms, and the voltage drops to 0V within 5ms. After 20ms, the second pulse loading is performed. After the voltage rises to 3.6V~4.0V, the voltage is loaded five times with a single loading time of 5m~8ms. The loading voltage is 4.5V~4.8V, and the single loading interval time is 5m~8ms. After completing the five voltage loadings, the voltage is dropped to 0V within 25ms. After welding is completed, slowly lift the welding head, check the surface of the welding area and clean the welding area with an alcohol cotton ball.

[0025] Preferably, the silicon solar cell is fixed on the welding platform by a lower suction cup.

[0026] Crystalline silicon solar cells are divided into p-type and n-type according to the characteristics of the base material. In order to adapt to the strong high-energy particle radiation of space solar cells, p-type silicon solar cells are selected as power generation units. Pure silver interconnects with a thickness of 20-23 microns are used to complete the series connection between single power generation units through parallel gap resistance welding technology to achieve the high voltage required for normal power supply of satellites.

[0027] Example

[0028] like Figure 1 As shown, a pure silver paste HJT structure silicon solar cell with a length, width and height of 35mm×78mm×0.1mm and a battery surface electrode prepared by screen printing is fixed on the welding platform, and the fixing method adopts the lower suction cup method. A pure silver interconnection sheet with a width of 4mm, a thickness of 20 microns and a purity of 99.99% is cut with a cutter. The surface of the interconnection sheet is cleaned with an alcohol cotton ball, and the position of the interconnection sheet to be welded is aligned with the battery surface pad, and the welding head position of the resistance welding machine is adjusted to align the area of ​​the interconnection sheet to be welded. Set the welding parameters of the welding machine: after the pressure head is lowered and the interconnection sheet is pressed, the welding head voltage rises to 1.2V within 10ms, lasts for 25ms, and the voltage drops to 0V in 5ms. After 20ms, the second pulse loading is performed, and after the voltage rises to 3.6V, 5 voltage loadings with a single loading time of 5ms are performed, and the loading voltage is 4.8V, wherein the single loading interval time is 5ms. After completing 5 voltage loadings, the voltage is reduced to 0V within 25ms. After welding is completed, slowly lift the welding head, check the surface of the welding area and clean the welding area with an alcohol cotton ball.

[0029] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for connecting heterojunction silicon solar cells for space use, characterized in that: The silicon solar cell is a p-type silicon solar cell, the interconnection sheet is a silver interconnection sheet with a thickness of 20-23 microns and a purity of 99.99%, and the welding method between the interconnection sheet and the battery electrode adopts a two-step, multi-pulse parallel gap resistance welding method, including the following steps: The first step is pulse pre-treatment with a voltage of 1.2V to 1.5V and an interval of 25ms to 30ms to clean the surface to be welded and remove the oxide film on the electrode surface; In the second step, the voltage is increased to 3.6V~4.0V, and pulse pressure treatment is performed 5 times with a single pulse of 5m~8ms and a loading voltage of 4.5V~4.8V to complete the welding of the silver interconnect and the battery.

2. The method for connecting heterojunction silicon solar cells for space use according to claim 1, characterized in that: The thickness of the silicon solar cell is controlled to be between 80 microns and 100 microns.

3. The method for connecting heterojunction silicon solar cells for space use according to claim 1, characterized in that: The width of the silver interconnection sheet is 3mm-8mm.

4. The method for connecting heterojunction silicon solar cells for space use according to any one of claims 1 to 3, characterized in that: The welding method between the interconnection sheet and the battery electrode comprises the following steps: (1) The silicon solar cell is fixed on the welding platform, the surface of the interconnection sheet is cleaned with an alcohol cotton ball, the position of the interconnection sheet to be welded is aligned with the welding pad on the surface of the cell, and the welding head position of the resistance welding machine is adjusted to align with the area of ​​the interconnection sheet to be welded; (2) Setting the welding parameters of the welding machine, after the pressure head descends to press the interconnection sheet, the welding head voltage rises to 1.2V~1.5V within 5m~8ms, lasts for 25ms~30ms, and the voltage drops to 0V within 5ms. After 20ms, the second pulse loading is performed. After the voltage rises to 3.6V~4.0V, the voltage is loaded five times with a single loading time of 5m~8ms. The loading voltage is 4.5V~4.8V, and the single loading interval time is 5m~8ms. After completing the five voltage loadings, the voltage is dropped to 0V within 25ms. After welding is completed, slowly lift the welding head, check the surface of the welding area and clean the welding area with an alcohol cotton ball.

5. The method for connecting heterojunction silicon solar cells for space use according to claim 4, characterized in that: The silicon solar cell is fixed on the welding platform by a lower suction cup.

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