A metal alloy series-connected shingled photovoltaic module cell string and preparation method thereof

Abstract

The present invention relates to a shingled photovoltaic module battery string connected in series by a metal alloy and a preparation method, wherein the shingled photovoltaic module battery string has a plurality of battery cells; the front of each battery cell is provided with a front electrode, and the back of each battery cell is provided with a back electrode; the front electrode includes a front fine grid electrode, a front main grid electrode and a front side main grid electrode, wherein the front fine grid electrode is connected to the front main grid electrode, and the front main grid electrode is connected to the front side main grid electrode; the front side main grid electrode of the previous battery cell and the back electrode of the next battery cell are partially stacked and connected together at the stacking position by a metal alloy solidified after melting to form a series connection. The present invention replaces the traditional conductive glue with a metal alloy, which can effectively solve the problem of aging and resistance increase caused by long-term operation, and can also effectively solve the problem of fire caused by resistance heating.

Description

Technical Field

[0001] The invention relates to a photovoltaic module and a preparation process thereof, and in particular to a shingled photovoltaic module cell string connected in series with a metal alloy and a preparation method thereof. Background Art

[0002] Shingled photovoltaic modules came into being in response to the market demand for products with high output power density. With its unique structural arrangement, it fully utilizes the gaps between the series-connected cells and can achieve a 6% output power gain for a single photovoltaic module. As photovoltaic crystalline silicon raw materials, battery processes and module packaging process technologies are reaching their "technical ceiling", a 6% output power gain is undoubtedly a technological advancement. This process improvement does not require very complex battery structure design and large-scale equipment introduction, but only requires a few technical improvements in the traditional battery process to achieve it.

[0003] In addition, since traditional shingled module products entered the market, there has been a problem that the failure rate of photovoltaic modules due to fire is higher than that of conventional photovoltaic modules. The reason for the failure is that traditional shingled modules use glue (mainly conductive glue) on the main grid electrode on the side of the cell to achieve the series connection of the cell, and the glue is uneven or does not completely cover the main grid electrode of the adjacent cell, or because the main component of the conductive glue is a high molecular polymer. Among them, thermal oxidation and time aging of the conductive glue are the main causes of failure of shingled modules, and since this conductive glue system will inevitably increase the resistivity with aging, that is, as long as the shingled modules connected in series with the conductive glue system, the resistance of the adjacent cells (or battery strips) will increase with the extension of the operation time of the photovoltaic modules, resulting in a significant increase in the volume resistivity of the conductive glue. Therefore, the photogenerated charge generated by the solar cell will be concentrated in the conductive glue part with a large volume resistivity, causing resistance heating, which further aggravates the local temperature rise of the photovoltaic module, and it is inevitable that the failure of fire will occur. Summary of the invention

[0004] The first object of the present invention is to provide a shingled photovoltaic module cell string connected in series by a metal alloy, which can effectively solve the problems of aging and increased resistance caused by long-term operation, and can also effectively solve the problem of fire caused by resistance heating.

[0005] The technical solution for achieving the first purpose of the present invention is: the cell string of the shingled photovoltaic module connected in series by a metal alloy in the present invention has a plurality of cells; a front electrode is provided on the front side of each cell, and a back electrode is provided on the back side of each cell; the front electrode includes a front fine grid electrode, a front main grid electrode and a front side main grid electrode, wherein the front fine grid electrodes are all connected to the front main grid electrodes, and the front main grid electrodes are connected to the front side main grid electrodes; the front side main grid electrodes of the previous cell and the back electrode portions of the next cell are stacked and connected together at the stacking position by a metal alloy solidified after melting to form a series connection.

[0006] The back electrode includes a back main grid electrode and a back electric field.

[0007] As a further optimized design, the back electrode also includes a back side main gate electrode, which is connected to the back side main gate electrode; the front side main gate electrode of the previous battery cell and the back side main gate electrode of the next battery cell are partially stacked and connected together at the stacking point by a metal alloy that solidifies after melting to form a series connection.

[0008] The above metal alloy is a silicon-based alloy.

[0009] As a further optimization, the above metal alloy is Ag-Si alloy or Al-Si alloy or Ag-Al-Si alloy.

[0010] The metal alloy is formed by solidifying the front side main gate electrode and the back side main gate electrode melted at the stacking position.

[0011] The back of the cell is also provided with a passivation layer, which is a laminated passivation layer of Al2O3 and SiNx, or a single-layer passivation layer of SiNx, or a laminated passivation layer of SiO2 and SiNx, or a multi-layer passivation layer of SiO2, Al2O3 and SiNx.

[0012] The second object of the present invention is to provide a method for preparing a string of cells of a shingled photovoltaic module connected in series with the above-mentioned metal alloy. The method does not require laser cutting and effectively reduces area loss. At the same time, by adjusting the high-temperature sintering step, it not only simplifies the preparation method, but also ensures the formation of the metal alloy that plays a series role.

[0013] The technical solution to achieve the second object of the present invention is: the method for preparing the above-mentioned metal alloy series-connected shingled photovoltaic module cells in the present invention comprises the following steps:

[0014] S1. Printing the back main grid electrode on the back of the cell;

[0015] S2. Drying the slurry for printing the main grid electrode on the back

[0016] S3, printing the back electric field on the back of the battery cell;

[0017] S4, drying the slurry for back electric field printing;

[0018] S5. Printing a front fine grid electrode and a front main grid electrode on the front side of the cell; wherein the width of the front main grid electrode is set to match the width of the metal probe selected for the test, or a thinner metal probe is replaced to match the width of the front main grid electrode;

[0019] S6, drying the slurry printed on the front fine gate electrode and the front main gate electrode;

[0020] S7, test sorting: select the cells that meet the voltage and current requirements; mainly classify them according to Impp (maximum power point current) to facilitate the subsequent series connection of cells;

[0021] S8, screen printing a main grid electrode on the front side of the battery cell;

[0022] S9, drying the slurry printed on the main grid electrode on the front side;

[0023] S10, dispensing glue or screen printing a layer of glue or applying adhesive tape on the main grid electrode on the front side of the stack to achieve bonding and series connection of adjacent battery cells;

[0024] S11, high temperature sintering: high temperature sintering the printed paste at the stack of adjacent battery cells to form a molten metal alloy; the temperature range of high temperature sintering is set at 700-1000°C;

[0025] S12, cooling: The molten metal alloy at the stack is solidified by cooling to form a metal and silicon-based alloy system, and finally a shingled photovoltaic module cell string is obtained.

[0026] The specific steps of the above step S10 are as follows:

[0027] A. Apply glue or screen print a layer of glue or tape on the main grid electrode on the front side of the stack to achieve bonding and series connection of adjacent cells;

[0028] B. Press or blow high-pressure air with a wind knife to the stacking area to ensure full contact between adjacent battery cells;

[0029] C. 80-200℃ volatilizes and decomposes the organic components in the screen printing glue or dot glue or adhesive tape;

[0030] D. Press twice or blow high-pressure air with a wind knife to make the adjacent battery cells fully contact with each other and ensure that the battery cells are in full and close contact when entering high-temperature sintering.

[0031] Among them, the glue solution contains polymerized organic substances that decompose rapidly at high temperatures (for example, [Ding Grace1] can be used. [Ding Grace1] is the conductive glue PA-10 for Time Creation overlapping shingles. The purpose is to decompose the glue solution polymer in the subsequent high-temperature sintering process step, so that the pastes of adjacent solar cells can fully contact and melt in the high-temperature sintering process at 700-900 °C, thereby realizing the rapid mutual diffusion of metal particles in the paste between adjacent solar cells and ensuring the recrystallization and solidification of the metal in the cooling process after high-temperature sintering.

[0032] The wind pressure of the high-pressure air blown by the above air knife > 1 atmospheric pressure.

[0033] The paste used for printing in steps S1 and S5 is silver paste or silver-aluminum paste; the paste for printing the front side main grid electrode in step S8 is based on silver paste or silver-aluminum paste and added with organic substances with adhesive effects. Its specific components and proportions are: 80% ultrafine silver powder, 5% glass powder, 13% acrylic polymer, and 2% of others are thickeners, thixotropic agents, and defoaming agents; among them, the ultrafine silver powder is used as the conductive functional phase, and the acrylic polymer is used as the organic binder.

[0034] The conductive functional phase in the paste for printing the front side main grid electrode in the above step S8 can be one or more of copper powder, silver powder, aluminum powder, gold powder, carbon nanotubes, and graphene.

[0035] Before the above step S10, the back side main grid electrode is also printed on the back of the solar cell and dried; in the above step S10, the front side main grid electrode of the upper solar cell and the back side main grid electrode of the lower solar cell are partially stacked and form a series connection.

[0036] In the above step S10, dispensing is performed on the front side main grid electrode at the stacking position. The front side main grid electrode of the upper solar cell and the back side main grid electrode of the lower solar cell are adhesively bonded through dispensing and form a series connection; among them, the number of dispensing points is 2-10.

[0037] The width of the above front side main grid electrode is generally controlled at 2-10 mm.

[0038] The present invention has positive effects: (1) The present invention does not need to use laser cutting, effectively solving the problem of the reduced light-receiving area of a single solar cell; at the same time, using metal alloy to replace the traditional series connection method of conductive glue that is prone to aging and increased resistivity, the series connection method of metal alloy will slow down the problem of the significant increase in resistivity of the overlapping shingle photovoltaic module as the operation time extends. Therefore, the failure probability of the traditional photovoltaic overlapping shingle module catching fire due to the increase in series connection resistance will be greatly reduced.

[0039] (2) The present invention places the high-temperature sintering process step of the battery cell after the screen printing of the front side main grid electrode and the back side main grid electrode, and uses the high temperature of 700-1000°C of the screen printing paste high temperature sintering process to achieve the metal alloy series connection between the battery cells. Because the sintering temperature is usually around 850°C, it is enough to make the printed paste in a molten state and achieve a close eutectic connection between adjacent battery cells, and the high temperature of 700-1000°C is enough to volatilize and decompose the organic matter in the glue used to connect the adjacent battery cells.

[0040] (3) The main purpose of high temperature sintering in the present invention is to achieve the sintering of the printed paste at the stacking position to form a silicon Ag-Si alloy or Ag-Al-Si alloy system. In the high temperature range of 700-1000°C, the glass powder component in the paste will corrode the passivation film layer on the surface of the battery cell. Under the high temperature environment, the molecular thermal motion of the Ag particles in the paste system will be greatly accelerated and diffuse into the paste system of the silicon substrate and the adjacent side main grid electrode area, forming mutual diffusion under the high temperature environment; at the same time, the high temperature environment will also completely decompose and volatilize other organic components in the paste, leaving only the molten metal layer.

[0041] (4) The main purpose of printing the paste for the front side main grid electrode in the present invention is to collect the photogenerated carriers of the front solar cell, especially the photogenerated carriers transmitted from the front fine grid electrode and the front main grid electrode, and also the photogenerated carriers collected from the silicon substrate covered by the front side main grid electrode; therefore, the choice of paste is not limited to silver paste with good conductivity but high cost, and includes paste doped with other conductive functional phases, such as copper powder, aluminum powder, gold powder, carbon nanotubes, and graphene.

[0042] (5) The metal alloy series connection in the present invention is based on silicon-based alloy connection. The specific mechanism is that the high temperature of 700-1000°C provides a high-temperature rapid diffusion environment for the paste printed on the side electrodes of the battery cell. Under high temperature environment, the lattice vibration of the silicon crystal is intensified, resulting in instability of the silicon atoms covalently bonded in the silicon crystal. Some silicon atoms will be separated from the original covalent bond connection system, and the lattice vibration of the metal particles in the paste is also intensified at high temperature, resulting in the rapid diffusion of the metal particles into the silicon matrix of the battery cell, forming a metal-silicon eutectic system. In the present invention, preferably, an alloy system of Ag-Si, Al-Si or Ag-Al-Si is formed. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] In order to make the content of the present invention more clearly understood, the present invention is further described in detail below according to specific embodiments and in conjunction with the accompanying drawings, wherein

[0044] Figure 1 This is a process flow chart for the traditional shingled photovoltaic module cell string;

[0045] Figure 2 is a process flow chart of the preparation method of the present invention;

[0046] Figure 3 A front printed image of a shingled photovoltaic module cell string connected in series with a metal alloy in the present invention;

[0047] Figure 4 A printed image of the back electrode of a shingled assembly battery string connected in series with a metal alloy in the present invention;

[0048] Figure 5 A schematic diagram of the side structure between adjacent battery cells of a shingled assembly battery string connected in series with a metal alloy in the present invention;

[0049] Figure 6 It is a schematic diagram of the structure of a shingled photovoltaic module cell string connected in series with metal alloys in the present invention. DETAILED DESCRIPTION

[0050] The process of traditional shingled photovoltaic cell string is as follows Figure 1 As shown, when conventional cells are transferred to the component production end, they need to be cut into strips by a laser cutter. The specific area of ​​the cut cells depends on the component design. Among them, cutting the cells reduces the area of ​​the cells, which reduces the light-receiving area of ​​a single cell. The current of the cell is positively correlated with the light-receiving area of ​​the cell, and the voltage of the cell depends on the material properties and structural properties of the cell, which is a fixed value. Then, conductive glue is applied to the side main grid electrode by glue dispensing to achieve series connection of adjacent cells.

[0051] (Example 1)

[0052] See Figures 3 to 6 The cell string of the shingled photovoltaic module connected in series by the metal alloy in the present invention has 6 cells 1; each cell 1 is provided with a front electrode on the front side, and each cell 1 is provided with a back electrode on the back side; the front electrode includes a front fine grid electrode 2, a front main grid electrode 3 and a front side main grid electrode 4, wherein the front fine grid electrode 2 is connected to the front main grid electrode 3, and the front main grid electrode 3 is connected to the front side main grid electrode 4; the back electrode includes a back side main grid electrode 5, a back electric field 6 and a back side main grid electrode 7, and the back side main grid electrode 5 is connected to the back side main grid electrode 7; the front side main grid electrode 4 of the previous cell 1 and the back side main grid electrode 7 of the next cell 1 are partially stacked and connected together at the stacking position by a metal alloy 8 solidified after melting to form a series connection. The metal alloy 8 is solidified by the front side main grid electrode 4 and the back side main grid electrode 7 melted at the stacking position.

[0053] The metal alloy 8 is Ag-Al-Si alloy.

[0054] A passivation layer is also provided on the back of the cell 1. The passivation layer can be any one of a stacked passivation layer of Al2O3 and SiNx, a single-layer passivation layer of SiNx, a stacked passivation layer of SiO2 and SiNx, and a multi-layer passivation layer of SiO2, Al2O3 and SiNx.

[0055] See Figure 2 The method for preparing the above-mentioned metal alloy series-connected shingled photovoltaic module cells in the present invention comprises the following steps:

[0056] S1, printing the back main grid electrode 5 on the back side of the battery cell 1, using silver paste as the printing paste;

[0057] S2, drying the slurry printed on the back main grid electrode 5

[0058] S3, printing a back electric field 6 on the back side of the battery cell 1;

[0059] S4, drying the slurry printed by the back electric field 6;

[0060] S5, printing the front fine grid electrode 2 and the front main grid electrode 3 on the front side of the battery cell 1; the printing paste is silver paste;

[0061] S6, drying the slurry printed on the front fine gate electrode 2 and the front main gate electrode 3;

[0062] S7, test sorting: select the battery cells 1 whose voltage and current meet the requirements;

[0063] S8, screen printing a main grid electrode 4 on the front side of the battery cell 1;

[0064] S9, drying the slurry printed on the main grid electrode 4 on the front side;

[0065] S10, applying glue to the main grid electrode 4 on the front side of the stack to achieve gluing and connecting adjacent battery cells 1 in series;

[0066] S11, high temperature sintering: high temperature sintering the printed paste at the stack of adjacent battery cells 1 to form a molten metal alloy 8; the temperature of the high temperature sintering is set at 700-1000° C.;

[0067] S12, cooling: The metal alloy 8 in the molten state at the stack is solidified by cooling to form a metal and silicon-based alloy system, and finally a shingled photovoltaic module cell string is obtained.

[0068] The specific steps of step S9 are as follows:

[0069] A. Apply glue dots on the front side main grid electrode 4 at the stacking position to achieve adhesive series connection of adjacent solar cells 1; the number of glue dots is 2 - 10;

[0070] B. Apply pressure or blow high - pressure air with an air knife on the stacking position to ensure sufficient contact between adjacent solar cells 1;

[0071] C. Volatilize and decompose the organic components in the screen - printed glue, the applied glue dots, or the attached tape at 80 - 200 °C;

[0072] D. Apply secondary pressure or blow high - pressure air with an air knife to ensure secondary sufficient contact between adjacent solar cells 1 and ensure that the solar cells 1 are in full and tight contact when entering high - temperature sintering. The glue contains a polymer organic compound [Ding Grace1] that decomposes rapidly at high temperature, and [Ding Grace1] is the conductive glue PA - 10 for Time - Creation shingled cells.

[0073] In step S8, the paste for printing the front side main grid electrode 4 includes ultrafine silver powder as the main conductive functional phase, glass powder, acrylic polymer organic binder, and thickener, thixotropic agent, defoamer. Among them, the acrylic polymer acts as the organic binder to achieve the bonding effect. Its specific components and proportions are: ultrafine silver powder 80%, glass powder 5%, acrylic polymer 13%, and the other 2% components are thickener, thixotropic agent, and defoamer.

[0074] Before step S9, print the back side main grid electrode 7 on the back of the solar cell 1 and dry it; in step S9, the front side main grid electrode 4 of the upper solar cell 1 and the back side main grid electrode 7 of the lower solar cell 1 are partially stacked to form a series connection.

[0075] (Example 2)

[0076] In the present invention, the components of the paste for printing the front side main grid electrode 4 in step S8 are: ultrafine silver powder 80%, glass phase 3%, acrylic polymer 15%, thickener 1.5%, thixotropic agent 0.4%, defoamer 0.1%. Among them, the ultrafine silver powder serves as the conductive functional phase.

[0077] Other technical features are the same as those in Example 1.

[0078] (Example 3)

[0079] In the present invention, before step S9, do not print the back side main grid electrode 7, and directly stack the front side main grid electrode 4 of the upper solar cell 1 and the back electrode of the lower solar cell 1 to form a series connection.

[0080] Other technical features are the same as those in Example 1.

[0081] (Example 4)

[0082] The conductive functional phase in the present invention can be one or more of silver powder, copper powder, aluminum powder, gold powder, carbon nanotubes, and graphene. Other technical features are the same as those in Example 2.

[0083] The specific embodiments described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. 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 preparing a metal alloy series-connected shingled photovoltaic module cell string, characterized in that The following steps are involved: S1, printing a back main grid electrode (5) on the back side of the battery cell (1); S2. Drying the slurry printed on the back main grid electrode (5) S3, printing a back electric field (6) on the back side of the battery cell (1); S4, drying the slurry printed by the back electric field (6); S5, printing a front fine grid electrode (2) and a front main grid electrode (3) on the front side of the battery cell (1); S6, drying the slurry printed on the front fine grid electrode (2) and the front main grid electrode (3); S7, test sorting: selecting the battery cells (1) whose voltage and current meet the requirements; S8, screen printing a front side main grid electrode (4) on the front side of the battery cell (1); S9, drying the slurry printed on the main grid electrode (4) on the front side; S10, dispensing or screen-printing a layer of glue or applying adhesive tape on the main grid electrode (4) on the front side of the stack to achieve adhesive connection of adjacent battery cells (1) in series; S11, high temperature sintering: performing high temperature sintering on the printed paste at the stack of adjacent battery cells (1) to form a molten metal alloy (8); The temperature of high temperature sintering is set at 700-900℃; S12, cooling: The molten metal alloy (8) in the stack is solidified by cooling to form a metal and silicon-based alloy system, and finally a shingled photovoltaic module cell string is obtained.

2. The method for preparing a metal alloy series-connected shingled photovoltaic module cell string according to claim 1, characterized in that: The specific steps of step S10 are as follows: A. applying glue or screen printing a layer of glue or applying adhesive tape on the main grid electrode (4) on the front side of the stack to achieve gluing and connecting adjacent battery cells (1) in series; B. Pressing or blowing high-pressure air with a wind knife to the stacked area so that adjacent battery cells (1) are in full contact; C. 80-200℃ volatilizes and decomposes the organic components in the screen printing glue or dot glue or adhesive tape; D. Pressing a second time or blowing high-pressure air with a wind knife to ensure that the adjacent battery cells (1) are in full contact with each other and that the battery cells (1) are in full and close contact when entering high-temperature sintering.

3. The method for preparing a metal alloy series-connected shingled photovoltaic module cell string according to claim 1, characterized in that: The slurry used for printing in step S1 and step S5 is silver paste or silver-aluminum paste; the slurry used for printing the main grid electrode (4) on the front side in step S8 is based on silver paste or silver-aluminum paste and added with organic matter with adhesive effect, and its specific composition and proportion are: ultrafine silver powder 80%, glass powder 5%, acrylic polymer 13%, and other 2% components are thickener, thixotropic agent, and defoaming agent; wherein the ultrafine silver powder serves as the conductive functional phase, and the acrylic polymer serves as the organic adhesive.

4. The method for preparing a metal alloy series-connected shingled photovoltaic module cell string according to claim 3, characterized in that: In the step S8, the conductive functional phase in the paste for printing the main grid electrode (4) on the front side is one or more of copper, silver, aluminum, gold, carbon nanotubes, and graphene.

5. The method for preparing a metal alloy series-connected shingled photovoltaic module cell string according to claim 1, characterized in that: Prior to step S9, a back side main grid electrode (7) is printed on the back side of the cell (1) and dried; in step S9, the front side main grid electrode (4) of the previous cell (1) and the back side main grid electrode (7) of the next cell (1) are partially stacked and connected in series.

6. The method for preparing a metal alloy series-connected shingled photovoltaic module cell string according to claim 5, characterized in that: In the step S9, glue is dispensed on the front side main grid electrode (4) at the stacking position, and the front side main grid electrode (4) of the previous battery cell (1) and the back side main grid electrode (7) of the next battery cell (1) are glued together by glue dispensing to form a series connection; wherein the number of glue dispensings is 2-10.

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