Back structure of a double-sided P-type battery cell and preparation method thereof

Abstract

The present invention discloses a back structure of a double-sided P-type cell and a preparation method thereof, comprising a silicon substrate layer, a passivation layer arranged on the silicon substrate layer, an aluminum layer arranged on the passivation layer, the aluminum layer being able to pass through the passivation layer and contact the silicon substrate layer, the aluminum layer generating an aluminum silicon compound at a high temperature, and a metal wire layer being arranged on the aluminum silicon compound. The invention of this structure makes it possible to replace silver paste printing with low-cost copper electroplating of double-sided P-type cells into a simple and feasible process, which helps to significantly reduce the production cost of double-sided P-type cells. At the same time, since copper electroplating is used to replace screen-printed silver paste, the light receiving area can be increased and the fill factor (FF) can be improved, thereby improving the overall battery power generation efficiency. The aluminum silicon compound is formed when the double-sided electroplating of the cell is performed, so that the back of the battery can form a good electrical contact path with the cathode, avoiding the impedance being too high to form a complete electroplating circuit, which is conducive to the passage of large current during electroplating, thereby improving the electroplating efficiency and the qualified rate of mass-produced products.

Description

Technical Field

[0001] The present invention relates to the field of photovoltaic cells, and in particular to a novel back structure of a double-sided P-type cell sheet and a preparation method thereof. Background Art

[0002] With the continuous expansion and rapid development of the photovoltaic industry, since ISFH (Institute for Solar Energy Research Hamelin, Germany) and SolarWorld (a photovoltaic industry company located in Germany) first proposed bifacial P-type cells in 2015, bifacial P-type cell technology has been widely adopted by solar cell manufacturers. The rapid commercialization of bifacial P-type cells is mainly due to its manufacturing process that is very similar to that of single-sided PERC cells, which happens to be the mainstream technology in the photovoltaic industry. The existing P-type cells still use printed silver paste on the front of the cell, while a large amount of aluminum paste and silver-aluminum paste are used to make grid lines on the back; silver paste, silver-aluminum paste and aluminum paste account for more than 25% of the total cost of producing photovoltaic cells. Obviously, for bifacial P-type cells, if low-cost metals can be used to replace part or even all of the silver paste, silver-aluminum paste and aluminum paste, it will have a significant significance in reducing the production cost of crystalline silicon photovoltaic cells.

[0003] However, due to the discontinuous laser opening on the back of the battery in the existing P-type battery technology, aluminum-metal silicide (AlSix) can only be partially formed, and a complete electrical contact path cannot be formed during the electroplating process; secondly, due to the porous structure formed after the aluminum paste is printed and sintered (see the attached figure), during the electroplating process, a large amount of electroplating solution will not only damage the wire welding points formed by the silver-aluminum paste printing on the back of the double-sided P-type battery, but also seal the electroplating solution residue in this porous structure, which will have an unpredictable negative impact on the quality and reliability of the battery.

[0004] Therefore, the inventor of the present invention, in view of the above technical problems, aims to invent a back side structure of a double-sided P-type battery cell and a preparation method thereof. Summary of the invention

[0005] In order to overcome the above disadvantages, the object of the present invention is to provide a back side structure of a double-sided P-type battery cell and a preparation method thereof.

[0006] In order to achieve the above purpose, the technical solution adopted by the present invention is: a back structure of a double-sided P-type battery cell, including a silicon substrate layer, a passivation layer is arranged on the silicon substrate layer, an aluminum layer is arranged on the passivation layer, and the aluminum layer can pass through the passivation layer to contact the silicon substrate layer, and the aluminum layer generates an aluminum silicon compound at a high temperature, and a metal wire layer is arranged on the aluminum silicon compound.

[0007] Preferably, the passivation layer is provided with continuous through holes in a grid shape, that is, the continuous through holes in a grid shape facilitate the arrangement of the aluminum layer, and then facilitate the reaction between the aluminum layer and the silicon substrate layer to generate aluminum silicon compound.

[0008] Preferably, the area of ​​the continuous through hole accounts for 2-98% of the surface area of ​​the passivation layer, that is, the area of ​​the aluminum silicon compound is guaranteed, and the conductive performance is guaranteed.

[0009] Preferably, the passivation layer includes at least one aluminum oxide film layer and at least one silicon nitride film layer, that is, the passivation layer is composed of two film layers, aluminum oxide (Al2O3) film layer and silicon nitride (SiNx), and the formation of the passivation layer ensures the protection of the silicon substrate layer.

[0010] Preferably, the metal conductor layer is provided with three layers, which are nickel layer, copper layer, tin layer or silver layer in sequence, that is, the nickel layer is in direct contact with the aluminum silicon compound layer, and the tin layer and the silver layer can be selected according to the requirements.

[0011] A method for preparing a back side structure of a double-sided P-type solar cell comprises the following steps:

[0012] S1, setting a passivation layer: at least an aluminum oxide film layer and at least one silicon nitride film layer are sequentially set on a silicon substrate layer, and the two film layers constitute a passivation layer; the passivation layer is mainly set by a vapor deposition method.

[0013] S2, setting continuous through holes: using laser to act on the passivation layer above the passivation layer, and the laser can burn through the passivation layer and expose the silicon substrate layer, the laser works continuously on the passivation layer, and the burned through pattern is a continuous through hole;

[0014] S3, disposing an aluminum layer: disposing an aluminum layer on the continuous through hole, and the aluminum layer is in contact with the silicon substrate layer;

[0015] S4, formation of aluminum silicon compound: the finished product in the previous step is fired at 500-800 degrees Celsius for 30-60 minutes to obtain aluminum silicon compound;

[0016] S5, setting a metal conductive layer: setting a metal conductor layer on the aluminum silicon compound, and the metal conductor layer is set to three layers, which are a nickel layer, a copper layer, a tin layer or a silver layer in sequence.

[0017] Preferably, the aluminum layer in S3 is provided by printing, metal sputtering or metal evaporation.

[0018] Preferably, the line width of the aluminum layer in S3 can completely cover the continuous through holes on the passivation layer, and the aluminum layer is higher than the passivation layer and is not higher than 3um. If the aluminum layer is grown by metal sputtering or metal evaporation, the aluminum layer does not exceed 990nm of the passivation layer. Since the thickness is not easy to control during printing, while the thickness is easy to control by metal sputtering or metal evaporation, the range is narrowed.

[0019] Preferably, in S4-S5, an aluminum layer removal step is also provided to make the aluminum layer and the passivation layer at the same height, that is, to facilitate the subsequent arrangement of the metal wire layer.

[0020] Preferably, the metal wire layer is provided by electroplating in S5. While electroplating the metal wire layer, the other side of the P-type solar cell may also be electroplated at the same time.

[0021] The beneficial effect of the back structure of a double-sided P-type battery cell of the present invention is that the invention of this structure makes the low-cost electroplating of copper on the double-sided P-type battery cell replace the silver paste printing to become a simple and feasible process, which helps to significantly reduce the production cost of the double-sided P-type battery. At the same time, since the electroplating of copper is used instead of the screen-printed silver paste, the light-receiving area can be increased and the fill factor (FF) can be improved, thereby improving the overall battery power generation efficiency.

[0022] The beneficial effect of the method for preparing the back structure of a double-sided P-type battery cell of the present invention is that the aluminum silicon compound is formed so that the back of the battery can form a good electrical contact path with the cathode during double-sided electroplating of the battery cell, avoiding the impedance being too high to form a complete electroplating circuit, which is beneficial to the passage of large current during electroplating, thereby improving the electroplating efficiency and the qualified rate of mass-produced products. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 Schematic diagram of the first step of a method for preparing a back side structure of a double-sided P-type solar cell.

[0024] Figure 2 It is a schematic diagram of the second step of the method for preparing the back structure of a double-sided P-type solar cell.

[0025] Figure 3 It is a schematic diagram of the third step of the method for preparing the back structure of a double-sided P-type solar cell.

[0026] Figure 4 Schematic diagram of the removal of the aluminum layer after the production of aluminum silicon compound.

[0027] Figure 5 It is a schematic diagram of the fifth step of the method for preparing the back structure of a double-sided P-type solar cell.

[0028] In the figure:

[0029] 1-silicon substrate layer, 2-passivation layer, 3-aluminum layer, 4-aluminum silicon compound, 5-metal wire layer, 6-continuous through hole,

[0030] 21-aluminum oxide film layer, 22-silicon nitride film layer,

[0031] 51 - nickel layer, 52 - copper layer, 53 - silver layer. DETAILED DESCRIPTION

[0032] The preferred embodiments of the present invention are described in detail below in conjunction with the accompanying drawings so that the advantages and features of the present invention can be more easily understood by those skilled in the art, thereby making a clearer and more definite definition of the protection scope of the present invention.

[0033] See attached Figure 1-5 As shown, the back structure of a double-sided P-type solar cell in this embodiment includes a silicon substrate layer 1, a passivation layer 2 is arranged on the silicon substrate layer 1, an aluminum layer 3 is arranged on the passivation layer 2, and the aluminum layer 3 can pass through the passivation layer 2 to contact the silicon substrate layer 1, and the aluminum layer 3 generates an aluminum silicon compound 4 at a high temperature, and a metal wire layer 5 is arranged on the aluminum silicon compound 4.

[0034] The passivation layer 2 is provided with continuous through holes 6 in a grid shape, that is, the continuous through holes 6 in a grid shape facilitate the arrangement of the aluminum layer 3, and then facilitate the reaction between the aluminum layer 3 and the silicon substrate layer 1 to generate the aluminum silicon compound 4.

[0035] The area of ​​the continuous through hole 6 accounts for 2-98% of the surface area of ​​the passivation layer 2, that is, the area of ​​the aluminum silicon compound 4 is guaranteed, and the conductive performance is guaranteed.

[0036] The passivation layer 2 includes at least one aluminum oxide film layer 21 and at least one silicon nitride film layer 22. That is, the passivation layer 2 is composed of two film layers, aluminum oxide (Al2O3) film layer and silicon nitride (SiNx). The formation of the passivation layer 2 ensures the protection of the silicon substrate layer 1.

[0037] The metal conductor layer 5 is provided with three layers, namely, a nickel layer 51, a copper layer 52, and a tin layer or a silver layer 53. That is, the nickel layer 51 is in direct contact with the aluminum silicon compound layer 4, and the tin layer or the silver layer 53 can be selected according to the requirements.

[0038] A method for preparing a back side structure of a double-sided P-type solar cell comprises the following steps:

[0039] S1, setting the passivation layer 2: at least an aluminum oxide film layer 21 and at least a silicon nitride film layer 22 are sequentially set on the silicon substrate layer 1, and the two film layers constitute the passivation layer 2; the passivation layer 2 is mainly set by vapor deposition method. Figure 1 shown.

[0040] S2, setting continuous through holes 6: using laser to act on the passivation layer 2 above the passivation layer 2, and the laser can burn through the passivation layer 2 and expose the silicon substrate layer 1, the laser works continuously on the passivation layer 2, and the pattern of the burned through continuous through holes 6, see the attached Figure 2 As shown;

[0041] S3, disposing aluminum layer 3: disposing aluminum layer 3 on continuous through hole 6, and aluminum layer 3 is in contact with silicon substrate layer 1, see attached Figure 3 As shown;

[0042] S4, formation of aluminum silicon compound 4: the finished product in the previous step is fired at 500-800 degrees Celsius for 30-60 minutes to obtain aluminum silicon compound 4;

[0043] S5, setting a metal conductive layer: setting a metal wire layer 5 on the aluminum silicon compound 4, the metal wire layer 5 is provided with three layers, which are a nickel layer 51, a copper layer 52, and a tin layer or a silver layer 53 in sequence. Figure 5 shown.

[0044] The aluminum layer 3 in S3 is provided by printing, metal sputtering or metal evaporation.

[0045] The line width of the aluminum layer 3 in S3 can completely cover the continuous through hole 6 on the passivation layer 2, and the aluminum layer 3 is higher than the passivation layer 2 and is not higher than 3um. If the aluminum layer 3 is grown by metal sputtering or metal evaporation, the aluminum layer 3 does not exceed 2990nm of the passivation layer. Since the thickness is not easy to control during printing, and the thickness is easy to control by metal sputtering or metal evaporation, the range is narrowed, see the attached Figure 3 shown.

[0046] In S4-S5, there is also a step of removing the aluminum layer 3, so that the aluminum layer 3 and the passivation layer 2 are at the same height. That is, it is convenient to set the subsequent metal wire layer 5, see the attached Figure 4 shown.

[0047] In S5, electroplating is used to form the metal wire layer 5. While electroplating the metal wire layer 5, electroplating can also be performed on the other side of the P-type solar cell.

[0048] The beneficial effect of the back structure of a double-sided P-type battery cell is that the invention of this structure makes the low-cost electroplating of copper on the double-sided P-type battery cell replace the silver paste printing to become a simple and feasible process, which helps to significantly reduce the production cost of the double-sided P-type battery. At the same time, since electroplating copper is used instead of screen-printed silver paste, the light-receiving area can be increased and the fill factor (FF) can be improved, thereby improving the overall battery power generation efficiency.

[0049] A method for preparing the back structure of a double-sided P-type battery cell has the beneficial effect of forming an aluminum silicon compound 4 so that the back of the battery can form a good electrical contact path with the cathode during double-sided electroplating of the battery cell, avoiding the impedance being too high to form a complete electroplating circuit, which is beneficial to the passage of large current during electroplating, thereby improving the electroplating efficiency and the qualified rate of mass-produced products.

[0050] Furthermore, when the double-sided P-type photovoltaic cell adopting the present structure is subjected to the double-sided electroplating process, it is ensured that the back side of the cell will not be damaged by the electroplating solution when passing through the double-sided horizontal electroplating equipment, or the solution will remain in the porous structure on the back side, causing uncertain negative impact on the quality and reliability of the cell.

[0051] The above implementation modes are only for illustrating the technical concept and features of the present invention, and their purpose is to enable people familiar with this technology to understand the content of the present invention and implement it, and they cannot be used to limit the protection scope of the present invention. Any equivalent changes or modifications made according to the spirit of the present invention should be included in the protection scope of the present invention.

Claims

1. A back side structure of a double-sided P-type solar cell, characterized in that: The invention comprises a silicon substrate layer, a passivation layer is arranged on the silicon substrate layer, a continuous through hole is arranged on the passivation layer, and the continuous through hole is in a grid shape, an aluminum layer is arranged on the grid-shaped continuous through hole, the aluminum layer can pass through the passivation layer and contact the silicon substrate layer, and the aluminum layer generates aluminum silicon compound at a high temperature, and a metal wire layer is arranged on the aluminum silicon compound; The passivation layer includes at least one aluminum oxide film layer and at least one silicon nitride film layer.

2. The back side structure of a double-sided P-type solar cell according to claim 1, characterized in that: The area of ​​the continuous through hole accounts for 2-98% of the surface area of ​​the passivation layer.

3. The back side structure of a double-sided P-type solar cell according to claim 1, characterized in that: The metal conductor layer is provided with three layers, which are a nickel layer, a copper layer, a tin layer or a silver layer in sequence.

4. A method for preparing a back side structure of a double-sided P-type solar cell, characterized in that: The following steps are involved: S1, setting a passivation layer: sequentially setting at least one aluminum oxide film layer and at least one silicon nitride film layer on the silicon substrate layer, and the two film layers constitute a passivation layer; S2, setting continuous through holes: using laser to act on the passivation layer above the passivation layer, and the laser can burn through the passivation layer and expose the silicon substrate layer, the laser works continuously on the passivation layer, and the pattern of the burn-through is a continuous through hole, the passivation layer is provided with continuous through holes, and the continuous through holes are in a grid shape; S3, disposing an aluminum layer: disposing an aluminum layer on the continuous through hole, and the aluminum layer is in contact with the silicon substrate layer; S4, formation of aluminum silicon compound: the finished product in the previous step is fired at 500-800 degrees Celsius for 30-60 minutes to obtain aluminum silicon compound; S5, setting a metal conductive layer: setting a metal conductor layer on the aluminum silicon compound, and the metal conductor layer is set to three layers, which are a nickel layer, a copper layer, a tin layer or a silver layer in sequence.

5. The method for preparing the back side structure of a double-sided P-type solar cell according to claim 4, characterized in that: The aluminum layer in S3 is provided by printing, metal sputtering or metal evaporation.

6. The method for preparing a back side structure of a double-sided P-type solar cell according to claim 4, characterized in that: The line width of the aluminum layer in S3 can completely cover the continuous through holes on the passivation layer, and the aluminum layer is higher than the passivation layer and is not higher than 3 um.

7. The method for preparing the back side structure of a double-sided P-type solar cell according to claim 6, characterized in that: In S4-S5, an aluminum layer removal step is also provided to make the aluminum layer and the passivation layer at the same height.

8. The method for preparing the back side structure of a double-sided P-type solar cell according to claim 4, characterized in that: In S5, electroplating is used to set the metal conductor layer.

Images