Preparation method of back contact battery and back contact battery
By changing the distribution ratio of N and P regions in the back contact battery, and forming multiple sets of spaced doping regions and doping positions through etching, the problem of overprinting of fine gate line paste is solved, and the battery efficiency and performance are improved .
Patent Information
- Application Number
- CN202411371674.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-09-29
- Publication Date
- 2025-01-10
AI Technical Summary
The interdigital distribution of P and N regions in the back contact battery results in difficulty in accurately overprinting the fine gate slurry of the positive and negative electrodes, which easily leads to leakage and efficiency losses.
By changing the area size of the secondary P region, flexibly changing the distribution proportion of P region and N region, and by etching, multiple sets of spaced N-type doping regions and N-type doping positions are formed to form multi-directional distribution PN junctions to reduce leakage situation to improve efficiency.
It realizes flexible grooves of P and N regions, improves the efficiency of the back contact battery, reduces leakage, and the pattern of the screen-printed fine grid silver paste is no longer a one-way linear distribution, but multi-directional distribution. Improves battery performance.
Smart Images
Figure CN119300516A_ABST
Abstract
Description
Technical Field
[0001] The present disclosure belongs to the technical field of solar cells, and in particular, relates to a method for preparing a back-contact cell and a back-contact cell. Background Art
[0002] A back-contact cell is a solar cell structural design in which the front side of the photovoltaic module is transparent and can absorb and convert sunlight into electrical energy, while the circuit connection points of the cell are located on the back side of the cell.
[0003] The back of the back-contact battery is the P region and the N region, which are distributed in a forked-finger shape and arranged alternately. Therefore, the distribution ratio of the P region and the N region is relatively fixed, and the laser patterns of the P region and the N region are prone to be too thin during the grooving process, resulting in the printed positive and negative electrode fine grid line pastes being difficult to accurately overprint in the corresponding P region and N region, which can easily cause leakage and efficiency loss. Summary of the invention
[0004] To solve the above problems, the present disclosure provides a method for preparing a back-contact battery and a back-contact battery, which can flexibly change the distribution ratio of the P region and the N region by changing the area size of the secondary P region, thereby reducing the risk of difficulty in overprinting fine grid lines in the corresponding P region and N region after grooving, thereby improving the efficiency of the back-contact battery.
[0005] A first aspect of the present disclosure provides a method for preparing a back-contact battery, comprising: providing a substrate; forming a P-type doped film layer based on one side of the substrate; forming a mask layer based on a side of the P-type doped film layer away from the substrate; etching the mask layer portion along a first direction to form a plurality of groups of spaced N-type doped regions, each group of N-type doped regions comprising a plurality of N-type doped positions spaced apart along a second direction, the first direction intersecting the second direction; forming an N-type doped film layer based on the N-type doped regions; and forming a metal layer on the P-type doped film layer and the N-type doped film layer.
[0006] In this way, a plurality of groups of spaced N-type doping regions are etched on the substrate, and each group of N-type doping regions includes a plurality of N-type doping positions, so that P regions are formed between the spaced N-type doping regions and between the spaced N-type doping positions, thereby facilitating changing the distribution size of the N region and the P region by changing the etched N-type doping regions and the N-type doping positions, and then changing the distribution ratio of the N region and the P region, thereby realizing flexible grooving of the substrate, so that the printed positive and negative fine grid line pastes are overprinted in the corresponding P region and N region, thereby reducing leakage and realizing efficiency improvement.
[0007] In some embodiments, forming a P-type doped film layer based on one side of the substrate includes: establishing a P-type doped region based on one side of the substrate; applying boron element to the P-type doped region; and high-temperature annealing the P-type doped region after applying boron element on the substrate.
[0008] This arrangement allows boron atoms to be released from the source material at high temperature and move to the P-type doped region to replace tetravalent silicon atoms in the substrate silicon, forming holes until a stable P-type semiconductor region is formed after annealing.
[0009] In some embodiments, forming a mask layer based on a side of the P-type doped film layer facing away from the substrate includes: a material of the mask layer includes silicon nitride covering the surface of the substrate.
[0010] This arrangement allows a layer of silicon nitride to be deposited on the surface of the substrate as a protective mask to prevent the current generated by light from flowing directly back to the back of the battery and causing a short circuit, while protecting the substrate from chemical reactions.
[0011] In some embodiments, the mask layer is partially etched along the first direction to form a plurality of groups of spaced N-type doped regions, each group of N-type doped regions includes a plurality of N-type doped positions spaced apart along the second direction, and the intersection of the first direction and the second direction includes: punching an N-type laser pattern on the substrate; etching the mask layer and the substrate along the first direction based on the laser pattern to form a plurality of groups of spaced N-type doped regions, and each group of spaced N-type doped regions has a plurality of N-type doped positions spaced apart along the second direction.
[0012] With this arrangement, an N-type laser pattern is pre-printed, so that the laser etches the substrate according to the laser pattern to form an N-type doping region, which helps to form multiple spaced N-type doping positions, thereby reducing the situation where the N-type doping region is grooved too thin.
[0013] In some embodiments, the mask layer is partially etched along the first direction to form multiple groups of spaced N-type doped regions, each group of N-type doped regions includes multiple N-type doped positions spaced along the second direction, and the intersection of the first direction and the second direction includes: two adjacent N-type doped positions forming a P region; two adjacent groups of N-type doped regions forming a sub-P region.
[0014] Such a setting is used to flexibly change the distribution ratio of the P region and the N region by changing the area size of the secondary P region, so as to improve the efficiency of the back contact battery.
[0015] In some embodiments, the mask layer is partially etched along the first direction to form multiple groups of spaced N-type doped regions, each group of N-type doped regions includes multiple N-type doped positions spaced apart along the second direction, the first direction intersects with the second direction, and also includes: cleaning and texturing the N-type doped regions.
[0016] This arrangement makes it easier to remove damage to the substrate caused by laser etching and remove the boron element in the N-type doped area to form a pyramid velvet surface to reduce light reflection.
[0017] In some embodiments, after forming an N-type doped film layer based on the N-type doped region and before forming a metal layer based on the P-type doped film layer and the N-type doped film layer, it includes: forming a passivation layer based on the side of the substrate away from the P-type doped film layer and the N-type doped film layer, and on the P-type doped film layer and the N-type doped film layer.
[0018] This arrangement allows the deposition of a passivation layer to reduce light reflection and improve the passivation performance of the battery.
[0019] A second aspect of the present disclosure provides a back-contact battery, which includes: a substrate; a P-type doped film layer, which is arranged on one side of the substrate; a mask layer, which is arranged on the side of the P-type doped film layer away from the substrate, the mask layer having a plurality of groups of N-type doped regions arranged at intervals along a first direction, each group of the N-type doped regions including a plurality of N-type doped positions arranged at intervals along a second direction, the first direction intersecting with the second direction; an N-type doped film layer, which is arranged in the N-type doped region; and a metal layer, which is arranged on the N-type doped film layer and the P-type doped film layer.
[0020] This arrangement allows for flexible grooving of the substrate by changing the distribution size of the N-type doped area and the ratio of the N area to the P area, so that the printed positive and negative fine gate line pastes can be overprinted in the corresponding P area and N area, reducing leakage and improving efficiency.
[0021] In some embodiments, each of the N-type doping sites includes a plurality of doping grooves arranged at intervals along the first direction.
[0022] Such arrangement enables a plurality of doping grooves to form N-type doping sites, so that the distribution ratio of the N region and the P region can be controlled by etching the doping grooves during laser etching, thereby further achieving size control of the N region and the P region.
[0023] In some embodiments, the doping grooves include dot-shaped grooves and strip-shaped grooves.
[0024] In this way, discontinuous dots or line segments are punched by laser to form doping grooves in the form of dots or strips, so that the diffused doping after laser grooving is on the discontinuous grooving points or discontinuous lines. The left and right sides of these discontinuous points or lines are areas without grooving, and corresponding P areas can be formed. Moreover, since the laser punches discontinuous dots or discontinuous line segments, there are also areas without laser punching between dots and dots, and between line segments. This part can be used as a sub-P area to increase the area of the discontinuous dots or discontinuous line segments to increase the proportion of the area of this area. The PN junction produced is no longer a unidirectional linear distribution, but a multi-directional distribution is achieved.
[0025] Compared with the prior art, the present invention has the following advantages:
[0026] 1. By changing the etched N-type doping area and N-type doping position to change the distribution size of the N area and the P area, and then changing the distribution ratio of the N area and the P area, the substrate can be flexibly slotted to facilitate the overprinting of the printed positive and negative fine gate line pastes in the corresponding P area and N area, reducing leakage and improving efficiency;
[0027] 2. When screen printing fine grid line silver paste, the screen pattern is no longer a straight line, but dots or discontinuous lines printed in the corresponding slotted area. By increasing the area of discontinuous dots or discontinuous line segments, the proportion of the area of the area is increased. The PN junction produced is no longer a unidirectional linear distribution, but a multi-directional distribution.
[0028] Other features and advantages of the present disclosure will be described in the following description, and partly become apparent from the description, or be understood by implementing the present disclosure. The purpose and other advantages of the present disclosure can be realized and obtained by the structures pointed out in the description, claims and drawings. BRIEF DESCRIPTION OF THE DRAWINGS
[0029] In order to more clearly illustrate the embodiments of the present disclosure or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present disclosure. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.
[0030] Figure 1 is a flow chart of a method for preparing a back contact battery provided in an embodiment of the present disclosure;
[0031] Figure 2 is a schematic cross-sectional view of a back contact battery according to an embodiment of the present disclosure;
[0032] Figure 3 is a schematic diagram of a substrate laser pattern provided by an embodiment of the present disclosure;
[0033] Figure 4 It is a schematic diagram of a substrate printing pattern provided by an embodiment of the present disclosure. DETAILED DESCRIPTION
[0034] In order to make the purpose, technical solution and advantages of the embodiments of the present disclosure clearer, the technical solution in the embodiments of the present disclosure will be clearly and completely described below in conjunction with the drawings in the embodiments of the present disclosure. Obviously, the described embodiments are part of the embodiments of the present disclosure, not all of the embodiments. Based on the embodiments in the present disclosure, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present disclosure.
[0035] The following is a brief introduction to some concepts that may be involved in the embodiments of the present disclosure.
[0036] Back Contact Cell (BC Cell): A special cell technology, whose main feature is that the cell's PN junction and metal contact are located on the back of the cell, rather than on the front of the traditional cell. This design leaves the front of the cell free of electrode shielding, thereby increasing the area of the cell that absorbs sunlight and improving the efficiency of light energy conversion.
[0037] In terms of structure, the P and N regions of existing back contact batteries are distributed in a forked-finger shape, and the P and N regions are arranged alternately, and the distribution ratio of the P and N regions cannot be flexibly changed. In addition, the laser patterns of the P and N regions are easily grooved too thin during the groove cutting process, resulting in the printed positive and negative electrode fine grid line pastes. It is difficult to accurately overprint them in the corresponding P and N regions, which can easily cause leakage and efficiency loss. Therefore, it is necessary to use a new I BC (Interd igitated Back Contact) structure battery to achieve both flexible change of the distribution ratio of the P and N regions and improvement of efficiency.
[0038] To this end, the present disclosure provides a method for preparing a back contact battery. During the preparation of the back contact battery, the area size of the secondary P region is changed to flexibly change the distribution ratio of the P region and the N region, thereby improving the efficiency of the back contact battery. Figure 1 As shown, Figure 1 : is a flow chart of a method for preparing a back contact battery provided by an embodiment of the present disclosure, the preparation method comprising the following steps:
[0039] S100 . Provide a substrate.
[0040] In this embodiment, the surface of the silicon wafer of the substrate is first polished and cleaned to remove line marks, metal impurities, etc. on the surface of the silicon wafer.
[0041] S200, forming a P-type doped film layer based on one side of the substrate.
[0042] In this embodiment, a P-type doped region is established on one side of the substrate, and then boron is applied to the P-type doped region, and the P-type doped region after the boron is applied to the substrate is subjected to high temperature annealing. It can be understood that the doped region is created by laser or mechanical scribing, and the doped region is applied, and the silicon wafer is placed in a high temperature furnace (about 800°C to 1200°C). At this temperature, boron atoms are released from the source material and move to the doped region, replacing the tetravalent silicon atoms in the silicon to form holes. As the temperature increases and the time increases, the diffusion of boron atoms in the silicon wafer becomes more uniform, so that the entire doped region presents the desired concentration. After the diffusion is completed, the silicon wafer needs to be slowly cooled to stop the diffusion of impurity atoms and form a stable P-type semiconductor region.
[0043] S300, forming a mask layer based on the side of the P-type doped film layer facing away from the substrate.
[0044] In this embodiment, a layer of silicon nitride is deposited on the surface of the silicon wafer, and the P-type doped area on the silicon wafer is also covered as a protective mask to prevent light from directly irradiating the PN junction inside the battery, avoiding the current generated by light from directly flowing back to the back of the battery to cause a short circuit, thereby protecting the electrical integrity of the battery.
[0045] S400, etching a portion of the mask layer along the first direction to form a plurality of groups of spaced N-type doping regions, each group of N-type doping regions including a plurality of N-type doping sites spaced apart and arranged along the second direction.
[0046] In this embodiment, the first direction intersects with the second direction. First, an N-type laser pattern is formed on the substrate, and a laser is used to groove the pattern along the first direction and the second direction on the substrate. Since the pattern not grooved by the laser has a silicon nitride film as a mask protection layer, when diffuse doping is performed later, doping will only be performed at the laser grooved location, that is, doping is performed in the N-type doped area to form an N area. Then, the N-type doped area is cleaned and textured to remove the damage caused by the laser, so as to remove the boron in the P area, form a pyramid velvet surface, and reduce light reflection.
[0047] It should be noted that the length of the laser grooving is related to the size of the silicon wafer, which is generally 1-5 mm smaller than the length of the silicon wafer, and the depth is generally 0.5-10 μm.
[0048] For example, Figure 2 and Figure 3 As shown, Figure 2 is a schematic diagram of a substrate laser pattern provided by an embodiment of the present disclosure, Figure 3It is a schematic diagram of the substrate printing pattern provided by the embodiment of the present disclosure. Two adjacent N-type doping positions form a P region. Two adjacent groups of N-type doping regions form a sub-P region, and intermittent line segments or dots are punched by laser as the N region. The diffuse doping after laser grooving will only be doped on the intermittent grooving points or intermittent lines. The left and right sides of these intermittent points or lines are areas without grooving, which are the corresponding P regions. Moreover, since the laser punches intermittent points or intermittent line segments, there are also areas without laser punching between the points, which serve as sub-P regions; the distribution size of the N region and the P region can be changed by changing the etched N-type doping area and the N-type doping position, and then the distribution ratio of the N region and the P region can be changed, so as to realize flexible grooving of the substrate, so that the printed positive and negative fine grid line slurry can be overprinted in the corresponding P region and N region, reducing leakage and achieving efficiency improvement.
[0049] It should be noted that the diameter of the dots is 5-50 μm, the spacing between the dots is no more than 300 μm, the length of the line segment is 50-500 μm, and the length of the line segment is no more than 3 mm.
[0050] When screen printing fine grid line silver paste, the screen pattern is no longer a straight line, but dots or discontinuous lines printed in the corresponding slotted area. By increasing the area of the discontinuous dots or discontinuous line segments, the proportion of the area of the area is increased. The PN junction produced is no longer a unidirectional linear distribution, but a multi-directional distribution.
[0051] S500 , forming an N-type doped film layer based on the N-type doped region.
[0052] In this embodiment, phosphorus doping is performed in the N-type doped area, that is, in the area where the laser is turned on, and a laser of a specific wavelength is used to create a shallow and precise oxide layer on the silicon wafer to leave a hole under the silicon, called a photogenerated hole. Subsequently, a dopant containing phosphorus, such as a phosphide solution, is applied to this exposed silicon surface. Phosphorus is a group II and IV element that can introduce additional free electrons, and phosphorus is N-type, turning silicon into an N-type semiconductor. At an appropriate temperature (usually between 800°C and 1100°C), phosphorus atoms diffuse into the silicon lattice, fill the holes generated by the oxidation reaction, and increase the electron density. After cooling down, the position of the phosphorus atoms is fixed, forming a stable N-type region, forming a PN junction with the surrounding P region.
[0053] S600 , forming a metal layer on the P-type doped film layer and the N-type doped film layer.
[0054] In this embodiment, silver grid line patterns are printed, respectively printed on the P region and the N region to form metal contacts. The metal is usually aluminum, copper or silver, which serves as a back contact electrode to achieve current collection and facilitate conduction.
[0055] Based on the above method, the present disclosure also provides a back contact battery corresponding to the above method, see Figure 2 and Figure 3 , Figure 2 is a schematic cross-sectional view of a back contact battery according to an embodiment of the present disclosure, Figure 3 It is a schematic diagram of the substrate laser pattern provided in an embodiment of the present disclosure; the back contact battery includes: a substrate 10, a P-type doped film layer 20, a mask layer 30, an N-type doped film layer 40, a passivation layer 50 and a metal layer 60.
[0056] In this embodiment, the P-type doped film layer is disposed on one side of the substrate 10. The mask layer 30 is disposed on the side of the P-type doped film layer 20 away from the substrate 10. The mask layer 30 is provided with a plurality of groups of N-type doped regions arranged at intervals along a first direction, each group of N-type doped regions includes a plurality of N-type doped positions arranged at intervals along a second direction, the first direction intersects with the second direction, and the first direction and the second direction are parallel to the surface of the substrate. The N-type doped film layer 40 is disposed in the N-type doped region. The passivation layer 50 is disposed on the side of the substrate 10 away from the P-type doped film layer 20 and the N-type doped film layer 40, and on the P-type doped film layer 20 and the N-type doped film layer 40. The metal layer 60 is disposed on the N-type doped film layer 40 and the P-type doped film layer 20.
[0057] Exemplarily, two adjacent N-type doping sites form a P region, and two adjacent groups of N-type doping regions form a sub-P region. Moreover, each N-type doping site includes a plurality of doping grooves arranged at intervals along the first direction, and the doping grooves include dot-shaped grooves or strip-shaped grooves, that is, the dots and line segments mentioned in the above method.
[0058] For example Figure 3 As shown, 1 is a silicon wafer, 2 is an N region, 3 is a sub-P region, and 4 is a P region. By punching a laser pattern on the silicon wafer 1, an N region 2 is formed at the laser pattern position when doping is performed by diffusion. The area adjacent to the left and right of the N region 2 that is not lasered is the sub-P region 3, and the area in the middle of the upper and lower directions where the N region is lasered is not lasered is the P region 4. It can be understood that the sub-P region 3 and the P region 4 surround the N region in the middle, and the printing is also corresponding.
[0059] Therefore, by increasing the proportion of the sub-P region, the distribution ratio of the P region and the N region can be flexibly changed to improve the efficiency of the back contact battery.
[0060] For example Figure 4 As shown, Figure 4 5 is a schematic diagram of a substrate printing pattern provided by an embodiment of the present disclosure; 5 is a silver grid line in the N region, 6 is a silver grid line in the P region, 7 is a silver grid line in the auxiliary P region, and the silver grid line 5 is as shown in FIG. Figure 2As shown in the metal layer 60 in FIG. The N region silver grid line 5 is responsible for current collection and conduction of the entire N region 2, the P region silver grid line 6 is responsible for current collection and conduction of the entire P region 4, the sub-P region silver grid line is responsible for current collection and conduction of the entire sub-P region 3, and the sub-P region silver grid line and the P silver grid line are connected and converged together through horizontal lines.
[0061] It is worth noting that the P region and the N region can be interchanged, and this can be achieved by simply changing the doping source. Doping with phosphorus is the N region, and doping with boron is the P region.
[0062] Although the present disclosure has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present disclosure.
Claims
1. A method for preparing a back contact battery, characterized in that: The method comprises: providing a substrate; forming a P-type doped film layer based on one side of the substrate; forming a mask layer based on a side of the P-type doped film layer facing away from the substrate; Etching a portion of the mask layer along a first direction to form a plurality of groups of spaced N-type doping regions, each group of N-type doping regions comprising a plurality of N-type doping sites spaced apart and arranged along a second direction, the first direction intersecting the second direction; forming an N-type doped film layer based on the N-type doped region; A metal layer is formed on the P-type doped film layer and the N-type doped film layer.
2. The method according to claim 1, characterized in that The forming of a P-type doped film layer based on one side of the substrate comprises: Establishing a P-type doped region based on one side of the substrate; Applying boron element to the P-type doping region; The P-type doped region on the substrate coated with boron element is subjected to high temperature annealing.
3. The method according to claim 1, characterized in that The forming of a mask layer based on a side of the P-type doped film layer away from the substrate comprises: The material of the mask layer includes silicon nitride covering the surface of the substrate.
4. The method according to claim 1, characterized in that: The mask layer is partially etched along the first direction to form a plurality of groups of spaced N-type doping regions, each group of N-type doping regions includes a plurality of N-type doping positions spaced along the second direction, and the intersection of the first direction and the second direction includes: Producing an N-type laser pattern on the substrate; Based on the laser pattern, the mask layer and the substrate are etched along the first direction to form a plurality of groups of spaced N-type doping regions, and each group of spaced N-type doping regions has a plurality of N-type doping positions spaced apart along the second direction.
5. The method according to claim 4, characterized in that The mask layer is partially etched along the first direction to form a plurality of groups of spaced N-type doping regions, each group of N-type doping regions includes a plurality of N-type doping positions spaced along the second direction, and the intersection of the first direction and the second direction includes: Two adjacent N-type doping sites form a P region; Two adjacent groups of N-type doped regions form a sub-P region.
6. The method according to claim 4 or 5, characterized in that: The mask layer is partially etched along the first direction to form a plurality of groups of spaced N-type doping regions, each group of N-type doping regions includes a plurality of N-type doping sites spaced along the second direction, the first direction intersecting the second direction, and further comprising: The N-type doped area is cleaned and textured.
7. The method according to any one of claims 1 to 5, characterized in that: After forming the N-type doped film layer based on the N-type doped region and before forming the metal layer on the P-type doped film layer and the N-type doped film layer, the method comprises: A passivation layer is formed on a side of the substrate away from the P-type doped film layer and the N-type doped film layer, and on the P-type doped film layer and the N-type doped film layer.
8. A back contact battery, characterized in that: The back contact battery comprises: substrate; A P-type doped film layer is disposed on one side of the substrate; A mask layer is disposed on a side of the P-type doped film layer away from the substrate, the mask layer is provided with a plurality of groups of N-type doped regions arranged at intervals along a first direction, each group of the N-type doped regions includes a plurality of N-type doped positions arranged at intervals along a second direction, and the first direction intersects with the second direction; An N-type doped film layer is disposed in the N-type doped region; The metal layer is arranged on the N-type doped film layer and the P-type doped film layer.
9. The back contact cell according to claim 8, characterized in that: Each of the N-type doping sites includes a plurality of doping grooves arranged at intervals along the first direction.
10. The back contact cell according to claim 9, characterized in that: The doping grooves include dot-shaped grooves and strip-shaped grooves.