WO2012031371A1

WO2012031371A1 - Metal wrap through back contact solar cell and manufacturing method thereof and module thereof

Info

Publication number: WO2012031371A1
Application number: PCT/CN2010/001346
Authority: WO
Inventors: 艾可凡; 王玉林; 蔡昭; 杨健; 陈如龙; 薛小兴; 张光春
Original assignee: 无锡尚德太阳能电力有限公司
Priority date: 2010-09-06
Filing date: 2010-09-06
Publication date: 2012-03-15

Abstract

A metal wrap through back-contact solar cell, a manufacturing method thereof and a module thereof are provided. The solar cell includes: a first conductive type region and a second conductive type region in a cell substrate (110) and a sub gate (130) formed on the front of the cell substrate (110), and holes (140) penetrating through the cell substrate (110), a main electrode (150) on the back of the cell substrate (110), a second electrode (160) located on the back of the cell substrate (110) and gate isolate trenches (171,176); the second electrode (160) is also used for self-aligned compensation doping in the second conductive type region, which contacts with the second electrode (160); the current flow created by the first conduction type area is outputted to the second electrode (160) by the second conduction type area, which is self-aligned compensation doped. In the manufacturing method, the sub gate (130) is patterned on the front cell substrate (110); the main gate electrode (150) and the second electrode (160) are formed on the back of the cell substrate (110); the second electrode (160) is used for self-aligned compensation doping in the second conductive type region contacted with the second electrode (160). The process of back contact solar cell is simple and the cost is low.

Description

Metal wound-type back contact solar cell, preparation method and component thereof

The invention belongs to the field of photovoltaic technology, and particularly relates to metal winding type (Metal Wrap)

Through, MWT ) Back contact solar cells, methods of preparation, and components thereof. Background technique

Due to the limited supply of conventional energy sources and the increasing pressure on environmental protection, many countries in the world have set off a boom in the development and utilization of solar energy and renewable energy. Solar energy utilization technology has been rapidly developed, in which the solar photovoltaic technology is used to convert solar energy into The use of electrical energy is becoming more widespread. Solar cells are among the most popular devices used to convert solar energy into electrical energy. In practical applications, a battery assembly in which a plurality of solar cells are connected in series (connected in series by interconnecting strips) is generally used as a basic application unit.

Generally, solar cells include a pn junction, and the internal photocurrent generated by the solar cell on its battery substrate (such as crystalline silicon) needs to be collected through the electrodes of the battery and brought together. The solar cell includes a front side and a back side, wherein one side of the solar cell when the battery is operated is defined as the front side of the solar cell, and the opposite side of the front side is defined as the back side. Conventionally, a sub-gate line (or a sub-gate line) for collecting current and a main gate electrode for collecting current on the sub-gate line are formed on the front surface thereof; a back surface electrode is formed on the back surface thereof to extract current.

With the development of solar cells, a back contact type solar cell in which a main gate electrode of a front surface of a battery is placed on the back surface of a battery substrate has been proposed in recent years. Compared with the conventional solar cell, the back contact type solar cell has at least the following advantages: First, the back contact type solar cell has the shielding loss of the front main gate electrode to the sunlight (the shading area is reduced) The second is that the main gate electrode and the back electrode are formed on the same surface (on the back side), so that it is easier to equip the battery packs with the battery pack, and the manufacturing cost is lower; The main gate electrode is placed on the back side to give the battery a more uniform appearance, and the resulting battery assembly is relatively more aesthetically pleasing (beautiful is important for some applications, 'for example, photovoltaic building integration applications).

Wherein, the metal winding type is one of back contact solar cells. In the battery, a plurality of through holes are formed in the battery substrate, and the front sub-gate line and the main gate electrode disposed on the back surface of the battery are electrically connected through the through holes. connection. U.S. Patent No. 6,384,317 B1, entitled "Solar Cell and Process of Manufacturing the Same"

Confirmation Specifically, a metal-wound-type back contact solar cell is disclosed.

Figure 1 is a schematic view showing the structure of a prior art metal-wound-type back contact solar cell. This battery is disclosed by the above mentioned patents. As shown in FIG. 1, 10 is a sub-gate line formed on the front surface of the battery substrate, the main gate electrode 9 is formed on the back surface of the battery substrate, the sub-gate line and the main gate electrode are electrically connected through the through holes, and the back surface electrode 6 is also formed in the battery. The back side of the substrate. The back electrode 6 is for drawing current generated by the first semiconductor type region 7 of the battery substrate, and the sub gate line and the main gate electrode 9 are for drawing current generated by the second semiconductor type region 8 of the battery substrate. In order to prevent the back electrode 6 from forming an ohmic contact with the first semiconductor type region 7 and causing a short circuit between the positive and negative electrodes of the battery, the exposed region of the first semiconductor type region 7 is generally reserved on the back side when the second semiconductor type region 8 is formed, in which Patterning forms the back electrode. Thus, when diffusion doping forms the second semiconductor type region 8, an additional mask lithography is required, and the mask is removed after diffusion, and the process is complicated. This is not conducive to reducing the cost of solar cells. In addition, in the embodiment disclosed in the patent US Pat. No. 6,384,317 B1, as shown in FIG. 2 and FIG. 3, at the electrical connection between the sub-gate line and the main gate electrode, the connection is made through a single through hole 3, so that the wire is used. When the screen printing process prints the conductive paste in the through hole, it is more likely that the slurry cannot completely fill the through hole, so that the main gate electrode on the back side and the sub-gate line disposed on the front side of the battery cannot form an effective electrical connection and the series resistance. Become bigger

Therefore, in view of the defects of the prior art, it is required to develop a metal-wound-type back contact solar cell which is low in manufacturing cost, simple in process, and good in contact. Summary of the invention

The technical problem to be solved by the present invention is to reduce the manufacturing cost of the back contact solar cell, simplify the process flow of the back contact solar cell, and improve the connection reliability between the sub-gate line and the main gate electrode disposed on the back surface of the battery.

In order to solve the above technical problems, according to an aspect of the invention, a metal-wound-type back contact solar cell comprising:

a first conductivity type region among the battery substrates and a second conductivity type region disposed over the first conductivity type region;

a sub-gate line electrically connected to the second conductive type region formed on a front surface of the battery village;

a through hole passing through the battery substrate;

Patterning formed on the battery lining based on the connection of the via hole and the sub-gate line a main gate electrode on the back of the bottom;

Forming a second electrode electrically connected to the first conductive type region on the back surface of the battery substrate;

a first isolation trench for isolating the main gate electrode and the second electrode; wherein the second electrode is further configured to compensate for doping of the second conductivity type region contacted by the second electrode The current generated by the first conductivity type region is output to the first electrode through the second conductivity type region doped by the self-alignment compensation.

In one embodiment of the solar cell of the present invention, the first isolation trench is formed by quasi-wetting etching patterning or by laser patterning.

In still another embodiment of the solar cell of the present invention, a hollow region is provided in the main gate electrode.

Preferably, the hollowed out region is provided in a square shape, a circular hole shape or other irregular shape, and is disposed between the through holes.

In still another embodiment of the solar cell of the present invention, the second electrode is an aluminum or aluminum alloy material.

In still another embodiment of the solar cell of the present invention, two or more of the through holes are provided for each of the sub-gate lines and the connection to the main gate electrode.

Preferably, the main gate electrode is a silver or silver alloy material.

Preferably, the solar cell further includes a front side anti-reflection layer formed over the second conductivity type region. The anti-reflection layer may be silicon nitride.

In one embodiment, the first conductive type region is a p-type semiconductor region, and the second conductive type region is an n-type semiconductor region.

Preferably, the solar cell further includes a connection point disposed on a back surface of the solar cell.

Preferably, the connection point is the same as the main gate electrode of silver or the same as a silver alloy material, and the connection point is formed by synchronous screen printing or stencil printing with the main gate electrode.

In one embodiment, the solar cell further includes an edge isolation region formed on a front surface and/or a back surface of the battery substrate at a peripheral edge region of the solar cell. A second isolation trench is disposed on the edge isolation region.

According to still another aspect of the present invention, there is provided a method of fabricating a metal-wound-type back contact solar cell comprising the steps of:

(1) providing a battery substrate of a first conductivity type for preparing a solar cell; (2) positioning a through hole in the battery substrate;

(3) performing a doping of a second conductivity type on the surface of the battery substrate to form a second conductivity type region;

(4) patterning a main gate electrode and a second electrode on a back surface of the battery substrate, and patterning a front gate line on a front surface of the battery substrate, the second conductivity type to which the second electrode contacts Area self-alignment compensates for doping.

In an embodiment of the solar cell preparation method of the present invention, after the step (4), the method further comprises the step of: laser engraving forming the isolation trench. Specifically, the isolation trench may include: a first isolation trench for isolating the main gate electrode and the second electrode; and a second isolation trench disposed at an edge isolation region of the four peripheral regions of the solar cell .

In another embodiment of the solar cell preparation method of the present invention, after the step (3) and before the step (4), the method further includes the step of: quasi-wet etching forming the isolation of the main gate electrode and the The first isolation trench of the two electrodes.

Preferably, when the first isolation trench is etched by the quasi-wet method, the PN junction of the edge isolation region of the four peripheral regions of the solar cell is simultaneously quasi-wet etched.

The through hole may be formed by photolithography etching, mechanical drilling, laser drilling, or electron beam drilling.

Preferably, between the step (2) and the step (3), a washing step and a texturing step are further included.

Preferably, the step of removing the phosphosilicate glass is further included after the step (3) and before the step (4).

Preferably, after step (3) and before step (4), the method further comprises the step of: depositing an anti-reflection layer on the front side of the battery substrate.

Preferably, in the step (4), the main gate electrode is formed by printing with the first silver paste, and then the second gate line is formed by printing with the second silver paste.

Preferably, in the step (4), further comprising forming a plurality of connection points on the back surface of the battery substrate. Wherein, the connection point is the same as the main gate electrode as silver or the same as a silver alloy material, and the connection point is formed by synchronous screen printing or stencil printing with the main gate electrode; The main gate electrode and the connection point are formed by screen printing or stencil printing after printing.

According to still another aspect of the present invention, a solar cell module is provided, wherein the solar cell module includes any one of the above-described solar cells, and the solar cells pass between The interconnecting strips are connected and formed by laminating and framing the front substrate, the back sheet, and the sealing bonding layer.

The technical effect of the present invention is that in the invention, the second conductivity type region can be self-aligned and supplemented with the second electrode as a diffusion source, so that no additional patterning step is needed when forming the second conductivity type region, the second electrode Self-aligned to form an ohmic contact with the first conductivity type region. Therefore, the MWT back contact solar cell is simple in process and low in cost. DRAWINGS

1 is a schematic structural view of a prior art metal-wound-type back contact solar cell; FIG. 2 is a front view of a prior art metal-wound-type back contact solar cell;

3 is a front elevational view showing another embodiment of a prior art metal-wound-type back contact solar cell;

4 is a schematic view showing the front structure of an MWT back contact solar cell according to an embodiment of the present invention;

Figure 5 is a schematic illustration of the back structure of an MWT back contact solar cell in accordance with an embodiment of the present invention;

6 is a partial cross-sectional structural view of the MWT back contact solar cell of the embodiment shown in FIGS. 4 and 5.

7 is a schematic view showing a process of a method for preparing a MWT back contact solar cell according to a first embodiment of the present invention;

8 to FIG. 13 are schematic diagrams showing the structural changes of the process according to the preparation method shown in FIG. 7. FIG. 14 is a schematic view showing the process of preparing the MWT back contact solar cell according to the second embodiment of the present invention;

15 to 17 are schematic views showing the structural changes of the process according to the preparation method shown in Fig. 14. detailed description

The following is a description of some of the various possible embodiments of the invention, which are intended to provide a basic understanding of the invention and are not intended to identify key or critical elements of the invention. In the drawings, for the sake of clarity, it is possible to enlarge the thickness of the layer or the area of the region, but as a schematic diagram, it should not be considered to strictly reflect the proportional relationship of the geometric dimensions. In the drawings, the same reference numerals are given to the same structural parts, and the description thereof will be omitted. The "front surface of the solar cell" in the present invention refers to the side that receives the sunlight when the battery is operated, that is, the light receiving surface, and the "back surface of the solar cell" in the present invention refers to the opposite side to the "front surface of the solar cell". .

4 is a schematic view showing the front structure of an MWT back contact solar cell according to an embodiment of the present invention. Fig. 5 is a schematic view showing the structure of the back surface of an MWT back contact solar cell according to an embodiment of the present invention. Fig. 6 is a partial cross-sectional structural view showing the MWT back contact solar cell of the embodiment shown in Figs. 4 and 5. The solar cell of the present invention will be described in detail below with reference to Figs. 4, 5 and 6.

The MWT back contact solar cell 100 of this embodiment is formed based on the battery substrate 110. In this embodiment, a p-type single crystal silicon wafer is selected as the battery substrate, but this is not limitative. For example, the battery substrate 110 may also be a polysilicon material or other type of solar cell base material. The specific shape of the battery substrate 1 10 of the solar cell is also not limited by the illustrated embodiment. As shown in Fig. 6, in this embodiment, the battery substrate 1 10 includes a p-type semiconductor region 1 12 of the substrate itself and an n-type semiconductor region 11 1 formed by doping the substrate. The p-type semiconductor region 1 12 and the n-type semiconductor region 1 11 form a pn junction of the solar cell, the current of the n-type semiconductor region is drawn through the front sub-gate line of the solar cell and the main gate electrode, and the current of the p-type semiconductor region passes through the solar cell The back electrode is led out.

Referring to Figure 4, on the front side 120 of the solar cell, a plurality of sub-gate lines 130 are formed for collecting current generated by the front surface 120 of the solar cell. Conventionally, the sub-gate lines 130 are arranged in parallel, and the pitch between the sub-gate lines 130 and the width of the sub-gate lines 130 themselves are not limited by the present invention. Generally, the sub-gate line 130 may be formed by screen printing with a silver paste. In this embodiment, the sub-gate line 130 is formed on the surface of the n-type semiconductor region 1 1 1 on the front side.

To form the MWT back contact solar cell, a plurality of vias 140 penetrating the cell substrate 110 are formed on the sub-gate line 130. Each of the sub-gate lines 130 is cross-connected with the main gate electrode 150 (shown in FIGS. 4 and 6) after being separated by a certain distance, so that the main gate electrode 150 can effectively collect and extract the front side of the battery collected by the sub-gate line 130. Current. In the invention, at the junction of each of the sub-gate lines 130 and the corresponding main gate electrode 150, two or more through holes 140 are provided (for example, preferably two through holes are provided) so as to be at least at the joint The main gate electrode 150 may be connected through two via holes 140. The via 140 may be formed by photolithography etching, mechanical drilling, laser drilling, electron beam drilling, or the like. In order to reduce the cost and increase the speed of the process, in the prior art, the connection of each of the sub-gate lines 130 to the corresponding main gate electrode 150 Usually only one through hole is provided (as shown in Figure 2), or multiple sub-gate lines share one through hole (as shown in Figure 3). However, as the thickness of the solar cell becomes thinner and the hole making process is continuously improved, for example, by laser hole making, the manufacturing cost of the through hole 140 is lower and lower, and the processing speed is also faster and faster; When the main gate electrode 150 is formed by printing, the paste is relatively difficult to fill the via hole 140. Therefore, when the number of via holes is small, there is a possibility that a small number of via holes are not effectively filled, thereby affecting the sub gate line 130 and the main gate electrode 150. The reliability of the connection between. When two or more through holes are provided at the joint, the reliability problem caused by the through-hole filling connection can be greatly reduced or avoided, and the connection reliability of the sub-gate line and the main gate electrode is greatly improved. Preferably, as shown in the embodiment of FIG. 4, two through holes 140 are provided at the junction of the sub-gate line 130 and the corresponding main gate electrode 150, and the distance between the two through holes 140 depends on the width of the main gate electrode 150. The two adjacent vias 140 fall substantially simultaneously within the width of the main gate electrode 150.

Referring to Fig. 5, the main gate electrode 150 is printed by silver paste screen printing or stencil printing, and a plurality of main gate electrodes 150 are formed in parallel on the back surface of the solar cell. A second electrode, that is, a back electrode 160 is also formed on the back surface of the solar cell. As shown in FIGS. 5 and 6, a positive and negative isolation region 170 is disposed between the main gate electrode 150 and the back electrode 160. In this embodiment, the positive and negative isolation regions 170 surround the main gate electrode 150. An isolation trench 171 (or 172) (described in detail below) is disposed on each of the positive and negative isolation regions 170. At the edge of the solar cell, positive and negative isolation trenches or isolation regions are also provided on the front or back of the battery substrate. For example, an edge isolation region 175 surrounding all of the main gate electrode 150 and all of the back electrodes 160 is formed on the back side of the battery. There are two implementation methods for the isolation trench 171 (or 172) on the positive and negative isolation regions 170 and the isolation trench 176 on the rim isolation region 175. One is to use a quasi-wet isolation method, that is, by dispensing or screen printing. The method, the chemical slurry reacted with the semiconductor substrate 110 is coated on the battery isolation substrate 175 and the positive and negative isolation regions 170 of the isolation trench, and is etched by the chemical paste and the semiconductor: substrate 110. The pn junction of the coated region is effectively removed, thereby forming an isolation trench corresponding to the edge isolation region 175 and the positive and negative isolation regions 170; the other is directly using the laser grooving method in the positive and negative isolation regions 170 and the edge isolation region 175. An isolation groove is formed on the upper surface.

Continuing with FIG. 5 and FIG. 6, in the via 140, the main gate electrode 150 may form an ohmic contact with the n-type semiconductor region 1 11 . Of course, the main gate electrode 150 may also form an ohmic contact with the _n -type semiconductor region 111 on the back surface. . Preferably, a plurality of vacant regions 151 are disposed on the main gate electrode 150, so that the main gate electrode metal and silicon can be greatly reduced (ie, n-type The contact area of the semiconductor region 1 1 1 ) effectively reduces the recombination ratio of metal to silicon, thereby improving the conversion efficiency of the solar cell. At the same time, setting the hollowed out area can also greatly reduce the amount of metal used in the main gate electrode (such as silver paste), thereby reducing the cost of the solar cell. The hollow region 151 is provided in a square structure in this embodiment, but its specific shape is not limited by the embodiment of the present invention, and may be, for example, a circular hole shape or other irregular shape or the like. The position and shape of the hollow region 151 on the main gate electrode are such that the electrical connection between the main gate electrode and the metal in the via hole is not affected.

Continuing with Fig. 6, the back electrode 160 itself is formed directly over the n-type semiconductor region to be in contact with the local n-type semiconductor region 11 1 . By selecting the type of the electrode, it is possible to compensate the doping of the n-type semiconductor region 11 1 to which it is contacted, for example, the metal element of the germanium cluster is selected as the back electrode material, and preferably, the back electrode 160 is aluminum or an aluminum alloy. Therefore, aluminum can be p-doped with the n-type semiconductor region 11 1 to which it is contacted (especially during metallization in which an aluminum electrode is formed). Thus, a compensation doping region 180 is formed on the battery substrate adjacent to each of the back electrodes 160. In this embodiment, the compensation doping region 180 is a p-type semiconductor region, and the p-type doping concentration thereof can be selected to be larger than the doping concentration of the p-type semiconductor region 112, thereby facilitating ohmic contact with the back surface electrode 160, reducing the electrode 160. Contact resistance with the battery substrate. It should be noted that the compensation doping region 180 and the p-type semiconductor region 112 are generally not clearly defined as shown in FIG. 6 because the back electrode is doped as a doping source to the bottom of the battery, according to the diffusion. The doping characteristics, the doping element aluminum will always diffuse into the p-type semiconductor region 112.

Therefore, the current generated by the p-type semiconductor region 111 can be output to the back surface electrode 160 through the compensation doping region 180, and the ohmic contact can be formed in self-alignment between the back surface electrode 160 and the p-type semiconductor region 112, and an n-type semiconductor is formed in the preparation. The region does not require an additional photolithographic patterning process and the manufacturing cost is reduced.

Continuing with the isolation of the main gate electrode 150 and the back surface electrode 160 on the back side, an isolation trench 171 is disposed on the positive and negative isolation regions 170, and the isolation trench 171 surrounds the periphery of the main gate electrode 150, thereby physically implementing Well isolated. In this embodiment, the isolation trench 171 is formed by a high speed laser dicing process, the depth of the isolation trench being greater than the thickness of the n-type semiconductor region 11 1 and smaller than the thickness of the semiconductor substrate 110, for example, when the n-type semiconductor region 1 1 1 When the thickness ranges from 0.2 microns, the depth of the isolation trench is at least greater than 0.2 microns. The specific width of the isolation trench 171 is not limiting. Meanwhile, in the embodiment shown in FIG. 6, the isolation trench 176 surrounding all the sub-gate lines 130 is disposed on the front surface of the battery substrate. Preferably, all the main gate electrodes and the 150 and back electrodes may be disposed on the back surface of the battery substrate. 160 Isolation slot 176. The front and/or back isolation trenches 176 are all disposed in the edge isolation regions 175 of the four peripheral regions of the solar cell. The edge isolation trench 176 is also formed by a high speed laser dicing process, and the isolation trench 176 passes through the anti-reflection layer 113, the n-type semiconductor region 112 to the p-type semiconductor region 112.

Continuing with Figure 6, in yet another embodiment, solar cell 100 further includes an anti-reflective layer 1 13 deposited over the n-type semiconductor region on the front side of the cell substrate. The anti-reflection layer 1 13 may be a material such as silicon nitride, and the specific thickness may range from 70 to 90 nm. By setting the anti-reflection layer 1 13, the conversion efficiency of the solar cell can be effectively improved.

Referring to FIG. 5, in this embodiment, the solar cell 100 further includes a connection point 161 disposed on the back surface of the battery, which is mainly used to provide a connection medium between the battery and the battery when preparing the component, for improving the battery and The connection characteristics of the interconnecting strips are beneficial to improve the connection reliability of the solar cells connected to each other to form a solar cell module. The number of connection points 161 can be determined according to the required connection strength and the characteristics of the interconnection bars used, which are not limitative. Preferably, the connection point 161 selects the same material as the main gate electrode 150, such as silver, so that the main gate electrode 150 can be formed during the screen printing or stencil printing process, and the pattern formation can be simultaneously synchronized, which is advantageous for further simplifying the preparation of the battery. Process steps to reduce the cost of manufacturing solar cells.

The process of the preparation method of the IWT back contact solar cell of the embodiment shown in Figs. 4 to 5 will be specifically described below.

Fig. 7 is a schematic view showing the process of the MWT back contact solar cell according to the first embodiment of the present invention. Fig. 8 to Fig. 13 are schematic diagrams showing the structural changes of the preparation process according to Fig. 7. The process of the preparation method of this embodiment will be described below with reference to Figs. 7 and 8 to 13, and the specific structure of the MWT back contact solar cell will also be schematically illustrated.

First, in step S10, a battery substrate of a first conductivity type for preparing a solar cell is provided. As shown in Fig. 8, in this embodiment, a solar cell is formed based on a battery substrate 110, and p-type single crystal silicon is selected as the battery substrate 1 10 (i.e., the first conductivity type is p-type). Specifically, the specific resistance of the p-type single crystal silicon may be O. l ohm -cm - l Oohm -cm , but is not limited to this range. The front surface 120 of the battery cell 1 10 is illuminated by sunlight, and the back surface 190 of the battery substrate 1 10 is not exposed to sunlight when the battery is in operation.

Further, in step S30, a through hole is formed in the battery substrate. As shown in FIG. 9, a plurality of through holes 140 are formed in the battery substrate 110, and the through holes 140 are formed from the front surface of the battery substrate. Penetrate to the back of the battery base. The through hole 140 may be formed by photolithography etching, mechanical drilling, laser drilling, electron beam drilling, etc. Generally, laser drilling is selected. The specific shape of the through hole 140 is related to the selected manufacturing process, for example, when laser drilling is selected, a cylindrical through hole as shown in Fig. 9 is formed. The via hole 140 is mainly used to extract the main gate electrode from the back side, and its specific shape and size are not limitative. For example, the through holes may be selected to be substantially cylindrical holes having diameters ranging from about 10 microns to 1000 microns. The via hole 140 is formed at a position where the sub-gate line is to be patterned, and by locating the position of the via hole 140, the position of the connection of the sub-gate line 130 and the corresponding main gate electrode 150 can be positioned.

Further, in step S50, doping of the second conductivity type is performed on the surface of the battery substrate. As shown in Fig. 10, in this embodiment, the surface of the battery substrate 110 is n-type doped to form an n-type semiconductor region 11 1 on the surface of the battery substrate 110. Specifically, methods such as diffusion doping, ion implantation doping, and the like can be selected. In the invention, it is not necessary to additionally perform a photolithography patterning step for the doping step, and therefore, in this step of the embodiment, the n-type semiconductor region 111 surrounds the original p-type semiconductor region 112.

It should be noted that, in order to remove the phosphosilicate glass layer formed on the surface of the battery substrate during the doping process, the step of dephosphorizing the silicon glass is generally performed after the doping of the second conductivity type, wherein the dephosphorus glass can be chemically cleaned. The method is removed.

It should be further noted that, in another embodiment, generally, after step S30, before step S50, a cleaning step and a texturing step are further included, and the battery lining can be removed by manufacturing the through hole by the cleaning step and the texturing. Damage to the bottom surface, especially thermal damage to the bottom surface of the battery when laser drilling; it can also remove the cutting damage caused by wafer cutting; and form a suede on the surface of the battery substrate (not shown), which is beneficial to The conversion efficiency of the battery is improved; at the same time, the through hole is also roughened by the formed pile surface, which is advantageous for improving the reliability of the slurry filling.

Further, in step S70, an anti-reflection layer is deposited on the front surface of the battery substrate. As shown in FIG. 11, an anti-reflection layer 1 13 deposited on the front surface of the n-type semiconductor region may be formed by a method such as PECVD or PVD, and the anti-reflection layer 113 may be selected as a material such as silicon nitride, and the specific thickness range thereof may be It is 70-90 nm. By setting the anti-reflection layer 1 13 , the conversion efficiency of the solar cell can be effectively improved.

Further, in step S90, the main gate electrode 150 and the connection point 161 are patterned on the back surface of the battery substrate, and then the back surface electrode 160 is patterned; and the sub-gate line is patterned on the front surface of the battery substrate. As shown in Figure 12, you can choose to use conventional screen printing or stencil printing, etc. The process pattern formation includes a sub-gate line 130 and a main gate electrode 150 and a back surface electrode 160. Among them, since the materials of the sub-gate line 130, the main gate electrode 150, and the back surface electrode 160 are different, they are usually formed by patterning steps of different screen printing or stencil printing. Preferably, the main gate electrode 150 and the connection point 161 may be formed by first printing with the first silver paste. At this time, the first silver paste fills the via hole 140; then the second silver paste may be used to form the sub-gate. The line 130, the sub-gate line 130 is electrically connected to the conductive paste in the via 140, so that the main gate electrode 150 can form good electrical contact with the sub-gate line. The back electrode 160 may be screen printed on the back surface of the battery substrate 110 by an aluminum paste, and the process sequence may be between forming the main gate electrode 150 and the sub-gate line 130. Preferably, the main gate electrode 150 and the connection point 161 may be selected by screen printing first, and since the same paste is selected, the main gate electrode 150 and the connection point 160 may be simultaneously formed, which is advantageous for the barreling process, thereby reducing the manufacturing cost.

In addition, preferably, when the main gate electrode is formed by screen printing, a plurality of hollow regions 151 (as shown in FIG. 5) may be formed when the main gate electrode 150 is formed by printing by providing a screen pattern, so that the main can be greatly reduced. The contact area of the gate electrode metal and silicon (that is, the n-type semiconductor region 1 1 1 ) effectively reduces the recombination of the metal and the silicon, thereby improving the conversion efficiency of the solar energy. At the same time, setting the hollowed out area can also greatly reduce the amount of metal used in the main gate electrode (such as silver paste), thereby reducing the cost of the solar cell. The hollow region 151 is provided in a square structure in this embodiment, but its specific shape is not limited by the embodiment of the present invention, and may be, for example, a circular hole shape or the like. The position of the hollow region 151 on the main gate electrode and the shape are such that the connection between the main gate electrode and the metal in the via hole is not affected.

It should be noted that the paste used for forming the sub-gate line 130, the main gate electrode 150, and the back surface electrode 160 may further include a doped alloying element. For example, the silver paste is doped with other metal elements to form a silver alloy electrode, and the aluminum paste is doped with other metal elements to form an aluminum alloy electrode.

Further, in step S95, the laser groove forms an isolation groove. As shown in FIG. 13, the isolation region 170 between the back electrode and the main gate electrode is patterned to form isolation trenches 171, and is surrounded by four peripheral regions on the front and/or back side (front side and back side in this embodiment) of the battery. Isolation trenches 176 are patterned in the edge isolation regions 175. The isolation trench 171 is formed by a high-speed laser grooving process, and the isolation trench 171 surrounds the periphery of the main gate electrode 150. The depth of the isolation trench 171 is larger than the thickness of the n-type semiconductor region 11 1 and smaller than the thickness of the semiconductor substrate 110, thereby physically Achieve good isolation. In this embodiment, the edge isolation region 175 is separated The vent 176 is also implemented by a high speed laser grooving process.

Thus far, the MWT back contact solar cell of the embodiment shown in Fig. 6 is basically formed.

Fig. 14 is a schematic view showing the process of the preparation method of the M WT back contact solar cell according to the second embodiment of the present invention. Compared with the preparation method process of the embodiment shown in FIG. 7, the main difference is the difference in the method of forming the isolation trench for the positive and negative electrode isolation and the isolation trench of the edge isolation region, and therefore, steps S10 to S50 are the same, here No longer. 15 to 17 are schematic views showing the structural changes of the process according to the preparation method shown in Fig. 14. The process of the preparation method of this embodiment will be further described below with reference to Figs. 14 and 15 to 17.

Step S60, the quasi-wet etching forms an isolation trench for isolating the main gate electrode and the back electrode, and an isolation trench for edge isolation. As shown in FIG. 15, the isolation trench 1 72 is formed by a quasi-wet etching process, that is, a chemical paste which reacts with the semiconductor substrate 1 10 is applied by a dot or screen printing method to form an isolation trench. On the battery substrate 1 10 of the edge isolation region 175 and the positive and negative isolation regions 170, the pn junction of the coated region is effectively removed by chemical etching and semiconductor substrate 1 10 etching reaction. In this embodiment, the chemical slurry is applied to the periphery of the battery substrate 110, so that the portion of the n-type semiconductor region 1 1 1 on the peripheral surface can be removed by etching, so that the pn junction is etched away, which can be effectively Edge isolation between the p-type semiconductor region and the n-type semiconductor region is achieved. In this embodiment, the region surrounded by the isolation trench 172 will be patterned to form the main gate electrode 150, the depth of the isolation trench being greater than the thickness of the _n -type semiconductor region ill, thereby physically achieving good isolation.

Further, in step S70, an anti-reflection layer is deposited on the front side of the battery base. As shown in FIG. 16, an anti-reflection layer 1 13 is deposited on the front side of the n-type semiconductor region, which can be formed by PECVD, PVD, etc., and the anti-reflection layer 1 13 can be selected as a material such as silicon nitride, and the specific thickness thereof. The range can be 70-90 nm. By setting the anti-reflection layer 1 1 3, the conversion efficiency of the solar cell can be effectively improved.

Further, in step S90, a main gate electrode 150, a connection point 161 and a back surface electrode 160 are patterned on the back surface of the battery substrate; and a sub-gate line is formed on the front surface of the battery substrate. This step is basically the same as step S90 of the preparation method of the embodiment shown in Fig. 7, and will not be described again here. Through this step, a solar cell as shown in Fig. 17 is formed. The main difference compared to the solar cell structure shown in Fig. 13 is that the isolation trench 172 is formed by quasi-wet etching.

So far, the solar cell of the embodiment shown in Fig. 17 has been basically formed.

The solar cell module can be assembled and formed by a plurality of MWT back contact solar cells as shown in FIG. 4 and FIG. 5, and as shown in FIG. 5, a plurality of MWT back contact solar cells are passed through each other. The strips are connected to form a battery string, and then the front substrate (usually glass), the back sheet and the sealing bonding layer are laminated and framed to form a solar cell module having a certain power output.

It should be noted that all of the above embodiments are described based on the p-type conductivity type of the battery substrate. However, it is known to those skilled in the art that the battery substrate can also be selected as an n-type conductivity type, and similarly similar solar cell structures can be formed. When the battery substrate is of an n-type conductivity type, the battery substrate includes an n-type semiconductor region and a p-type semiconductor region surrounding the n-type semiconductor region, wherein the sub-gate line is directly connected to the p-type semiconductor region, and the main gate electrode is disposed on the battery The other electrode on the back side is correspondingly a back electrode electrically connected to the n-type semiconductor region.

The above examples mainly illustrate the MWT back contact solar cell of the present invention, various preparation methods, and solar cell modules thereof. Although only a few of the embodiments of the present invention have been described, it will be understood by those skilled in the art that the invention may be practiced in many other forms without departing from the spirit and scope of the invention. Accordingly, the present invention is to be construed as illustrative and not restrictive, and the invention may cover various modifications without departing from the spirit and scope of the invention as defined by the appended claims With replacement.

Claims

Rights request

1. A metal wound-through back contact solar cell comprising:

a sub-gate line electrically connected to the second conductive type region formed on a front surface of the battery substrate;

a through hole passing through the bottom of the battery;

Forming a main gate electrode formed on a back surface of the battery substrate based on the via hole and the sub-gate line;

Forming a second electrode electrically connected to the first conductive type region formed on a back surface of the battery substrate;

a first isolation trench for isolating the main gate electrode and the second electrode; wherein the second electrode is further configured to compensate for doping of the second conductivity type region contacted by the second electrode The current generated by the first conductivity type region is output to the second electrode through the second conductivity type region doped by the self-alignment compensation.

The solar cell according to claim 1, wherein the first isolation trench is formed by quasi-wet etching etching or by laser patterning.

The solar cell according to claim 1, wherein a hollow region is provided in the main gate electrode.

The solar cell according to claim 3, wherein the hollowed out region is provided in a square shape, a circular hole shape or other irregular shape, and is disposed between the through holes.

The solar cell according to claim 1, wherein the second electrode is made of aluminum or an aluminum alloy material.

6. The solar cell of claim 1 wherein each of said sub-gates Two or more of the through holes are provided at a line connecting the main gate electrode.

The solar cell according to claim 1 or 2 or 3 or 5, wherein the main gate electrode is a silver or silver alloy material.

A solar cell according to any one of claims 1 or 2 or 3 or 5, further comprising a front side anti-reflection layer formed over said second conductivity type region.

The solar cell according to claim 8, wherein the anti-reflection layer is silicon nitride.

The solar cell according to any one of claims 1 or 2 or 3 or 5, wherein the first conductivity type region is a p-type semiconductor region, and the second conductivity type region is an n-type semiconductor region.

The solar cell according to claim 5, wherein the solar cell further comprises a connection point provided on a back surface of the battery.

The solar cell according to claim 1 , wherein the connection point and the main gate electrode are silver or the same as a silver alloy material, and the connection point is synchronous with the main gate electrode. Printing or stencil printing is formed.

The solar cell according to any one of claims 1 or 2 or 3 or 5, wherein the solar cell further comprises a solar cell formed on a front surface and/or a back surface of the battery substrate The edge isolation zone of the four peripheral areas.

The solar cell according to any one of claims 13 to 13, wherein the edge isolation region is provided with a second isolation trench.

15. A method of fabricating a metal-wound-type back contact solar cell, characterized in that it comprises the steps of:

(1) providing a battery substrate of a first conductivity type for preparing a solar cell; (2) forming a through hole in the battery substrate;

(3) performing a second conductivity type doping on the bottom surface of the battery to form a second conductivity type region;

(4) patterning a main gate electrode and a second electrode on a back surface of the battery substrate, and patterning a sub-gate line on a front surface of the battery substrate, the second conductivity type to which the second electrode contacts Area self-alignment compensates for doping.

16. The method according to claim 15, wherein after the step (4), the method further comprises the step of: laser engraving forming the isolation trench.

17. The method of claim 16, wherein the isolation trench comprises: a first isolation trench for isolating the main gate electrode and the second electrode; and disposed around the solar cell The second isolation trench of the edge isolation region of the edge region.

The method according to claim 15, wherein after step (3) and before step (4), the method further comprises the steps of: quasi-wet etching forming for isolating the main gate electrode and the The first isolation trench of the two electrodes.

The method according to claim 18, wherein, in the quasi-wet etching of the first isolation trench, the PN junction of the edge isolation region of the four peripheral regions of the solar cell is simultaneously quasi-wet etching .

The method according to claim 15 or 16 or 18, wherein the through hole is formed by photolithography etching, mechanical drilling, laser drilling or electron beam drilling.

The method according to claim 15 or 16 or 18, characterized in that the step (2) and the step (3) further comprise a washing step and a texturing step.

The method according to claim 15 or 16 or 18, further comprising, after the step (3) and before the step (4), the step of: depositing an anti-reflection layer on the front side of the battery substrate.

The method according to claim 15 or 16 or 18, wherein the step (3) and the step (4) further comprise a step of removing the phosphosilicate glass.

The method according to claim 15 or 16 or 18, wherein in the step (4), the main gate electrode is formed by printing in a first silver paste, and then printed in a second silver paste. The sub-gate lines are formed.

The method according to claim 15 or 16 or 18, wherein in the step (4), further comprising forming a plurality of connection points on the back surface of the battery substrate.

The method according to claim 25, wherein the connection point and the main gate electrode are silver or the same as a silver alloy material, and the connection point is synchronously screen printed with the main gate electrode or Stencil printing is formed; the second electrode is formed by screen printing or stencil printing after printing of the main gate electrode and the connection point.

A solar cell module, characterized in that the solar cell module comprises a plurality of solar cells according to any one of claims 1 to 14, wherein the solar cells are connected by an interconnect, and The front substrate, the back sheet, and the sealing adhesive layer are laminated and framed.