KR101335195B1 - Back contact solar cell and method for fabricating the same - Google Patents

Abstract

The present invention relates to a back-electrode solar cell and a method of manufacturing the same, which can suppress photoreduction of a small number of carriers and improve the photoelectric conversion efficiency of the solar cell. The back-electrode solar cell according to the present invention is an n-type crystalline silicon substrate. And a p-type doping layer and an n-type doping layer disposed adjacent to a rear surface of the substrate, wherein an interface between the p-type doping layer or the n-type doping layer and the inside of the substrate is a first interface, The surface of is a second interface, the n-type doped layer is exposed in the form of a dot pattern at the first interface, the p-type doped layer is characterized in that the exposed in the form of a dot pattern.

Description

Back contact solar cell and method of manufacturing the same {Back contact solar cell and method for fabricating the same}

The present invention relates to a back-electrode solar cell and a method for manufacturing the same, and more particularly, to a back-electrode solar cell and a method of manufacturing the same to suppress the recombination of minority carriers to improve the photoelectric conversion efficiency of the solar cell. will be.

A solar cell is a core element of photovoltaic generation that converts photovoltaic power directly to electricity. It is basically a diode made of p-n junction. In the process of converting sunlight into electricity by solar cells, when solar light enters into the silicon substrate of the solar cell, electron-hole pairs are generated, and electrons move to n layers and holes move to p layers by the electric field. Thus, photovoltaic power is generated between the pn junctions, and when a load or a system is connected to both ends of the solar cell, current flows to generate power.

On the other hand, a general solar cell has a structure in which a front electrode and a rear electrode are provided on the front and the rear, respectively, and as the front electrode is provided on the front surface, the light receiving area is reduced by the area of the front electrode. In order to solve the problem of reducing the light receiving area, a rear electrode type solar cell has been proposed. The back electrode type solar cell is provided with a (+) electrode and a (-) electrode on the rear surface of the solar cell, thereby maximizing the light receiving area of the solar cell front surface.

As shown in FIG. 1, the back electrode solar cell has a structure in which the p-type doping layer 102 and the n-type doping layer 103 are repeatedly arranged and disposed inside the back of the substrate 101, and the p-type doping layer ( 102 is connected to the p electrode 105 and the n-type doping layer 103 is connected to the n electrode 106. In this case, in order to prevent the p electrode 105 and the n electrode 106 from being short-circuited, a dielectric layer 104 is formed on the back surface of the substrate 101 and is selectively patterned to connect the doping layer and the electrode through the opening.

In such a back electrode solar cell, electrons (-) generated by photoelectric conversion inside the substrate 101 are moved to the n electrode 106 via the n-type doping layer 103, and the holes (+) It is moved to the p electrode 105 via the p-type doping layer 102. On the other hand, when the substrate 101 is an n-type silicon substrate 101, electrons are the major carriers and holes are the minor carriers, and electrons with the multiple carriers are the n-type doping layer 103. While stably collected through the n electrode 106, holes that are a minority carrier are likely to be recombined and disappear in the path collected through the p-type doping layer 102 and to the p electrode 105.

Specifically, holes (+), which are minority carriers generated inside the substrate 101, are recombined to contact the surface of the n-type doped layer 103 during movement (see ⓐ in FIG. 2), or the p-type doped layer 102. Even if the movement is successful, it disappears by combining with the surface defects existing on the back surface of the substrate 101 (see ⓑ of FIG. 2). The recombination of the minority carriers acts as a factor to lower the photoelectric conversion characteristics of the solar cell.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object thereof is to provide a back electrode solar cell and a method of manufacturing the same, which can improve photoelectric conversion efficiency of a solar cell by suppressing recombination of minority carriers. .

The back electrode solar cell according to the present invention for achieving the above object comprises an n-type crystalline silicon substrate, a p-type doping layer and an n-type doping layer disposed adjacent to the inside of the back of the substrate, p The interface between the doping layer or the n-type doping layer and the inside of the substrate is a first interface, the surface of the back surface of the substrate is a second interface, the n-type doping layer is exposed in the form of a dot pattern at the first interface, The p-type doped layer is exposed in the form of a dot pattern at the second interface.

The surface area of the p-type doped layer at the first interface is larger than the surface area of the n-type doped layer, and the surface area of the n-type doped layer at the second interface is larger than the surface area of the p-type doped layer.

Some regions of the p-type doping layer and the n-type doping layer overlap each other, in which the p-type doping layer is provided on the upper portion, the n-type doping layer is provided on the lower portion, and the p-type doping layer is formed at the first interface. The type doping layer forms a horizontally expanded form, and the n-type doping layer forms a form of horizontally expanded at the second interface.

And a dielectric layer provided on a back surface of the substrate including the p-type doping layer and the n-type doping layer, wherein the dielectric layer exposes the p-type doping layer and the n-type doping layer in the form of a dot pattern, respectively, A p-type finger electrode and an n-type finger electrode are respectively provided on the p-type doping layer and the n-type doping layer, and the p-type busbar electrode and the n-type busbar electrode are further formed on the p-type finger electrode and the n-type finger electrode, respectively. It may be provided.

A method of manufacturing a back-electrode solar cell according to the present invention includes the steps of preparing an n-type crystalline silicon substrate, forming a mask pattern of a dot pattern on the rear surface of the substrate at regular intervals, and on the rear surface of the substrate. Applying a p-type doping source to the substrate, heat-treating the substrate to form a p-type doping layer inside the back of the substrate, and forming a diffusion byproduct layer on the p-type doping layer, and removing the mask pattern. Exposing the substrate on which the p-type doping layer is not formed, and patterning the diffusion byproduct layer in the form of a dot pattern to expose a portion of the p-type doping layer, and a rear surface of the substrate including the diffusion byproduct layer of the dot pattern. Applying an n-type doping source onto the substrate and heat-treating the substrate to form an n-type doping layer in a portion where the mask pattern is removed, and partially exposing the thickness of the exposed p-type doping layer to n And converting it into a type doped layer.

The interface between the p-type doping layer or the n-type doping layer and the inside of the substrate is a first interface, the surface of the back surface of the substrate is a second interface, the n-type doping layer is exposed in the form of a dot pattern at the first interface, At the second interface, the p-type doped layer is exposed in the form of a dot pattern.

And forming a dielectric layer on the p-type and n-type doped layers, selectively patterning the dielectric layer to locally expose the p-type and n-type doped layers, and the exposed p Forming a p-type finger electrode and an n-type finger electrode on the doping layer and the n-type doping layer, respectively, and forming the p-type busbar electrode and the n-type busbar electrode on the p-type finger electrode and the n-type finger electrode, respectively. It may further comprise forming a.

In addition, a portion where the p-type doping layer is exposed may correspond to a position where the diffusion byproduct layer of the dot pattern is provided, and a portion where the n-type doping layer is exposed may correspond to a position where the mask pattern is provided. .

The back electrode solar cell and a method of manufacturing the same according to the present invention have the following effects.

Maximizing the area of the p-type doped layer and minimizing the area of the n-type doped layer in the n-type substrate may increase the probability that holes, which are minority carriers, are collected into the p-type doped layer. In addition, by minimizing the p-type doped layer exposed on the surface of the back surface of the substrate, it is possible to suppress the recombination of the holes by the surface defects.

1 is a cross-sectional view of a back electrode solar cell according to the prior art.
2 is a reference diagram for explaining a factor of the minority carrier recombination in the back-electrode solar cell according to the prior art.
3A and 3B are perspective views of a back electrode solar cell according to an embodiment of the present invention.
Figure 4 is a reference diagram for explaining the movement path of the minority carrier in the back-electrode solar cell according to an embodiment of the present invention.
5A to 5J are cross-sectional views illustrating a method of manufacturing a back electrode solar cell according to an exemplary embodiment of the present invention.

Hereinafter, a back electrode solar cell and a method of manufacturing the same according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings. 3A and 3B are perspective views of a back electrode solar cell according to an embodiment of the present invention, and FIG. 4 is a reference for explaining a collecting path of minority carriers in a back electrode solar cell according to an embodiment of the present invention. It is also.

3A and 3B, a back electrode solar cell according to an embodiment of the present invention first includes a crystalline silicon substrate 301 of a first conductivity type. In this case, the first conductivity type is the opposite conductivity type to the second conductivity type, hereinafter, the first conductivity type will be described based on the n type and the second conductivity type p.

The p-type doping layer 304 and the n-type doping layer 307 are disposed adjacent to the inside of the back surface of the n-type silicon substrate 301, and the p-type doping layer 304 and the n-type doping layer 307, respectively The silver is formed to a predetermined depth into the substrate 301 from the surface of the back surface of the substrate 301. Hereinafter, for convenience of description, the surfaces of the p-type doping layer 304 and the n-type doping layer 307 in contact with the inside of the substrate 301 are referred to as a first interface, and the p-type doping exposed on the surface of the back surface of the substrate 301 is described. The surface of layer 304 (or n-type doped layer 307) will be referred to as a second interface.

One of the key features of the present invention is to suppress the minority carriers from recombining and disappearing in the travel path. To realize this, it is necessary to maximize the surface area of the p-type doped layer 304 at the first interface and minimize the surface area of the p-type doped layer 304 at the second interface. In the present invention, a configuration is disclosed in which the n-type doped layer 307 is locally exposed at the first interface and the p-type doped layer 304 is locally exposed at the second interface.

Specifically, the n-type doped layer 307 is exposed in a dot pattern (of a predetermined area) at the first interface, and the p-type doped layer 304 is exposed in a dot pattern (of a predetermined area) at the second interface. The dot patterns are repeated and arranged at regular intervals along the length direction of the substrate 301, and the n-type and p-type finger electrodes 310 are provided in regions where the dot patterns are provided.

In other words, it can be said that the dot patterns are arranged in a plurality of columns based on the plane of the substrate 301, the odd columns are the dot patterns of the n-type doped layer 307, and the even columns are the dots of the p-type doped layer 304. It can be called a pattern. In addition, the dot pattern of the n-type doped layer 307 is connected to the n-type finger electrode 311, and the dot pattern of the n-type doped layer 307 is connected to the p-type finger electrode 310. In this case, the p-type finger electrode 310 and the n-type finger electrode 311 are also connected to the dot pattern of the p-type doping layer 304 and the n-type doping layer 307 in the form of a dot.

In addition, some regions of the p-type doped layer 304 and the n-type doped layer 307 have an overlapping structure. That is, in the case where the p-type doping layer 304 and the n-type doping layer 307 are disposed, the p-type doping layer 304 is provided in the upper part and the n-type doping layer 307 is provided in the lower part. It has a structure.

Through the structure as described above, by increasing the surface area of the p-type doping layer 304 and the surface area of the n-type doping layer 307 relatively small at the first interface, It is possible to suppress the recombination of the holes (+) at the surface of the n-type doped layer 307 at the first interface and to improve the probability that holes can be collected into the p-type doped layer 304. In addition, since the area where the p-type doping layer 304 is in contact with the surface of the rear surface of the substrate 301 at the second interface is minimized, the minority holes (+) are suppressed from recombining with the surface defects of the rear surface of the substrate 301. can do. For reference, if the substrate 301 is a p-type substrate 301 rather than an n-type, the minority carrier becomes an electron, in which case the area of the n-type doped layer 307 is maximized at the first interface and the p-type at the second interface. The area of the doped layer 304 is maximized.

Meanwhile, a dielectric layer 309 is provided on the back surface of the substrate 301 including the p-type doping layer 304 and the n-type doping layer 307, and an opening is provided in the dielectric layer 309 so that the p-type doping layer ( 304 and the n-type doped layer 307 are exposed in the form of a dot pattern. In addition, a p-type finger electrode 310 and an n-type finger electrode 311 are provided in each of the p-type doped layer 304 and the n-type doped layer 307 exposed in a dot pattern form. In addition, a p-type busbar electrode 312 is provided on the plurality of p-type finger electrodes 310, and an n-type busbar electrode 313 is provided on the plurality of n-type finger electrodes 311. An insulating film (not shown) may be further provided between the busbar electrodes and the dielectric layer 309 to prevent a short circuit caused by a pinhole.

The back electrode solar cell according to the exemplary embodiment of the present invention has been described above. Next, a method of manufacturing a back electrode solar cell according to an embodiment of the present invention will be described.

First, as shown in FIG. 5A, an n-type crystalline silicon substrate 301 is prepared. Thereafter, a mask pattern 302 is formed on the rear surface of the substrate 301. The mask pattern 302 has a dot pattern shape having a predetermined area and is formed on the rear surface of the substrate 301 at a predetermined interval. In addition, the position where the mask pattern 302 is provided corresponds to the position where the n-type finger electrode 311 to be described later is provided. In addition, the mask pattern 302 is disposed in the form of a plurality of columns, each of which corresponds to an area in which the n-type busbar electrode 313 to be described later is provided.

In the state where the mask pattern 302 is provided, a doping source including a p-type impurity (for example, boron (B)), that is, a p-type doping source 303 is coated on the back surface of the substrate 301. (See FIG. 5B). The p-type doping source 303 may be applied in the form of a paste or spray, or may be deposited by a deposition method such as chemical vapor deposition (PECVD) or atmospheric vapor deposition (APCVD). In addition, the p-type ion implantation layer may be formed using an ion implantation method inside the substrate in the region where the p-type doping source 303 is to be applied without applying the p-type doping source 303.

In the state where the p-type doping source 303 is applied, as shown in FIG. 5C, as shown in FIG. 5C, the p-type doping layer is formed inside the back surface of the substrate 301 except for the region where the mask pattern 302 is provided. 304 is formed. In addition, a BSG (boro-silicate glass) film is formed on the p-type doped layer 304 by diffusion. The BSG film 305 is formed by reacting p-type impurities B in the p-type doping source 303 with silicon (Si) of the substrate 301. On the other hand, when the p-type ion implantation layer is formed in place of the p-type doping source, the BSG film may be formed on the p-type ion implantation layer by heat treatment under an oxidizing atmosphere.

In this state, the mask pattern 302 is removed and the BSG film 305 is selectively patterned to form a dot pattern (see FIG. 5D). The BSG film 305 processed in the form of a dot pattern may have the same shape as the mask pattern 302, and similarly to the mask pattern 302, the BSG film 305 may be formed in a plurality of rows on the back surface of the substrate 301. 301 is disposed on the rear surface.

Then, a doping source containing n-type impurities (for example, phosphorus (P)) on the entire surface of the rear surface of the substrate 301 including the BSG film 305 processed in the dot pattern form, that is, n-type doping source 306 is apply | coated and heat processing is progressed (refer FIG. 5E).

Like the p-type doping source 303, the n-type doping source 306 may be applied in the form of a paste or spray, or may be deposited by a deposition method such as chemical vapor deposition (PECVD) or atmospheric pressure vapor deposition (APCVD). The n-type ion implantation layer may be formed using an ion implantation method inside the substrate in the region where the n-type doping source 306 is to be applied without applying the n-type doping source 306.

Accordingly, as shown in FIGS. 5F and 5G, n-type impurities are diffused into the back surface of the substrate 301 in the region where the mask pattern 302 is removed to form an n-type doping layer 307. In addition, n-type impurities are also diffused in the p-type doping layer 304 exposed by the BSG film 305 of the dot pattern, so that a part of the thickness of the p-type doping layer 304 is converted into the n-type doping layer 307. The p-type doped layer 304 located relatively far from the surface of the back surface of the substrate 301 is maintained as it is. At this time, the BSG film serves as a diffusion barrier to prevent n-type impurities from being diffused into the substrate.

As a result, only the n-type doped layer 307 is formed at the portion where the mask pattern 302 is removed. In addition, an n-type doping layer 307 is formed near the surface of the back surface of the substrate 301 at a portion where the BSG film 305 is selectively removed to expose the p-type doping layer 304, and a lower portion of the BSG film 305 is formed thereon. The doping layer 304 is formed to form a structure in which the n-type doping layer 307 and the p-type doping layer 304 overlap each other in a vertical structure. On the other hand, a PSG film 308, which is a diffusion byproduct layer, is formed on the n-type doping layer 307. When the PSG film 308 and the remaining BSG film 305 are removed, the p-type according to an embodiment of the present invention is removed. The structures of the doped layer 304 and the n-type doped layer 307 are completed (see FIG. 5G).

Looking at the structures of the completed p-type doping layer 304 and n-type doping layer 307, the n-type doping layer 307 is exposed in the form of a dot pattern at the first interface, the p-type doping layer at the second interface The structure 304 is exposed in the form of a dot pattern. Accordingly, the surface area of the p-type doping layer 304 is maximized at the first interface to maximize the collection efficiency of minority carriers (holes), and the p-type at the second interface. The surface area of the doped layer 304 can be minimized to suppress the recombination of holes with minority carriers with defects on the surface of the substrate 301.

In the state where the p-type doping layer 304 and the n-type doping layer 307 are formed, the dielectric layer 309 is stacked on the back surface of the substrate 301. The dielectric layer 309 is then selectively patterned to expose the p-type doped layer 304 and n-type doped layer 307 locally, for example in the form of a dot pattern (see FIG. 5H). In this case, a portion where the p-type doping layer 304 is exposed corresponds to a position where the BSG film 305 of the dot pattern is provided, and a portion where the n-type doping layer 307 is exposed is the mask pattern ( 302 may correspond to the location provided.

In this state, p-type finger electrodes 310 and n-type finger electrodes 311 are formed on the exposed p-type doping layer 304 and n-type doping layer 307, respectively (see FIG. 5I). Accordingly, the p-type finger electrodes 310 and the n-type finger electrodes 311 are formed in a row on the back surface of the substrate 301, the rows of the p-type finger electrodes 310 and the n-type finger electrodes 311. When the p-type busbar electrode 312 and the n-type busbar electrode 313 are formed on the columns of (see FIG. 5J), the manufacturing method of the back-electrode solar cell according to the exemplary embodiment of the present invention is completed. .

301: n-type substrate 302: mask pattern
303: p-type doping source 304: p-type doping layer
305: BSG film 306: n-type doping source
307: n-type doped layer 308: PSG film
309 dielectric layer 310 p-type finger electrode
311 n-type finger electrode 312 p-type busbar electrode
313 n-type busbar electrode

Claims (10)

n-type crystalline silicon substrate;
It comprises a p-type doping layer and an n-type doping layer disposed adjacent to the inside of the back of the substrate,
The interface between the p-type doping layer or the n-type doping layer and the inside of the substrate is the first interface,
The surface of the back of the substrate is a second interface,
The n-type doped layer is exposed in the form of a dot pattern at the first interface,
At the second interface, the p-type doped layer is exposed in the form of a dot pattern,
The surface area of the p-type doped layer at the first interface is larger than the surface area of the n-type doped layer, and the surface area of the n-type doped layer at the second interface is larger than the surface area of the p-type doped layer. Solar cells.
delete The method of claim 1, wherein a portion of the p-type doping layer and the n-type doping layer has an overlapping structure, the p-type doping layer is provided on the upper portion, the n-type doping layer is provided on the lower portion,
The p-type doped layer forms a horizontally extended form at the first interface, and the n-type doped layer forms a horizontally expanded form at the second interface.
The semiconductor device of claim 1, further comprising a dielectric layer provided on a rear surface of the substrate including the p-type doping layer and the n-type doping layer, wherein the dielectric layer comprises the p-type doping layer and the n-type doping layer in the form of a dot pattern, respectively. P-type finger electrodes and n-type finger electrodes are provided on the exposed p-type and n-type doped layers, respectively, and p-type busbar electrodes and n-type finger electrodes on the p-type and n-type finger electrodes, respectively. Back electrode type solar cell, characterized in that the bus bar electrode is further provided.
preparing an n-type crystalline silicon substrate;
Forming a mask pattern of a dot pattern at a predetermined interval on a rear surface of the substrate;
Applying a p-type doping source on the back side of the substrate;
Heat-treating the substrate to form a p-type doping layer inside the substrate backside and to form a diffusion byproduct layer on the p-type doping layer;
Removing the mask pattern to expose the substrate on which the p-type doping layer is not formed, and patterning the diffusion byproduct layer in the form of a dot pattern to expose a portion of the p-type doping layer;
Applying an n-type doping source on the back surface of the substrate including the dot pattern diffusion byproduct layer; And
And heat-treating the substrate to form an n-type doped layer in a portion where the mask pattern is removed, and converting a part of the exposed p-type doped layer into an n-type doped layer,
The diffusion byproduct layer is a manufacturing method of a back-electrode solar cell, characterized in that the role of preventing the n-type doping source is diffused into the substrate.
The method of claim 5, wherein the interface between the p-type doping layer or the n-type doping layer and the inside of the substrate is a first interface, the surface of the back surface of the substrate is a second interface,
The n-type doped layer is exposed in the form of a dot pattern at the first interface, the p-type doped layer is exposed in the form of a dot pattern at the second interface.
The method of claim 5, wherein a portion of the p-type doped layer and the n-type doped layer has an overlapping structure, the p-type doped layer is provided on the upper portion, the n-type doping layer is provided on the lower portion,
The p-type doped layer forms a horizontally extended form at the first interface, the n-type doped layer forms a horizontally expanded form at the second interface.
The method of claim 5, wherein
Forming a dielectric layer on the p-type and n-type doped layers,
Selectively patterning the dielectric layer to locally expose the p-type and n-type doped layers;
Forming p-type finger electrodes and n-type finger electrodes on the exposed p-type and n-type doped layers, respectively;
And forming a p-type busbar electrode and an n-type busbar electrode on the p-type finger electrode and the n-type finger electrode, respectively.
The method of claim 8, wherein the portion of the p-type doped layer is exposed to correspond to the position where the diffusion byproduct layer of the dot pattern is provided, and the portion of the n-type doped layer is exposed to correspond to the position of the mask pattern. Method for producing a back-electrode solar cell, characterized in that.
The method of claim 5, wherein the p-type doping source or the n-type doping source is applied in the form of a paste or spray or deposited by chemical vapor deposition.

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