KR20090069417A - Thin film type solar cell and manufacturing method thereof - Google Patents

Abstract

The present invention, a substrate; A plurality of front electrodes spaced apart at predetermined intervals on the substrate; A plurality of semiconductor layers spaced apart from each other on the front electrode with a contact portion for inter-electrode connection and a separator for separation between unit cells; A plurality of back electrodes electrically connected to the front electrode through the contact part and spaced apart from each other with the separation part interposed therebetween; And an insulating film insulated between the back electrode and the semiconductor layer in the contact portion, and a method of manufacturing the same.

According to the present invention, since an insulating film is formed between the side surface of the semiconductor layer and the back electrode in the contact portion, direct contact between the semiconductor layer and the back electrode in the contact portion is blocked by the insulating film. Therefore, the decrease in solar cell efficiency due to the leakage current generated by the direct contact between the semiconductor layer in the contact portion and the back electrode is prevented.

Description

Thin film type solar cell and method for manufacturing same

The present invention relates to a thin film type solar cell, and more particularly, to a thin film type solar cell separated into a plurality of unit cells.

Solar cells are devices that convert light energy into electrical energy using the properties of semiconductors.

The structure and principle of the solar cell will be briefly described. The solar cell has a PN junction structure in which a P (positive) type semiconductor and a N (negative) type semiconductor are bonded to each other. Holes and electrons are generated in the semiconductor by the energy of the incident solar light. At this time, the holes (+) are moved toward the P-type semiconductor by the electric field generated in the PN junction. Negative (-) is the principle that the electric potential is generated by moving toward the N-type semiconductor to generate power.

Such solar cells may be classified into a substrate type solar cell and a thin film type solar cell.

The substrate type solar cell is a solar cell manufactured using a semiconductor material such as silicon as a substrate, and the thin film type solar cell is a solar cell manufactured by forming a semiconductor in the form of a thin film on a substrate such as glass.

Although the substrate type solar cell is somewhat superior in efficiency to the thin film type solar cell, there is a limitation in minimizing the thickness in the process and the manufacturing cost is increased because an expensive semiconductor substrate is used.

Although the thin film type solar cell has a somewhat lower efficiency than the substrate type solar cell, the thin film solar cell is suitable for mass production because the thin film solar cell can be manufactured in a thin thickness and a low cost material can be used to reduce the manufacturing cost.

The thin film solar cell is manufactured by forming a front electrode on a substrate such as glass, a semiconductor layer on the front electrode, and a back electrode on the semiconductor layer. Here, since the front electrode forms a light receiving surface on which light is incident, a transparent conductive material such as ZnO is used as the front electrode.

However, as the substrate becomes larger, the resistance of the front electrode made of the transparent conductive material increases, thereby causing a problem in that the power loss is increased.

Therefore, a method of minimizing the resistance of the front electrode made of a transparent conductive material has been devised by dividing the thin film type solar cell into a plurality of unit cells and connecting the plurality of unit cells in series.

Hereinafter, a method of manufacturing a thin film solar cell having a structure in which a plurality of unit cells are connected in series will be described with reference to the drawings.

1A to 1F are cross-sectional views illustrating a manufacturing process of a thin film solar cell having a structure in which a plurality of unit cells are connected in series.

First, as shown in FIG. 1A, the front electrode layer 20a is formed on the substrate 10 using a transparent conductive material such as ZnO.

Next, as shown in FIG. 1B, a predetermined portion of the front electrode layer 20a is removed by laser scribing to form a plurality of front electrodes 20 spaced at predetermined intervals.

Next, as shown in FIG. 1C, the semiconductor layer 30a is formed on the entire surface of the substrate 10.

Next, as shown in FIG. 1D, a predetermined portion of the semiconductor layer 30a is removed using a laser scribing method to form a contact portion 35 for inter-electrode connection. A plurality of semiconductor layers 30 spaced at predetermined intervals are formed by the contact portion 35.

Next, as shown in FIG. 1E, a back electrode layer 50a is formed on the entire surface of the substrate 10. Then, the front electrode 20 and the back electrode layer 50a are electrically connected through the contact portion 35.

Next, as can be seen in Figure 1f, by using a laser scribing method to remove the predetermined portion of the back electrode layer (50a) to form a separator 45 for separating the solar cell into a unit cell. A plurality of rear electrodes 50 spaced at predetermined intervals are formed by the separator 45.

As described above, by dividing the thin film solar cell into a plurality of unit cells and connecting the plurality of unit cells in series, even if the substrate is enlarged, the resistance of the front electrode does not increase and power loss does not occur.

However, such a conventional thin film solar cell has a problem in that a leakage current is generated at a junction surface between the side surface of the semiconductor layer 30 and the rear electrode 50 in the contact portion 35. Such leakage current causes a decrease in efficiency of the solar cell.

The present invention is designed to solve the problems of the conventional thin-film solar cell described above,

An object of the present invention is to provide a thin-film solar cell and a method of manufacturing the same for minimizing the leakage current generated at the junction between the semiconductor layer side and the rear electrode to prevent the decrease in efficiency of the solar cell.

The present invention, in order to achieve the above object; A plurality of front electrodes spaced apart at predetermined intervals on the substrate; A plurality of semiconductor layers spaced apart from each other on the front electrode with a contact portion for inter-electrode connection and a separator for separation between unit cells; A plurality of back electrodes electrically connected to the front electrode through the contact part and spaced apart from each other with the separation part interposed therebetween; And an insulating film insulated between the back electrode and the semiconductor layer in the contact portion.

On the upper surface of the semiconductor layer and the lower surface of the back electrode, a plurality of transparent conductive layers may be additionally arranged to be spaced apart between the contact portion for inter-electrode connection and the separation portion for separation between unit cells.

The insulating layer may be made of silicon oxide or silicon nitride.

The present invention also provides a process for forming a plurality of front electrodes spaced apart at predetermined intervals on a substrate; Forming a plurality of semiconductor layers spaced apart from each other with a contact portion for inter-electrode connection therebetween on the front electrode; Forming an insulating film on a side surface of the semiconductor layer in the contact portion; Forming a back electrode layer electrically connected to the front electrode through the contact portion; And removing a predetermined region of the back electrode layer and the semiconductor layer to form a separator.

Prior to forming the insulating film, further comprising forming a protective layer on the upper surface of the semiconductor layer to prevent the insulating film is formed on the upper surface of the semiconductor layer, and after the forming of the insulating film, the semiconductor The method may further include removing a protective layer formed on the upper surface of the layer.

The method may further include forming a plurality of transparent conductive layers spaced apart from each other on the upper surface of the semiconductor layer and the lower surface of the back electrode layer with a contact portion interposed therebetween.

The insulating film forming process may be performed after the transparent conductive layer forming process.

The forming of the insulating layer may be performed by forming a silicon oxide using a thermal oxidation method, a plasma oxidation method, a chemical oxidation method, or a natural oxidation method.

The forming of the insulating layer may be performed by forming a silicon nitride using a thermal nitriding method, a plasma nitriding method, or a chemical nitriding method.

According to the present invention as described above, since an insulating film is formed between the side of the semiconductor layer and the back electrode in the contact portion, the direct contact between the semiconductor layer and the back electrode in the contact portion is blocked by the insulating film. Therefore, the decrease in solar cell efficiency due to the leakage current generated by the direct contact between the semiconductor layer in the contact portion and the back electrode is prevented.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

<Thin Film Solar Cell>

2 is a cross-sectional view of a thin film solar cell according to an embodiment of the present invention.

As can be seen in Figure 2, the thin-film solar cell according to an embodiment of the present invention, including a substrate 100, the front electrode 200, the semiconductor layer 300, the insulating film 500 and the rear electrode 600 Is done.

The substrate 100 may be made of glass or transparent plastic.

A plurality of front electrodes 200 are arranged on the substrate 100 at predetermined intervals. The front electrode 200 may be made of a transparent conductive material such as ZnO, ZnO: B, ZnO: Al, ZnO: H, SnO ₂ , SnO ₂ : F, or ITO (Indium Tin Oxide). Since the front electrode 200 is formed on the surface where the solar light is incident, the surface of the front electrode 200 may have a bumpy concave-convex structure so that the incident sunlight can be absorbed to the inside of the solar cell as much as possible. have.

The semiconductor layer 300 is formed on the front electrode 200, and a plurality of semiconductor layers 300 are spaced apart from each other with a contact portion 350 for connecting between electrodes and a separation portion 650 for separation between unit cells. The semiconductor layer 300 may be formed of a silicon-based semiconductor material such as amorphous silicon or microcrystalline silicon. The semiconductor layer 300 has a PIN structure in which a P-type semiconductor layer, an I-type semiconductor layer, and an N-type semiconductor layer are stacked in this order. In this case, the I-type semiconductor layer is formed on the P-type semiconductor layer and the N-type semiconductor layer. Depletion causes an electric field to be generated therein, and holes and electrons generated by sunlight are drifted by the electric field to be collected in the P-type semiconductor layer and the N-type semiconductor layer, respectively. On the other hand, when the semiconductor layer 300 is formed in a PIN structure, it is preferable to form a P-type semiconductor layer first, and then form an I-type semiconductor layer and an N-type semiconductor layer in order. Since the drift mobility of the holes is low due to the drift mobility of the electrons, the P-type semiconductor layer is formed close to the light receiving surface in order to maximize the collection efficiency by incident light.

The insulating layer 500 is formed between the semiconductor layer 300 and the back electrode 600 in the contact portion 350 to insulate the semiconductor layer 300 and the back electrode 600. do. Therefore, the conventional problem that the leakage current occurs because the side surface of the semiconductor layer 30 in the contact portion 35 and the back electrode 50 do not directly contact due to the insulating film 500 is solved.

The back electrode 600 is electrically connected to the front electrode 200 through the contact unit 350, and a plurality of the rear electrodes 600 are spaced apart from each other with the separation unit 650 therebetween. The back electrode 600 may be formed of Ag, Al, Ag + Al, Ag + Mg, Ag + Mn, Ag + Sb, Ag + Zn, Ag + Mo, Ag + Ni, Ag + Cu, Ag + Al + Zn, or the like. It may be made of metal.

3 is a cross-sectional view of a thin film solar cell according to another exemplary embodiment of the present invention, which is provided in accordance with FIG. 2 except that a transparent conductive layer 400 is further formed between the semiconductor layer 300 and the back electrode 600. Same as thin film solar cell. Therefore, detailed description of the same configuration will be omitted.

As can be seen in FIG. 3, the transparent conductive layer 400 is formed on the top surface of the semiconductor layer 300 and the bottom surface of the back electrode 600, and contacts for inter-electrode connection are the same as the semiconductor layer 300. The plurality 350 is spaced apart from each other with the separation unit 650 for separation between the unit 350 and the unit cell.

The transparent conductive layer 400 may be made of a transparent conductive material such as ZnO, ZnO: B, ZnO: Al, ZnO: H, Ag.

The transparent conductive layer 400 scatters sunlight at various angles to enhance light transmittance and protects the upper surface of the semiconductor layer 300 when the insulating film 500 is formed. A function of protecting the upper surface of the semiconductor layer 300 by the transparent conductive layer 400 will be described in detail in an embodiment of a method of manufacturing a thin film solar cell, which will be described later.

<Method of manufacturing thin film solar cell>

4A to 4G are cross-sectional views illustrating a manufacturing process of a thin film solar cell according to an embodiment of the present invention, which illustrates a manufacturing process of the thin film solar cell according to FIG. 2.

First, as shown in FIG. 4A, a plurality of front electrodes 200 arranged on the substrate 100 at predetermined intervals are formed.

The front electrode 200 may be formed by sputtering or metal organic chemical vapor deposition (MOCVD) on the entire surface of the substrate 100 using ZnO, ZnO: B, ZnO: Al, SnO ₂ , Forming a transparent conductive layer, such as SnO ₂ : F, ITO (Indium Tin Oxide), and removing a predetermined region of the transparent conductive layer by using a laser scribing method.

Alternatively, the process of forming the front electrode 200 may be performed using screen printing, inkjet printing, gravure printing, or microcontact printing. The transparent conductive layers such as ZnO, ZnO: B, ZnO: Al, SnO ₂ , SnO ₂ : F, Indium Tin Oxide (ITO), and the like may be directly disposed on the substrate 100 at predetermined intervals.

The screen printing method is a method of transferring a target material to a work using a screen and a squeeze to form a predetermined pattern, and the ink jet printing method uses a jet of ink to spray a target material onto the work to provide a predetermined pattern. The method of forming a pattern, the gravure printing method is a method of forming a predetermined pattern by applying the target material to the groove of the concave plate and transfer the target material back to the workpiece, the micro-contact printing method is a predetermined mold It is a method of forming a target material pattern on a work piece.

The laser scribing process causes a large amount of particles to contaminate the substrate and short circuits of the device due to particles, while screen printing, inkjet printing, and gravure The printing method or the microcontact printing method does not cause such a problem.

On the other hand, in order to improve the absorption rate of the sunlight absorbed into the solar cell by performing a texturing process on the front electrode 200 can be formed in the concave-convex structure.

Next, as shown in FIG. 4B, a plurality of semiconductor layers 300 are formed on the front electrode 200 and are spaced apart from each other with a contact portion 350 for inter-electrode connection therebetween.

The process of forming the semiconductor layer 300 may include forming a silicon-based semiconductor layer such as amorphous silicon or microcrystalline silicon by using plasma CVD, and removing a predetermined region of the semiconductor layer by using a laser scribing method. The semiconductor layer 300 is spaced apart from each other by the contact portion 350 by using a predetermined mask when forming the silicon-based semiconductor layer using the plasma CVD method. It can also form directly.

The semiconductor layer 300 may have a PIN structure in which a P-type semiconductor layer, an I-type semiconductor layer, and an N-type semiconductor layer are sequentially stacked.

Next, as shown in FIG. 4C, a protective layer 450 is formed on the upper surface of the semiconductor layer 300.

The protective layer 450 is to prevent the insulating film from being formed on the upper surface of the semiconductor layer 300 during the insulating film forming process to be described later. The protective layer 450 may be formed using a photoresist.

Next, as shown in FIG. 4D, an insulating film 500 is formed on the side surface of the semiconductor layer 300 in the contact portion 350.

The process of forming the insulating film 500 may be performed by oxidizing silicon constituting the semiconductor layer 300 in an oxygen atmosphere to form a silicon oxide film. Specific silicon oxide film forming methods include thermal oxidation, plasma oxidation, Chemical oxidation, natural oxidation, and the like.

The forming of the insulating film 500 may be performed by forming a silicon nitride film by nitriding silicon constituting the semiconductor layer 300 in a nitrogen atmosphere. Specific silicon nitride film forming methods may include a thermal nitride method and a plasma nitride film. Chemical nitriding method, chemical nitriding method, etc. are mentioned.

Next, as shown in FIG. 4E, the protective layer 450 formed on the upper surface of the semiconductor layer 300 is removed. Since the protective layer 450 is to prevent the insulating film 500 from being formed on the upper surface of the semiconductor layer 300 as described above, the protective layer 450 is removed after the forming process of the insulating film 500. Removing the protective layer 450 is performed using a selective etching method.

Next, as can be seen in Figure 4f, through the contact portion 350 to form a back electrode layer 600a electrically connected to the front electrode 200.

The back electrode layer 600a may be formed of Ag, Al, Ag + Al, Ag + Mg, Ag + Mn, Ag + Sb, Ag + Zn, Ag + Mo, Ag + Ni, Ag + Cu, Ag + Al + Zn, or the like. A metal is formed using a printing method or sputtering method.

Next, as can be seen in Figure 4g, to remove the predetermined region of the back electrode layer 600a and the semiconductor layer 300 to form a separator 650. Then, the rear electrode 600 is spaced apart at predetermined intervals with the separation unit 650 therebetween.

Meanwhile, between FIG. 4E and FIG. 4F, a transparent conductive layer having the same pattern as the semiconductor layer 300 may be further formed on the upper surface of the semiconductor layer 300. That is, the plurality of transparency layers having the protective layer 450 formed on the upper surface of the semiconductor layer 300 are removed, and then spaced apart from each other with a contact portion 350 interposed therebetween on the upper surface of the semiconductor layer 300. After forming the entire layer, the back electrode layer 600a may be formed. In this case, a thin film solar cell having a structure as shown in FIG. 3 is finally manufactured.

5A to 5F are cross-sectional views illustrating a manufacturing process of a thin film solar cell according to another embodiment of the present invention, which illustrates a manufacturing process of the thin film solar cell according to FIG. 3. Detailed description of the same configuration as the above-described embodiment will be omitted.

First, as shown in FIG. 5A, a plurality of front electrodes 200 that are spaced apart at predetermined intervals is formed on the substrate 100.

Next, as shown in FIG. 5B, the semiconductor layer 300a and the transparent conductive layer 400a are sequentially formed on the front electrode 200.

The transparent conductive layer 400a scatters sunlight at various angles to enhance light transmittance, and protects the upper surface of the semiconductor layer 300a when forming the insulating film 500 to be described later. In particular, since the process of forming the insulating film 500 to be described later is performed by a silicon oxide film forming process or a silicon nitride film forming process, the transparent conductive layer 400a is preferably made of a non-oxide or a metal nitride.

The transparent conductive layer 400a may be formed of a transparent conductive material such as ZnO, ZnO: B, ZnO: Al, Ag by using a sputtering method or a metal organic chemical vapor deposition (MOCVD) method.

Next, as can be seen in Figure 5c, to remove the predetermined region of the semiconductor layer 300a and the transparent conductive layer (400a) to form a contact portion 350 for the inter-electrode connection. As a result, a plurality of semiconductor layers 300 and a transparent conductive layer 400 are spaced apart from each other with the contact portion 350 interposed therebetween.

The process of removing predetermined regions of the semiconductor layer 300a and the transparent conductive layer 400a may be performed by using a laser scribing method.

Next, as shown in FIG. 5D, an insulating film 500 is formed on the side surface of the semiconductor layer 300 in the contact portion 350.

In the present embodiment, since the transparent conductive layer 400 is formed on the upper surface of the semiconductor layer 300, there is no need to additionally form a protective layer as in the above-described embodiment.

Next, as can be seen in Figure 5e, through the contact portion 350 to form a back electrode layer 600a electrically connected to the front electrode 200.

Next, as can be seen in Figure 4g, to remove the predetermined region of the back electrode layer 600a and the semiconductor layer 300 to form a separator 650.

1A to 1F are cross-sectional views illustrating a manufacturing process of a thin film solar cell having a structure in which a plurality of unit cells are connected in series.

2 is a cross-sectional view of a thin film solar cell according to an embodiment of the present invention.

3 is a cross-sectional view of a thin film solar cell according to another embodiment of the present invention.

4A to 4G are cross-sectional views illustrating a manufacturing process of a thin film solar cell according to an embodiment of the present invention.

5A to 5F are cross-sectional views illustrating a manufacturing process of a thin film solar cell according to another exemplary embodiment of the present invention.

<Description of Signs of Major Parts of Drawing>

100: substrate 200: front electrode

300: semiconductor layer 350: contact portion

400: transparent conductive layer 500: insulating film

600: rear electrode 650: separator

Claims (9)

Board; A plurality of front electrodes spaced apart at predetermined intervals on the substrate; A plurality of semiconductor layers spaced apart from each other on the front electrode with a contact portion for inter-electrode connection and a separator for separation between unit cells; A plurality of back electrodes electrically connected to the front electrode through the contact part and spaced apart from each other with the separation part interposed therebetween; And The thin film type solar cell comprising an insulating film insulated between the back electrode and the semiconductor layer in the contact portion. The method of claim 1, The thin film solar cell of claim 1, further comprising a plurality of transparent conductive layers spaced apart from each other on the upper surface of the semiconductor layer and the lower surface of the back electrode, with the contact portion for inter-electrode connection and the separation portion for separation between unit cells interposed therebetween. The method of claim 1, The insulating film is a thin film solar cell, characterized in that made of silicon oxide or silicon nitride. Forming a plurality of front electrodes spaced apart at predetermined intervals on the substrate; Forming a plurality of semiconductor layers spaced apart from each other with a contact portion for inter-electrode connection therebetween on the front electrode; Forming an insulating film on a side surface of the semiconductor layer in the contact portion; Forming a back electrode layer electrically connected to the front electrode through the contact portion; And And removing a predetermined region of the back electrode layer and the semiconductor layer to form a separator. The method of claim 4, wherein Prior to forming the insulating film, further comprising the step of forming a protective layer on the upper surface of the semiconductor layer to prevent the insulating film is formed on the upper surface of the semiconductor layer, After the step of forming the insulating film, the method of manufacturing a thin film solar cell further comprising the step of removing the protective layer formed on the upper surface of the semiconductor layer. The method of claim 4, wherein And forming a plurality of transparent conductive layers on the upper surface of the semiconductor layer and the lower surface of the back electrode layer, the plurality of transparent conductive layers being spaced apart from each other with contact portions interposed therebetween. The method of claim 6, And the insulating film forming process is performed after the transparent conductive layer forming process. The method of claim 4, wherein The method of forming the insulating film is a method of manufacturing a thin film solar cell, characterized in that the step of forming a silicon oxide using a thermal oxidation method, a plasma oxidation method, a chemical oxidation method, or a natural oxidation method. The method of claim 4, wherein The method of forming the insulating film is a method of manufacturing a thin-film solar cell, characterized in that for forming a silicon nitride using a thermal nitriding method, a plasma nitriding method or a chemical nitriding method.

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