KR101231284B1 - Solar cell and method of fabircating the same - Google Patents

Abstract

Solar cell according to the embodiment is a substrate; A window layer on the substrate, a buffer layer on the window layer, and a light absorbing layer on the buffer layer; A plurality of solar cells in which a rear electrode layer is formed on the light absorbing layer; A plurality of diodes formed on the substrate and connected in parallel with the plurality of solar cells; And a connection electrode electrically connecting the plurality of solar cells and the plurality of diodes.

Description

SOLAR CELL AND METHOD OF FABIRCATING THE SAME}

An embodiment relates to a solar cell and a manufacturing method thereof.

Recently, as energy demand increases, development of a solar cell converting solar energy into electrical energy is in progress.

In particular, CIGS-based solar cells that are pn heterojunction devices having a substrate structure including a glass substrate, a metal back electrode layer, a p-type CIGS-based light absorbing layer, a high resistance buffer layer, an n-type window layer, and the like are widely used.

In such a solar cell, a plurality of cells are formed in one panel, and the cells are connected in series.

If a failure occurs in any one of these cells, the panel is not used and is discarded.

In addition, when a shadow is caused by an external object on the solar cell panel, or when foreign matter such as impurities is attached to the solar cell panel, the shadowed or foreign matter is attached to the cell, which causes a problem that the load becomes large and overheats.

The embodiment provides a solar cell and a method of manufacturing the same, which can be used as a solar cell without deterioration even when a defective cell is generated or a shadow is generated on the solar cell panel, and a process is simplified and integrated by forming a diode on the upper surface of the substrate. .

Solar cell according to the embodiment is a substrate; A window layer on the substrate, a buffer layer on the window layer, and a light absorbing layer on the buffer layer; A plurality of solar cells in which a rear electrode layer is formed on the light absorbing layer; A plurality of diodes formed on the substrate and connected in parallel with the plurality of solar cells; And a connection electrode electrically connecting the plurality of solar cells and the plurality of diodes.

The solar cell according to the embodiment forms a cell unit including a plurality of cells on the substrate and a diode connected in parallel with the plurality of cells, and then connects each cell in series, and forms a diode between the plurality of cells.

Therefore, when one of the cells is shadowed or foreign matter is formed on the cell, the charge is formed to bypass the diode, so that a defective cell or a shadow on the solar cell panel does not cause deterioration of the solar cell. Can be used.

In addition, since a plurality of diodes are formed on one substrate, when a defective cell occurs, current may be bypassed by a diode connected in parallel with the corresponding cell, and other cells may be utilized, thereby improving reliability.

In addition, since diodes may be integrated at the edges of the upper surface of the substrate and diodes may be formed in the process of forming solar cells, the process may be simplified and productivity may be improved.

1 is a plan view showing a solar cell according to an embodiment.
FIG. 2 is a cross-sectional view illustrating a cross section taken along AA ′ in FIG. 1.
3 is a cross-sectional view taken along the line BB ′ of FIG. 1.
4 to 12 are cross-sectional views illustrating a method of manufacturing a solar cell according to an embodiment.

In the description of the embodiments, where each substrate, layer, film, or electrode is described as being formed "on" or "under" of each substrate, layer, film, or electrode, etc. , “On” and “under” include both “directly” or “indirectly” other components. In addition, the upper or lower reference of each component is described with reference to the drawings. The size of each component in the drawings may be exaggerated for the sake of explanation and does not mean the size actually applied.

12 is a plan view illustrating a solar cell according to an embodiment.

As shown in FIG. 12, the solar cell according to the embodiment includes a first cell C1, a second cell C2, a third cell C3, a fourth cell C4, a fifth cell C5, It includes a sixth cell (C6).

The first cell C1 is electrically connected to the first bus bar 810, and the sixth cell C6 is electrically connected to the second bus bar 820.

The window layer 600 formed in the first cell C1 is electrically connected to the light absorbing layer 300 formed in the second cell C2. Therefore, the first cell C1 and the second cell C2 are electrically connected. With the above configuration, the first cell C1, the second cell C2, the third cell C3, the fourth cell C4, the fifth cell C5, and the sixth cell C6 are connected in series. Can be connected.

In addition, the first bus bar 810 and the second bus bar 820 may be parallel to the first cells C1 to sixth cell C6 and formed at both ends of the substrate 100.

First, second and third diodes D1, D2, and D3 are formed on the substrate 100. The first, second, and third diodes D1, D2, and D3 may be formed in a deposition and patterning process of each layer to form the first cells C1 to 6th cell C6.

The first, second, and third diodes D1, D2, and D3 are connected in parallel with the first cells C1 to sixth cell C6. In detail, the first diode D1 is connected in parallel with the first cell C1 and the second cell C2, and the second diode D2 is parallel with the third cell C3 and the fourth cell C4. The third diode D3 may be connected to the fifth cell C5 and the sixth cell C6 in parallel. The first, second, and third diodes D1, D2, and D3 and the plurality of cells C1 to C6 may be connected by the back electrode layer 200 formed by different patterns.

In addition, three or more diodes may be formed. That is, the cells may be formed at positions corresponding to the first cells C1 to the sixth cell C6, respectively, and one or more cells may be connected in parallel with one diode.

The first, second, and third diodes D1, D2, and D3 are edges of the substrate 100 on which the cells C1, C2... Are not formed on the substrate 100. It may be formed in the region, but is not limited thereto.

When the first, second, and third diodes D1, D2, and D3 have a shadow on one of the cells C1, C2..., Or a foreign substance is formed on the solar panel. And a current can be diverted to the diode.

Hereinafter, it will be described in more detail according to the manufacturing process of the solar cell.

1 is a plan view illustrating a solar cell according to an embodiment, FIG. 2 is a cross-sectional view taken along line AA ′ of FIG. 1, and FIG. 3 is a cross-sectional view taken along line BB ′ of FIG. 1. It is a cross section.

As shown, the first, second, and third diodes D1, D2, and D3 are formed in the same pattern as the plurality of cells C1, C2... The first, second, and third diodes D1, D2, and D3 may be formed under the outer frame.

Since the first cells C1 to 6th cell C6 are formed in the same shape, and the first to third diodes D1, D2, and D3 are formed in the same shape, only a part of the cross-sectional view is presented.

2 and 3, the first through holes TH1 of the region where the first cell C1 to the sixth cell C6 are formed are the first, second, and third diodes D1, It is formed at a relatively narrow interval compared to the first through holes TH1 ′ in the areas where D2 and D3 are formed.

That is, one of the first through holes TH1 in the region where the first cell C1 to the sixth cell C6 is formed is the first, second, and third diodes D1, D2, and D3. It may extend into the first through hole TH1 ′ of the formed region. That is, one of the first through holes TH1 is formed longer than other through holes so that the first through holes in the region where the first, second, and third diodes D1, D2, and D3 are formed. TH1 ').

In the present exemplary embodiment, the first, second, and third diodes D1, D2, and D3 are arranged to be spaced apart from each other between the first cells C1 to the sixth cell C6, but each of the plurality of cells Diodes may be formed in the same number as the plurality of cells so as to be connected to the plurality of cells. In addition, the number of cells connected in parallel with the diode may be different.

The first, second, and third diodes D1, D2, and D3 and the first cells C1 to 6th cell C6 may be formed of the same material in the same process. That is, the connection electrode layer 210 and the back electrode layer 200 are formed of the same material, and the light absorbing layer 300, the first conductive layer 310, the window layer 600, and the second conductive layer 610 are made of the same material. It can be formed as.

4 to 12 are cross-sectional views illustrating a method of manufacturing a solar cell according to an embodiment.

4 is a diagram illustrating a substrate 100 and a back electrode layer 200 in a region in which a plurality of cells are formed, and FIG. 5 is a diagram in a region in which a plurality of diodes are formed.

4 and 5, the first cell C1, the second cell C2, the third cell C3, the fourth cell C4, the fifth cell C5, and the sixth cell C6. Preparing a substrate 100 for supporting the.

The substrate 100 may be glass, and a ceramic substrate such as alumina, stainless steel, a titanium substrate, or a polymer substrate may also be used.

Soda lime glass may be used as the glass substrate, and polyimide may be used as the polymer substrate.

In addition, the substrate 100 may be rigid or flexible.

Next, the back electrode layer 200 is formed on the substrate 100.

The back electrode layer 200 may be formed by forming a back electrode film on the substrate 100 and then patterning the photo electrode by a photo-lithography process.

Alternatively, after the mask is disposed on the substrate 100, the back electrode layer 200 may be formed only in each region.

The back electrode layer 200 may be formed of a conductor such as metal.

For example, the back electrode layer 200 may be formed by a sputtering process using a molybdenum (Mo) target.

This is due to the high electrical conductivity of molybdenum (Mo), the ohmic junction with the light absorbing layer, and the high temperature stability under Se atmosphere.

In addition, although not shown in the drawings, the back electrode layer 200 may be formed of at least one layer. When the back electrode layer 200 is formed of a plurality of layers, the layers constituting the back electrode layer 200 may be formed of different materials.

In addition, the back electrode layer 200 may be arranged in a stripe form or a matrix form and may correspond to each cell.

However, the back electrode layer 200 is not limited to the above form and may be formed in various forms.

Referring to FIG. 6, the lengths of the first through holes TH1 ′ of the regions formed in the first, second, and third diodes D1, D2, and D3 are the first to sixth cells C1 to 6. It may have a value larger than the length of the first through holes TH1 formed in the cell C6.

The first through holes TH1 ′ and the first cells C1 to 6 in the region where the first, second, and third diodes D1, D2, and D3 are formed by different patterning in the same process. First through holes TH1 formed in the cell C6 may be formed.

Subsequently, as shown in FIG. 7, the light absorbing layer 300, the buffer layer 400, and the high resistance buffer layer 500 are formed on the back electrode layer 200.

The light absorbing layer 300 includes an I-III-VI compound. In more detail, the light absorbing layer 300 includes a copper-indium-gallium-selenide-based (Cu (In, Ga) Se ₂ , CIGS-based) compound.

Alternatively, the light absorbing layer 300 may include a copper-indium selenide-based (CuInSe ₂ , CIS-based) compound or a copper-gallium-selenide-based (CuGaSe ₂ , CIS-based) compound.

For example, in order to form the light absorbing layer 300, a CIG-based metal precursor film is formed on the back electrode layer 200 using a copper target, an indium target, and a gallium target.

Thereafter, the metal precursor film is reacted with selenium (Se) by a selenization process to form a CIGS-based light absorbing layer 300.

In addition, the light absorbing layer 300 may form copper, indium, gallium, selenide (Cu, In, Ga, Se) by co-evaporation.

The light absorbing layer 300 receives external light and converts the light into electrical energy. That is, the light absorbing layer 300 generates photo electromotive force by the photoelectric effect.

The buffer layer 400 is formed of at least one layer, and any one or a stack of cadmium sulfide (CdS), ITO, ZnO, and i-ZnO on the substrate 100 on which the light absorbing layer 300 is formed. Can be formed.

At this time, the buffer layer 400 is an n-type semiconductor layer and the light absorption layer 300 is a p-type semiconductor layer. Accordingly, the light absorption layer 300 and the buffer layer 400 form a pn junction. In this case, since the difference between the lattice constant and the energy band gap is large between the light absorbing layer 300 and the window layer 600, a good junction may be formed by inserting the buffer layer 400 having a band gap in between the two materials. Can be.

The buffer layer 400 is disposed between the light absorbing layer 300 and the window layer 600 to be formed later.

The high resistance buffer layer 500 may be formed on the buffer layer 400. The high resistance buffer layer 500 may include zinc oxide (i-ZnO) that is not doped with impurities. The energy bandgap of the high resistance buffer layer 500 is about 3.1 eV to 3.3 eV.

Subsequently, as shown in FIG. 8, second through holes TH2 penetrating the light absorbing layer 300, the buffer layer 400, and the high resistance buffer layer 500 are formed.

The second through holes TH2 may be formed by a mechanical method, and a portion of the back electrode layer 200 is exposed.

As illustrated in FIG. 9, a transparent conductive material is stacked on the high resistance buffer layer 500 to form a window layer 600 and a connection wiring 700.

When the transparent conductive material is stacked on the high resistance buffer layer 500, the transparent conductive material may also be inserted into the second through holes TH2 to form the connection wiring 700. That is, the window layer 600 and the connection wiring 700 may be formed of the same material.

The back electrode layer 200 and the window layer 600 are electrically connected by the connection wiring 700.

The window layer 600 is formed of zinc oxide doped with aluminum by performing a sputtering process on the substrate 100.

The window layer 600 is a layer for forming a pn junction with the light absorbing layer 300. Since the window layer 600 functions as a transparent electrode on the front of the solar cell, the window layer 600 is formed of zinc oxide (ZnO) having high light transmittance and good electrical conductivity.

At this time, an electrode having a low resistance value can be formed by doping zinc oxide with aluminum.

The zinc oxide thin film as the window layer 600 may be formed by a method of depositing using a ZnO target by RF sputtering, reactive sputtering using a Zn target, and organometallic chemical vapor deposition.

In addition, a double structure in which an indium tin oxide (ITO) thin film having excellent electro-optical properties is laminated on a zinc oxide thin film may be formed.

Next, as shown in FIG. 10, third through holes TH3 penetrating the light absorbing layer 300, the buffer layer 400, the high resistance buffer layer 500, and the window layer 600 are formed.

The separation pattern 320 may be formed by a mechanical method, and a portion of the back electrode layer 200 is exposed.

The buffer layer 400, the high resistance buffer layer 500, and the window layer 600 may be divided by the third through holes TH3, and each cell may be divided by the third through holes TH3. Can be separated from each other.

The buffer layer 400, the high resistance buffer layer 500, and the window layer 600 may be arranged in the form of a stripe or a matrix by the third through holes TH3.

Next, portions of the light absorbing layer and the window layer formed in the region where the first through holes TH1 are not formed are etched to form first, second, and third diodes D1, D2, and D3. The first, second, and third diodes D1, D2, and D3 may include the same layer as the first to sixth cells C6 to C6. That is, the first, second, and third diodes D1, D2, and D3 are formed by stacking the same layer in the process of forming the first to sixth cells C6, and during the etching process. As a result, the first cell C1 to the sixth cell C6 are formed separately.

As shown in FIG. 11, the first bus bar 810 and the second bus bar 820 are formed to be connected to the back electrode layer 200.

The first bus bar 810 and the second bus bar 820 are the light absorbing layer 300, the buffer layer 400, the high resistance buffer layer 500, and the window layer 600 formed at the end of the substrate 100. A portion of the back electrode layer 200 may be removed and then formed.

In the present exemplary embodiment, the first bus bar 810 and the second bus bar 820 are connected to the rear electrode layer 200, but the present invention is not limited thereto. The first bus bar may be formed on the window layer 600. 810 and the second bus bar 820 may be formed.

A first bus bar 810 is formed in the first cell C1, and a second bus bar 820 is formed in the sixth cell C6. The first bus bar 810 may be connected to the (+) electrode, and the second bus bar 820 may be connected to the (-) electrode.

The plurality of cells and the first, second, and third diodes D1, D2, and D3 may be electrically connected by the back electrode layer 200.

Usually, current flows through the plurality of cells C1, C2, C3 ..., but the shadow of any one of the plurality of cells C1, C2, C3 ... or the foreign matter is solar cells. When formed on the panel, the cell in which the failure occurs is operated like a passive element, that is, a resistor, rather than an active element generating power, and thus counter electromotive force is generated in the cell.

Therefore, a conduction voltage is applied to the diode connected to the cell so that current flows through the diode, not the cell. That is, the current is bypassed through the first, second, and third diodes D1, D2, and D3.

For example, if the third cell C3 has a shadow or a failure, the resistance is increased in the shadowed cell or the cell in which the failure occurs.

Therefore, in this case, charge is transferred from the second bus bar 820 through the sixth cell C6, the fifth cell C5, and the second diode D2. The cell moves to one cell C1 and moves through the first bus bar 810.

In addition, when the shadow or the failure occurs in the fourth cell (C4) is operated as described above.

If a shadow or a defect occurs in any one of the third cell C3 and the fourth cell C4, the current flow may be as described above.

Accordingly, the first cell C1, the second cell C2 is the first cell unit, the third cell C3, the fourth cell C4 is the second cell unit, the fifth cell C5, The sixth cell C6 can be thought of as being bundled into a third cell unit.

That is, when the shadow is or a defect occurs in the first cell unit, a current flows through the first diode D1, and when the shadow or a defect occurs in the second cell unit, the second diode D2 is generated. When a current flows through the third cell unit and a shadow occurs or a defect occurs, the current flows through the third diode D3.

The first, second, and third diodes D1, D2, and D3 may be disposed on an upper surface of the substrate 100 and may be formed in an outer corner region.

In the solar cell according to the embodiment described above, when one of the cell units has a shadow or a foreign substance is formed on the cell unit, a defective cell is generated by forming a current to bypass the diode connected to the cell. In addition, even if a shadow occurs on the solar panel can use the solar cell without deterioration.

In addition, since the diode is formed inside the module, not the junction box, that is, the edge of the upper surface of the substrate, integration of the device is possible.

First, second and third diodes D1, D2, and D3 are formed on the substrate 100. Since the first, second, and third diodes D1, D2, and D3 may be formed in a deposition and patterning process of each layer for forming the first to sixth cells C6, the process may be performed. It is simplified.

In addition, since a plurality of diodes are formed in one module, even if an error occurs in any one of the plurality of solar cells in the module, current flows through the diode connected to the corresponding cell, so that other cells normally operating in the same module are available. .

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, but, on the contrary, It will be understood that various modifications and applications are possible. For example, each component specifically shown in the embodiments can be modified and implemented. It is to be understood that all changes and modifications that come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.

Claims (9)

Board;
A window layer on the substrate, a buffer layer on the window layer, and a light absorbing layer on the buffer layer; A plurality of solar cells in which a rear electrode layer is formed on the light absorbing layer;
A plurality of diodes formed on the substrate and connected in parallel with the plurality of solar cells; And
And a connection electrode electrically connecting the plurality of solar cells and the plurality of diodes.
Each of the plurality of diodes,
A first conductive layer; And
A second conductive layer;
The first conductive layer is formed of the same material as the light absorbing layer of the plurality of solar cells,
The second conductive layer is a solar cell formed of the same material as the window layer of the plurality of solar cells. The method of claim 1,
The plurality of diodes are formed in the edge (edge) area of the substrate. The method of claim 1,
The plurality of solar cells include a back electrode layer, a light absorbing layer, a window layer. The method of claim 1,
The connection electrode and the back electrode layer is a solar cell formed of the same material. delete delete The method of claim 1,
Each of the plurality of diodes is a solar cell connected in parallel with one or more of the solar cell. The method of claim 1,
And a first bus bar and a second bus bar electrically connected to the plurality of solar cells and having opposite polarities. 9. The method of claim 8,
The first bus bar and the second bus bar are formed in the peripheral region of the substrate.

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