KR101154571B1 - Solar cell module and method of fabricating the same - Google Patents

Abstract

Disclosed are a solar cell module and a method of manufacturing the same. A solar cell according to an embodiment includes a solar cell including a back electrode, a light absorbing layer, and a front electrode layer stacked on a substrate; And a bus bar formed on the front electrode layer and formed of a low temperature baking paste composition. Therefore, a bus bar is formed on the solar cell by the paste composition of low temperature baking, thereby improving sheet resistance and light transmittance.

Solar cell, bus bar

Description

SOLAR CELL MODULE AND METHOD OF FABRICATING THE SAME

An embodiment relates to a solar cell module.

The photovoltaic module that converts light energy into electrical energy using the photoelectric conversion effect is widely used as a means of obtaining pollution-free energy that contributes to the preservation of the global environment.

As photovoltaic conversion efficiency of solar cells is improved, many solar power systems with photovoltaic modules have been installed outside of commercial buildings as well as in residential applications.

In order to output the power generated from the photovoltaic module having a solar cell that generates power from daylight to the outside, bus bars serving as positive and negative electrodes are disposed in the photovoltaic module.

The bus bar may be attached to the solar cell by a thermal fusion method using solder metal.

Such a bus bar requires a relatively large adhesive area, so that a lot of heat treatment work and high contact resistance can reduce the photovoltaic characteristics of the solar cell.

In addition, since the shape of the bus bar is exposed through the transparent electrode layer of the solar cell as it is, it may act as a factor that damages the aesthetics.

Embodiments provide a solar cell module having an improved appearance and power generation efficiency and a method of manufacturing the same.

A solar cell module according to an embodiment includes a solar cell including a back electrode, a light absorbing layer, and a front electrode layer stacked on a substrate; And a bus bar formed on the front electrode layer and formed of a low temperature baking paste composition.

A method of manufacturing a solar cell module according to an embodiment includes forming a solar cell including a back electrode, a light absorbing layer, and a front electrode layer on a substrate; Forming a bus bar by coating a low temperature baking paste composition to be connected to the front electrode layer of the solar cell, wherein the bus bar is made of silver (Ag), copper (Cu), titanium (Ti), or an alloy thereof. It is formed of a paste composition.

In the solar cell module and the method of manufacturing the same according to the embodiment, a bus bar formed of a low temperature baking paste may be formed on the solar cell.

Therefore, the sheet resistance and light transmittance of the solar cell can be improved.

In addition, since the bus bar is formed by a low temperature baking process using silver paste, damage to the front electrode of the solar cell can be prevented to the maximum.

In addition, it is possible to improve the efficiency of the solar cell module by lowering the contact resistance by improving the adhesion of the bus bar and the front electrode.

In addition, since the bus bar is formed in a single layer, the shape of the bus bar can be adjusted, thereby improving aesthetics.

In addition, the bus bar can be produced by an automated process such as screen printing, thereby improving productivity.

In the description of the embodiment, each substrate, film, electrode, groove, layer or bar is formed on or under the substrate, film, electrode, groove, layer or bar. In the case of what is described as being to be taken, "on" and "under" include both being formed "directly" or "indirectly" through 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.

1 is a plan view illustrating a solar cell module according to an embodiment. 2 is a plan view showing a screen mesh used for screen printing. 3 is a cross-sectional view taken along line AA ′ of FIG. 1.

Referring to FIG. 1, the solar cell module includes a solar cell array 10 and a bus bar 170.

The solar cell array 10 may be a CIGS-based solar cell, a silicon-based solar cell, a dye-sensitized solar cell, a II-VI compound semiconductor solar cell, or a III-V compound semiconductor solar cell.

The solar cell array 10 may be disposed on a transparent substrate 100 such as a glass substrate.

The solar cell array 10 includes a plurality of solar cells C1, C2 ... Cn. The solar cells C1, C2 ... Cn are separated by a separation pattern T.

The solar cell array 10 may be arranged in a stripe shape. In addition, the solar cell array 10 may be arranged in various forms such as a matrix (matrix) form.

The bus bar 170 includes a first bus bar 171 and a second bus bar 172.

The first bus bar 171 contacts the top surface of the solar cell C1 at one end of the solar cell array 10, and the second bus bar 172 is the other of the solar cell arrays 10. It may be in contact with the top surface of the solar cell (Cn) of one end.

The bus bar 170 may be formed to be in contact with the solar cell C1 and may be connected to a junction box (not shown) on the rear surface of the substrate 100 through a hole 180 formed in the substrate 100. .

The bus bar 170 may be a conductor, and may be a low-temperature baking paste. That is, the bus bar 170 may be a paste composition capable of baking at 100 to 150 ° C.

The specific resistance of the bus bar 170 may be 5 to 15 μm in thickness, and may be 3 × 10 ⁻⁶ to 5 × 10 ⁻⁶ Ωcm or less under a width of 1 to 4 mm.

For example, the bus bar 170 may be a metal such as silver (Ag).

The bus bar 170 may be formed by screen printing, inkjet printing, offset printing, or silk screen printing.

For example, after the pattern is printed on the paste composition by screen printing, the bus bar 170 may be formed by heat treatment at a temperature of 100 to 150 ° C.

Specifically, when the bus bar 170 is formed by screen printing, the screen mesh 200 as shown in FIG. 2 may be used.

The screen mesh 200 includes a first opening 210 and a second opening 220. The first and second openings 210 and 220 may be patterned in various forms according to the shape of the bus bar 170.

The screen mesh 200 is positioned on the solar cell array 10. Then, the metal paste is applied to the first and second openings 210 and 220 of the screen mesh 200 and then printed with a roller.

Thereafter, the bus bar 170 may be formed by performing a heat treatment process at a temperature of 100 to 150 ° C. and 1 to 30 minutes in a heat treatment apparatus such as an infrared apparatus and an oven.

In particular, as shown in FIG. 11, during the heat treatment process, the metal paste forming the bus bar 170 may be diffused to the surface of the front electrode layer 150 to form a junction region 175.

The adhesion between the front electrode layer 150 and the bus bar 170 may be improved by the junction region 175.

The bus bar 170 may be formed of a low temperature baking paste composition to reduce contact resistance by improving adhesion to the solar cell.

The bus bar 170 is formed at a low temperature, thereby preventing damage to the solar cell and improving light transmittance.

The bus bar 170 is formed by an automated process such as screen printing, thereby improving productivity.

The bus bar 170 may be formed only in a selective region by screen printing, thereby improving aesthetics.

The bus bar 170 may be formed as a single layer and thinned to improve aesthetics of the solar cell module.

3 is a cross-sectional view taken along line AA ′ of FIG. 1, illustrating the structure of a solar cell.

Referring to FIG. 3, the solar cell C1 includes a back electrode 110, a light absorbing layer 120, a buffer layer 130, a high resistance buffer layer 140, a front electrode 150, and a connection wiring formed on a substrate. 160 and bus bar 170.

The substrate 100 has a plate shape and may be an insulator.

The back electrode 110 is disposed on the substrate 100. The back electrode 110 may be formed of a conductor such as metal. For example, the back electrode may be a metal such as molybdenum (Mo).

In addition, the back electrode 110 may include two or more layers. In this case, each layer may be formed of a different material.

The light absorbing layer 120 is disposed on the back electrode 110.

The light absorbing layer 120 includes an Ib-IIIb-VIb-based compound.

For example, the light absorbing layer 120 is a copper-indium-gallium-selenide-based (Cu (In, Ga) Se ₂ , CIGS-based) compound, a copper-indium-selenide-based (CuInSe ₂ , CIS-based) compound Or a copper-gallium-selenide-based (CuGaSe ₂ , CGS-based) compound.

The buffer layer 130 is disposed on the light absorbing layer 120. The buffer layer 130 may be cadmium sulfide (CdS).

The high resistance buffer layer 140 is disposed on the buffer layer 130. The high resistance buffer layer 140 may be formed as a transparent electrode layer.

The front electrode 150 is disposed on the high resistance buffer layer 140. The front electrode 150 is transparent and a conductive layer.

The front electrode 150 is a window layer forming a pn junction with the light absorbing layer 120. Since the front electrode 150 functions as a transparent electrode on the front of the solar cell, the front electrode 150 may be formed of a material having high light transmittance and high electrical conductivity. .

For example, the front electrode layer 150 may be aluminum doped zinc oxide (Al doped ZnO: AZO).

The bus bar 170 is disposed on the front electrode layer 150. The bus bar 170 serves as an electrode for outputting power generated from the solar cell C1.

The bus bar 170 may be a paste composition capable of low temperature baking.

For example, the bus bar 170 may be silver (Ag).

The bus bar 170 may be formed in various shapes including a stripe shape.

The bus bar 170 formed of the paste composition may have improved adhesion to the front electrode 150 to reduce contact resistance.

In addition, transmittance and sheet resistance of the front electrode 150 may be improved.

4 to 11 are cross-sectional views illustrating a method of manufacturing the solar cell module according to the embodiment. For the description of the manufacturing method refer to the description of the solar cell module described above.

Referring to FIG. 4, the back electrode layer 110 is formed on the substrate 100.

The substrate 100 may be glass, and a ceramic substrate, a metal substrate, or a polymer substrate may also be used.

For example, soda lime glass or high strained point soda glass may be used as the glass substrate. As the metal substrate, a substrate including stainless steel or titanium may be used. As the polymer substrate, polyimide may be used.

The substrate 100 may be transparent. The substrate 100 may be rigid or flexible.

The back electrode layer 110 may be formed of a conductor such as metal.

Since the back electrode layer 110 is formed of a metal, the series resistance characteristics may be improved to increase conductivity. For example, the back electrode layer 110 may have a thickness of about 500 to 1500 nm and a sheet resistance of 0.1 to 1 Ω / □ or less.

For example, the back electrode layer 110 may be formed by a sputtering process using a molybdenum (Mo) target.

This is because of the high conductivity of molybdenum (Mo), ohmic bonding with the light absorbing layer, and high temperature stability under Se atmosphere.

The molybdenum (Mo) thin film, which is the back electrode layer 110, must have a low specific resistance as an electrode and have excellent adhesion to a substrate so that peeling does not occur due to a difference in thermal expansion coefficient.

The material forming the back electrode layer 110 is not limited thereto, and may be formed of molybdenum (Mo) doped with sodium (Na) ions.

Although not shown in the drawing, the back electrode layer 110 may be formed of at least one layer. When the back electrode layer 110 is formed of a plurality of layers, the layers constituting the back electrode layer 110 may be formed of different materials.

Referring to FIG. 5, a first through hole P1 is formed in the back electrode layer 110.

The first through hole P1 may selectively expose the top surface of the substrate 100. A plurality of back electrodes 110 are formed on the substrate 100 by the first through holes P1. That is, the back electrode 110 corresponding to each cell is defined by the first through hole P1. For example, the rear electrodes positioned on one side and the other side of the first through groove P1 are referred to as a first rear electrode and a second rear electrode, respectively.

The first through hole P1 is patterned by laser scribing. The first through hole P1 may have a width of about 50 μm to about 70 μm.

The back electrodes 110 may be arranged in a stripe shape or a matrix shape.

Referring to FIG. 6, the light absorbing layer 120, the buffer layer 130, and the high resistance buffer layer 140 are sequentially formed on the back electrode 110. In addition, the light absorbing layer 120 is filled in the first through hole P1.

The light absorbing layer 120 includes an Ib-IIIb-VIb-based compound.

For example, the light absorbing layer 120 is a copper-indium-gallium-selenide-based (Cu (In, Ga) Se ₂ , CIGS-based) compound, a copper-indium-selenide-based (CuInSe ₂ , CIS-based) compound Or a copper-gallium-selenide-based (CuGaSe ₂ , CGS-based) compound.

In order to form the light absorbing layer 120, a CIG-based metal precursor film is formed on the back electrode 110 using a copper target, an indium target, and a gallium target.

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

In addition, the light absorbing layer 120 may form copper (Cu), indium (In), gallium (Ga), selenide (Se) by co-evaporation.

For example, the light absorbing layer 120 may be formed to a thickness of 1000 ~ 2000nm.

The light absorbing layer 120 receives external light and converts the light into electrical energy. The light absorbing layer 120 generates photo electromotive force by the photoelectric effect.

Thereafter, cadmium sulfide (CdS) is deposited on the light absorbing layer 120 by a sputtering process, and the buffer layer 130 is formed. The buffer layer 130 may be formed to a thickness of 10 ~ 100nm.

In this case, the buffer layer 130 is an n-type semiconductor layer, the light absorbing layer 120 is a p-type semiconductor layer. Accordingly, the light absorbing layer 120 and the buffer layer 130 form a pn junction.

Zinc oxide (i-ZnO) is deposited on the buffer layer 130 by a sputtering process, and the high resistance buffer layer 140 is formed. The high resistance buffer layer 140 may be formed to a thickness of 10 ~ 100nm.

Referring to FIG. 7, a second through hole P2 penetrating the light absorbing layer 120, the buffer layer 130, and the high resistance buffer layer 140 is formed. The second through hole P2 may expose a portion of the second back electrode 110.

The second through hole P2 may be formed adjacent to the first through hole P1. The second through hole P2 may be patterned by a mechanical device such as a tip or a laser device.

For example, the width of the second through hole P2 may be 70 to 90 μm. In addition, the gap G1 between the first through hole P1 and the second through hole P2 may be 60 to 100 μm.

Referring to FIG. 8, the front electrode layer 150 is formed on the high resistance buffer layer 140. A material forming the front electrode layer 160 may also be filled in the second through hole P2, and a connection wiring 160 may be formed.

Therefore, the second rear electrode 110 and the front electrode layer 150 may be electrically connected by the connection wiring 160.

The front electrode layer 150 may be formed of zinc oxide or indium tin oxide (ITO) including impurities such as aluminum (Al), alumina (Al ₂ O ₃ ), magnesium (Mg), and gallium (Ga). .

For example, the front electrode layer 150 may be formed of zinc oxide doped with aluminum or alumina by a sputtering process to form an electrode having a low resistance value.

That is, the front electrode layer 150 is a window layer that forms a pn junction with the light absorbing layer 120. Since the front electrode layer functions as a transparent electrode on the front of the solar cell, zinc oxide (ZnO) having high light transmittance and high electrical conductivity is provided. Is formed.

For example, the front electrode layer 150 may be formed to a thickness of about 100 ~ 1000nm. In addition, the front electrode layer 150 has a sheet resistance of about 10 to 30 Ω / □, and may have a light transmittance of 80 to 90%.

9, a third through hole P3 penetrating the front electrode layer 150, the high resistance buffer layer 140, the buffer layer 130, and the light absorbing layer 120 is formed. The third through hole P3 may expose a portion of the second back electrode 110.

The third through hole P3 may be formed adjacent to the second through hole P2. The third through hole P3 may be patterned by a mechanical device or a laser device.

For example, the width of the third through hole P3 may be 70 to 90 μm. In addition, the gap G2 between the second through hole P2 and the third through hole P3 may be 60 to 100 μm.

That is, the front electrode layer 150 may be patterned to define a plurality of front electrodes and a plurality of cells C1 and C2.

Referring to FIG. 10, a bus bar 170 is formed on the front electrode 150.

The bus bar 170 may be formed of a low temperature baking paste composition.

For example, the bus bar 170 may be formed of a metal paste capable of low temperature baking at 100 to 150 ° C. The bus bar 170 may be formed of silver (Ag), copper (Cu), titanium (Ti), or an alloy thereof.

When the bus bar 170 is formed, aluminum doped zinc oxide (Al doped ZnO), which is a material constituting the front electrode 150, may be recrystallized. Accordingly, the sheet resistance and transmittance of the front electrode 150 can be improved.

In addition, during the heat treatment process, the metal paste forming the bus bar 170 may be diffused into the front electrode layer 150 to form a junction region 175.

For example, the bus bar 170 may have a resistivity of 5 × 10 ⁻⁶ Ωcm at a thickness of 1 to 10 μm and a width of 1 to 4 mm.

As an example, a process of forming the bus bar 170 by a screen printing process is as follows.

First, a low temperature baking paste composition for forming the bus bar 170 is formed.

Silver powder and PbO-SiO ₂ based, PbO-SiO ₂ -B ₂ O ₃ based, ZnO-SiO ₂ based, ZnO-B ₂ O ₃ -SiO ₂ based or Bi ₂ to obtain a paste composition An organic vehicle is prepared in which an O ₃ -B ₂ O ₃ -ZnO-SiO ₂ -based glass powder, a binder polymer, and a solvent are mixed. On the other hand, examples of the material used for the conductive particles include silver, copper, titanium and alloys thereof.

The silver powder may be mixed with a glass powder and a vehicle, which is a solvent, to be used as a conductive paste material. In this case, each composition ratio may be 50 to 85wt% silver powder, 1 to 20wt% glass powder and 10 to 48wt% vehicle.

The paste composition may be printed on the front electrode 150 by screen printing. That is, a screen mesh is placed on the front electrode 150, the paste composition is applied, and then printed with a roller. At this time, the paste composition is printed at a constant pressure and speed to a thickness of about 5 ~ 50um.

In order to remove the vehicle of the paste composition, the paste may be dried at 80 to 200 ° C. to form the bus bar 170.

Since the bus bar 170 is formed by a low temperature process using a low temperature baking paste composition, damage to the front electrode 150 may be prevented as much as possible.

Referring to FIG. 11, in the bus bar 170, a metal material may be diffused into the front electrode 150 by a heat treatment process to form a junction region 175.

Therefore, adhesion between the front electrode 150 and the bus bar 170 may be secured, thereby ensuring more excellent characteristics.

By the low temperature heat treatment process, the sheet resistance and transmittance of the bus bar 170 and the front electrode 150 may be improved.

In addition, it is possible to improve the efficiency of the solar cell module by lowering the contact resistance by improving the adhesion between the bus bar 170 and the front electrode 150.

In addition, since the bus bar 170 is formed in a single layer, its shape can be adjusted, thereby improving aesthetics.

In addition, the bus bar 170 can be produced by an automated process such as screen printing, thereby improving productivity.

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 embodiment can be modified. And differences relating to these modifications and applications will have to be construed as being included in the scope of the invention defined in the appended claims.

Experimental Example

Table 1 is an experimental example of a heat treatment process of the silver paste composition for forming a bus bar.

After the silver paste was coated on the front electrode layer by the screen printing method, heat treatment was performed in an infrared device, a first oven, and a second oven, respectively. At this time, the thickness of the paste composition was all coated with the same 1 ~ 10㎛.

In the infrared device, the heat treatment process was performed at 120 ° C. for 2 to 3 minutes, the heat treatment process was performed at 150 ° C. for 10 to 20 minutes in the first oven, and the heat treatment process was performed at 150 ° C. for 20 to 30 minutes in the second oven. Progressed.

According to the experimental example, it was confirmed that the specific resistance of the bus bar formed in the second oven was the lowest as 3 × 10 ⁻⁶ Ωcm.

Heat treatment device Temperature time Paste composition thickness Resistivity Infrared device (IR) 120 DEG C 2-3 minutes 1 ~ 10㎛ 5 × 10 ^-6 Ωcm Box oven 150 ℃ 10-20 minutes 1 ~ 10㎛ 5 × 10 ^-6 Ωcm Box oven 150 ℃ 20-30 minutes 1 ~ 10㎛ 3 × 10 ^-6 Ωcm

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

FIG. 2 is a plan view illustrating the shape of a screen mesh for forming the bus bar shown in FIG. 1.

3 is a cross-sectional view taken along the line A-A of FIG.

4 to 11 are cross-sectional views showing a manufacturing process of the solar cell module according to the embodiment.

Claims (7)

A CIGS solar cell including a back electrode, a light absorbing layer, a buffer layer and a front electrode layer stacked on a substrate; And And a bus bar formed on the front electrode layer and formed of a low temperature baking paste composition at 100 ° C. to 150 ° C., The paste composition is a silver powder and the conductive particles, PbO-SiO ₂ -based, PbO-SiO ₂ -B ₂ O ₃ -based, ZnO-SiO ₂ -based, ZnO-B ₂ O ₃ -SiO ₂ -based, or Bi ₂ O ₃ -B ₂ O ₃ -ZnO-SiO ₂ -based At least one glass powder, A solar cell module comprising at least one of an organic vehicle in which a binder polymer and a solvent are mixed. The method of claim 1, The bus bar is a solar cell module formed of a paste composition composed of silver (Ag), copper (Cu), titanium (Ti) or alloys thereof. The method of claim 1, The bus bar further includes a junction region diffused into the front electrode layer. Forming a CIGS solar cell including a back electrode, a light absorbing layer, a buffer layer and a front electrode layer on a substrate; Coating a low temperature baking paste composition at 100 to 150 ° C. to be connected to the front electrode layer of the solar cell, thereby forming a bus bar; The bus bar is formed of a paste composition composed of silver (Ag), copper (Cu), titanium (Ti), or an alloy thereof. The paste composition is a silver powder and the conductive particles, PbO-SiO ₂ -based, PbO-SiO ₂ -B ₂ O ₃ -based, ZnO-SiO ₂ -based, ZnO-B ₂ O ₃ -SiO ₂ -based, or Bi ₂ O ₃ -B ₂ O ₃ -ZnO-SiO ₂ -based At least one glass powder, A method of manufacturing a solar cell module obtained by manufacturing an organic vehicle in which a binder polymer and a solvent are mixed. 5. The method of claim 4, The bus bar is a method of manufacturing a solar cell module is formed by any one of screen printing, inkjet printing, offset printing and silk screen printing method. 5. The method of claim 4, Forming the bus bar, Forming a paste composition; Selectively coating a paste composition on an upper surface of the solar cell; And Performing a heat treatment process for the low temperature calcined material, The heat treatment process is a method of manufacturing a solar cell module, characterized in that for 1 to 30 minutes at a temperature of 100 ~ 150 ℃ using an infrared apparatus (IR) or oven (oven). The method of claim 6, The paste composition is a method of manufacturing a solar cell module further comprises forming a junction region by the paste composition to the front electrode layer during the heat treatment step.

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