KR101550927B1 - Solar cell and method of fabircating the same - Google Patents

Abstract

A solar cell according to an embodiment includes an electrode substrate including a plurality of rear electrodes and an insulating bonding unit interconnecting the rear electrodes; And a light absorbing layer, a buffer layer, and a front electrode layer formed on the electrode substrate. The rear electrode may be formed as a supporting substrate to improve the efficiency of the solar cell.

Solar cell, substrate

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a solar cell,

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

As energy demand has increased in recent years, development of solar cells that convert solar energy into electrical energy is underway.

In particular, a CIGS-based solar cell as a pn heterojunction device having a substrate structure including a film-type substrate, a metal back electrode layer, a p-type CIGS light absorbing layer, a high resistance buffer layer, and an n-type window layer is widely used.

Such a solar cell is formed sequentially from the back surface of the substrate, and the film may be deformed when the layers are formed.

In addition, physical damage may occur due to difficulty in maintaining the flatness of the substrate during the patterning process for each layer.

Embodiments provide a solar cell in which a back electrode and a supporting substrate are integrated, and a method of manufacturing the solar cell.

A solar cell according to an embodiment includes an electrode substrate including a plurality of rear electrodes and an insulating bonding unit interconnecting the rear electrodes; And a light absorption layer, a buffer layer, and a front electrode layer formed on the electrode substrate.

A method of manufacturing a solar cell according to an embodiment includes forming a first rear electrode and a second rear electrode that are separated from each other; And forming an electrode substrate by bonding the first back electrode and the second back electrode with an insulating adhesive, and forming a light absorption layer, a buffer layer, and a front electrode layer on the electrode substrate.

According to the embodiment, the rear electrodes can be connected to each other by the insulating bonding portion.

Accordingly, since the rear electrode and the insulating bonding part can serve as the supporting substrate, a separate substrate can be omitted.

In addition, since the rear electrode is electrically separated by the insulating bonding portion, a separate patterning process can be omitted.

 That is, since it is not necessary to perform the rear electrode deposition and patterning process on the substrate as in the conventional art, the short circuit of the rear electrode can be prevented in advance and the process can be simplified.

Since the rear electrode and the insulating bonding portion can be flexible, they can be applied to various products.

In the description of the embodiments, in the case where each substrate, layer, film or electrode is described as being formed "on" or "under" of each substrate, layer, film, , "On" and "under" all include being formed "directly" or "indirectly" through "another element". 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.

Referring to Fig. 1, an electrode substrate 100 is prepared.

The electrode substrate 100 may be a flexible substrate.

The electrode substrate 100 includes a plurality of rear electrodes 110 and 120 and an insulating bonding unit 150 disposed between the rear electrodes 110 and 120.

For example, the rear electrodes 110 and 120 adjacent to each other are referred to as a first rear electrode 110 and a second rear electrode 120, respectively.

That is, the first and second rear electrodes 110 and 120 may be connected to each other by the insulating bonding unit 150.

The first back electrode 110, the second back electrode 120 and the insulating bonding part 150 may have the same thickness and the electrode substrate 100 may have a flat upper surface.

Accordingly, the electrode substrate 100 can serve both as a support substrate and as an electrode

The first and second rear electrodes 110 and 120 may be formed of a conductive material such as a metal.

For example, the first and second rear electrodes 110 and 120 may be formed of a material including at least one of Mo, Al, Cu, and An, or may be an alloy film of the materials.

The insulating bonding portion 150 may be an insulating adhesive or an insulating adhesive such as epoxy, UV adhesive, and thermosetting adhesive.

That is, the first and second rear electrodes 110 and 120 are connected to each other by the insulating bonding part 150, which is an insulating adhesive, and may be formed in a flat substrate shape.

The first and second electrodes 110 and 120 are electrically isolated from each other by the insulating bonding unit 150.

Accordingly, the light absorbing layer and the window layer forming process may be performed in a subsequent process on the electrode substrate 100 including the first and second back electrodes 110 and 120.

In order to form the electrode substrate 100, the first rear electrode 110 and the second rear electrode 120 are formed by performing a patterning process.

Although not shown, the first and second rear electrodes 110 and 120 may be patterned by cutting a metal thin film such as a metal foil.

Next, an insulating adhesive is coated on the sidewalls of the first and second back electrodes 110 and 120 to form the insulating bonding part 150. The electrode substrate 100 may be formed by bonding the first and second back electrodes 110 and 120 with the insulating bonding unit 150.

As shown in FIG. 2, an insulating adhesive is coated on the upper or lower edge of the first and second back electrodes 110 and 120 to form an insulating bonding part 150.

The first and second rear electrodes 110 and 120 are positioned such that the edges of the first and second rear electrodes 110 and 110 overlap with each other. The electrode 120 can be bonded.

That is, a portion of the second rear electrode 120 may overlap the upper or lower edge of the first rear electrode 110.

Thereafter, a rolling process is performed on the first and second rear electrodes 110 and 120 with the insulating bonding part 150 interposed therebetween, and the surface of the electrode substrate 101 is planarized .

In particular, step portions 115 and 125 are formed in the overlapping regions of the first and second back electrodes 110 and 120 by the rolling process. In addition, the insulating bonding portion 150 may be formed in a stepped shape along the shape of the stepped portions 115 and 125.

Accordingly, the bonding area between the first and second back electrodes 110 and 120 and the insulating bonding part 150 can be enlarged.

In addition, since the stepped portions 115 and 125 are filled with the insulating bonding portion 150, bonding strength between the first and second rear electrodes 110 and 120 can be improved.

As described above, the rear electrodes 110 and 120 are connected to each other by the insulating bonding part 150, and the electrode substrates 100 and 101 can be formed.

Accordingly, since the electrode substrates 100 and 101 serve as the supporting substrate of the solar cell, the size and thickness of the solar cell can be reduced.

In addition, since the rear electrodes 110 and 120 are insulated by the insulating bonding parts 150 and 155, it is possible to prevent short-circuiting of the electrodes during the patterning process.

In addition, since the rear electrodes 110 and 120 corresponding to respective cells are formed on the electrode substrates 100 and 101, a separate rear electrode deposition and patterning process can be omitted and the productivity can be improved.

In addition, since the electrode substrates 100 and 101 are formed of the thin film type back electrodes 110 and 120 and the insulating bonding parts 150 and 155, they can have a flexible material.

4 to 8, a method of forming a solar cell on an electrode substrate including a rear electrode will be described.

4, a light absorption layer 201, a buffer layer 301, and a high-resistance buffer layer 401 are formed on an electrode substrate 100. [

The electrode substrate 100 includes a first rear electrode 110, a second rear electrode 120, and an insulating bonding unit 150.

That is, the first rear electrode 110 and the second rear electrode 120 are bonded to each other by the insulating bonding portion 150, and the electrode substrate 100 may be formed.

3, step portions 115 and 125 are formed on the first rear electrode 110 and the second rear electrode 120, and the insulating bonding portion 150 is formed on the step portions 115 and 125, May be formed of the electrode substrate 100 in which the electrode substrate 100 is interposed.

The insulating bonding unit 150 may electrically isolate the first and second back electrodes 110 and 120 from each other.

That is, the insulating bonding part 150 physically connects and electrically isolates the first and second rear electrodes 110 and 120.

For example, the insulating bonding portion 150 may have a width of 0.1 to 3 mm.

Since the electrode substrate 100 has a flat surface, the components of the solar cell formed on the electrode substrate 100 can be easily formed.

A light absorbing layer 201 is formed on the electrode substrate 100.

The light absorption layer 201 includes a compound of the formula Ib-IIIb-VIb.

More specifically, the light absorption layer 201 includes a copper-indium-gallium-selenide (Cu (In, Ga) Se ₂ , CIGS system) compound.

Alternatively, the light absorption layer 201 may include a copper-indium-selenide (CuInSe ₂ , CIS) compound or a copper-gallium-selenide (CuGaSe ₂ , CIS) compound.

For example, in order to form the light absorption layer 201, a CIG-based metal precursor film is formed on the first and second rear electrodes 110 and 120 using a copper target, an indium target, and a gallium target do.

Thereafter, the metal precursor film is reacted with selenium (Se) by a selenization process to form a CIGS light absorbing layer 201.

The light absorption layer 201 may be formed by co-evaporation of copper, indium, gallium, selenide (Cu, In, Ga, Se).

For example, the light absorption layer 201 may be about 2000 +/- 500 nm.

The light absorbing layer 201 receives external light and converts it into electric energy. The light absorption layer 201 generates a photoelectromotive force by a photoelectric effect.

Referring to FIG. 4, a buffer layer 301 and a high-resistance buffer layer 401 are formed on the light absorption layer 201.

The buffer layer 301 may be formed of at least one layer on the light absorption layer 201, and may be formed by laminating CdS by CBD process.

For example, the buffer layer 301 may have a thickness of 50 ± 10 nm.

At this time, the buffer layer 301 is an n-type semiconductor layer, and the light absorption layer 201 is a p-type semiconductor layer. Therefore, the light absorption layer 201 and the buffer layer 301 form a pn junction.

The high resistance buffer layer 401 may be formed as a transparent electrode layer on the buffer layer 301.

For example, the high resistance buffer layer 401 may be formed of any one of ITO, ZnO, and i-ZnO.

The high resistance buffer layer 401 may be formed of a zinc oxide layer by performing a sputtering process using zinc oxide (ZnO) as a target.

For example, the high resistance buffer layer 401 may be formed to a thickness of 50 +/- 10 nm.

The buffer layer 301 and the high-resistance buffer layer 401 are disposed between the light absorption layer 201 and a front electrode formed afterward.

That is, since the difference between the lattice constant and the energy band gap is large between the light absorption layer 201 and the front electrode layer, the buffer layer 301 and the high resistance buffer layer having the bandgap between the two materials are inserted to form a good junction can do.

In this embodiment, two buffer layers are formed on the light absorbing layer 201, but the present invention is not limited to this, and the buffer layer 301 may be formed of only one layer.

Referring to FIG. 5, a through hole 450 is formed through the high resistance buffer layer 401, the buffer layer 301, and the light absorbing layer 201. The through holes 450 may selectively expose the first and second back electrodes 110 and 120.

The light absorbing layer 201, the buffer layer 301 and the high resistance buffer layer 401 are patterned by unit cells through the through holes 450. The light absorbing pattern 200, the buffer pattern 300, (400) is formed.

The through hole 450 may be formed by a mechanical device such as a tip or a laser device.

The through hole 450 may be formed adjacent to the insulating bonding portion 150.

For example, the width of the through hole 450 may be 80 μm ± 20, and the gap G 1 between the through hole 450 and the insulating bonding portion 150 may be 80 μm ± 20 μm.

Referring to FIG. 6, a front electrode layer 501 is formed by laminating a transparent conductive material on the high-resistance buffer layer 401.

When the front electrode layer 501 is formed, the transparent conductive material may be inserted into the through holes 450 to form the connection wiring 600.

The front electrode layer 501 is formed of zinc oxide doped with aluminum (Al) or alumina (Al ₂ O ₃ ) through a sputtering process.

For example, the front electrode layer 501 may have a thickness of 500 nm ± 100, a sheet resistance of about 0.2 Ω / □, and a transparency of 80 to 95%.

The front electrode layer 501 is a window layer that forms a pn junction with the light absorption pattern 200. The front electrode layer 501 functions as a transparent electrode on the entire surface of the solar cell and thus has a high light transmittance and excellent electrical conductivity. .

Therefore, by doping the zinc oxide with aluminum or alumina, an electrode having a low resistance value can be formed.

The zinc oxide thin film that is the front electrode layer 501 may be formed by a method of depositing using a ZnO target by an RF sputtering method, reactive sputtering using a Zn target, and an organic metal chemical vapor deposition method.

In addition, a double structure in which an ITO (Indium Thin Oxide) thin film excellent in electro-optical characteristics is laminated on a zinc oxide thin film may be formed.

7, a front electrode layer 501, a high-resistance buffer pattern 400, a buffer pattern 300, and a separation pattern 550 penetrating the light absorption pattern 200 are formed.

The separation pattern 550 may selectively expose the first and second rear electrodes 110 and 120. The separation pattern 550 may be formed adjacent to the through-hole 450.

For example, the width of the separation pattern 550 may be 80 μm ± 20, and the gap G 2 between the separation pattern 550 and the through hole 450 may be 80 μm ± 20 μm.

The separation pattern 550 may be formed by irradiating a laser or by a mechanical method such as a tip.

Therefore, the front electrode 500 can be divided into unit cells by the separation pattern 550. That is, each of the cells C1 and C2 can be separated from each other by the separation pattern 550.

The light absorption pattern 200, the buffer patterns 300 and 400, and the front electrode 500 may be arranged in a stripe form or a matrix form by the separation pattern 550.

The separation pattern 550 is not limited to the above-described embodiment, and may be formed in various shapes.

At this time, each of the cells C1 and C2 may be connected to each other by the connection wiring 600. That is, the connection wiring 600 physically connects the first rear electrode 110 of the first cell C1 and the front electrode 600 of the second cell C2 adjacent to the first cell C1, Can be electrically connected.

Referring to FIG. 8, a bus bar 700 is formed on one of the cells C1 and C2.

The bus bar 700 may function as both an electrode and a negative electrode in order to output power generated in the cells C1 and C2 to the outside.

For example, the bus bar 700 may be attached to the front electrode 500 by a thermal fusion method using solder metal.

Next, a back sheet 10 is attached to the rear surface of the electrode substrate 100 to protect the electrode substrate 100.

For example, the backsheet 10 may be an eva film.

The back sheet 10 is attached to the rear surface of the electrode substrate 100 to protect and insulate the rear electrodes 110 and 120 from each other.

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 the present invention may be embodied in many other specific forms without departing from the spirit or essential characteristics thereof.

1 to 3 are sectional views showing an electrode substrate according to an embodiment.

4 to 8 are cross-sectional views illustrating a manufacturing process of a solar cell according to an embodiment.

Claims (9)

An electrode substrate including a plurality of rear electrodes and an insulating bonding portion interconnecting the rear electrodes; And A light absorbing layer formed on the electrode substrate, a buffer layer, and a front electrode layer, Further comprising a first step formed in an edge region of the rear electrode, Wherein the insulating bonding portion includes a second step portion corresponding to the shape of the first step portion. The method according to claim 1, Wherein the insulating bonding portion is an insulating adhesive or an insulating adhesive. The method according to claim 1, Wherein the rear electrode comprises any one of Mo, Al, Cu and Sn. The method according to claim 1, Wherein the insulating bonding portion has a width of 0.1 to 3 mm. delete Forming a first rear electrode and a second rear electrode mutually separated; And And bonding the first back electrode and the second back electrode with an insulating adhesive to form an electrode substrate, A part of the first rear electrode and a part of the second rear electrode are positioned to overlap with each other, A step is formed in the first back electrode, the insulating adhesive and the second back electrode by a rolling process, And forming a light absorption layer, a buffer layer, and a front electrode layer on the electrode substrate. The method according to claim 6, And bonding the first and second back electrodes to each other using an insulating adhesive, and then performing a rolling process on the first and second back electrodes. delete The method according to claim 6, Wherein the insulating adhesive is one of an epoxy, a UV adhesive, and a thermosetting adhesive.

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