KR101480394B1 - Low-resistance metal layer including backcontact and solar cell using the same, and methods of manufacturing them - Google Patents

Abstract

The present invention relates to a CIGS thin film solar cell having multiple layers of back electrodes, and in particular, to a method of manufacturing a solar cell rear electrode in a back electrode (200) formed on a substrate (100) Forming a low-resistance metal layer 210 on the substrate 100 of the battery by forming a low-resistance metal layer 210 on the low-resistance metal layer 210; (ii) forming a molybdenum (Mo) The photoelectric conversion efficiency of the solar cell is increased.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a back electrode having a low-resistance metal layer, a solar cell using the same, and a method of manufacturing the same,

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solar cell having an improved rear electrode and a method of manufacturing the same.

The solar cell is a device that converts light energy into electrical energy, and has attracted much attention as an environmentally friendly future energy source. A solar cell produces electricity using the properties of a semiconductor. Specifically, the solar cell has a PN junction structure in which a P (positive) semiconductor and a N (negative) semiconductor are bonded. When solar light enters the solar cell, Holes and electrons are generated in the semiconductor due to the energy of the solar light. At this time, the holes move to the P-type semiconductor due to the electric field generated at the PN junction, and the electrons move to the N-type semiconductor And a potential is generated.

The solar cell can be classified into a substrate type solar cell and a thin film type solar cell. The substrate type solar cell is a solar cell using a semiconductor material itself such as silicon as a substrate. The thin film type solar cell has a thin film type To form a semiconductor layer to manufacture a solar cell. Recently, as shown in Fig. 1, the efficiency is improved by developing a solar cell using a CIGS light absorbing layer.

In order to increase the photoelectric conversion efficiency of the solar cell, the proportion of sunlight absorbed in the light absorbing layer must be increased. In the case of a thin film solar cell, the manufacturing cost can be lowered by using a thin film light absorbing layer as compared with a substrate solar cell, but the light absorption rate is lowered. In order to overcome such a decrease in the light absorptivity, there is a method of imparting surface unevenness to the unit functional film of the solar cell.

When the sunlight is incident in a state in which the surface uneven structure is formed, scattering of sunlight occurs when the sunlight strikes the unevenness, so that the ratio of sunlight absorbed in the light absorbing layer can be increased. That is, the scattered light spreads the light path in the light absorbing layer, and even if the light absorbing layer is made into a thin film, the probability of being absorbed into the light absorbing layer is increased, and the efficiency of the solar cell can be increased.

The CIGS light-absorbing layer-based solar cell is manufactured by sequentially forming a back-surface electrode (backcontact) such as molybdenum and a CIGS light absorption layer on a glass substrate. A method for manufacturing such a rear electrode is disclosed in U.S. Patent No. 6,258,620. In this patent, molybdenum is deposited on a bilayer by sputter deposition,

Structure in which a first molybdenum layer exhibiting a high adhesion to the substrate is formed under a relatively high argon pressure in a first step and a second molybdenum layer is formed on the first layer in a second step under a relatively low argon pressure, To form a second molybdenum layer of low resistivity. However, the above-mentioned patent only discloses the formation of a conductive layer of a bi-layer structure, and it has been confirmed that the conductive layer produced by the patent fails to exhibit a sufficiently low resistivity to a desired degree. In addition, according to the above patent, the high density between metal atoms causes the diffusion of sodium supplied from the substrate to be suppressed, thereby lowering the effective process concentration, which is an important factor for the performance of the solar cell.

Korean Patent Registration No. 10-0838167 is directed to a method of manufacturing a back electrode of a solar cell having a CI (G) S (Cupper-Indium-Gallium-Selenide) light absorbing layer. In a sputtering process for forming a back electrode, And the RF bias is simultaneously applied to the substrate during the DC sputtering to improve the characteristics of the electrode. That is, a method of manufacturing a back contact of a solar cell including a CI (G) S (Cupper-Indium-Gallium-Selenide) light absorbing layer, comprising the steps of: (a) performing DC sputtering under a reaction gas of 5 to 15 mTorr pressure Forming a first conductive layer on the substrate by the first conductive layer; And (b) forming a second conductive layer on the first conductive layer by DC sputtering while applying an RF bias on the substrate under a reaction gas of 1 to 5 mTorr pressure in a range lower than the pressure of the process (a) . According to the present invention, by changing the pressure of the reactive gas supplied in the sputtering process, it is possible to manufacture a rear electrode which is excellent in adhesion between the electrode and the glass substrate and facilitates sodium diffusion, By applying the bias at the same time, it is possible to manufacture a back electrode having a relatively low resistivity electrode characteristic. However, since materials other than molybdenum are not presented for the material of the rear electrode, there is a limit in improving the resistivity.

In order to increase the photoelectric conversion efficiency of the solar cell, it is important to increase the ratio of the sunlight absorbed in the light absorbing layer, but it is also not negligible to reduce the resistance of the rear electrode. That is, a technique of minimizing the loss of the generated current and reducing the specific resistance of the back electrode is required.

Accordingly, the present invention provides a method of manufacturing a solar cell back electrode,

(i) forming (S1000) a low-resistance metal layer 210 on the substrate 100 of the solar cell with a low-resistance metal having a resistance lower than that of molybdenum (Mo);

(ii) forming a molybdenum (Mo) layer 220 on the low-resistance metal layer 210 (s2000);

To solve the above problems.

According to the present invention, the molybdenum of the molybdenum (Mo) layer forms selenized molybdenum by selenization reaction with selenium (Se) of the CIGS light absorption layer to improve the contact resistance of the rear electrode, and the low resistance metal layer at the bottom of the molybdenum layer It has the effect of lowering the overall sheet resistance value.

As a result, it is possible to increase the photoelectric conversion efficiency of the solar cell by reducing the resistivity of the rear electrode and improving the contact resistance to reduce the recombination of electrons and holes.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a cross-sectional view of a main part of a solar cell using a general CIGS light absorption layer. FIG.
FIG. 2 is an exploded perspective view of a backlight unit 200 and a solar cell according to an embodiment of the present invention.
3 is a cross-sectional view showing a backside electrode 200 and a solar cell according to the present invention.
4 is an explanatory view for explaining the formation of molybdenum selenide (MoSe) at the interface between the back electrode 200 and the light absorbing layer 300 of the present invention.
5 is a flow chart illustrating a method of manufacturing a solar cell of the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION One embodiment of a method of manufacturing a solar cell having a double back electrode having a concavo-convex structure according to the present invention will be described below with reference to the accompanying drawings.

FIG. 2 is an exploded perspective view showing the back electrode and the solar cell according to the present invention. FIG. 3 is a cross-sectional view of a main part showing a back electrode 200 and a solar cell according to the present invention.

The present invention relates to a method of manufacturing a solar cell rear electrode,

(i) forming (S1000) a low-resistance metal layer 210 on the substrate 100 of the solar cell with a low-resistance metal having a resistance lower than that of molybdenum (Mo);

(ii) forming a molybdenum (Mo) layer 220 on the low-resistance metal layer 210 formed of a low-resistance metal having a resistance lower than that of the molybdenum (s2000);

And a control unit.

The low-resistance metal in step (s1000) of forming the low-resistance metal layer 210 with a low-resistance metal having resistance lower than molybdenum (Mo) on the substrate 100 of the solar cell (i) is silver (Ag), copper Cu), aluminum (Al), and zinc (Zn).

In step (s1000) of forming a low-resistance metal layer 210 with a low-resistance metal on the substrate 100 of the solar cell, the low-resistance metal layer 210 may be formed by sputtering a low resistance metal, The deposition method, electron beam deposition, chemical vapor deposition, atomic layer deposition, electrochemical deposition, spray coating, doctor blade coating, screen printing, inkjet coating, thermal evaporation, electron beam evaporation, electrodeposition, plating, sputtering, , And a plating method using at least one method.

Preferably, the low-resistance metal layer 210 has a thickness of 100 nm to 10 μm through the deposition process.

The molybdenum (Mo) layer 220 is formed in step (s2000) of forming a molybdenum (Mo) layer 220 on the metal layer 210 formed of a low resistance metal having lower resistance than the low resistance molybdenum (Mo) Sputtering, cathodic arc deposition, vapor deposition, electron beam deposition, chemical vapor deposition, atomic layer deposition, electrochemical deposition, spray coating, doctor blade coating, screen printing, inkjet coating, thermal evaporation, electron beam evaporation, electrodeposition, Deposition method, electron beam deposition method, electrodeposition method, or plating method.

The thickness of the molybdenum (Mo) layer 220 is preferably 100 nm to 5 μm. As shown in FIG. 4, the molybdenum layer has a high basic resistance value. However, since the molybdenum layer is formed to reduce the contact resistance by forming selenium (Se) and selenized molybdenum in the CIGS layer, .

In addition, the molybdenum (Mo) layer 220 is not limited to a single layer and may be composed of multiple layers. For example, it is possible to constitute a molybdenum lower layer doped with sodium (Na) and a molybdenum upper layer composed solely of molybdenum for ease of sodium (Na) diffusion, forming a first conductive layer on the substrate by DC sputtering under a reaction gas of mTorr pressure; And a method of forming a second conductive layer on the first conductive layer by DC sputtering while applying an RF bias on the substrate under a reaction gas of 1 to 5 mTorr pressure in a range lower than the pressure of the process It is. In the case of such a multilayer structure, it is preferable that the thickness of each layer is evenly divided into the thickness of the entire molybdenum layer 220.

The present invention further provides a method of manufacturing a solar cell using the above-described rear electrode.

5 is a flow chart illustrating a method of manufacturing the solar cell of the present invention. As shown in Fig. 5, in the method for manufacturing a solar cell of the present invention,

(i) preparing a substrate 100 (s100);

(ii) forming a rear electrode layer 200 on the substrate (s200);

(iii) forming (S 300) a CIGS light absorption layer 300 including copper, indium, gallium, and selenium on the rear electrode layer 200;

(iv) forming (S400) a buffer layer 400 including at least one of CdS, ZnS, and InOH on the light absorption layer 300;

(v) In the case where zinc oxide, gallium oxide, aluminum oxide, indium oxide, lead oxide, copper oxide, titanium oxide, tin oxide, iron oxide, tin dioxide, indium tin oxide and oxides of two or more of these substances (S500) forming a transparent conductive layer (500) including at least one of the transparent conductive layer (500);

Wherein:

The step (s200) of forming the rear electrode layer 200 on the substrate includes a method of fabricating the rear electrode having the above-described low resistance metal layer.

The step of forming a CIGS light absorbing layer 300 including copper, indium, gallium and selenium on the rear electrode layer 200 may include a coevaporation method, a sputtering method, an electrodeposition method, Any one of MOCVD, molecular beam epitaxy (MBE), screen printing, and particle deposition may be used.

Molybdenum selenide is formed on the interface between the molybdenum layer 220 and the light absorbing layer 300 after the CIGS light absorbing layer 300 is formed on the rear electrode layer 200. By forming the above-mentioned molybdenum selenide or the like, contact resistance is reduced and electron-hole recombination is reduced.

The step of forming a buffer layer 400 including at least one of CdS, ZnS and InOH on the light absorption layer 300 may be performed by a solution growth method (CBD), an electrodeposition method, a coevaporation method, In addition, the sputtering method, the atomic layer epitaxy method, the atomic layer deposition method, the chemical vapor deposition method, the metalorganic chemical vapor deposition method, the molecular beam epitaxy method, the spray pyrolysis method, It is preferable to apply at least one of the following methods: Spray pyrolysis, Ion Layer Gas Reaction (ILGAR), and Pulsed Laser Deposition.

An oxide of gallium oxide, gallium oxide, aluminum oxide, indium oxide, lead oxide, copper oxide, titanium oxide, tin oxide, iron oxide, tin dioxide, indium tin oxide and oxides of two or more of these The transparent conductive layer 500 may be formed by a sputtering method, an RF sputtering method, a DC sputtering method, a reactive sputtering method, a reactive sputtering method, (E-beam evaporation), MOCVD, Atomic Layer Epitaxy, Molecular Beam Growth (MBE), or Electrodeposition, which is one of the methods of evaporation, evaporation, evaporation, E-beam evaporation, To be deposited. Also, a front electrode 600 (a grid electrode) and an antireflection film 700 may be provided on the transparent conductive layer 500.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it should be understood that various changes and modifications will be apparent to those skilled in the art. Obviously, the invention is not limited to the embodiments described above. Accordingly, the scope of protection of the present invention should be construed according to the following claims, and all technical ideas which fall within the scope of equivalence by alteration, substitution, substitution, Range. In addition, it should be clarified that some configurations of the drawings are intended to explain the configuration more clearly and are provided in an exaggerated or reduced size than the actual configuration.

100: substrate
200: rear electrode
210: Low resistance metal layer
200: molybdenum (Mo) layer
300: light absorbing layer
400: buffer layer
500: transparent conductive layer
600: front electrode layer
700: antireflection film

Claims (13)

A method of manufacturing a solar cell rear electrode,
(i) forming (S1000) a low-resistance metal layer 210 on the substrate 100 of the solar cell with a low-resistance metal having a resistance lower than that of molybdenum (Mo);
(ii) forming a molybdenum (Mo) layer 220 on the low-resistance metal layer 210 formed of a low-resistance metal having a resistance lower than that of the molybdenum (s2000);
/ RTI >
The low resistance metal in step (s1000) of forming the low resistance metal layer 210 with a low resistance metal having a resistance lower than that of molybdenum (Mo) on the substrate 100 of the solar cell (i) is silver (Ag) Zinc (Zn), the thickness of the low-resistance metal layer 210 is 100 nm to 10 μm,
In step (s2000) of forming a molybdenum (Mo) layer 220 on the low-resistance metal layer 210 formed of a low-resistance metal having lower resistance than molybdenum (Mo), the molybdenum (Mo) And the molybdenum (Mo) layer 220 is composed of a molybdenum lower layer 221 doped with sodium (Na) and a molybdenum upper layer 222 composed only of molybdenum Wherein the metal layer has a lower resistance than that of molybdenum (Mo).
delete The method according to claim 1,
The low-resistance metal layer 210 of the step (s1000) of forming the low-resistance metal layer 210 with a low-resistance metal having a resistance lower than that of molybdenum (Mo) on the substrate 100 of the solar cell is performed by sputtering, The present invention relates to a method of forming a metal film by vapor deposition, vapor deposition, electron beam evaporation, chemical vapor deposition, atomic layer deposition, electrochemical deposition, spray coating, doctor blade coating, screen printing, inkjet coating, thermal evaporation, electron beam evaporation, electrodeposition, , An electrodeposition method, and a plating method. The method for manufacturing a rear electrode according to claim 1, wherein the metal layer is formed of a metal having a lower resistance than molybdenum (Mo).
delete The method according to claim 1,
The molybdenum (Mo) layer 220 of step (s2000) of forming a molybdenum (Mo) layer 220 on the low resistance metal layer 210 formed of a low resistance metal having a lower resistance than the molybdenum (Mo) Sputtering, cathodic arc deposition, vapor deposition, electron beam deposition, chemical vapor deposition, atomic layer deposition, electrochemical deposition, spray coating, doctor blade coating, screen printing, inkjet coating, thermal evaporation, electron beam evaporation, electrodeposition, Wherein the metal layer is formed by vapor deposition using at least one of vacuum evaporation, evaporation, electron beam evaporation, electrodeposition, and plating.
delete delete A method of manufacturing a solar cell,
(i) preparing a substrate 100 (s100);
(ii) forming a rear electrode layer 200 on the substrate (s200);
(iii) forming (S 300) a CIGS light absorption layer 300 including copper, indium, gallium, and selenium on the rear electrode layer 200;
(iv) forming (S400) a buffer layer 400 including at least one of CdS, ZnS, and InOH on the light absorption layer 300;
(v) In the case where zinc oxide, gallium oxide, aluminum oxide, indium oxide, lead oxide, copper oxide, titanium oxide, tin oxide, iron oxide, tin dioxide, indium tin oxide and oxides of two or more of these substances (S500) forming a transparent conductive layer (500) including at least one of the transparent conductive layer (500);
Wherein:
A method of manufacturing a solar cell according to claim 1, wherein the step (s200) of forming the rear electrode layer (200) on the substrate (ii) comprises the method according to any one of claims 1, 3 and 5.
In the rear electrode 200 formed on the substrate 100 of the solar cell,
The rear electrode 200 is composed of multiple layers of a low-resistance metal layer 210 and a molybdenum layer 220, the resistance of which is lower than that of molybdenum (Mo)
The low resistance metal of the low resistance metal layer 210 may include silver (Ag) or zinc (Zn)
The low-resistance metal layer 210 has a thickness of 100 nm to 10 μm,
Wherein the molybdenum layer (220) is formed to have a thickness of 90 nm to 5 nm so as to have a thickness smaller than that of the low-resistance metal layer.
delete delete delete In solar cells,
A back layer 200 formed on the substrate 100; a light absorption layer 300 formed on the rear electrode layer 200; a buffer layer 400 formed on the light absorption layer 300; And a transparent conductive layer 500 formed on the buffer layer 400,
The rear electrode layer 200 is formed as the rear electrode of claim 9;
Wherein the light absorption layer (300) is a CIGS light absorption layer comprising copper, indium, gallium, and selenium.

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