KR101765922B1 - Solar cell apparatus and method of fabricating the same - Google Patents

Abstract

A solar cell according to an embodiment includes a substrate; A back electrode layer on the substrate; A light absorbing layer on the back electrode layer; A buffer layer on the light absorbing layer; And a first window layer containing impurities of at least one of a Group 6 element or a Group 9 element on the buffer layer.

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 the demand for energy has increased in recent years, the development of solar cells for converting solar energy into electric energy is underway.

Particularly, a CIGS-based solar cell which is a pn heterojunction device of a supporting substrate structure including a glass supporting substrate, a metal back electrode layer, a p-type CIGS light absorbing layer, a buffer layer, and an n-type transparent electrode layer is widely used.

Various studies are underway to increase the efficiency of such solar cells.

The embodiments are directed to a solar cell including a window layer having improved chemical resistance, and a manufacturing method thereof.

A solar cell according to an embodiment includes a substrate; A back electrode layer on the substrate; A light absorbing layer on the back electrode layer; A buffer layer on the light absorbing layer; And a first window layer containing impurities of at least one of a Group 6 element or a Group 9 element on the buffer layer.

A method of manufacturing a solar cell according to an embodiment includes forming a back electrode layer on a substrate; Forming a light absorption layer on the back electrode layer; Forming a buffer layer on the light absorbing layer; And forming a first window layer including at least one impurity of a Group 6 element or a Group 9 element on the buffer layer.

In general, the window layer of a CIS-based solar cell is vulnerable to acids and bases and has low chemical resistance. Thus, in the patterning process for separating into a plurality of solar cells, over etching may occur outside the etching region, which may cause contact failure. Also, when the window layer is exposed to the outside, reliability is deteriorated depending on the surrounding environment.

In the present invention, the window layer is doped with at least one element of the group 6 element or the group 9 element to improve chemical resistance, thereby providing a solar cell with improved contact reliability and improved reliability.

1 is a plan view showing a photovoltaic generator according to an embodiment.
FIG. 2 is a cross-sectional view showing a section cut along AA 'in FIG. 1; FIG.
3 is a cross-sectional view showing a contact failure of the window layer according to the prior art.
4 to 6 are cross-sectional views illustrating a method of manufacturing a solar cell according to an embodiment.

In the description of the embodiments, when it is described that each supporting substrate, layer, film or electrode is formed "on" or "under" of each supporting substrate, layer, film, The terms " 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.

1 is a cross-sectional view taken along the line AA 'in FIG. 1, and FIG. 3 is a cross-sectional view of the photovoltaic device according to the prior art, Fig.

2, a solar cell according to an embodiment includes a support substrate 100, a back electrode layer 200, a light absorption layer 300, a buffer layer 400, a high resistance buffer layer 500, and a window layer 600 do.

The supporting substrate 100 has a plate shape and supports the back electrode layer 200, the light absorbing layer 300, the buffer layer 400, the high resistance buffer layer 500, and the window layer 600.

The support substrate 100 may be an insulator. The support substrate 100 may be a glass substrate, a plastic substrate, or a metal substrate. More specifically, the support substrate 100 may be a soda lime glass substrate.

When the supporting substrate 100 is soda lime glass, sodium (Na) contained in the soda lime glass can be diffused into the light absorption layer 300 formed by CIGS during the manufacturing process of the solar cell, whereby the light absorption layer 300 May be increased. This can be a factor for increasing the photoelectric conversion efficiency of the solar cell.

In addition, as the material of the support substrate 100, a ceramic substrate such as alumina, stainless steel, a flexible polymer, or the like can be used. The support substrate 100 may be transparent and rigid or flexible.

The back electrode layer 200 is disposed on the support substrate 100. The back electrode layer 200 is a conductive layer. The back electrode layer 200 allows electric charges generated in the light absorbing layer 300 of the solar cells to move, thereby allowing a current to flow to the outside of the solar cell. The back electrode layer 200 must have high electrical conductivity and small specific resistance in order to perform this function.

In addition, the back electrode layer 200 must maintain high temperature stability during heat treatment in a sulfur (S) or selenium (Se) atmosphere accompanied with the formation of a CIGS compound. In addition, the back electrode layer 200 should have excellent adhesion with the supporting substrate 100 to prevent peeling from the supporting substrate 100 due to a difference in thermal expansion coefficient.

The back electrode layer 200 may be formed of any one of molybdenum (Mo), gold (Au), aluminum (Al), chromium (Cr), tungsten (W), and copper (Cu). In particular, molybdenum (Mo) has a smaller difference in thermal expansion coefficient from that of the supporting substrate 100 than other elements, so that it is possible to prevent the peeling phenomenon from occurring due to the excellent adhesion, It is possible to satisfy the required characteristics as a whole.

The back electrode layer 200 may include two or more layers. At this time, the respective layers may be formed of the same metal or may be formed of different metals.

The first through-holes TH1 are formed in the back electrode layer 200. The first through- The first through holes (TH1) are open regions that expose a part of the upper surface of the supporting substrate (100). The first through grooves TH1 may have a shape extending in one direction when viewed in a plan view.

The width of the support substrate 100 exposed by the first through holes TH1 may be about 40 to 150 mu m.

The back electrode layer 200 is divided into a plurality of back electrode layers by the first through holes TH1. That is, the backside electrodes are defined by the first through holes TH1.

The back electrodes are arranged in a stripe shape. Alternatively, the backside electrodes may be arranged in a matrix. At this time, the first through grooves TH1 may be formed in a lattice form when viewed from a plane.

A light absorption layer 300 may be formed on the back electrode layer 200. The light absorption layer 300 includes a p-type semiconductor compound. More specifically, the light absorbing layer 300 includes an I-III-VI group compound. For example, the light absorbing layer 300 is copper-indium-gallium-selenide-based (Cu (In, Ga) Se _2; CIGS-based) crystal structure, a copper-indium-selenide-based or copper-gallium-selenide Crystal structure.

A buffer layer 400 and a high-resistance buffer layer 500 may be formed on the light absorption layer 300. The solar cell having the CIGS compound as the light absorbing layer 300 forms a pn junction between the CIGS compound thin film as the p-type semiconductor and the thin film of the window layer 600 as the n-type semiconductor. However, since the two materials have a large difference between the lattice constant and the band gap energy, a buffer layer in which a band gap is located between two materials is required in order to form a good junction.

The buffer layer 400 may be formed of CdS or ZnS, and CdS is relatively excellent in terms of power generation efficiency of the solar cell.

The high-resistance buffer layer 500 includes zinc oxide (i-ZnO) that is not doped with impurities. The energy band gap of the high resistance buffer layer 500 is about 3.1 eV to 3.3 eV.

A window layer 600 is formed on the high-resistance buffer layer 500. The window layer 600 is transparent and is a conductive layer. In addition, the resistance of the window layer 600 is higher than the resistance of the back electrode layer 200.

The window layer 600 includes an oxide. For example, the window layer 600 may include zinc oxide (ZnO), indium tin oxide (ITO), or indium zinc oxide (IZO).

The oxide may include a conductive impurity such as aluminum (Al), alumina (Al ₂ O ₃ ), magnesium (Mg), or gallium (Ga). More specifically, the window layer 600 may include at least one of Al doped zinc oxide (AZO), B doped zinc oxide (BZO), or gallium doped zinc oxide (GZO) ), And the like.

The window layer 600 is a layer located on the upper layer of the PV cell of the solar cell and is easily exposed to the external environment. The window layer 600 is poor in chemical resistance and can be easily oxidized And the reliability of the device may be deteriorated.

Referring to FIG. 3, third through-holes TH3 are formed in the patterning process for separating into a plurality of solar cells. In the process of forming through the etching, over etching is performed in addition to the etching region TH3. Can occur. Accordingly, the connection portions 650 and the window layer 600 are electrically insulated as in the case of the 'B' region, thereby causing a contact failure.

Therefore, in order to prevent this, it is necessary to secure the chemical resistance within a range that can maintain the electric conduction of the window layer 600. To this end, an impurity may be doped, and the impurity may include a Group 6 element or a Group 9 element. In detail, the impurities may include Cr ₂ O ₃ , CoO or CoCl ₂ . The doping concentration of the impurity may be 0.1 wt% to 5 wt% of the window layer 600.

Since the impurities have excellent chemical resistance, the connection portions 650 and the window layer 600 are electrically isolated from each other in the etching process for forming the third through grooves TH3.

For example, CoCl ₂ (chromium oxide) is a corundum structure formed by a hexagonal close packed array of oxygen anions. CoCl ₂ is a brittle material that is robust and has a Mohs hardness of 8 to 8.5 and has strong chemical properties to acids and bases.

At least one impurity of the Group 6 element or the Group 9 element may be doped during the deposition of the window layer, and at least one impurity of the Group 6 element or the Group 9 element may be doped into the Group 6 element or Group 9 element At least one impurity may form a doped window layer.

In detail, when the window layer 600 is doped with at least one impurity such as a Group 6 element or a Group 9 element, the window layer 600 may include ZnO, for example, and may contain 1 wt% to 3 wt% And Cr ₂ O ₃ may be doped at a ratio of 0.1 wt% to 5 wt%.

And a window layer containing at least one impurity of a Group 6 element or a Group 9 element is deposited after the deposition of a window layer that is not doped with an impurity of a Group 6 element or a Group 9 element, Al may be doped with 1 wt% to 3 wt% of Al, ZnO: Al doped with Al in a proportion of 1 wt% to 3 wt%, and at least one of Group 6 elements or Group 9 elements Doped impurity doping layer may be formed at a ratio of 0.1 wt% to 5 wt%.

The window layer doped with at least one impurity of the Group 6 element or the Group 9 element may be deposited to a thickness of 10 nm to 80 nm.

The connection portions 650 are disposed inside the second through-holes TH2. The connection portions 650 extend downward from the window layer 600 and are connected to the back electrode layer 200. For example, the connection portions 650 extend from the window of the first cell and are connected to the back electrode of the second cell.

Accordingly, the connection units 650 connect adjacent cells. More specifically, the connection portions 650 connect the window and the back electrode included in the neighboring cells C1, C2, ..., respectively.

The connection portions 650 are formed integrally with the window layer 600. That is, the material used for the connection portions 650 is the same as the material used for the window layer 600.

A plurality of solar cells may be connected in series by the connection portions 650.

As described above, since the chemical resistance is improved due to the impurities contained in the window layer 600, it is possible to prevent contact failure that may occur during the process of forming the third through grooves TH3, Battery can be provided.

FIGS. 4 to 6 are cross-sectional views illustrating a method of manufacturing a solar cell according to an embodiment. The description of this manufacturing method refers to the description of the photovoltaic device described above.

Referring to FIG. 4, a back electrode layer 200 is formed on a supporting substrate 100, and the back electrode layer 200 is patterned to form first through holes TH1. Accordingly, a plurality of back surface electrodes are formed on the supporting substrate 100. The back electrode layer 200 may be patterned by a laser.

The first through holes TH1 expose the upper surface of the supporting substrate 100 and may have a width of about 40 탆 to about 150 탆.

Further, an additional layer such as a diffusion barrier layer may be interposed between the supporting substrate 100 and the back electrode layer 200, and the first through holes TH1 expose the upper surface of the additional layer .

Referring to FIG. 5, a light absorption layer 300, a buffer layer 400, and a high-resistance buffer layer 500 are formed on the back electrode layer 200.

The light absorption layer 300 may be formed by a sputtering process or an evaporation process.

(Cu (In, Ga) Se ₂ ; CIGS-based) light-emitting layer is formed while simultaneously evaporating the copper, indium, gallium and selenium simultaneously or separately in order to form the light absorption layer 300. A method of forming the light absorbing layer 300 and a method of forming the metal precursor film by a selenization process are widely used.

After the metal precursor film is formed and then subjected to selenization, a metal precursor film is formed on the back electrode 200 by a sputtering process using a copper target, an indium target, and a gallium target.

Then, the metal precursor film is formed with a light absorbing layer 300 of copper-indium-gallium-selenide (Cu (In, Ga) Se _2, CIGS system) by a selenization process.

Alternatively, the copper target, the indium target, the sputtering process using the gallium target, and the selenization process may be performed simultaneously.

Alternatively, the CIS-based or CIG-based optical absorption layer 300 can be formed by using only a copper target and an indium target, or by a sputtering process and a selenization process using a copper target and a gallium target.

Then, cadmium sulfide is deposited by a sputtering process or a chemical bath deposition (CBD) process, and the buffer layer 400 is formed.

Then, zinc oxide is deposited on the buffer layer 400 by a sputtering process or the like, and the high-resistance buffer layer 500 is formed.

Then, the light absorbing layer 300, the buffer layer 400, and the high-resistance buffer layer 500 are partially removed to form the second through-holes TH2.

The second through grooves TH2 may be formed by a mechanical device such as a tip or a laser device.

At this time, the width of the second through grooves TH2 may be about 50 mu m to about 200 mu m.

The second through grooves TH2 are formed to expose a part of the top surface of the back electrode layer 200. [

Referring to FIG. 6, a window layer 600 is formed on the high-resistance buffer layer 500. That is, the window layer 600 is formed by depositing a transparent conductive material on the high-resistance buffer layer 500 and the second through-holes TH2.

At this time, the transparent conductive material is filled in the second through grooves TH2 and the window layer 600 is electrically connected to the back electrode layer 200 through the connection portions 650. [

The window layer 600 may be formed by depositing a transparent conductive material. More specifically, the window layer 600 may be formed by depositing aluminum oxide-doped zinc oxide in an inert gas atmosphere containing no oxygen, but is not limited thereto.

Next, the buffer layer 400, the high-resistance buffer layer 500, and a part of the window layer 600 are removed to form third through-holes TH3. Accordingly, the window layer 600 is patterned to define a plurality of windows and a plurality of cells (C1, C2, ...). The width of the third through-holes TH3 may be about 80 占 퐉 to about 200 占 퐉.

The third through grooves TH3 may be formed by a mechanical device such as a tip, a laser device, or the like, or may be formed by wet etching. The window layer 600, which is doped with impurities and has improved chemical resistance, It is possible to prevent the window layer 600 from being etched in a region other than the etching region in the process of forming the third through grooves TH3 through the contact holes 650 and the window layer 600, It can be prevented from being insulated.

The impurity may be formed by including a Group 6 element or a Group 9 element. The Group 6 element has a high melting point, a high boiling point, a valence of +6, and is stable and low in chemical reactivity.

As illustrated, the connection units 650 connect adjacent cells. More specifically, the connection portions 650 connect the window layer 600 included in each of the adjacent cells C1, C2, ... to the back electrode.

As described above, according to the embodiment, the chemical resistance of the window layer 600 is improved, and the reliability of the solar cell can be improved.

In addition, the features, structures, effects and the like described in the embodiments are included in at least one embodiment of the present invention, and are not necessarily limited to only one embodiment. Furthermore, the features, structures, effects and the like illustrated in the embodiments can be combined and modified by other persons skilled in the art to which the embodiments belong. Therefore, it should be understood that the present invention is not limited to these combinations and modifications.

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 (8)

Board;
A back electrode layer disposed on the substrate;
A light absorbing layer disposed on the back electrode layer;
A buffer layer disposed on the light absorbing layer;
A high resistance buffer layer disposed on the buffer layer;
A window layer disposed on the high-resistance buffer layer;
A first through-hole penetrating the back electrode layer;
A second penetrating groove penetrating the light absorption layer, the buffer layer, and the high resistance buffer layer; And
And a third penetrating groove penetrating the light absorbing layer, the buffer layer, the high resistance buffer layer, and the window layer,
Wherein the high-resistance buffer layer comprises zinc oxide (i-ZnO) not doped with an impurity,
The width of the first through-hole is 40 to 150 탆,
The width of the second through groove is 50 to 200 탆,
The width of the third through-hole is 80 占 퐉 to 200 占 퐉,
The resistance of the window layer is higher than the resistance of the back electrode layer,
The window layer
A first window layer disposed on the high-resistance buffer layer; And
And a second window layer disposed on the first window layer,
Wherein the first window layer and the second window layer comprise zinc oxide (AZO) doped with aluminum,
Wherein the doping concentration of the aluminum doped in the first window layer and the second window layer is 1 wt% to 3 wt% of the window layer,
Wherein the second window layer further comprises at least one impurity of Cr ₂ O ₃ , CoO and CoCl ₂ ,
The doping concentration of the impurity further included in the second window layer is 0.1 wt% to 5 wt% of the window layer,
And the second window layer has a thickness of 10 nm to 80 nm. delete delete The method according to claim 1,
Wherein the light absorption layer comprises a p-type semiconductor compound, and the window layer comprises an n-type semiconductor. delete Forming a back electrode layer on the substrate;
Forming a first through-hole in the back electrode layer;
Forming a light absorption layer on the back electrode layer;
Forming a buffer layer on the light absorbing layer;
Forming a high resistance buffer layer on the buffer layer;
Forming a second through hole in the light absorption layer, the buffer layer, and the high resistance buffer layer;
Forming a window layer on the high-resistance buffer layer; And
And forming a third through hole in the light absorption layer, the buffer layer, the high resistance buffer layer, and the window layer,
The width of the first through-hole is 40 to 150 탆,
The width of the second through groove is 50 to 200 탆,
The width of the third through-hole is 80 占 퐉 to 200 占 퐉,
The resistance of the window layer is higher than the resistance of the back electrode layer,
Wherein forming the window layer comprises:
Forming a first window layer on the high-resistance buffer layer; And
And forming a second window layer on the first window layer,
Wherein the first window layer is doped with at least one impurity of a Group 6B element or a Group 9 element,
Wherein the first window layer and the second window layer comprise zinc oxide (AZO) doped with aluminum,
Wherein the doping concentration of the aluminum doped in the first window layer and the second window layer is 1 wt% to 3 wt% of the window layer,
Wherein the second window layer further comprises at least one impurity of Cr ₂ O ₃ , CoO and CoCl ₂ ,
The doping concentration of the impurity further included in the second window layer is 0.1 wt% to 5 wt% of the window layer,
And the second window layer has a thickness of 10 nm to 80 nm. delete The method according to claim 6,
Wherein the light absorption layer and the window layer form a pn junction.

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