KR101417321B1 - Solar cell and method of fabricating the same - Google Patents

Abstract

A solar cell according to an embodiment includes a substrate; A rear electrode layer formed on the upper surface of the substrate; A light absorption layer formed on the upper surface of the rear electrode layer; A buffer layer formed on the upper surface of the light absorbing layer; And a front electrode layer formed on the upper surface of the buffer layer, wherein the substrate includes a metal layer including a metal or a metal oxide.
A solar cell manufacturing method according to an embodiment includes: forming a metal layer in a substrate; Forming a rear electrode layer on the substrate; Forming a light absorption layer on the rear electrode layer; Forming a buffer layer on the light absorbing layer; And forming a front electrode layer on the buffer layer.

Description

SOLAR CELL AND METHOD OF FABRICATING THE SAME

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

A manufacturing method of a solar cell for solar power generation is as follows. First, a substrate is provided, a back electrode layer is formed on the substrate, and the back electrode layer is patterned by a laser to form a plurality of back surface electrodes.

Then, a light absorption layer, a buffer layer, and a high-resistance buffer layer are sequentially formed on the back electrodes. A method of forming a light absorbing layer of copper-indium-gallium-selenide (Cu (In, Ga) Se 2; CIGS system) while simultaneously or separately evaporating copper, indium, gallium and selenium in order to form the above- A method in which a metal precursor film is formed and then formed by a selenization process is widely used. The band gap of the light absorption layer is about 1 to 1.8 eV.

Thereafter, a buffer layer containing cadmium sulfide (CdS) is formed on the light absorption layer by a sputtering process. The energy band gap of the buffer layer is about 2.2 to 2.4 eV. Then, a high resistance buffer layer containing zinc oxide (ZnO) is formed on the buffer layer by a sputtering process. The energy band gap of the high resistance buffer layer is about 3.1 to 3.3 eV.

Then, a groove pattern may be formed in the light absorption layer, the buffer layer, and the high resistance buffer layer.

Thereafter, a transparent conductive material is laminated on the high-resistance buffer layer, and the transparent conductive material is filled in the groove pattern. Accordingly, a transparent electrode layer is formed on the high-resistance buffer layer, and connection wirings are formed inside the groove pattern, respectively. Examples of the material used for the transparent electrode layer and the connection wiring include aluminum-doped zinc oxide and the like. The energy band gap of the transparent electrode layer is about 3.1 to 3.3 eV.

Thereafter, a groove pattern is formed on the transparent electrode layer and the like to form a plurality of solar cells. The transparent electrodes and the high-resistance buffers correspond to respective cells. The transparent electrodes and the high resistance buffers may be arranged in a stripe form or a matrix form.

The transparent electrodes and the back electrodes are mutually misaligned, and the transparent electrodes and the back electrodes are electrically connected to each other by the connection wirings. Accordingly, a plurality of solar cells can be electrically connected to each other in series.

Thus, various types of photovoltaic devices can be manufactured and used to convert sunlight into electrical energy. Such a photovoltaic power generation apparatus is disclosed in, for example, Japanese Patent Application Laid-Open No. 10-2008-0088744.

The embodiments are intended to provide a solar cell having an improved photoelectric conversion efficiency and a method of manufacturing the same.

A solar cell according to an embodiment includes a substrate; A rear electrode layer formed on the upper surface of the substrate; A light absorption layer formed on the upper surface of the rear electrode layer; A buffer layer formed on the upper surface of the light absorbing layer; And a front electrode layer formed on the upper surface of the buffer layer, wherein the substrate includes a metal layer including a metal or a metal oxide.

A solar cell manufacturing method according to an embodiment includes: forming a metal layer in a substrate; Forming a rear electrode layer on the substrate; Forming a light absorption layer on the rear electrode layer; Forming a buffer layer on the light absorbing layer; And forming a front electrode layer on the buffer layer.

A solar cell according to an embodiment includes a metal layer sandwiched within a support substrate.

Thus, the band gap at the rear end portion in the light absorption layer can be raised. That is, the bandgap of the rear end portion in the light absorption layer can be increased according to the doping effect by the metal such as aluminum and / or silver contained in the metal layer.

In addition, the metal layer can simultaneously reflect the absorption of light of a long wavelength by simultaneously performing the function of the reflection layer.

Therefore, the solar cell according to the embodiment can improve the efficiency of the entire solar cell by the metal layer.

1 is a plan view showing a solar cell according to an embodiment.
FIG. 2 is a cross-sectional view showing one end surface of a solar cell according to an embodiment.
3 to 9 are views for explaining a method of manufacturing a solar cell according to an embodiment.

In the description of the embodiments, it is to be understood that each layer (film), area, pattern or structure may be referred to as being "on" or "under / under" Quot; includes all that is formed directly or through another layer. The criteria for top / bottom or bottom / bottom of each layer are described with reference to the drawings.

The thickness or the size of each layer (film), region, pattern or structure in the drawings may be modified for clarity and convenience of explanation, and thus does not entirely reflect the actual size.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

Hereinafter, a solar cell according to an embodiment will be described in detail with reference to FIGS. 1 and 2. FIG. FIG. 1 is a plan view of a solar cell according to an embodiment, and FIG. 2 is a cross-sectional view illustrating a solar cell according to an embodiment.

1 and 2, a solar cell according to an embodiment includes a support substrate 100, a rear electrode layer 200, a light absorption layer 300, a buffer layer 400, and a front electrode layer 500.

The supporting substrate 100 has a plate shape and supports the rear electrode layer 200, the light absorbing layer 300, the buffer layer 400, and the front electrode layer 500.

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. Alternatively, a ceramic substrate such as alumina, stainless steel, a flexible polymer, or the like may be used as the support substrate 100. The supporting substrate 100 may be transparent. The support substrate 100 may be rigid or flexible.

The support substrate 100 may include a metal layer 110. The metal layer 110 includes a metal or a metal oxide. Preferably, the metal layer 110 comprises aluminum (Al), silver (Ag), or an oxide containing the same. Alternatively, the metal layer 110 may include aluminum and silver together, or may include aluminum oxide and silver oxide.

The metal layer 110 may be positioned within the support substrate 100. In detail, the metal layer 110 may be sandwiched within the support substrate 100. That is, the supporting substrate 100 may include a first supporting substrate directly contacting the lower surface of the metal layer and a second supporting substrate contacting the upper surface of the metal layer directly, And sandwiched between the substrate and the second support substrate.

The metal layer 110 may be located on the upper portion of the supporting substrate 100. In detail, the metal layer 110 may be located on the upper surface of the support substrate 100 at a distance of 1/10 of the entire thickness. More specifically, the metal layer 110 is sandwiched between the first support substrate and the second support substrate, and the length ratio of the thickness of the first support substrate and the second support substrate is 8: 2 to 9: 1 .

The metal layer 110 may improve the back grading effect at the interface between the rear electrode layer 200 and the light absorbing layer 300. That is, in the band align of the light absorbing layer, the band gap of the rear half portion is higher than the band gap of the front end portion, which is effective for current collection by electron drift. At this time, raising the bandgap in the latter half is referred to as backgraining effect.

In the solar cell according to the embodiment, the metal layer 110 included in the substrate can raise the bandgap of the rear half to improve the backgraining effect. That is, the doping effect of aluminum and / or silver may occur in the interface direction of the light absorbing layer 300 and the rear electrode layer 200 by the metal layer including aluminum and / or silver or an oxide containing the aluminum and / or silver, , The backgraining effect can be improved and the overall efficiency of the solar cell can be improved.

In addition, the metal layer 110 can simultaneously serve as a reflective layer, and can reflect light of a long wavelength to be absorbed, thereby improving the efficiency of the entire solar cell.

The rear electrode layer 200 is disposed on the supporting substrate 100. The rear electrode layer 200 is a conductive layer. The rear electrode layer 200 may be formed of any one of molybdenum (Mo), gold (Au), aluminum (Al), chromium (Cr), tungsten (W), and copper (Cu). Of these, molybdenum has a smaller difference in thermal expansion coefficient than the support substrate 100 in comparison with other elements, so that it is possible to prevent peeling phenomenon from occurring due to its excellent adhesiveness.

In addition, the rear 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.

First through holes (TH1) are formed in the rear electrode layer (200). The first through grooves TH1 are open regions that expose the upper surface of the supporting substrate 100. [ The first through grooves TH1 may have a shape extending in a first direction when viewed from a plane.

The width of the first through-holes TH1 may be about 80 to 200 mu m.

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

The rear electrodes are spaced apart from each other by the first through holes TH1. The rear electrodes are arranged in a stripe shape.

Alternatively, the rear 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.

The light absorption layer 300 is disposed on the rear electrode layer 200. In addition, the material contained in the light absorption layer 300 is filled in the first through holes TH1.

The light absorption 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.

The energy band gap of the light absorption layer 300 may be about 1 eV to 1.8 eV.

Then, the buffer layer 400 is disposed on the light absorption layer 300. The buffer layer 400 is in direct contact with the light absorption layer 300. The buffer layer 400 includes cadmium sulfide, ZnS, InXSY and InXSeYZn (O, OH). The thickness of the buffer layer 400 may be about 50 nm to about 150 nm, and the energy band gap of the buffer layer 400 may be about 2.2 eV to about 2.4 eV.

A high resistance buffer layer may be further disposed on the buffer layer 400. The high-resistance buffer layer includes zinc oxide (i-ZnO) not doped with an impurity. The energy band gap of the high resistance buffer layer may be about 3.1 eV to about 3.3 eV. Further, the high-resistance buffer layer may be omitted.

Second through holes (TH2) may be formed on the buffer layer (400). The second through grooves TH2 are open regions that expose the upper surface of the supporting substrate 100 and the upper surface of the rear electrode layer 200. [ The second through grooves TH2 may have a shape extending in one direction when viewed in a plan view. The width of the second through grooves TH2 may be about 80 to 200 mu m, but is not limited thereto.

The buffer layer 400 is defined as a plurality of buffer layers by the second through grooves TH2. That is, the buffer layer 400 is divided into the buffer layers by the second through grooves TH2.

Next, the front electrode layer 500 is disposed on the buffer layer 400. More specifically, the front electrode layer 500 is disposed on the high-resistance buffer layer. The front electrode layer 500 is transparent and is a conductive layer. Also, the resistance of the front electrode layer 500 is higher than the resistance of the rear electrode layer 500.

The front electrode layer 500 includes an oxide. Examples of the material used for the front electrode layer 500 include Al doped ZnC (indium zinc oxide), indium zinc oxide (IZO), indium tin oxide (ITO) And the like.

The thickness of the front electrode layer 500 may be about 500 nm to about 1.5 占 퐉. In addition, when the front electrode layer 500 is formed of zinc oxide doped with aluminum, aluminum may be doped at a ratio of about 2.5 wt% to about 3.5 wt%.

Third through holes TH3 are formed in the buffer layer 400 and the front electrode layer 500. [ The third through holes TH3 may pass through a part or all of the buffer layer 400, the high resistance buffer layer, and the front electrode layer 500. [ That is, the third through holes TH3 may expose the upper surface of the rear electrode layer 200. [

The third through grooves TH3 are formed at positions adjacent to the second through grooves TH2. More specifically, the third through-holes TH3 are disposed beside the second through-holes TH2. That is, when viewed in plan, the third through grooves TH3 are arranged next to the second through grooves TH2. The third through grooves TH3 may have a shape extending in the first direction.

The third through holes (TH3) penetrate the front electrode layer (500). More specifically, the third through-holes TH3 may partially or wholly penetrate the light absorption layer 300, the buffer layer 400, and / or the high-resistance buffer layer.

The front electrode layer 500 is divided into a plurality of front electrodes by the third through holes TH3. That is, the front electrodes are defined by the third through holes TH3.

The front electrodes have a shape corresponding to the rear electrodes. That is, the front electrodes are arranged in a stripe form. Alternatively, the front electrodes may be arranged in a matrix form.

Further, a plurality of solar cells C1, C2, ... are defined by the third through-holes TH3. More specifically, the solar cells (C1, C2, ...) are defined by the second through-holes (TH2) and the third through-holes (TH3). That is, the photovoltaic apparatus according to the embodiment is divided into the solar cells C1, C2, ... by the second through grooves TH2 and the third through grooves TH3. The solar cells C1, C2, ... are connected to each other in a second direction intersecting with the first direction. That is, current can flow in the second direction through the solar cells C1, C2, ....

That is, the solar cell panel 10 includes the support substrate 100 and the solar cells C1, C2,. The solar cells C1, C2, ... are disposed on the support substrate 100 and are spaced apart from each other. Further, the solar cells C1, C2, ... are connected to each other in series by the connecting portions.

The connection portions are disposed inside the second through-holes TH2. The connection portions 600 extend downward from the front electrode layer 500 and are connected to the rear electrode layer 200. For example, the connection portions extend from the front electrode of the first cell C1 and are connected to the rear electrode of the second cell C2.

Accordingly, the connection portions connect adjacent solar cells. More specifically, the connection units connect front electrodes and rear electrodes, respectively, included in adjacent solar cells.

The connection part is integrally formed with the front electrode layer 500. That is, the material used for the connection part is the same as the material used for the front electrode layer 500.

As described above, the solar cell according to the embodiment includes a metal layer sandwiched in the support substrate.

Thus, the band gap at the rear end portion in the light absorption layer can be raised. That is, the bandgap of the rear end portion in the light absorption layer can be increased according to the doping effect by the metal such as aluminum and / or silver contained in the metal layer.

In addition, the metal layer can simultaneously reflect the absorption of light of a long wavelength by simultaneously performing the function of the reflection layer.

Therefore, the solar cell according to the embodiment can improve the efficiency of the entire solar cell by the metal layer.

Hereinafter, a method of manufacturing a solar cell according to an embodiment will be described with reference to FIGS.

3 to 9 are views for explaining a method of manufacturing a solar cell according to an embodiment.

Referring to FIG. 3, a back electrode layer 200 is formed on the supporting substrate 100. The rear electrode layer 200 may be formed by PVD (Physical Vapor Deposition) or plating.

Also, a metal layer 110 is formed in the support substrate 100. The support substrate 100 includes a first support substrate that is in direct contact with the lower surface of the metal layer 110 and a second support substrate that is in direct contact with the upper surface of the metal layer 110. [ 2 supporting substrate. The metal layer 110 is positioned between the first support substrate and the second support substrate and is sandwiched between the first support substrate and the second support substrate.

The metal layer 110 may include or include an oxide including silver and / or aluminum. The metal layer 110 may be located on the upper portion of the supporting substrate 100. May be located at about 1/10 to 2/10 of the entire thickness of the supporting substrate 100 from the upper surface of the supporting substrate 100. More specifically, when the metal layer 110 is sandwiched by the first support substrate and the second support substrate, the length ratio of the thickness of the first support substrate and the second support substrate may be from 8: 2 to 9: 1 have.

Referring to FIG. 4, the rear electrode layer 200 is patterned to form first through-holes TH1. Accordingly, a plurality of rear electrodes are formed on the supporting substrate 100. The rear electrode layer 200 is 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 80 mu m to about 200 mu m, but the present invention is not limited thereto.

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

Referring to FIG. 5, a light absorption layer 300 is formed on the rear electrode layer 200. The light absorption layer 300 may be formed by a sputtering process or an evaporation process.

For example, a copper-indium-gallium-selenide-based (Cu (In, Ga) Se 2; CIGS-based) light-emitting layer is formed while simultaneously evaporating copper, indium, gallium, 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.

When a metal precursor film is formed and then subjected to selenization, a metal precursor film is formed on the rear 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.

Referring to FIG. 6, a buffer layer 400 is formed on the light absorption layer 300. The method of manufacturing the buffer layer 400 is not particularly limited as long as it is used in the art for manufacturing a buffer layer of a solar cell. For example, the buffer layer 400 may be formed by a sputtering method, an evaporation method, a CVD (Chemical Vapor Deposition) method, an MOCVD method, a close-spaced sublimation (CSS) , Spray pyrolysis, chemical spraying, screen printing, non-vacuum liquid deposition, CBD (chemical vapor deposition), VTD (vapor transport deposition), atomic layer deposition , An atomic layer deposition (ALD), and an electrodeposition method. More specifically, the buffer layer 400 may be formed by chemical growth deposition (CBD), atomic layer deposition (ALD), or metal organic chemical vapor deposition (MOCVD).

Then, zinc oxide is deposited on the buffer layer 400 by a deposition process or the like, and the high resistance buffer layer may be further formed.

The high resistance buffer layer may be formed by chemical vapor deposition (CVD), metal organic chemical vapor deposition (MOCVD), or atomic layer deposition (ALD). Preferably, the high-resistance buffer layer may be formed through metal-organic chemical vapor deposition.

Referring to FIG. 7, the light absorbing layer 300 and a part of the buffer layer 400 are removed to form second through holes TH2.

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

For example, the light absorbing layer 300 and the buffer layer 400 and / or the high resistance buffer layer can be patterned by a tip having a width of about 40 占 퐉 to about 180 占 퐉. The second through-holes TH2 may be formed by a laser having a wavelength of about 200 to 600 nm.

At this time, the width of the second through grooves TH2 may be about 80 mu m to about 200 mu m. The second through holes TH2 are formed to expose a part of the upper surface of the rear electrode layer 200. [

Referring to FIG. 8, a front electrode layer may be formed on the buffer layer 400. For example, the front electrode layer 800 may be formed using a ZnO target by a RF sputtering method, a reactive sputtering method using a Zn target, or an MOCVD method.

9, the light absorbing layer 300, the buffer layer 400, and a part of the front electrode layer 500 are removed to form third through holes TH3. Accordingly, the front electrode layer 500 is patterned to define a plurality of front electrodes and a first cell C1, a second cell C2, and a third cell C3. The width of the third through grooves TH3 may be about 80 占 퐉 to about 200 占 퐉.

As described above, the solar cell manufactured by the solar cell manufacturing method according to the embodiment includes the metal layer in the support substrate.

Thus, the band gap at the rear end portion in the light absorption layer can be raised. That is, the bandgap of the rear end portion in the light absorption layer can be increased according to the doping effect by the metal such as aluminum and / or silver contained in the metal layer.

In addition, the metal layer can simultaneously reflect the absorption of light of a long wavelength by simultaneously performing the function of the reflection layer.

Therefore, the solar cell manufactured by the solar cell manufacturing method according to the embodiment can improve the efficiency of the entire solar cell by the metal layer.

The features, structures, effects and the like described in the foregoing embodiments are included in at least one embodiment of the present invention and are not necessarily limited to one embodiment. Further, the features, structures, effects, and the like illustrated in the embodiments may be combined or modified in other embodiments by those 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 clearly understood that the same is by way of illustration and example only and is not to be construed as limiting the scope of the present invention. It can be seen that various modifications and applications are possible. For example, each component specifically shown in the embodiments may 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.

Claims (10)

Board;
A rear electrode layer formed on the upper surface of the substrate;
A light absorption layer formed on the upper surface of the rear electrode layer;
A buffer layer formed on the upper surface of the light absorbing layer; And
And a front electrode layer formed on an upper surface of the buffer layer,
Wherein the substrate comprises a metal layer comprising a metal or a metal oxide,
Wherein:
A first substrate directly contacting the lower surface of the metal layer; And
And a second substrate directly contacting the upper surface of the metal layer,
Wherein the length ratio of the thickness of the first substrate to the thickness of the second substrate is 8: 2 to 9: 1. The method according to claim 1,
Wherein the metal layer comprises silver (Ag), aluminum (Al), or an oxide containing the same. The method according to claim 1,
Wherein the metal layer comprises silver and aluminum. delete The method according to claim 1,
Wherein the metal layer is sandwiched between the first substrate and the second substrate. delete Forming a metal layer in the substrate;
Forming a rear electrode layer on the substrate;
Forming a light absorption layer on the rear electrode layer;
Forming a buffer layer on the light absorbing layer; And
And forming a front electrode layer on the buffer layer,
Wherein:
A first substrate directly contacting the lower surface of the metal layer; And
And a second substrate directly contacting the upper surface of the metal layer,
Wherein the length ratio of the thickness of the first substrate to the thickness of the second substrate is 8: 2 to 9: 1. 8. The method of claim 7,
Wherein the metal layer is sandwiched between the first substrate and the second substrate, delete 8. The method of claim 7,
Wherein the metal layer comprises silver, aluminum, or an oxide thereof.

Images