WO2013094940A1

WO2013094940A1 - Solar cell module and method of fabricating the same

Info

Publication number: WO2013094940A1
Application number: PCT/KR2012/010968
Authority: WO
Inventors: Jin Ho Gwon; Chin Woo Lim
Original assignee: Lg Innotek Co., Ltd.
Priority date: 2011-12-19
Filing date: 2012-12-14
Publication date: 2013-06-27
Also published as: KR101306525B1; KR20130070458A

Abstract

Disclosed are a solar cell module and a method of fabricating the same. The solar cell module includes a plurality of solar cells, wherein each solar cell includes a back electrode layer on a support substrate; a light absorbing layer on the back electrode layer; and a front electrode layer on the light absorbing layer, and wherein the solar cells are separated from each other by a through hole inclined with respect to the support substrate.

Description

SOLAR CELL MODULE AND METHOD OF FABRICATING THE SAME

The embodiment relates to a solar cell module and a method of fabricating the same.

Solar cells may be defined as devices to convert light energy into electric energy through a photovoltaic effect of generating electrons when light is incident onto a P-N junction diode. The solar cell may be classified into a silicon solar cell, a compound semiconductor solar cell mainly including a group I-III-VI compound or a group III-V compound, a dye-sensitized solar cell, and an organic solar cell according to materials constituting the junction diode.

A solar cell made from CIGS (CuInGaSe), which is one of group I-III-VI Chalcopyrite-based compound semiconductors, represents superior light absorption, higher photoelectric conversion efficiency with a thin thickness, and superior electro-optic stability, so the CIGS solar cell is spotlighted as a substitute for a conventional silicon solar cell.

Referring to FIG. 1, generally, a CIGS thin film solar cell is fabricated by sequentially forming a substrate 10 including sodium, a back electrode layer 20, a light absorbing layer 30, a buffer layer 40, and a front electrode layer 60. In addition, different from a bulk solar cell, the CIGS thin film solar cell includes a plurality of unit cells connected to each other in series or in parallel through patterning processes P1 to P3.

The embodiment provides a solar cell module including an inclined through hole and a method of fabricating the same.

According to the first embodiment, a solar cell module includes a plurality of solar cells, wherein each solar cell includes a back electrode layer on a support substrate; a light absorbing layer on the back electrode layer; and a front electrode layer on the light absorbing layer, and wherein the solar cells are separated from each other by a through hole inclined with respect to the support substrate.

According to the second embodiment, the solar cell module includes a first solar cell including a first back electrode, a first light absorbing part, and a first front electrode that are sequentially arranged on a support substrate; and a second solar cell including a second back electrode, a second light absorbing part, and a second front electrode that are sequentially arranged on the support substrate. The first and second solar cells are separated from each other by the through hole inclined with respect to the support substrate.

According to the embodiment, a method of fabricating a solar cell module includes forming a back electrode layer on a support substrate, forming a light absorbing layer on the back electrode layer, forming a through hole exposing a portion of the back electrode layer through the light absorbing layer, and inclined with respect to the support substrate, and forming a front electrode layer on the light absorbing layer.

As described above, the solar cell module according to the embodiment includes the through hole inclined with respect to the support substrate. The through hole not only performs a function of electrically connecting the solar cells to each other, but also performs a function of separating the solar cells from each other.

Therefore, according to the method of fabricating the solar cell module of the embodiment, since the solar cell module can be fabricated without an additional patterning process to separate the solar cells from each other, the fabricating process can be simplified. Accordingly, the process time can be shortened and the process cost can be reduced.

FIG. 1 is a sectional view showing a solar cell module according to the related art;

FIG. 2 is a sectional view showing a solar cell module according to the first embodiment;

FIG. 3 is a sectional view showing a solar cell module according to the second embodiment; and

FIGS. 4 to 7 are sectional views showing a method of fabricating a solar cell module according to the embodiment.

In the description of the embodiments, it will be understood that, when a substrate, a layer, a film, or an electrode is referred to as being “on” or “under” another substrate, another layer, another film, or another electrode, it can be “directly” or “indirectly” on the other substrate, the other layer, the other film, or the other electrode, one or more intervening layers may also be present. Such a position of each layer has been described with reference to the drawings. The size of each component shown in the drawings may be exaggerated for the purpose of convenience or clarity, and the size of each component does not utterly reflect an actual size.

FIG. 2 is a sectional view showing a solar cell module according to the first embodiment. Referring to FIG. 2, the solar cell module according to the first embodiment includes a plurality of cells C1 and C2 of the solar cell. In addition, each of the cells C1 and C2 includes a support substrate 100, a back electrode layer 200, a light absorbing layer 300, and a front electrode layer 400.

The support substrate 100 has a plate shape and supports the back electrode layer 200, the light absorbing layer 300, and the front electrode layer 400. The support substrate 100 may include an insulator. The support substrate 100 may include a glass substrate, a plastic substrate, or a metallic substrate. In more detail, the support substrate 100 may include a soda lime glass substrate. The support substrate 100 may be transparent. The support substrate 100 may be rigid or flexible.

The back electrode layer 200 is a conductive layer. The back electrode layer 200 may include one selected from the group consisting of molybdenum (Mo), gold (Au), aluminum (Al), chrome (Cr), tungsten (W), and copper (Cu). Among them, Mo represents a less thermal expansion coefficient difference from the support substrate 100 as compared with that of another element, so that Mo has a superior adhesive strength to prevent delamination from the support substrate 100. In addition, Mo may satisfy the characteristics required for the back electrode layer 200.

In addition, the back electrode layer 200 includes a first division pattern P1. The first division pattern P1 is an open region to expose the top surface of the support substrate 100. The first division pattern P1 may be formed by a laser, but the embodiment is not limited thereto. The back electrode layer 200 may be divided into a plurality of back electrodes by the first division pattern P1. The width of the first division pattern P1 may be in the range of about 50 ㎛ to about 100 ㎛, but the embodiment is not limited thereto.

The light absorbing layer 300 is provided on the back electrode layer 200. The light absorbing layer includes a group I-III-VI based compound. For example, the light absorbing layer 300 may have a Cu (In,Ga) Se2 (CIGS) crystal structure, a Cu (In) Se2 crystal structure, or a Cu (Ga) Se2 crystal structure. The light absorbing layer 300 may be divided into a plurality of light absorbing parts by a through hole TH.

The front electrode layer 400 is formed on the light absorbing layer 300. The front electrode layer 400 may have the characteristic of an N type semiconductor. In other words, the front electrode layer 400 includes the N type semiconductor to form a PN junction structure together with the light absorbing layer 300 serving as a P type semiconductor layer. For example, the front electrode layer 400 may include an Al-doped zinc oxide (AZO). In addition, the front electrode layer 400 may be divided into a plurality of electrodes by the through hole TH.

Meanwhile, although not shown in drawings, a buffer layer (not shown) and a high resistance buffer layer (not show) may be additionally formed between the light absorbing layer 300 and the front electrode layer 400. The buffer layer may include cadmium sulfide (CdS), zinc sulfide (ZnS), InXSY, and InXSeYZn(O, OH), and the high resistance buffer layer may include i-ZnO which is not doped with silver (Ag) impurities, but the embodiment is not limited thereto.

The solar cells C1 and C2 including the

layers

200, 300, and 400 are divided by the through hole. In other words, the through hole TH may divide a plurality of the solar cells C1 and C2 from each other. Regarding the cells according to the related art, the solar cells C1 and C2 are connected to each other by forming a P2 pattern as shown in FIG. 1, and divided from each other by forming a P3 pattern. According to the embodiment, an inclined through hole TH is formed, so that the connection and the division of the solar cells C1 and C2 are simultaneously performed.

Hereinafter, the through hole TH and the cells C1 and C2 will be described in more detail with reference to FIG. 3.

Referring to FIG. 3, a solar cell module according to the second embodiment includes a first solar cell C1 and a second solar cell C2. The first solar cell C1 includes a first back electrode 210, a first light absorbing part 310, and a first electrode 410 sequentially provided on the support substrate 100. In addition, the second solar cell C2 includes a second back electrode 220, a second light absorbing part 320, and a second front electrode 420 sequentially formed on the support substrate 100. In addition, the first and second solar cells C1 and C2 are separated from each other by the through hole TH.

The through hole TH includes a first inner surface 301 and a second inner surface 302 opposite to the first inner surface 301. The first inner surface 301 makes contact with the first solar cell C1. In addition, the second inner surface 302 makes contact with the second solar cell C2.

Referring to FIG. 3, the first front electrode 410 extends downward along the first inner surface 301 of the through hole TH, and makes contact with the second back electrode 220 of the second cell C2. Accordingly, the first solar cell C1 is electrically connected to the second solar cell C2.

In addition, the first front electrode 410 extending downward along the first inner surface 301 does not make contact with the second front electrode 420. For example, the first electrode 410 may not be formed on the second inner surface 302 of the through hole TH. This is because the lower portion of the second inner surface L2 is hidden by the shadow effect of the inclined second inner surface L2 of the through hole TH when the

front electrodes

410 and 420 are formed on the light absorbing layers 310 and 320. Therefore, according to the method of fabricating the solar cell module of the embodiment, since the solar cells C1 and C2 may be divided without a P3 patterning process to divide the solar cells, the fabrication process can be simplified. Accordingly, the process time can be shortened and the process cost can be reduced.

The inclination angle of the through hole TH can be adjusted in order to connect the solar cells C1 and C2 to each other or separate the solar cells C1 and C2 from each other. For example, the inclination angles θ1, and θ2 between the through hole TH and the support substrate 100 may be in the range of about 45° to about 60°. In detail, the angles θ1 and θ2 between the inner surface of the through hole TH and the top surface of the support substrate 100 may be in the range of 45° to 60°.

If the through hole TH is inclined at an angle of about 45° or less about the support substrate 100, the short may occur between the

front electrodes

410 and 420 because the shadow effect is insufficient. In addition, if the through hole TH is inclined at an angle of about 60° about the support substrate 100, one end of the second inner surface 302 of the through hole TH is thin so that the end of the second inner surface 302 may be broken.

In more detail, the angle between the first inner surface 301 of the through hole TH and the support substrate 100 and the angle between the second inner surface 302 and the support substrate 100 may be in the range of about 45° to about 60°. In addition, the angle between the first inner surface 301 and the support substrate 100 may be equal to or different from the angle between the second inner surface 302 and the support substrate 100.

In addition, in order to allow the through hole TH to easily separate the solar cells C1 and C2 from each other, the lengths L1 and L2 of the first and second

inner surfaces

301 and 302 of the through hole TH are preferably adjusted in relation to the thicknesses of the

front electrodes

410 and 420. For example, the length L1 of the first inner surface 301 and the length L2 of the second inner surface 302 are three times greater than the thickness W1 of the

front electrodes

410 and 420, but the embodiment is not limited thereto. For example, if the thickness W1 of the front electrode layer is in the range of about 0.7 ㎛ to about 1.0 ㎛, the lengths L1 and L2 of the

inner surfaces

301 and 302 may be in the range of about 2.1 ㎛ to about 3.0 ㎛, but the embodiment is not limited thereto. Accordingly, the through hole TH may have a sufficient shadow effect, and the first and second

front electrodes

410 and 420 are separated from each other, so that the first and

second electrodes

410 and 420 are electrically insulated from each other.

FIGS. 4 to 7 are sectional views showing a method of fabricating the solar cell module according to the embodiment. The description of the method of fabricating the solar cell module according to the present embodiment will be incorporated in the above description of the solar cell module.

Referring to FIG. 4, the back electrode layer 200 is formed on the support substrate 100. The back electrode layer 200 may be formed through a physical vapor deposition (PVD) scheme or a plating scheme.

Referring to FIG. 5, the light absorbing layer 300 is formed on the back electrode layer 200. The light absorbing layer 300 may be formed through a sputtering process or an evaporation scheme. For example, a scheme of forming a Cu(In,Ga)Se2 (CIGS) based-light absorbing layer by simultaneously or separately evaporating Cu, In, Ga, and Se and a scheme of performing a selenization process after a metallic precursor film has been formed have been extensively used in order to form the light absorbing layer.

Regarding the details of the selenization process after forming the metallic precursor layer, the metallic precursor layer is formed on the back contact electrode 200 through a sputtering process employing a Cu target, an In target, or a Ga target. Thereafter, the metallic precursor layer is subject to the selenization process so that the Cu(In,Ga)Se2 (CIGS) based-light absorbing layer 300 is formed.

In addition, the sputtering process employing the Cu target, the In target, and the Ga target and the selenization process may be simultaneously performed.

In addition, a CIS or a CIG light absorbing layer 300 may be formed through a sputtering process employing only Cu and In targets or only Cu and Ga targets and the selenization process.

Referring to FIG. 6, the through hole TH, which exposes a portion of the back electrode layer 200 and is inclined with respect to the support substrate 100, is formed through the light absorbing layer 300.

The through hole TH may be formed through a mechanical process or a laser process. For example, the through hole TH may be formed by mechanically scrapping away the light absorbing layer 300 using a scribing tip. The scribing tip may be used in a direction in which the scribing tip is inclined with respect to the support substrate 100. Accordingly, the light absorbing layer 300 may be pressurized and patterned by the scribing tip in the direction in which the scribing tip is inclined. In this case, preferably, the needle force is adjusted to prevent scratches from being produced in a portion of the back electrode layer 200 exposed through the through hole TH.

In addition, the through hole TH may be patterned by a laser. In this case, the laser may be irradiated onto the light absorbing layer 300 in the direction in which the laser is inclined with respect to the support substrate 100. In this case, preferably, the laser power is adjusted to prevent scratches from being produced in a portion of the back electrode layer 200 exposed through the through hole TH

Referring to FIG. 7, the front electrode layer 400 is formed on the light absorbing layer 300. The front electrode layer 400 may be formed by stacking a transparent conductive material on the light absorbing layer 300. The transparent conductive material may include zinc oxide, indium tin oxide (ITO), or indium zinc oxide (IZO). In more detail, the front electrode layer 400 may be formed by using Al doped zinc oxide (AZO).

In more detail, the front electrode layer 400 may be formed through a sputtering process or a chemical vapor deposition process. In more detail, in order to form the front electrode layer 400 through the sputtering process, a deposition scheme based on an RF sputtering scheme using a ZnO target or a reactive sputtering scheme using a Zn target may be used.

The front electrode layer 400 may be formed by depositing a material for a front electrode on the light absorbing layer 300. In this case, since the through hole TH is inclined with respect to the support substrate 100, the material for the front electrode is not deposited on the lower portion of the inclined second inner surface 302 of the through hole TH by the shadow effect. Accordingly, the first and second

front electrodes

410 and 420 constituting the front electrode layer 400 may be separated from each other.

In this case, when the mask is not used as shown in FIG. 7A, the front electrode layer 400 may cover a portion of the second inner surface 302 of the through hole TH. Even in this case, the material for the front electrode is not deposited on the lower portion of the second inner surface 302 by the shadow effect. Accordingly, the solar cells C1 and C2 may be easily and electrically insulated from each other.

In contrast, as shown in FIG. 7B, the front electrode layer 400 may be deposited on the light absorbing layer 300 by using the mask M. In this case, the mask M is preferably formed over the through hole TH while corresponding to the through hole TH. The shadow effect can be more improved by the mask M, and the solar cells C1 and C2 are easily and electrically insulated from each other.

According to the solar cell module fabricated through the above scheme, the solar cells C1 and C2 may not only be connected to each other by the inclined through hole TH, but separated from each other by the inclined through hole TH. Therefore, according to the method of fabricating the solar cell module of the embodiment, since the solar cell module can be fabricated without a P3 patterning process to divide the solar cells C1 and C2, the fabricating process can be simplified. Accordingly, the process time can be shortened, and the process cost can be reduced.

Any reference in this specification to “one embodiment,” “an embodiment,” “example embodiment,” etc., means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the invention. The appearances of such phrases in various places in the specification are not necessarily all referring to the same embodiment. Further, when a particular feature, structure, or characteristic is described in connection with any embodiment, it is submitted that it is within the purview of one skilled in the art to effect such feature, structure, or characteristic in connection with other ones of the embodiments.

Although embodiments have been described with reference to a number of illustrative embodiments thereof, it should be understood that numerous other modifications and embodiments can be devised by those skilled in the art that will fall within the spirit and scope of the principles of this disclosure. More particularly, various variations and modifications are possible in the component parts and/or arrangements of the subject combination arrangement within the scope of the disclosure, the drawings and the appended claims. In addition to variations and modifications in the component parts and/or arrangements, alternative uses will also be apparent to those skilled in the art.

Claims

A solar cell module comprising:

a plurality of solar cells,

wherein each solar cell comprises:

a back electrode layer on a support substrate;

a light absorbing layer on the back electrode layer; and

a front electrode layer on the light absorbing layer, and

wherein the solar cells are separated from each other by a through hole inclined with respect to the support substrate.
The solar cell module of claim 1, wherein the through hole extends by passing through the light absorbing layer and exposes a portion of the back electrode layer.
The solar cell module of claim 1, wherein an angle between the through hole and the support substrate is in a range of 45° to 60°.
The solar cell module of claim 1, wherein an angle between an inner surface of the through hole and a top surface of the support substrate is in a range of 45° to 60°.
The solar cell module of claim 1, wherein a length of an inner surface of the through hole is at least three times greater than a thickness of the front electrode layer.
A solar cell module comprising:

a first solar cell including a first back electrode, a first light absorbing part, and a first front electrode that are sequentially arranged on a support substrate; and

a second solar cell including a second back electrode, a second light absorbing part, and a second front electrode that are sequentially arranged on the support substrate,

wherein the first and second solar cells are separated from each other by the through hole inclined with respect to the support substrate.
The solar cell module of claim 6, wherein the through hole includes a first inner surface making contact with the first solar cell, and a second inner surface provided in opposition to the first inner surface while making contact with the second solar cell.
The solar cell module of claim 7, wherein the first front electrode extends downward along the first inner surface such that the first electrode is electrically connected to the second back electrode.
The solar cell module of claim 8, wherein the first front electrode is not formed at a lower portion of the second inner surface.
The solar cell module of claim 7, wherein the second front electrode covers a portion of the second inner surface of the through hole.
The solar cell module of claim 7, wherein an angle between the first inner surface and the support substrate and an angle between the second inner surface and the support substrate are in a range of 45° to 60°.
The solar cell module of claim 7, wherein lengths of the first and second inner surfaces are at least three times greater than a thickness of a front electrode layer.
The solar cell module of claim 7, wherein the first front electrode is electrically insulated from the second front electrode.
A method of fabricating a solar cell module, the method comprising:

forming a back electrode layer on a support substrate;

forming a light absorbing layer on the back electrode layer;

forming a through hole exposing a portion of the back electrode layer through the light absorbing layer, and inclined with respect to the support substrate; and

forming a front electrode layer on the light absorbing layer.
The method of claim 14, wherein, in the forming of the through hole, a laser is irradiated onto the light absorbing layer in a direction in which the laser is inclined with respect to the support substrate.
The method of claim 14, wherein the forming of the front electrode layer includes depositing a material to form a front electrode layer after forming a mask over the through hole.