KR20120115890A

KR20120115890A - Solar cell apparatus and method of fabricating the same

Info

Publication number: KR20120115890A
Application number: KR1020110033471A
Authority: KR
Inventors: 박지홍
Original assignee: 엘지이노텍 주식회사
Priority date: 2011-04-11
Filing date: 2011-04-11
Publication date: 2012-10-19
Also published as: KR101762958B1

Abstract

Solar cell according to the embodiment is a substrate; A back electrode layer on the substrate; A light absorbing layer on the back electrode layer; A first buffer layer on the light absorbing layer; A high resistance buffer layer doped with impurities on the first buffer layer; And a window layer on the high resistance buffer layer.

Description

SOLAR CELL AND MANUFACTURING METHOD THEREOF {SOLAR CELL APPARATUS AND METHOD OF FABRICATING THE SAME}

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

Recently, as the demand for energy increases, development of solar cells for converting solar energy into electrical energy is in progress.

In particular, a CIGS-based solar cell, which is a pn heterojunction device having a support substrate structure including a glass support substrate, a metal back electrode layer, a p-type CIGS-based light absorbing layer, a first buffer layer, an n-type transparent electrode layer, and the like, is widely used.

In addition, various studies are underway to increase the efficiency of such solar cells.

Embodiments provide a solar cell including a sensor unit having a structure identical to that of solar cells, and provide a solar cell and a method of manufacturing the solar cell capable of knowing an operating temperature of the solar cell and an incident amount of sunlight.

A solar cell according to an embodiment includes at least one solar cell including 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 window layer on the buffer layer; And a sensor unit formed in a circumferential region on the substrate.

According to the embodiment, by manufacturing a solar cell including a sensor unit having the same structure as the solar cells, it is possible to know the operating temperature of the solar cell and the incident amount of sunlight.

1 is a plan view illustrating a solar cell apparatus according to an embodiment.
FIG. 2 is a cross-sectional view illustrating a cross section taken along AA ′ in FIG. 1.
3 to 6 are cross-sectional views illustrating a method of manufacturing a solar cell according to an embodiment.
7 is a plan view illustrating a junction box and a display unit disposed on a rear surface of a substrate.

In the description of the embodiments, when each support substrate, layer, film, or electrode is described as being formed "on" or "under" of each support substrate, layer, film, or electrode, etc. As used herein, “on” and “under” include both “directly” or “indirectly” other components. In addition, the upper or lower reference of each component is described with reference to the drawings. In the drawings, the size of each component may be exaggerated for description, and does not mean the size to be actually applied.

FIG. 1 is a plan view illustrating a photovoltaic device according to an embodiment, and FIG. 2 is a cross-sectional view illustrating a cross section taken along a line A-A 'of FIG. 1.

Referring to FIG. 1, a plurality of solar cells C1, C2, C3,... Are formed on a substrate 100, and the plurality of solar cells C1, C2, C3,... Grooves 130 are formed in some regions, and the sensor unit 150 is formed on the opposite side of the plurality of solar cells C1, C2, C3,... Based on the grooves 130.

The sensor unit 150 is formed in the circumferential region of the substrate 100 but is not limited thereto.

The sensor unit 150 is formed to have the same layer as the plurality of solar cells C1, C2, C3, ..., and the plurality of solar cells C1, C2, C3, ... It can similarly absorb sunlight. That is, the groove 130 is divided into a plurality of solar cells C1, C2, C3,..., And a sensor unit 150.

The groove 130 may be formed to separate the plurality of solar cells C1, C2, C3,... And the sensor unit 150. The sensor unit 150 is electrically separated from the plurality of solar cells C1, C2, C3, ..., and used as a sensor capable of sensing temperature and incident amount. That is, the top surface of the substrate 100 may be exposed by the groove 130.

The sensor unit 150 may be connected to the plurality of solar cells C1, C2, C3,... By separate wires 157 and 158 to transmit information of the sensor unit 150 to the outside. . The sensor unit 150 may be formed inside the module.

The signal of the sensor unit 150 can be used to check information such as the operating temperature and the amount of incidence of the module. The information can also be confirmed.

The sensor unit 150 may be formed to a length of 5mm to 20mm.

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

The support 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. In more detail, the support substrate 100 may be a soda lime glass substrate.

When the support substrate 100 is soda lime glass, sodium (Na) contained in the soda lime glass may be diffused into the light absorbing layer 300 formed of CIGS during the manufacturing process of the solar cell, whereby the light absorbing layer 300 ), The charge concentration may increase. This may be a factor that can increase the photoelectric conversion efficiency of the solar cell.

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

The rear electrode layer 200 is disposed on the supporting substrate 100. The back electrode layer 200 is a conductive layer. The back electrode layer 200 may allow electric charges generated in the light absorbing layer 300 of the solar cell to move to allow current to flow to the outside of the solar cell. The back electrode layer 200 should have high electrical conductivity and low specific resistance in order to perform this function.

In addition, the back electrode layer 200 should maintain high temperature stability during heat treatment under sulfur (S) or selenium (Se) atmosphere accompanying CIGS compound formation. In addition, the back electrode layer 200 should be excellent in adhesion with the support substrate 100 so that peeling does not occur with the support 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, since molybdenum (Mo) has a smaller difference in coefficient of thermal expansion and the support substrate 100 than other elements, it is excellent in adhesiveness and can prevent peeling from occurring. Overall required properties can be met.

The back electrode layer 200 may include two or more layers. In this case, each of the layers may be formed of the same metal, or may be formed of different metals.

First through holes TH1 are formed in the back electrode layer 200. The first through holes TH1 are open regions exposing a portion of an upper surface of the support substrate 100. The first through holes 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 μm to 150 μm.

By the first through holes TH1, the back electrode layer 200 is divided into a plurality of back electrodes. That is, back electrodes are defined 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 absorbing layer 300 may be formed on the back electrode layer 200. The light absorbing layer 300 includes a p-type semiconductor compound. In more detail, the light absorbing layer 300 includes a group I-III-VI 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 light absorbing layer 300 may have a bandgap of 1.1 eV to 1.2 eV.

The buffer layer 400 and the high resistance buffer layer 500 may be formed on the light absorbing 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 window layer 600 thin film as the n-type semiconductor. However, since the two materials have a large difference in lattice constant and band gap energy, a buffer layer having a band gap in between the two materials is required to form a good junction.

Materials for forming the buffer layer 400 include CdS, ZnS and the like, and CdS is relatively excellent in terms of power generation efficiency of the solar cell. The buffer layer 400 may have a band gap of 2.2 eV to 2.6 eV.

The high resistance buffer layer 500 is formed on the buffer layer 400. The high resistance buffer layer may include zinc oxide (ZnO).

The 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, indium tin oxide (ITO), or indium zinc oxide (IZO).

In addition, the oxide may include conductive impurities such as aluminum (Al), alumina (Al ₂ O ₃ ), magnesium (Mg), or gallium (Ga). More specifically, the window layer 600 may be formed of aluminum doped zinc oxide (AZO), boron doped zinc oxide (BZO), or gallium doped zinc oxide (GZO). ) May be included.

The energy bandgap of the window layer 600 is about 3.4 eV to 3.6 eV.

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

Therefore, the connection part 650 connects cells adjacent to each other. In more detail, the connection part 650 connects the window and the rear electrode included in the cells C1, C2 ... adjacent to each other.

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

As shown, a portion of the upper surface of the back electrode layer 200 may be exposed by the second through holes TH2. In addition, a plurality of solar cells may be connected in series by the window layer 600 formed to fill the second through holes TH2.

The window layer 600 may include AZO, BZO or GAZO.

3 to 6 are cross-sectional views illustrating a method of manufacturing the solar cell apparatus according to the embodiment. For a description of the present manufacturing method, refer to the description of the photovoltaic device described above.

Referring to FIG. 3, the back electrode layer 200 is formed on the support substrate 100, and the back electrode layer 200 is patterned to form first through holes TH1. Accordingly, a plurality of back electrodes are formed on the support substrate 100. The back electrode layer 200 may be patterned by a laser.

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

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. 4, the light absorbing layer 300, the buffer layer 400, and the 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.

In order to form the light absorbing layer 300, for example, copper, indium, gallium, selenium, or copper-indium-gallium-selenide-based (Cu (In, Ga) Se ₂ ; CIGS-based) A method of forming the light absorbing layer 300 and a method of forming a metal precursor film and then forming it by a selenization process are widely used.

When the metal precursor film is formed and selenization is subdivided, 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.

Thereafter, the metal precursor film is formed of a copper-indium-gallium-selenide-based (Cu (In, Ga) Se ₂ ; CIGS-based) light absorbing layer 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.

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

Subsequently, zinc oxide (ZnO) is deposited on the buffer layer 400 by a method such as sputtering, evaporation, metal organic chemical vapor deposition (MOCVD), and pulse laser deposition (PLD). Is formed.

The high resistance buffer layer 500 may be formed to a thickness of 30nm to 100nm. Cd may be doped into the high resistance buffer layer 500. That is, the high resistance buffer layer 500 may include zinc oxide (ZnO) and cadmium. The band gap of the high resistance buffer layer 500 may be adjusted by adjusting the element ratio of cadmium.

Thereafter, a portion of the light absorbing layer 300, the buffer layer 400, and the high resistance buffer layer 500 is removed to form second through holes TH2.

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

In this case, the width of the second through holes TH2 may be about 50 μm to about 200 μm.

In addition, the second through holes TH2 are formed to expose a portion of the top surface of the back electrode layer 200.

Referring to FIG. 5, 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 inside the second through holes TH2.

In this case, the transparent conductive material is filled in the second through holes TH2, and the window layer 600 is electrically connected to the back electrode layer 200.

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

Referring to FIG. 6, portions of the buffer layer 400, the high resistance buffer layer 500, and 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 μm to about 200 μm.

As shown, the contact layer 650 connects adjacent cells to each other. In more detail, the contact layer 650 connects the window layer 600 and the back electrode included in the cells C1, C2 ... adjacent to each other.

Next, grooves 130 may be formed in some regions of the cells C1, C2..., So that the cells C1, C2... And the sensor unit 150 may be electrically separated. That is, the top surface of the substrate 100 may be exposed by the groove 130.

The groove 130 may be formed through a laser or a physical method.

Thereafter, the first and second bus bars 710 and 720 having different polarities may be connected at both ends of the cells C1 and C2... And the display unit 155 may separate the wires 157 and 158. The sensor unit 150 may be connected to the sensor unit 150 to display information regarding temperature and incident amount.

The first bus bar 710 and the second bus bar 720 may include the light absorbing layer 300, the buffer layer 400, the high resistance buffer layer 500, and the window layer 600 formed in the circumferential region of the substrate 100. It may be formed after exposing the back electrode layer 200 by removing a portion of the).

The first bus bar 710 may be connected to the (+) electrode, and the second bus bar 720 may be connected to the (-) electrode, or vice versa.

FIG. 7 is a plan view illustrating the junction box 180 and the display unit 155 disposed on the rear surface of the substrate 100.

As shown in FIG. 7, the junction box 180 may be electrically connected to the first and second bus bars 710 and 720.

In addition, separate wires 157 and 158 connected to the sensor unit 150 and the display unit 155 may be connected to display information on a temperature and an incident amount. The display unit 155 may be included in the junction box 180 to display a temperature and an incident amount, and separate wires 157 and 158 may be connected to the outside to check the information from the outside.

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 may be combined or modified with respect to 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 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

At least one solar cell including 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 window layer on the buffer layer; And
And a sensor unit formed in a circumferential region on the substrate.

The method of claim 1,
The sensor unit is formed of a length of 5mm to 20mm solar cell.

The method of claim 1,
The sensor unit is a solar cell electrically separated from the solar cell.

The method of claim 1,
A solar cell comprising a groove formed between the sensor unit and the solar cell.

The method of claim 4, wherein
The groove is formed so that the upper surface of the substrate is exposed.

The method of claim 1,
The sensor unit has a solar cell having the same layer as the solar cell.

The method of claim 1,
And a first bus bar and a second bus bar formed at both ends of the at least one solar cell and electrically connected to the at least one solar cell and having different polarities.

The method of claim 7, wherein
And a wire electrically connected to the sensor unit.

9. The method of claim 8,
And a display unit electrically connected to the sensor unit through the wires.