WO2020040393A1

WO2020040393A1 - Compound semiconductor solar cell and method for manufacturing same

Info

Publication number: WO2020040393A1
Application number: PCT/KR2019/003133
Authority: WO
Inventors: 김건호; 김수현; 이홍철
Original assignee: 엘지전자 주식회사
Priority date: 2018-08-21
Filing date: 2019-03-18
Publication date: 2020-02-27
Also published as: KR20200021772A

Abstract

The present invention relates to a compound semiconductor solar cell and a method for manufacturing same. A method for manufacturing a compound semiconductor solar cell, according to one aspect of the present invention, comprises the steps of: forming a sacrificial layer on one surface of a mother substrate; forming a compound semiconductor layer on the sacrificial layer by using a regular growth method; forming a plurality of front electrodes in the shape of a grid on the front surface of the compound semiconductor layer and then annealing the plurality of front electrodes; performing mesa etching so as to form a plurality of cells comprising the front electrodes; using an adhesive material so as to attach a support film to the front surface of the compound semiconductor layer provided in each of the plurality of cells; performing an epitaxial lift off (ELO) process so as to separate the plurality of cells from the mother substrate; forming a back electrode on the back surface of the compound semiconductor layer provided in each of the plurality of cells; cutting the support film at a region between the plurality of cells; and modularizing each of the plurality of cells by using the cut support film as a front substrate.

Description

Compound semiconductor solar cell and method for manufacturing same

The present invention relates to a compound semiconductor solar cell and a method for manufacturing the same, and more particularly, a compound semiconductor solar cell having improved contact resistance and improved efficiency, and a compound semiconductor solar cell capable of increasing productivity and reducing costs of the solar cell. It relates to a method for producing.

An object of the present invention is to provide a compound semiconductor solar cell having improved contact resistance and an improved efficiency, and a method of manufacturing a compound semiconductor solar cell which can increase productivity and reduce cost of the solar cell.

Method of manufacturing a compound semiconductor solar cell according to an aspect of the present invention, forming a sacrificial layer on one side of the mother substrate; Forming a compound semiconductor layer on the sacrificial layer by using a regular growth method; Forming a plurality of grid-shaped front electrodes on a front surface of the compound semiconductor layer and then annealing; Performing a mesa etching to form a plurality of cells having the front electrode; Attaching a support film to the front surface side of the compound semiconductor layer provided in each of the plurality of cells using an adhesive material; Performing an epitaxial lift off (ELO) process to separate the plurality of cells from the mother substrate; Forming a back electrode on a back surface of the compound semiconductor layer provided in each of the plurality of cells; Cutting the support film in the region between the plurality of cells; And modularizing the plurality of cells using the cut support film as the front substrate.

In an embodiment of the present invention, after the mesa etching, an anti-reflection film may be formed on the front surface of the compound semiconductor layer, and then the supporting film may be attached.

The support film may be formed of a material having a refractive index of 1.0 to 2.0 and a light transmittance of 80% or more in the wavelength range of 450 nm to 950 nm, and the adhesive material may have a refractive index of 1.0 to 2.0 and 80% at a wavelength range of 450 nm to 950 nm. It has the above light transmissivity can be formed of a material having a bond strength of 100kgf / cm ² to 500kgf / cm ^2.

For example, the support film may be formed of polyethylene terephthalate (PET) or polyimide (PI), and the adhesive material may be formed of epoxy, ethylene-vinyl acetate, or UV curing agent.

The annealing may be performed at a temperature of 400 ° C. to 500 ° C. for 5 minutes to 15 minutes.

In the modularization step, a rear substrate may be installed below the rear electrode, and a sealing material may be disposed between the front substrate and the rear substrate, and the sealing material may be formed of the same material as the adhesive material or different materials.

The compound semiconductor solar cell manufactured by the manufacturing method of such a structure is a compound semiconductor layer; And a grid-shaped front electrode positioned on a front surface of the compound semiconductor layer, and the contact resistance of the front electrode may be formed to be ¹ mΩ / cm ² or less.

The front electrode may be formed of palladium (Pd) / germanium (Ge) / gold (Au), the palladium / germanium / gold may be formed to a thickness of 5nm / 20nm / 250nm.

According to the method for manufacturing a compound semiconductor solar cell according to the present invention, since the compound semiconductor layer is separated from the mother substrate after forming the front electrode and performing annealing, the contact resistance of the front electrode can be reduced.

In addition, the ELO process can be used as a front substrate of the module without removing the support film for supporting the compound semiconductor layer, thereby improving productivity and reducing manufacturing costs.

1 is a process chart showing a method of manufacturing a compound semiconductor solar cell according to an embodiment of the present invention.

FIG. 2 is a perspective view showing a schematic configuration of the compound semiconductor solar cell shown in FIG. 1.

3 is a photograph of the front electrode illustrated in FIG. 2.

4 is a graph showing a change in contact resistance according to the process conditions of the annealing step shown in FIG.

FIG. 5 is a table illustrating efficiency of a compound semiconductor solar cell according to whether or not annealing step illustrated in FIG. 1 is performed.

As the invention allows for various changes and numerous embodiments, particular embodiments will be illustrated in the drawings and described in detail in the written description. It is not intended to limit the invention to the specific embodiments, it can be understood to include all changes, equivalents, and substitutes included in the spirit and scope of the present invention.

In describing the present invention, terms such as first and second may be used to describe various components, but the components may not be limited by the terms. The terms may be used only for the purpose of distinguishing one component from another component.

For example, without departing from the scope of the present invention, the first component may be referred to as the second component, and similarly, the second component may also be referred to as the first component.

The term "and / or" may include a combination of a plurality of related items or any of a plurality of related items.

When a component is said to be "connected" or "coupled" to another component, it may be directly connected to or coupled to the other component, but other components may be present in the middle. Can be understood.

On the other hand, when a component is referred to as being "directly connected" or "directly coupled" to another component, it may be understood that there is no other component in between.

The terminology used herein is for the purpose of describing particular example embodiments only and is not intended to be limiting of the present invention. Singular expressions may include plural expressions unless the context clearly indicates otherwise.

In this application, the terms "comprise" or "have" are intended to indicate that there is a feature, number, step, operation, component, part, or combination thereof described in the specification, and one or more other features. It may be understood that the present invention does not exclude the possibility of the presence or addition of numbers, steps, operations, components, parts, or a combination thereof.

In the drawings, the thickness of layers, films, panels, regions, etc., are exaggerated for clarity. When a portion of a layer, film, region, plate, etc. is said to be "on top" of another part, this includes not only when the other part is "right over" but also when there is another part in the middle. On the contrary, when a part is "just above" another part, there is no other part in the middle.

Unless defined otherwise, all terms used herein, including technical or scientific terms, may have the same meaning as commonly understood by one of ordinary skill in the art.

Terms such as those defined in the commonly used dictionaries may be interpreted as having meanings consistent with the meanings in the context of the related art, and shall be interpreted in ideal or excessively formal meanings unless expressly defined in the present application. It may not be.

In addition, the following embodiments are provided to more fully describe those skilled in the art, and the shape and size of the elements in the drawings may be exaggerated for clarity.

Hereinafter, the present invention will be described with reference to the accompanying drawings.

3 is a photograph of the front electrode illustrated in FIG. 2.

First, the compound semiconductor solar cell manufactured by the manufacturing method of this invention is demonstrated with reference to FIG.

The compound semiconductor solar cell includes a light absorbing layer PV, a window layer 10 positioned on the front surface of the light absorbing layer PV, a grid-shaped front electrode 20 positioned on the front surface of the window layer 10, The front contact layer 30 positioned between the window layer 10 and the front electrode 20, the antireflection film 40 positioned on the window layer 10, and the rear contact layer positioned on the rear surface of the light absorbing layer PV ( 50 and a rear electrode 60 positioned on the rear surface of the rear contact layer 50.

Here, at least one of the anti-reflection film 40, the window layer 10, the front contact layer 30, and the rear contact layer 50 may be omitted. However, as shown in FIG. It demonstrates as an example.

The light absorbing layer (PV) is a group III-VI semiconductor compound, for example, a GaInP compound containing gallium (Ga), indium (In) and phosphorus (P), or a GaAs compound containing gallium (Ga) and arsenic (As). It may be formed to include.

The light absorption layer PV is a p-type semiconductor layer PV-p doped with an impurity of a first conductivity type, for example, a p-type impurity, and an n-type semiconductor doped with an impurity of a second conductivity type, for example, an n-type impurity. Layer (PV-n).

Although not shown, the light absorbing layer PV may further include a rear electric field layer disposed at the rear of the p-type semiconductor layer PV-p.

The light absorbing layer (PV) of this configuration can be prepared from a mother substrate by a metal organic chemical vapor deposition (MOCVD) method, a molecular beam epitaxy (MBE) method or any other suitable method for forming an epitaxial layer. Can be.

The window layer 10 may be formed between the light absorbing layer PV and the front electrode 20, and may be formed by doping a III-VI group semiconductor compound with a second conductivity type, that is, an n-type impurity.

The window layer 10 functions to passivate the front surface of the light absorbing layer PV, and may have an energy band gap higher than that of the light absorbing layer PV.

The anti-reflection film 40 may be located on the remaining area of the window layer 10 except for the area where the front electrode 20 and / or the front contact layer 30 is located.

Alternatively, the anti-reflection film 40 may be disposed on the front contact layer 30 and the front electrode 20 as well as the exposed window layer 10.

In this case, although not shown, the compound semiconductor solar cell may further include a busbar electrode for physically connecting the plurality of front electrodes 20, and the busbar electrode is not covered by the anti-reflection film 40 and exposed to the outside. Can be.

The front electrode 20 may be formed to extend in the first direction X-X ', and the plurality of front electrodes 20 may be spaced apart at regular intervals along the second direction Y-Y' perpendicular to the first direction. .

The front electrode 20 having such a configuration may be formed by including an electrically conductive material. For example, the front electrode 20 may include at least one of gold (Au), germanium (Ge), and nickel (Ni).

For example, the front electrode 20 may be formed of palladium (Pd) / germanium (Ge) / gold (Au), and the palladium / germanium / gold may be formed to a thickness of 5 nm / 20 nm / 250 nm.

The front contact layer 30 positioned between the window layer 10 and the front electrode 20 is formed by doping the group III-VI semiconductor compound with a second impurity at a doping concentration higher than the impurity doping concentration of the window layer 10. can do.

The rear contact layer 50 located on the rear surface of the p-type semiconductor layer PV-p of the light absorption layer PV is generally located on the rear surface of the light absorption layer PV, and has a first conductivity type in the group III-VI semiconductor compound. May be formed by doping at a higher doping concentration than the p-type semiconductor layer PV-p.

In addition, unlike the front electrode 20, the rear electrode 60 positioned on the rear surface of the rear contact layer 50 may be formed of a sheet-shaped conductor positioned entirely on the rear surface of the rear contact layer 50. . That is, the rear electrode 60 may also be referred to as a sheet electrode positioned on the entire rear surface of the rear contact layer 50.

In this case, the rear electrode 60 may be formed in the same plane as the light absorbing layer PV, and may include gold (Au), platinum (Pt), titanium (Ti), tungsten (W), silicon (Si), and nickel (Ni). ), Magnesium (Mg), palladium (Pd), copper (Cu), and germanium (Ge) may be formed as a single film or a multi-layer including at least one material selected from, and the material forming the rear electrode is It may be appropriately selected depending on the conductivity type of the contact layer.

Hereinafter, the manufacturing method of said compound semiconductor solar cell is demonstrated.

In the manufacturing method of the present invention, the sacrificial layer 120 is formed on one side of the mother substrate 110, and then the compound semiconductor layer CS is formed on the sacrificial layer 120 by using a regular growth method. Making; Forming a plurality of grid-shaped front electrodes 20 on the front surface of the compound semiconductor layer CS and then annealing; Performing mesa etching to form a plurality of cells C including the front electrode 20; Attaching the support film 140 to the front surface side of the compound semiconductor layer CS provided in each of the plurality of cells C using the adhesive material 130; Performing an epitaxial lift off (ELO) process to separate the plurality of cells (C) from the mother substrate (110); Forming a rear electrode (60) on a back surface of the compound semiconductor layer (CS) provided in each of the plurality of cells (C); Cutting the support film 140 in an area between the plurality of cells C; And modularizing the plurality of cells C using the cut support film 140 as a front substrate.

In more detail, first, the sacrificial layer 120 is formed on one side of a mother substrate 110 serving as a base for providing an appropriate lattice structure in which the light absorbing layer PV is formed, and is regular. The compound semiconductor layer CS is formed on the sacrificial layer 120 by using a regular growth method.

Here, the regular growth method refers to a method of sequentially forming the back contact layer 50, the light absorbing layer PV, the window layer 10, and the front contact layer 30 on the sacrificial layer 120. inverse) is a method of forming each layer in the reverse order of the regular growth method.

Subsequently, a plurality of grid-shaped front electrodes 20 are formed on the front surface of the compound semiconductor layer CS.

Here, the plurality of front electrodes 20 are formed to form a plurality of cells C by mesa etching the compound semiconductor layer CS formed on the sacrificial layer 120.

After the plurality of front electrodes 20 are formed, an annealing process is performed.

The annealing process is to reduce the contact resistance of the front electrode by heat treatment of the front electrode 20, it is carried out for 5 to 15 minutes at a temperature of 400 ℃ to 500 ℃.

FIG. 4 is a graph showing a change in contact resistance of the front electrode according to the process conditions of the annealing step illustrated in FIG. 1, and FIG. 5 illustrates the efficiency of a compound semiconductor solar cell according to whether or not the annealing step illustrated in FIG. As a table, FIG. 4 and FIG. 5 show the measurement results when the front electrode 20 is formed of 5 nm thick palladium (Pd) / 20 nm thick germanium (Ge) / 250 nm thick gold (Au).

The front electrode may be formed by any one of an evaporation method, a sputtering method, a plating method, and a screen printing method.

Referring to FIG. 4, when annealing the front electrode 20 at a temperature of 200 ° C. and a temperature of 300 ° C., the contact resistance of the front electrode 20 is about 10 mPa / cm ² regardless of the increase or decrease of the annealing time. Can be.

However, when annealing is performed for 5 minutes or more at a temperature of 400 ° C as disclosed in the present invention, it can be seen that the contact resistance of the front electrode 20 is lowered to about 1 mPa / cm ² or less.

Therefore, the annealing process of the front electrode 20 is preferably carried out for 5 to 15 minutes at a temperature of 400 ℃ to 500 ℃.

Referring to FIG. 5, the efficiency of the solar cell before (annealed) and after the annealing (invention) will be described with reference to FIG. 5. Compared with the solar cell, it is lower, respectively, and the short-circuit current density Jsc and the fill factor FF show that the solar cell after annealing is increased compared with the solar cell before annealing.

Therefore, when the annealing is performed after the front electrode 20 is formed as in the present invention, it can be seen that the efficiency Eff is increased as compared with the conventional case where the annealing is not performed.

As described above, the reason why the annealing process can be performed after the front electrode 20 is formed in the present invention is that the front electrode forming step and the annealing step are performed before the ELO process.

That is, compared with the conventional manufacturing method, conventionally, after forming a metal protective layer to support the compound semiconductor layer in the ELO process and to protect the compound semiconductor layer from the etching solution used in the ELO process, wax (wax) was used to attach the lamination film to the metal protective layer.

Therefore, according to the conventional method, the manufacturing cost of the compound semiconductor solar cell is increased due to a problem such as a high deposition time required for forming the metal protective layer or a cost increase due to the use of expensive metal, and also the metal protective layer and Since the lamination film needs to be removed, there is a problem in that the number of processes increases, and damage to the compound semiconductor layer occurs during the removal of the metal protective layer and the lamination film.

In addition, according to the conventional method, since the metal compound (front electrode) is formed in the compound semiconductor layer after the compound semiconductor layer is separated from the mother substrate by the ELO process, the carrier substrate for supporting the compound semiconductor layer in the front electrode formation step Should be attached to the compound semiconductor layer.

However, since the adhesive for attaching the carrier substrate to the compound semiconductor layer is very vulnerable to heat, it is difficult to proceed the heat treatment to reduce the contact resistance after electrode formation, which has a problem in that the efficiency of the compound semiconductor solar cell is limited. .

However, according to the manufacturing method of the present invention, since the annealing process is performed after the front electrode 20 is formed, and then the ELO process is performed, problems occurring in the conventional manufacturing method can be eliminated.

Meanwhile, in the manufacturing method of the present invention, the front electrode 20 is formed and the annealing process is performed before the EOL process, so that the mother substrate 110 is formed of the compound semiconductor layer CS in the process of forming the front electrode 20. I can definitely support it.

Therefore, as shown in FIG. 3, the effect of reducing misalignment of the front electrode can be obtained as compared with the conventional case in which the front electrode is formed after the ELO process (photo shown on the left side of FIG. 3).

After the annealing process is performed, the antireflection film 40 is formed.

The anti-reflection film 40 forming process may be omitted.

After the anti-reflection film 40 is formed, mesa etching is performed.

Here, mesa etching refers to an etching process for manufacturing a plurality of cells (C), that is, a plurality of compound semiconductor solar cells in one compound semiconductor layer (CS) by separating one compound semiconductor layer (CS) into several. do.

After the mesa etching is performed to form the plurality of cells C, the supporting film 140 is attached to the front surface side of the compound semiconductor layer CS provided in each of the plurality of cells C.

In this case, the support film 140 may be attached using the adhesive material 130.

By the way, in the manufacturing method of this invention, the support film 140 is not removed and is used as a front substrate in the modularization process of a compound semiconductor solar cell.

Therefore, in order to allow light to effectively enter the compound semiconductor layer CS, the support film 140 is formed of a material having a refractive index of 1.0 to 2.0 and a light transmittance of 80% or more in the wavelength range of 450 nm to 950 nm, and an adhesive material. 130 is preferably from 1.0 to have a refractive index and, 450nm to the light transmittance of 80% or more in the wavelength range of 950nm of 2.0 to form a material having a bond strength of 100kgf / cm ² to 500kgf / cm ^2.

After attaching the supporting film 140, an epitaxial lift off (ELO) process is performed to separate the plurality of cells C from the mother substrate 110.

Subsequently, the carrier substrate 150 is attached to the support film 140 by an adhesive, and the compound semiconductor layer provided in each of the plurality of cells C in the state in which the carrier substrate 150 is attached to the support film 140 ( After forming the back electrode 60 on the back surface of the CS, the carrier substrate 150 is removed.

In the manufacturing method of the present invention, the process of attaching and removing the carrier substrate 150 may be omitted if the supporting film 140 has a strength sufficient to support the compound semiconductor layer CS.

When the back electrode 60 is formed, the material forming the back electrode may be filled in the region between the cells C. The back electrode forming material filled in the region between the cells C may be formed in the support film 140 to be described later. Can be removed in the cutting process.

After the back electrode 60 is formed, the support film 140 is cut by irradiating a laser to a region between the plurality of cells C, and the back electrode forming material filled in the region between the cells C is removed.

Thereafter, the plurality of cells C are modularized using the cut support film 140 as the front substrate.

In the modularization step, the rear substrate 160 may be installed below the rear electrode 60, and the sealing material 170 may be disposed between the front substrate 140 and the rear substrate 160, in which case the sealing material 170 may be disposed. May be formed of the same material as the adhesive material 130 or may be formed of different materials.

Although the preferred embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements of those skilled in the art using the basic concepts of the present invention defined in the following claims are also provided. It belongs to the scope of rights.

Claims

Forming a sacrificial layer on one side of the mother substrate;

Forming a compound semiconductor layer on the sacrificial layer by using a regular growth method;

Forming a plurality of grid-shaped front electrodes on a front surface of the compound semiconductor layer and then annealing;

Performing a mesa etching to form a plurality of cells having the front electrode;

Attaching a support film to the front surface side of the compound semiconductor layer provided in each of the plurality of cells using an adhesive material;

Performing an epitaxial lift off (ELO) process to separate the plurality of cells from the mother substrate;

Forming a back electrode on a back surface of the compound semiconductor layer provided in each of the plurality of cells;

Cutting the support film in the region between the plurality of cells; And

Modularizing a plurality of cells, respectively, using the cut support film as the front substrate.

Method for producing a compound semiconductor solar cell comprising a.
In claim 1,

After the mesa etching, forming an anti-reflection film on the front surface of the compound semiconductor layer, and then attaching the support film.
The method of claim 1 or 2,

The support film is formed of a material having a refractive index of 1.0 to 2.0 and a light transmittance of 80% or more in the wavelength range of 450 nm to 950 nm,

The adhesive material of 1.0 to have a refractive index and, 450nm to the light transmittance of 80% or more in the wavelength range of 950nm of 2.0 100kgf / cm 2 to compound A method for fabricating a semiconductor solar cell formed of a material having an adhesive strength of 500kgf / cm 2.
In claim 3,

The support film is formed of polyethylene terephthalate (PET) or polyimide (PI), and the adhesive material is formed of epoxy (epoxy), EVA (ethylene-vinyl acetate), or a UV curing agent manufacturing method of a compound semiconductor solar cell.
In claim 3,

The annealing is carried out for 5 minutes to 15 minutes at a temperature of 400 ℃ to 500 ℃ manufacturing method of a compound semiconductor solar cell.
In claim 5,

In the modularizing step, a rear substrate is provided below the rear electrode and a sealing material is disposed between the front substrate and the rear substrate, wherein the sealing material is a manufacturing method of a compound semiconductor solar cell.
In claim 5,

In the modularization step, a rear substrate is installed below the rear electrode, and a sealing material is disposed between the front substrate and the rear substrate, wherein the sealing material is formed of a material different from the adhesive material. .
Compound semiconductor layers; And

Grid-shaped front electrode positioned on the front surface of the compound semiconductor layer

Including;

The contact resistance of the front electrode is 1 mPa / cm 2 or less compound semiconductor solar cell.
In claim 8,

The front electrode is a compound semiconductor solar cell formed of palladium (Pd) / germanium (Ge) / gold (Au).
In claim 9,

The palladium is formed to a thickness of 5nm, the germanium is formed to a thickness of 20nm, the gold compound semiconductor solar cell is formed to a thickness of 250nm.