KR102512703B1 - High-efficiency Flexible Solar Cell and Method for Manufacturing the Same - Google Patents

Abstract

Disclosed is a high-efficiency flexible solar cell and a method for manufacturing the same.
According to one aspect of this embodiment, a first transparent electrode, a Back Surface Field (BSF) layer laminated on the first transparent electrode, a first grading layer laminated on the BSF layer, and laminated on the first grading layer, A base layer that absorbs incident light and is laminated on the base layer to be pn-junctioned with the base layer, and when the base layer absorbs light, an emitter layer that generates current together with the base layer and laminated on the emitter layer Provides a solar cell characterized in that it comprises a second grading layer, a window layer stacked on the second grading layer and improving the incidence of light from the outside, and a second transparent electrode stacked on the window layer. .

Description

High-efficiency Flexible Solar Cell and Method for Manufacturing the Same

This embodiment relates to a flexible solar cell having high power generation efficiency and a method for manufacturing the same.

The contents described in this part merely provide background information on the present embodiment and do not constitute prior art.

Recently, as the reserves of traditional fossil fuels decrease and environmental pollution caused by fossil fuels becomes serious, interest in the use of environmentally friendly alternative energy is increasing. In particular, solar cells using sunlight are in the limelight as the most powerful alternative energy to replace traditional energy in the future due to technology accumulated through long research.

Solar cells are mainly installed in buildings or means of transportation because they need to be installed in locations where a lot of sunlight is irradiated. Since the solar cell is installed in such an open space, unlike the prior art, there is an increasing demand for a transparent solar cell that transmits visible light aesthetically.

In addition, there are cases where the solar cell is installed on a curved surface rather than a flat surface when installed in a building or means of transportation. Accordingly, a solar cell having a flexible feature is required. In order for the solar cell to have a flexible feature, the thickness should be less than 20 μm. However, when the solar cell is formed of silicon, since it has an indirect transition type energy band gap with high heat loss, the power generation efficiency decreases rapidly as the thickness decreases.

Due to these problems, there is a demand for a transparent solar cell having high power generation efficiency and flexible characteristics.

An object of one embodiment of the present invention is to provide a transparent solar cell having high power generation efficiency and flexible characteristics and a method for manufacturing the same.

According to one aspect of the present invention, a first transparent electrode, a back surface field (BSF) layer laminated on the first transparent electrode, a first grading layer laminated on the BSF layer, and laminated on the first grading layer, A base layer that absorbs incident light and is laminated on the base layer to be pn-junctioned with the base layer, and when the base layer absorbs light, an emitter layer that generates current together with the base layer and laminated on the emitter layer Provides a solar cell characterized in that it comprises a second grading layer, a window layer stacked on the second grading layer and improving the incidence of light from the outside, and a second transparent electrode stacked on the window layer. .

According to one aspect of the present invention, the BSF layer is characterized in that it is implemented with p-type AlInP or p-type AlGaInP.

According to one aspect of the present invention, the base layer is characterized in that it is implemented with p-type AlGaInP.

According to one aspect of the present invention, the emitter layer is characterized in that it is implemented with n-type AlGaInP.

According to one aspect of the present invention, the window layer is characterized in that it is implemented with n-type AlInP or n-type AlGaInP.

According to one aspect of the present invention, the first grading layer and the second grading layer are characterized in that they are implemented with p-type AlGaInP and n-type AlGaInP, respectively.

According to one aspect of the present invention, a first lamination process in which a sacrificial layer, a window layer, a second grading layer, an emitter layer, a base layer, a first grading layer, and a BSF layer are sequentially laminated on a substrate and onto the BSF layer A second lamination process in which a second transparent electrode is laminated, a deposition process in which a transparent film is attached or spin-coated deposited on the second transparent electrode, and the sacrificial layer is etched to laminate on the substrate except for the substrate and the sacrificial layer. It provides a solar cell manufacturing method comprising a separation process of separating the remaining layers and a third lamination process of laminating a first transparent electrode on the window layer.

As described above, according to one aspect of the present invention, the solar cell has the advantage of being transparent and flexible while having high power generation efficiency.

1 is a cross-sectional view of a solar cell according to an embodiment of the present invention.
2 is a graph showing light transmittance for each wavelength of a solar cell according to an embodiment of the present invention.
3 to 7 are diagrams illustrating a process of manufacturing a solar cell according to an embodiment of the present invention.

Since the present invention can make various changes and have various embodiments, specific embodiments will be illustrated in the drawings and described in detail. However, this is not intended to limit the present invention to specific embodiments, and should be understood to include all modifications, equivalents, or substitutes included in the spirit and technical scope of the present invention. Like reference numerals have been used for like elements throughout the description of each figure.

Terms such as first, second, A, and B may be used to describe various components, but the components should not be limited by the terms. These terms are only used for the purpose of distinguishing one component from another. For example, a first element may be termed a second element, and similarly, a second element may be termed a first element, without departing from the scope of the present invention. The terms and/or include any combination of a plurality of related recited items or any of a plurality of related recited items.

It is understood that when an element is referred to as being "connected" or "connected" to another element, it may be directly connected or connected to the other element, but other elements may exist in the middle. It should be. On the other hand, when an element is referred to as “directly connected” or “directly connected” to another element, it should be understood that no intervening element exists.

Terms used in this application are only used to describe specific embodiments, and are not intended to limit the present invention. Singular expressions include plural expressions unless the context clearly dictates otherwise. It should be understood that terms such as "include" or "having" in this application do not exclude in advance the possibility of existence or addition of features, numbers, steps, operations, components, parts, or combinations thereof described in the specification. .

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

Terms such as those defined in commonly used dictionaries should be interpreted as having a meaning consistent with the meaning in the context of the related art, and unless explicitly defined in the present application, they should not be interpreted in an ideal or excessively formal meaning. don't

In addition, each configuration, process, process or method included in each embodiment of the present invention may be shared within a range that does not contradict each other technically.

1 is a cross-sectional view of a solar cell according to an embodiment of the present invention.

Referring to FIG. 1 , a solar cell 100 according to an embodiment of the present invention includes a base layer 110, an emitter layer 120, a BSF layer 130, a window layer 140, and a first grading layer 150. ), a second grading layer 160, transparent electrodes 170 and 175, a tunnel junction layer 180, and an ohmic layer (not shown).

The base layer 110 and the emitter layer 120 absorb light to generate electricity. The emitter layer 120 is stacked on the base layer 110, and the base layer 110 and the emitter layer 120 are implemented with p-type AlGaInP and n-type AlGaInP, respectively. Accordingly, the base layer 110 absorbs light passing through the window layer 140 , the second grading layer 160 and the emitter layer 120 . The base layer 110 is PN-junctioned together with the emitter layer 120, and both 110 and 120 generate electricity by light absorption of the base layer 110. The generated electricity is transferred to the outside through the respective transparent electrodes 170 and 175 .

BSF (Back Surface Field) layer 130 is located below the base layer 110, and electrons and holes generated in the base layer 110 and the emitter layer 120 are transferred to the respective transparent electrodes 170 and 175 Let it be. In order to increase power generation efficiency, recombination of generated electrons and holes must be prevented. The BSF layer 130 is positioned below the base layer 110 and between the base layer 110 and the transparent electrode 175 . The BSF layer 130 is implemented with p-type AlInP or p-type AlGaInP and has a larger energy bandgap than the base layer 110 . Accordingly, holes generated in the base layer 110 and the emitter layer 120 pass through the BSF layer 130 and are transferred to the transparent electrode 175, while electrons generated in the base layer 110 and the emitter layer 120 is not transferred to the BSF layer 130 due to a difference in energy bandgap and is transferred to the transparent electrode 170 in the window direction.

The window layer 140 increases the amount of incident light on the solar cell 100 . The left layer 140 is disposed above the emitter layer 120 to increase the amount of incident light on the solar cell 100 . When the window layer 140 does not exist, light is reflected from the surface and is not completely incident to the solar cell, resulting in a drop in incident rate. To prevent this, the window layer 140 is disposed on the top surface of the emitter layer 120 and on the front surface excluding the transparent electrode 170 in the direction in which light is incident on the solar cell 100 .

The window layer 140 is implemented with n-type AlInP or n-type AlGaInP and has a larger energy bandgap than the emitter layer 120 or the base layer 110 . Accordingly, the window layer 140 partially absorbs light other than the wavelength band absorbed by the base layer 110 (light in a shorter wavelength band), but the window layer 140 partially absorbs light in a wavelength band longer than the wavelength band absorbed by the window layer 110 (base layer 140). Light in the wavelength band absorbed by (110) passes through completely. Accordingly, electricity may be generated in the emitter layer 120 and the base layer 110 .

The first grading layer 150 is positioned between the base layer 110 and the BSF layer 130 to smoothly change the energy band gap between the two layers 110 and 130 . The first grading layer 150 is implemented with p-type AlGaInP, and has an energy band gap between the base layer 110 and the BSF layer 130 to smoothly change the energy band gap between the two layers.

The second grading layer 160 is positioned between the emitter layer 120 and the window layer 140 to smoothly change the energy band gap between the two layers 120 and 140 . The first grading layer 150 is implemented with n-type AlGaInP, and has an energy bandgap between the emitter layer 120 and the window layer 140 to smoothly change the energy bandgap between the two layers.

Each of the above-described layers 110 to 160 has high light transmittance. This is shown in FIG. 2 .

2 is a graph showing light transmittance for each wavelength of a solar cell according to an embodiment of the present invention.

The layer of AlGaInP material has the transmittance shown in FIG. 2 . At this time, when looking at the light transmittance in the visible light wavelength band (550 to 700 nm), it can be confirmed that it has an average transmittance of 50%, and has a light transmittance of 60% or more in a specific wavelength band.

Referring back to FIG. 1 , since each of the layers 110 to 160 in the solar cell 100 has high light transmittance as shown in FIG. 2 , it can be implemented as a transparent solar cell.

In addition, since the solar cell (layer) implemented with group III-V elements has a direct transition energy band gap, even if the thickness is reduced, the power generation efficiency is not affected. Accordingly, the solar cell 100 including each of the above-described layers 110 to 160 may be implemented with a thin thickness and may have flexible characteristics.

A transparent electrode 170 is stacked on the window layer 140 . The transparent electrode 170 is disposed to transmit electricity (in particular, electrons) generated in the base layer 110 and the emitter layer 120 to the outside. As described above, each of the layers 110 to 160 in the solar cell 100 has transmittance greater than or equal to a certain standard value so that the solar cell 100 can be implemented as a transparent solar cell. Accordingly, a transparent electrode 170 having significantly higher light transmittance, rather than a normal electrode, is disposed on the window layer 140 so that the solar cell 100 can be more completely implemented as a transparent solar cell. For example, the transparent electrode 170 may be made of ITO or AZO.

An ohmic layer (not shown) is disposed between the window layer 140 and the transparent electrode 170 . An ohmic layer (not shown) is stacked on the window layer 140 so that the window layer 140 and the transparent electrode 170 can make ohmic contact. The ohmic layer (not shown) may be implemented with n ⁺ -GaAs. In this case, since the transmittance of light is reduced when the thickness of the ohmic layer (not shown) is too thick, the ohmic layer (not shown) may be stacked to 20 nm or less.

Similarly, a transparent electrode 175 is disposed below the BSF layer 130 . A transparent electrode 175 is disposed to transmit electricity (particularly, holes) generated in the base layer 110 and the emitter layer 120 to the outside. Since the window layer 140 is implemented with an n-type material, there is no difficulty in disposing the transparent electrode 170 on the window layer 140 . However, the BSF layer 130 disposed on top of the transparent electrode 175 is implemented with a p-type material. Therefore, it is difficult to directly laminate the BSF layer 130 on top of the transparent electrode 175 . Accordingly, a tunnel junction layer 180 is disposed between the transparent electrode 175 and the BSF layer 130 .

An upper surface (surface close to the BSF layer) of the tunnel junction layer 180 is implemented with a p-type material, and a lower surface (surface close to the transparent electrode) of the tunnel junction layer is implemented with an n-type material. For example, the tunnel junction layer 180 may be implemented with p ⁺ AlGaAs/n ⁺ GaAs. As such, the tunnel junction layer 180 is disposed between the transparent electrode 175 and the BSF layer 130, so that the transparent electrode 175 can be disposed close to the layer (BSF layer) made of n-type material. .

The solar cell 100 having the above-described structure has a transmittance of 50 to 60% and at the same time has a high power generation efficiency of 14% or more while having a flexible characteristic because it is implemented with a III-V group component, in particular, AlGaInP.

3 to 7 are diagrams illustrating a process of manufacturing a solar cell according to an embodiment of the present invention. The manufacturing process of FIGS. 3 to 7 may be performed by a solar cell manufacturing apparatus or the like.

Referring to FIG. 3 , a sacrificial layer 320 is stacked on a substrate 310, and a window layer 140, a second grading layer 160, an emitter layer 120, and a base layer are formed on the sacrificial layer 320. (110), the first grading layer 150, the BSF layer 130 and the tunnel junction layer 180 are stacked. Here, the substrate may be implemented with GaAs, and the sacrificial layer may be implemented with AlAs.

Referring to FIG. 4 , a transparent electrode 175 is deposited on the tunnel junction layer 180 . Since the tunnel junction layer 180 is stacked on the BSF layer 130 , a transparent electrode 175 may be deposited on the tunnel junction layer 180 .

Referring to FIG. 5 , a transparent film 510 is attached to the transparent electrode 175 or deposited by spin coating.

Referring to FIG. 6 , the substrate 310 and the solar cell layers 110 to 180 are separated by etching the sacrificial layer 320 . At this time, since a transparent film is attached or deposited on the transparent electrode 175, the substrate and the solar cell layer can be more easily separated.

Referring to FIG. 7 , a transparent electrode 170 is deposited on top of the window layer 140 in the solar cell layer separated from the substrate, and a solar cell is manufactured. At this time, in order to deposit the transparent electrode 170 on top of the window layer 140, an ohmic layer (not shown) may be preferentially deposited on top of the window layer 140, and the top of the ohmic layer (not shown) The transparent electrode 170 may be stacked as.

The above description is merely an example of the technical idea of the present embodiment, and various modifications and variations can be made to those skilled in the art without departing from the essential characteristics of the present embodiment. Therefore, the present embodiments are not intended to limit the technical idea of the present embodiment, but to explain, and the scope of the technical idea of the present embodiment is not limited by these embodiments. The scope of protection of this embodiment should be construed according to the claims below, and all technical ideas within the scope equivalent thereto should be construed as being included in the scope of rights of this embodiment.

100: solar cell
110: base layer
120: emitter layer
130: BSF layer
140: window layer
150, 160: grading layer
170, 175: transparent electrode
180: tunnel junction layer
310: substrate
320: sacrificial layer
510: transparent film

Claims (12)

a first transparent electrode;
a back surface field (BSF) layer laminated on the first transparent electrode and implemented with p-type AlInP or p-type AlGaInP;
a tunnel junction layer disposed between the first transparent electrode and the BSF layer;
a first grading layer laminated on the BSF layer and implemented with p-type AlGaInP;
a base layer stacked on the first grading layer and absorbing incident light;
an emitter layer stacked on the base layer, pn-junctioned with the base layer, and generating a current together with the base layer when the base layer absorbs light;
a second grading layer stacked on the emitter layer and implemented with n-type AlGaInP;
a window layer laminated on the second grading layer and implemented with n-type AlInP or n-type AlGaInP to improve the incident rate of light from the outside;
a second transparent electrode laminated on the window layer; and
An ohmic layer disposed between the window layer and the second transparent electrode so that the window layer and the transparent electrode are in ohmic contact,
The tunnel junction layer has an upper surface close to the BSF layer implemented with a p-type material and a lower surface close to the first transparent electrode implemented with an n-type material,
The solar cell, characterized in that the ohmic layer is implemented with n ⁺ -GaAs and laminated to a predetermined thickness or less. delete According to claim 1,
The base layer,
A solar cell characterized in that it is implemented with p-type AlGaInP. According to claim 1,
The emitter layer,
A solar cell characterized in that implemented with n-type AlGaInP. delete delete A sacrificial layer sequentially on the substrate, a window layer implemented with n-type AlInP or n-type AlGaInP, a second grading layer implemented with n-type AlGaInP, an emitter layer, a base layer, a first grading layer implemented with p-type AlGaInP, and BSF a first lamination process in which layers are laminated;
a second lamination process in which a second transparent electrode is laminated on the BSF layer;
a deposition process in which a transparent film is attached or spin coated on the second transparent electrode;
a separation step of separating the substrate and the remaining layers stacked on the substrate except for the sacrificial layer by etching the sacrificial layer; and
A third lamination process of laminating a first transparent electrode on the window layer,
An ohmic layer disposed between the window layer and the second transparent electrode, made of n+-GaAs so that the window layer and the transparent electrode are in ohmic contact, and laminated to a predetermined thickness or less;
A tunnel junction layer disposed between the first transparent electrode and the BSF layer, the top surface close to the BSF layer being implemented with a p-type material, and the bottom surface close to the first transparent electrode being implemented with an n-type material A method for manufacturing a solar cell, comprising: delete According to claim 7,
The base layer,
A method for manufacturing a solar cell, characterized in that it is implemented with p-type AlGaInP. According to claim 7,
The emitter layer,
A method for manufacturing a solar cell, characterized in that implemented with n-type AlGaInP. delete delete

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