WO2013073769A1

WO2013073769A1 - Rear surface electrode-type solar cell and method for manufacturing same

Info

Publication number: WO2013073769A1
Application number: PCT/KR2012/007159
Authority: WO
Inventors: 유승협; 김호연
Original assignee: 한국과학기술원
Priority date: 2011-11-18
Filing date: 2012-09-06
Publication date: 2013-05-23
Also published as: KR101218576B1

Abstract

According to the present invention, electrodes can be formed with nanometers therebetween on a nanostructure of a photoelectric transformation layer by using oblique angle deposition, which enables application of a rear electrode-type structure even on a solar cell having low electron and hole mobility. In addition, a transparent electrode becomes unnecessary due to the rear surface-type structure, which eliminates limitation on the size of a unit cell and dead space in a thin film solar cell. By eliminating the need for the transparent electrode, manufacturing cost of the solar cell can be reduced, and decreased dead space can improve efficiency of the solar cell. Also, the rear electrode-type structure can be applied to solar cells other than crystalline silicon solar cells, thereby eliminating limitation of size due to silicon ingots and thus obtaining the rear surface electrode-type solar cell having a large surface area.

Description

Back electrode solar cell and method for manufacturing same

The present invention relates to a back electrode solar cell and a method of manufacturing the same.

Recently, as the depletion of existing energy resources such as oil or coal is predicted, there is a growing interest in alternative energy to replace them. Among them, solar energy is particularly attracting attention because it is rich in energy resources and has no problems with environmental pollution. Solar energy uses solar energy to generate steam required to rotate a turbine using solar heat, and solar energy to convert photons into electrical energy using properties of a semiconductor.

A solar cell that converts sunlight into electrical energy has a junction structure between a p-type semiconductor and an n-type semiconductor, like a diode. When light is incident on a solar cell, it interacts with the light and the materials that make up the semiconductor, resulting in a negative charge. Electrons and positively charged holes are generated, and as they move, current flows.

This is called the photovoltaic effect. Among the p-type and n-type semiconductors constituting the solar cell, electrons are attracted to the n-type semiconductor and holes are pulled toward the p-type semiconductor, respectively. When they move to the electrodes bonded to the semiconductor and connect them with wires, electricity flows outward.

On the other hand, the structure of the back electrode solar cell has been proposed for the advantages of not using a metal grid and a transparent electrode on the front of the solar cell, and the advantage of being able to feel the neatness without wiring in the visual aspect.

However, these back electrode solar cells could be applied only to crystalline silicon solar cells with very good electron and hole mobility. In addition, when the back electrode type structure is applied to the crystalline silicon solar cell, there is a problem in that the size of the entire solar cell is limited by the size of the silicon ingot for manufacturing the solar cell.

The present invention aims to solve the above-mentioned problems of the prior art.

An object of the present invention is to enable the back electrode type structure to be applied to a thin film solar cell, thereby eliminating the need for a transparent electrode and removing the dead area.

It is an object of the present invention to collect electrons and holes without significant loss even in solar cells having low electron and hole mobility.

An object of the present invention is to be able to manufacture a large area back electrode solar cell.

According to an embodiment of the present invention, a photoelectric conversion layer which is formed on the rear surface of the substrate and has a nano-structured pattern on one surface of the two surfaces that are not in contact with the substrate; A first electrode formed in a first region on the nanostructure surface; A first insulating layer formed to cover at least a portion of the first electrode; And a second electrode formed at least partially in a second region on the surface of the nanostructure, but not formed in contact with the first electrode.

The nanostructure pattern may have a plurality of convex portions, at least a portion of the first electrode may be formed on a first inclined surface of the convex portion, and at least a portion of the second electrode may be formed on a second inclined surface of the convex portion.

The first electrode and the second electrode may include a buffer layer that determines the polarity.

The photoelectric conversion layer may be a photoelectric conversion layer having a bulk heterojunction structure.

The back electrode solar cell may further include a second insulating layer formed on an entire surface of the nanostructure pattern on which the first electrode, the first insulating layer, and the second electrode are formed.

The back electrode solar cell may further include a reflective layer formed on the second insulating layer.

On the other hand, according to another embodiment of the present invention, forming a photoelectric conversion layer having a nanostructured pattern on the substrate; Forming a first electrode on a first region on the nanostructure surface; Forming a first insulating layer to cover at least a portion of the first electrode; And forming a second electrode, wherein at least a part of the second electrode is formed in a second region on the surface of the nanostructure, and is not in contact with the first electrode.

The nanostructured pattern has a plurality of convex portions, and the first electrode forming step, the first insulating layer forming step and the second electrode forming step may include the first electrode, the first insulating layer, and the second electrode. Is carried out by a gradient deposition method such that the deposition angles of the first and second deposition angles are the first, second, and third angles, respectively. The deposition angle may be an acute angle among angles formed by the deposition direction and the plane including the substrate.

The first angle may be different from the second angle, and the third angle may be different from the second angle.

The second angle may be an angle between the first angle and a right angle.

The deposition direction of the first electrode may face the first inclined surface of the convex portion, and the deposition direction of the second electrode may face the second inclined surface of the convex portion.

The forming of the photoelectric conversion layer may include forming a pattern of the nanostructure by a lithography process or a stretching process after stretching.

The method of manufacturing the back electrode solar cell may further include forming a second insulating layer on an entire surface of the nanostructure pattern on which the first electrode, the first insulating layer, and the second electrode are formed.

The manufacturing method of the back electrode solar cell may further include forming a reflective layer on the second insulating layer.

According to the embodiment of the present invention, the electrode may be formed on the nanostructure of the photoelectric conversion layer by using the gradient deposition at intervals of nanometers, and thus the rear electrode type may be used for solar cells having low electron and hole mobility. The structure can be applied.

According to the embodiment of the present invention, since the back electrode type structure is used, there is no need for the transparent electrode, thereby removing the size limitation of the unit cell in the thin film solar cell and disappearing the dead area. Eliminating the need for a transparent electrode can reduce the manufacturing cost of the solar cell, the efficiency of the solar cell can be improved by reducing the dead zone.

According to the embodiment of the present invention, since the back electrode type structure can be applied to solar cells other than crystalline silicon, the size limitation due to the silicon ingot can be eliminated, and thus a large area back electrode type solar cell can be obtained. .

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

2 to 6 is a process chart for explaining the manufacturing process of the back-electrode solar cell according to an embodiment of the present invention.

DETAILED DESCRIPTION The following detailed description of the invention refers to the accompanying drawings that show, by way of illustration, specific embodiments in which the invention may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the invention. It should be understood that the various embodiments of the present invention are different but need not be mutually exclusive. For example, certain shapes, structures, and characteristics described herein may be embodied in other embodiments without departing from the spirit and scope of the invention with respect to one embodiment. In addition, it is to be understood that the location or arrangement of individual components within each disclosed embodiment may be changed without departing from the spirit and scope of the invention. The following detailed description, therefore, is not to be taken in a limiting sense, and the scope of the present invention, if properly described, is defined only by the appended claims, along with the full range of equivalents to which such claims are entitled. Like reference numerals in the drawings refer to the same or similar functions throughout the several aspects.

DETAILED DESCRIPTION Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art can easily implement the present invention.

[Preferred Embodiments of the Invention]

As used herein, the term "nano" is a concept that collectively refers to a level of several tens to hundreds of nanometers or a few micrometers. For example, the term "interval in nanometers" is a concept that encompasses the meaning of intervals of several to several hundred nanometers, intervals of several micrometers, and submicron levels. That is, in this specification, "nano" size is to be understood as a concept that includes both "nano-submicron" sizes.

Referring to FIG. 1, the back electrode solar cell of the present invention is formed on the back surface of the substrate 100 and is formed on the photoresist layer 200 having a fine concavo-convex structure, and the micro concave-convex structure of the photoconversion layer 200. The first electrode 300, the first insulating layer 400, the second electrode 500, the second insulating layer 600, and the reflective layer 700 may be included.

In the back electrode solar cell of the present invention, the photoelectric conversion layer 200 is formed on the back surface of the substrate 100, and the first electrode 300 and the second electrode are formed on the fine uneven structure formed in the photoelectric conversion layer 200. 500) are all deposited. That is, both the first electrode 300 and the second electrode 500 may be formed on the rear surface of the entire solar cell module.

The uneven structure formed in the photoelectric conversion layer 200 according to the embodiment of the present invention is a pattern of nano structure. In other words, the interval between the unevennesses is several nanometers or less. As shown in the figure, each uneven structure is formed with both the first electrode 300 and the second electrode 500, accordingly, the interval between the first electrode 300 and the second electrode 500 is several tens to Hundreds of nanometers or less. For example, when the organic solar cell is implemented, the distance between the

adjacent electrodes

300 and 500 may be about several tens to hundreds of nanometers, and when the inorganic solar cell is implemented, the

adjacent electrodes

300 and 500 may be used. The spacing between them may be several microns. In general, the back electrode structure may be applied to solar cells having high electron and hole mobility, but as described above, since the distance between the first electrode 300 and the second electrode 500 is in nanometer units, Even a low mobility solar cell may enable a back electrode type structure.

Meanwhile, as the back electrode type structure is implemented, the transparent electrode used in the conventional solar cell structure is lost. When the transparent electrode is present, the size limit of the unit cell due to the increase in the surface resistance is followed, whereby the portion connecting the unit cell becomes a dead zone in which no actual photoelectric conversion operation is performed. The efficiency was inevitably reduced compared to the module area. However, since the embodiment of the present invention employs the rear electrode type structure, the need for the transparent electrode is eliminated, the yarn area disappears, and the decrease in efficiency relative to the area of the solar cell can be prevented. In addition, the manufacturing cost can be reduced by not using the transparent electrode.

Hereinafter, the manufacturing process and each component of the back electrode solar cell according to the embodiment of the present invention will be described in detail.

2 to 6 is a process chart illustrating a manufacturing process of a back electrode solar cell according to an embodiment of the present invention.

First, referring to FIG. 2, the photoelectric conversion layer 200 is deposited on the substrate 100. The photoelectric conversion layer 200 may preferably be an organic photoelectric conversion layer having a bulk heterojunction structure, but may also be a photoelectric conversion layer implemented in a different kind and form. Any structure that can absorb light and convert it into electrical energy can be used as the photoelectric conversion layer 200 of the present invention.

As shown in FIG. 2, a nano pattern uneven structure may be formed on the photoelectric conversion layer 200. That is, the concave-convex structure is formed on the other surface of both surfaces of the photoelectric conversion layer 200 in contact with the substrate 100 at intervals of nanometers. The nanostructure pattern may include a convex portion B and a concave portion O formed at predetermined intervals (constant or irregular). Such nanostructured patterns may be formed by lithography processes (photolithography or soft lithography) or the like. In addition, the nanostructure may be formed by stretching and relaxing the photoelectric conversion layer 200 by a different method. As the photoelectric conversion layer 200 stretched as a stretch decreases again in the relaxing process, a naturally curved structure may be formed.

Referring to FIG. 3, the first electrode 300 is formed on the nanostructure of the photoelectric conversion layer 200. The nanostructure of the photoelectric conversion layer 200 may include a convex portion B formed at predetermined intervals. The first electrode 300 is formed on the first region of the convex portion B, and the second structure is formed on the second region. 2 electrodes 500 (see FIG. 5) should be formed. Accordingly, in order to ensure separation and dividing between the first region and the second region, the first electrode 300 is deposited using a gradient deposition method in the embodiment of the present invention. As shown in FIG. 3, when the nanostructure of the photoelectric conversion layer 200 includes, for example, an inclined surface in a first direction and an inclined surface in a second direction, most of the first electrode 300 may be inclined. It may be formed on the inclined surface in the first direction. The first electrode 300 may include a buffer layer to exhibit a first polarity. The first electrode 300 may be made of a conductive material such as a conductive metal or a conductive oxide.

Referring to FIG. 4, a first insulating layer 400 is formed on a nanostructure in which a first electrode 300 is formed on a first region. The first insulating layer 400 is formed to insulate between the first electrode 300 and the second electrode 500 to be deposited later (see FIG. 5), and the first insulating layer 400 is formed on the nanostructure. The first electrode 300 may be formed to cover at least a portion thereof. However, it is preferable to form the first electrode 300 to cover all of them. That is, all of the first electrodes 300 may be surrounded by all of the first insulating layers 400. However, since the second electrode 500 (see FIG. 5) must be deposited on at least a part of the surface of the nanostructure, the surface of the nanostructure may not be covered. Therefore, it is preferable that the first insulating layer 400 is also deposited by a gradient deposition method. The deposition angle during the gradient deposition for the deposition of the first insulating layer 400 may be different from that of the deposition of the first electrode 300 to cover at least some or all of the first electrodes 300, but not to cover all of the nanostructures. Can be selected in degrees. Here, the deposition angle is defined as an acute angle among angles formed by the deposition direction (arrow direction) and the plane including the substrate 100. That is, if the deposition angle when the first electrode 300 is deposited is the first angle, the deposition angle when the first insulating layer 400 is deposited may be the second angle. The second angle may be an angle closer to the right angle (90 °) than the first angle. However, since the contact area between the surface of the second electrode 500 (see FIG. 5) and the photoelectric conversion layer 200 should be present when the second electrode 500 (see FIG. 5) is deposited in the future, the second angle is equal to the first angle. It is preferable to select at an angle between right angles (90 degrees). The first insulating layer 400 may be made of, for example, a predetermined resin, but is not limited thereto.

Referring to FIG. 5, the second electrode 500 is formed on the nanostructure on which the first insulating layer 400 is formed. The second electrode 500 is formed on the nanostructure of the photoelectric conversion layer 200, and at least a part thereof should be formed on the surface of the photoelectric conversion layer 200, that is, the surface of the nanostructure. That is, at least a part of the second electrode 500 should be formed in an exposed area not covered with the first insulating layer 400 of the nanostructure surface of the photoelectric conversion layer 200. In addition, when the first electrode 300 is not entirely enclosed by the first insulating layer 400, the second electrode 500 should be formed so as not to contact the first electrode 300. To this end, the second electrode 500 may also be deposited by a gradient deposition method. As described above, the nanostructure of the photoelectric conversion layer 200 may include a convex portion B formed at predetermined intervals. For example, the deposition direction when the first electrode 300 is formed is the convex portion B. FIG. If facing toward the first inclined surface, the deposition direction when forming the second electrode 500 may be directed to the second inclined surface of the convex portion (B). In addition, the deposition angle at the time of depositing the first electrode 300 is a first angle, the deposition angle at the time of depositing the first insulating layer 400 is a second angle, and the deposition angle at the time of depositing the second electrode 500 is a third angle. In this case, the first angle and the second angle may be different from each other, and the second angle and the third angle may be different from each other. The first angle and the third angle may be the same or different. Meanwhile, the second electrode 500 may include a buffer layer to allow the electrode to exhibit a second polarity. The second electrode 500 may be made of a conductive material such as a conductive metal or a conductive oxide.

Referring to FIG. 6, a second insulating layer 600 may be further deposited on the entire surface of the nano pattern on which the first electrode 300, the first insulating layer 400, and the second electrode 500 are deposited. In addition, a reflective layer 700 may be further deposited so that light incident through the substrate 100 and transmitted through the photoelectric conversion layer 200 may be reflected back to the photoelectric conversion layer 200. The second insulating layer 600 may be made of a predetermined resin, preferably a resin having light transmittance. At least one of the second insulating layer 600 or the reflective layer 700 may be omitted in the solar cell according to the embodiment of the present invention.

As described above, the back electrode type structure has been generally applied only to crystalline silicon solar cells having good electron and hole mobility. In such a solar cell, the size of the solar cell was limited by the size of a silicon ingot for forming a wafer.

However, according to the back electrode solar cell of the present invention, the size of the substrate determines the size of the entire solar cell module while using the back electrode structure. Therefore, the large-area back electrode structure solar cell can be produced.

Although the present invention has been described by specific embodiments such as specific components and the like, but the embodiments and the drawings are provided to assist in a more general understanding of the present invention, the present invention is not limited to the above embodiments. For those skilled in the art, various modifications and variations can be made from these descriptions.

Therefore, the spirit of the present invention should not be limited to the embodiments described above, and all of the equivalents or equivalents of the claims, as well as the claims below, are included in the scope of the spirit of the present invention. I will say.

The present invention is applied to the manufacture of solar cells.

Claims

A photoelectric conversion layer formed on a rear surface of the substrate and having a nanostructured pattern on one surface of the two surfaces that do not contact the substrate;

A first electrode formed in a first region on the nanostructure surface;

A first insulating layer formed to cover at least a portion of the first electrode; And

And at least a portion of the second electrode formed in a second region on the surface of the nanostructure but not in contact with the first electrode.
The method according to claim 1,

The nanostructured pattern has a plurality of convex portions,

At least a portion of the first electrode is formed on the first inclined surface of the convex portion, and at least a portion of the second electrode is formed on the second inclined surface of the convex portion solar cell.
The method according to claim 1,

The first electrode and the second electrode of the back electrode type solar cell including a buffer layer for determining the polarity.
The method of claim 1,

The photovoltaic layer is a photovoltaic cell having a bulk heterojunction structure.
The method according to claim 1,

And a second insulating layer formed on a front surface of the nanostructure pattern on which the first electrode, the first insulating layer, and the second electrode are formed.
The method according to claim 5,

A back electrode solar cell further comprising a reflective layer formed on the second insulating layer.
Forming a photoelectric conversion layer having a nanostructured pattern on the substrate;

Forming a first electrode on a first region on the nanostructure surface;

Forming a first insulating layer to cover at least a portion of the first electrode; And

A method of manufacturing a back-electrode solar cell comprising forming a second electrode, at least a portion of which is formed in a second region on the surface of the nanostructure, but not in contact with the first electrode.
The method according to claim 7,

The nanostructured pattern has a plurality of convex portions,

The first electrode forming step, the first insulating layer forming step and the second electrode forming step,

The deposition angle of the first electrode, the first insulating layer, and the second electrode is performed by a gradient deposition method such that the first angle, the second angle, and the third angle are respectively formed;

The deposition angle is a method of manufacturing a back-electrode solar cell is an acute angle of the angle between the deposition direction and the plane comprising the substrate.
The method according to claim 8,

And the first angle is different from the second angle, and the third angle is different from the second angle.
The method according to claim 9,

And the second angle is an angle between the first angle and a right angle.
The method according to claim 8,

And a deposition direction of the first electrode faces a first inclined surface of the convex portion, and a deposition direction of the second electrode faces a second inclined surface of the convex portion.
The method according to claim 7,

The forming of the photoelectric conversion layer may include forming the nanostructured pattern by a lithography process or a stretching process after stretching.
The method according to claim 7,

And forming a second insulating layer on the entire surface of the nanostructure pattern on which the first electrode, the first insulating layer, and the second electrode are formed.
The method according to claim 13,

The method of manufacturing a back electrode solar cell further comprising the step of forming a reflective layer on the second insulating layer.