WO2012020944A2

WO2012020944A2 - Dye-sensitized solar cell having serial structure

Info

Publication number: WO2012020944A2
Application number: PCT/KR2011/005694
Authority: WO
Inventors: Gang-Beom Kim; Hyun-Seung Cho; Jong Min Jang
Original assignee: Tg Energy Inc.
Priority date: 2010-08-10
Filing date: 2011-08-03
Publication date: 2012-02-16
Also published as: KR101032916B1; WO2012020944A3

Abstract

The present invention relates to a dye-sensitized solar cell having a serial structure (or a sub-module), and more particularly, to a dye-sensitized solar cell having a serial structure, which does not have a dislocation of a connection arrangement or a short problem between unit cells and has improved durability and light conversion efficiency due to a reduction in the loss of a active area. The dye-sensitized solar cell having a serial structure comprises a working electrode, a counter electrode, a grid, protective barrier, and an electrolyte. The grid comprises a hole penetrating the working electrode and the counter electrode which face each other and conductive materials filling the hole.

Description

DYE-SENSITIZED SOLAR CELL HAVING SERIAL STRUCTURE

The present invention relates to a dye-sensitized solar cell having a serial structure (or a sub-module), and more particularly, to a dye-sensitized solar cell having a serial structure, which does not have a dislocation of a connection arrangement or a short problem between unit cells and has improved durability and light conversion efficiency due to a reduction in the loss of a active area.

Lots of researches are being carried out on a dye-sensitized solar cell (DSSC) after researchers including Michael Gratzel at Lausanne's Federal Institute of Technology (EPFL) developed the dye-sensitized solar cell in the year of 1991. The dye-sensitized solar cell is a photoelectrochemical solar cell, including dye molecules for generating electron-hole pairs by absorbing a visible light, transition metal oxides for transferring the generated electrons, and an electrolyte for performing an oxidation-reduction reaction as major materials.

The dye-sensitized solar cell has an advantage such as eco-friendly characteristics and infinite energy source because it generates electric energy using solar energy. Furthermore, there is a possibility that the dye-sensitized solar cell may replace the existing silicon-based solar cell because it is lower in the unit cost of production than the existing silicon-based solar cell.

The dye-sensitized solar cell is used by including one dye-sensitized solar cell on one pair of substrates or is used in the form of the dye-sensitized solar cell of a serial structure (or sub-module) or a parallel structure (or sub-module) in which a plurality of unit cells is interconnected on one pair of substrates. FIG. 1 is a cross-sectional view showing the structure of a conventional dye-sensitized solar cell having a serial structure. The dye-sensitized solar cell basically includes working electrode (transparent electrode) and counter electrode. The working electrode is comprised of a transparent conductive substrates 10b, on which porous nano-particle oxide layer 13b is coated. Photosensitive dyes are adsorbed on the porous nano-particle oxides. The counter electrode is comprised of a transparent conductive substrate 10a having carbon or metal layer 13a, such as platinum coated thereon. The transparent

conductive substrates

10a and 10b may be formed by coating transparent conductive materials 12a and 12b on

substrates

11a and 11b, respectively, or the transparent

conductive substrates

10a and 10b may use any one of the

substrates

11a and 11b as a metal substrate.

Referring to FIG. 1, the serial structure of the dye-sensitized solar cell includes the patterns of the porous nano-particle oxides layer 13b and the catalyst layer 13a which are formed in the working electrode and the counter electrode, respectively. Each of the porous nano-particle oxide layer 13b of working electrode and each of the catalyst layer 13a of the counter electrode face each other to form a unit cell. The unit cells are electrically insulated by a protective barrier 30, and an electrolyte 20 is filled between the working electrode and the counter electrode. The working electrode on one side and the counter electrode on the other side are electrically interconnected by a contact of

grids

40a and 40b. The

grids

40a and 40b are formed of metal belts which are formed in the respective transparent

conductive substrates

10a and 10b. The counter electrodes and the working electrodes face each other so that one end of each of the counter electrodes and the working electrodes in its dislocation direction is lengthily extended. An external electrode is provided at the end of the extended portion.

In the conventional serial structure, the solar cell must be fabricated so that the

grids

40a and 40b formed of the metal belts provided over the two substrates are brought into contact with each other and then electrically connected. If the ends of the

grids

40a and 40b do not accurately coincide with each other in this process, contact resistance is increased. In worse cases, if both the grids are not interconnected, the serial connection is short-circuited, so that it does not work to generate the electricity. Furthermore, if a solar cell is made of flexible material, there is a problem in that contact resistance may be increased or a short may be generated owing to the bending of the solar cell.

Furthermore, if the protective barrier 30 for insulating the unit cells is spread out to the contact portion of the

grids

40a and 40b, the connection between the

grids

40a and 40b may be short-circuited. In order to prevent this problem, the

grids

40a and 40b are spaced apart from the protective barrier 30 at a predetermined interval, as shown in FIG. 1. In this case, the loss of a active area is increased.

In order to solve the problems of the conventional dye-sensitized solar cell having a serial structure, Korean Patent Publication No. 10-2010-0041487 discloses a dye-sensitized solar cell module having a serial structure, wherein a second grid made of a metal belt is seated in the concave portion of a first grid made of a metal belt equipped with a concave portion. The above structure has a less possibility that the connection between the grids may be short-circuited because the grids are brought into contact with each other more stably but has problem that an increase in the loss of a active area due to a protective barrier cannot be solved and the loss of the active area is further increased because the area of the grids is wide as compared with the prior art.

G24 Innovations Limited (England) proposes a flexible dye-sensitized solar cell (metal base flexible DSSC) using a metal substrate as a working electrode G24 Innovations Limited attempted to solve the problem by forming convexity in the metal substrate (that is, a working electrode) and then bringing convex portion of the working electrode into contact with a counter electrode. According to this connection method, an electrical connection between the cells is more stable than the connection between the conventional grids made of the metal belts, but a short-circuit problem and the loss of the active area due to the protective barrier still remain. Furthermore, the structure can be applied to only a flexible dye-sensitized solar cell in which the metal substrate is used only in at least one of the counter electrode and the working electrode. Accordingly, the structure cannot be applied to a flexible dye-sensitized solar cell in which both electrodes are formed of conductive plastic substrates.

Accordingly, the present invention has been made in view of the above problems, and it is an object of the present invention to provide a dye-sensitized solar cell having a serial structure, which is capable of improving durability and minimizing the loss of a active area by electrically connecting unit cells without a dislocation problem of an arrangement between grids.

To achieve the above object, the present invention provides a dye-sensitized solar cell having a serial structure, comprising a working electrode, a counter electrode, a grid, protective barrier, and an electrolyte, wherein The grid comprises a hole penetrating the working electrode and the counter electrode which face each other and conductive materials filling the hole.

Metal belts are formed in the conductive substrate of any of the working electrode and the counter electrode or formed in both the conductive substrates of the working electrode and the counter electrode. The hole is formed to penetrate the metal belts. Accordingly, the unit cells can be electrically interconnected more stably.

The hole may be formed by a drill, waterjet, sandblast, punch, or the radiation of a laser. It is preferred that the diameter of the hole is 0.1 to 2.0 mm. If the diameter of the hole is too small, conductive materials are difficult to fill or contact resistance between the unit cells may be increased. If the diameter of the hole is too great, the loss of a active area is increased.

The one or more holes are formed in each connection portion of the unit cells. If plurality of holes is formed, it is preferred that the interval between the holes is 1 to 60 mm. If the interval between the holes is too small, there is a possibility that the substrate between the holes may be damaged. If the interval between the holes is too great, the ability to collect generated electrons is decreased and thus cell efficiency is reduced. Accordingly, it is preferred that the interval between the holes not exceed 60 mm by taking the size of the unit cell into account. The interval between the holes may be selected within a proper range according to the diameter of the hole or the size of the unit cell. The hole may have any shape, such as a circle, an oval, a regular quadrilateral, a rectangle, a triangle, or a polygon.

The conductive materials are paste, adhesives, or an ink type and may be filled in the holes by means of printing, dropping, dispensing, jetting, stamping, or sputtering.

As described above, in the dye-sensitized solar cell having a serial structure according to the present invention, the grids electrically connecting the unit cells are formed in the working electrode and the counter electrode, respectively, in the form of a metal belt. The grids do not come in contact with each other in an assembly process, but have metal posts in which the conductive materials are filled in the holes penetrating the working electrode and the counter electrode which face each other. Accordingly, durability is greatly improved because there is no problem of dislocation arrangement between the grids in the unit cell.

Furthermore, according to the present invention, since the grid has an integrated metal post, there is no problem in that the protective barrier may be spread out between the contact surfaces as in the conventional grid having the metal belt. Accordingly, the loss of a active area can be minimized because it is not necessary to form the interval between the protective barrier and the grid in order to prevent the spread of the protective barrier.

FIG. 1 is a cross-sectional view showing the structure of a conventional dye-sensitized solar cell having a serial structure;

FIG. 2 is a cross-sectional view showing the structure of a dye-sensitized solar cell having a serial structure according to an embodiment of the present invention;

FIG. 3 shows an assembly diagram illustrating a process of manufacturing the dye-sensitized solar cell having a serial structure according to an embodiment of the present invention; and

FIG. 4 shows an assembly diagram illustrating a process of manufacturing the dye-sensitized solar cell having a serial structure according to another embodiment of the present invention.

Embodiments of the present invention are described in detail with reference to the accompanying drawings. However, the drawings and the embodiments are only illustrative in order to easily describe the contents and range of the technical spirit of the present invention, and the technical scope of the present invention is not limited by the drawings and the embodiments. Furthermore, various modifications and changes of the present invention within a range of the technical spirit of the present invention will be evident to those skilled in the art.

FIG. 2 is a cross-sectional view showing the structure of a dye-sensitized solar cell having a serial structure according to an embodiment of the present invention.

Referring to FIG. 2, the dye-sensitized solar cell having a serial structure according to the present invention includes a working electrode, a counter electrode, a grid 40, protective barrier 30, and an electrolyte 20. The grid 40 includes a hole 45 penetrating the working electrode and the counter electrode facing each other and conductive materials filling the hole 45. Detailed materials or constructions and an assembly method of the working electrode, the counter electrode, and the protective barrier 30 are known in the art and may be properly selected by a person having ordinary skill in the art. Accordingly, a detailed description of the detailed materials or constructions and the assembly method is omitted.

FIG. 3 shows an assembly diagram illustrating a process of manufacturing the dye-sensitized solar cell having a serial structure according to an embodiment of the present invention.

Referring to FIG. 3, the dye-sensitized solar cell having a serial structure according to an embodiment of the present invention may be made by the following steps ; (A) step for forming a hole at the position where the grid 40 is formed in the working electrode on which the patterns of dye coated porous nano-oxide layer 13a are formed, and counter electrode on which the patterns of catalyst layer 13b and protective barrier 30 are formed; (B) step for matching and assembling the working electrode and the counter electrode; (C) step for filling the holes with the conductive materials. Although the protective barrier patterns are illustrated to be formed in the counter electrode, they may be formed in the working electrode or may be formed both in the counter electrode and the working electrode.

The dye-sensitized solar cell having a serial structure according to another embodiment of the present invention may be formed by the following steps; (A) step for matching and assembling the working electrode on which the patterns of the dye coated porous nano-particle oxides layer 13b are formed and the counter electrode on which the patterns of the catalyst layer 13a and the protective barrier 30 are formed; (B) step for forming the hole penetrating the working electrode and the counter electrode; (C) step for filling the hole with the conductive materials. Although the protective barrier patterns are illustrated to be formed in the counter electrode, the protective barrier patterns may be formed in the working electrode or may be formed both in the counter electrode and the working electrode.

If the dye-sensitized solar cell having a serial structure according to the present invention is manufactured using the assembly process of FIG. 4, the protective barrier 30 between the unit cells does not have the pattern of a dual band as shown in FIG. 3, but may have the pattern of a single band as shown in FIG. 4. Here, the hole 45 is formed by penetrating the working electrode, the protective barrier 30, and the counter electrode 13a. Alternatively, if the dye-sensitized solar cell is manufactured by the assembly process of FIG. 4, the protective barrier 30 may have the pattern of a dual band, such as that shown in FIG. 3.

In order to further strengthen an electrical connection between the grid 40 and

conductive substrates

10a and 10b on which the working electrode and the counter electrode are formed, respectively, metal belts 50 are formed in the transparent

conductive substrate

10a or 10b of the working electrode or the counter electrode and the transparent

conductive substrates

10a and 10b of the working electrode and the counter electrode as shown in FIG. 4. Furthermore, the hole is formed to penetrate the metal belts. Here, it is preferred that the hole be formed along the metal belt as shown in FIG. 5.

In the present invention, the grid 40 is electrically conductive to the conductive materials coated on the transparent

conductive substrates

10a and 10b, thereby electrically connecting the unit cells. Here, if the protective barrier 30 between the unit cells is formed in a single band, the grid 40 comes into contact with the transparent

conductive substrates

10a and 10b through only the cross sections of a layer on which the conductive materials are coated. However, the coating layer of the conductive materials forming the transparent

conductive substrates

10a and 10b has a small contact area because the coating layer is very thin. For this reason, the metal belts are formed on the transparent

conductive substrates

10a and 10b, and the hole is formed to penetrate the metal belts, as shown in FIG. 4. Accordingly, the electrical connection between the transparent

conductive substrates

10a and 10b and the grid 40 can be much more solid.

If the protective barrier 30 between the unit cells has the pattern of a dual band, the hole is filled with the conductive materials and thus positions in which the hole is not formed are also filled with the conductive materials when the grid 40 is formed, as shown in FIG. 3. Accordingly, the grid 40 comes into contact with not only the cross section of the coating layer of the conductive materials, but also the counter surface of the conductive substrate in which the hole is not formed (a surface where the working electrode and the counter electrode face each other). Accordingly, the unit cells can be electrically interconnected stably. However, if the protective barrier 30 has the pattern of a dual band, the metal belts may be first formed and the hole may be then formed to penetrate the metal belts as described above.

In the dye-sensitized solar cell having a serial structure according to the present invention, unlike in the prior art, the grids 40 of the metal belts formed in the working electrode and the counter electrode do not come into contact with each other because of the grid structure as described above. Accordingly, there is no problem in that contact resistance may be increased or an electrical short may be generated because the grid arrangements electrically connecting the unit cells are dislocated. Furthermore, there is no problem in that the electrical connections may have a short because the barrier rib member 30 is spread out to the contact surface of the grid 40. Accordingly, the loss of a active area can be reduced because it is not necessary to widely form the interval between the protective barrier.

In the present invention, it is preferred that the diameter of the hole 45 is from 0.1 to 2.0 mm. The hole may be formed by a drill, waterjet, sandblast, punch, or the radiation of a laser. If the diameter of the hole is too small, the filling of the conductive materials may be difficult or contact resistance between the unit cells may be increased. If the diameter of the hole is too great, the loss of the active area is increased.

The one or more holes are formed in each connection portion of the unit cells. If the plurality of holes is formed, it is preferred that the interval between the holes be 1 to 60 mm. In order to compare the efficiencies of solar cells according to the interval between the holes, the solar cells having a serial structure were fabricated by serially connecting the two unit cells, each made of materials shown in Table 1 and configured to have an active area of 8*100 mm, according to the interval between the holes shown in Table 2 in a form, such as that shown in FIG. 4. Each of the serial structure cells was irradiated with a solar simulated light source of 100 mW/ using Newport/Oriel Solar Simulator (class 3A, model no. 94083A). Energy conversion efficiency (η) was measured based on photocurrent (I_sc), short-circuit voltage (V_oc), and a fill factor (%), and the results are listed in Table 2 below.

Table 1

Table 2

From Table 2, it can be seen that cell efficiency is gradually reduced as the interval between the holes is increased and is sharply reduced when the interval between the holes is 60 mm or higher. It means that the ability to gather generated electrons drops because the electrons generated according to an increase of the interval between the holes are moved toward the grid 40 and then lost. Accordingly, it is preferred that the interval between the holes be narrows as possible. If the interval between the holes is too narrow, there is a problem in that the substrate between the holes may be damaged. Furthermore, an increase of the cell efficiency according to a reduction in the interval between the holes becomes slow. Accordingly, it is preferred that the interval between the holes be 1 mm or higher. The interval between the holes may be properly selected according to the diameter of the hole or the size of the unit cell.

The number of holes formed in the connection portions of the unit cells may be determined according to the diameter of the hole, the interval between the holes, and/or the size of the unit cell, and thus to determine the upper limit of the number of holes is meaningless. The hole may have a circle, an oval, a regular quadrilateral, a rectangle, a triangle, or a polygon, but not limited thereto.

The conductive materials filled in the hole may be paste, adhesives, or an ink type and may be filled in the hole by means of printing, dropping, dispensing, jetting, stamping, or sputtering. A screen printing method, an ink-jetting method, or a pad printing method may be used as the printing method.

While the invention has been described in connection with what is presently considered to be practical exemplary embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.

Claims

A dye-sensitized solar cell having a serial structure, comprising a transparent electrode, a counter electrode, a grid, protective barrier, and an electrolyte,

wherein the grid comprises:

a hole penetrating the working electrode and the counter electrode which face each other; and

conductive materials filling the hole.
The dye-sensitized solar cell as claimed in claim 1, wherein:

metal belts are formed in a conductive substrate of any of the working electrode and the counter electrode or formed in both the conductive substrates of the working electrode and the counter electrode, and

the hole is formed to penetrate the metal belts.
The dye-sensitized solar cell as claimed in claim 1 or 2, wherein the hole has a diameter of 0.1 to 2.0 mm.
The dye-sensitized solar cell as claimed in claim 1 or 2, wherein an interval between the holes is 1 to 60 mm.
The dye-sensitized solar cell as claimed in claim 1 or 2, wherein the hole is formed by a drill, waterjet, sandblast, punch, or a radiation of a laser.
The dye-sensitized solar cell as claimed in claim 1 or 2, wherein the conductive materials comprise paste, adhesives, or an ink type.
The dye-sensitized solar cell as claimed in claim 1 or 2, wherein the filling of the conductive materials is performed by means of printing, dropping, dispensing, jetting, stamping, or sputtering.
The dye-sensitized solar cell as claimed in claim 2, wherein the protective barrier have a dual band on both side of the grid with the grid between a unit cells interposed therebetween.