KR20120008902A - Manufacture Method of Partially Reduced Graphine Film By Heating, Manufacture Method of Counter Electrode of Dye-Sensitized Solar Cell and Dye-Sensitized Solar Cell - Google Patents

Abstract

PURPOSE: A method for manufacturing a partially thermally reduced graphene film and a method for manufacturing a counter electrode of a dye sensitive solar cell are provided to implement a graphene oxide structure without damaging a film by using graphene oxide. CONSTITUTION: A graphene oxide layer is formed on a transparent conductive layer. A partially thermally reduced graphene film is made by thermally processing a graphene oxide film at 50 to 400 degrees centigrade. The partially thermally reduced graphene film is contacted with ion conductive solutions.

Description

Manufacture Method of Partially Reduced Graphine Film By Heating, Manufacture Method of Counter Electrode of Dye-Sensitized Solar Cell and Dye -Sensitized Solar Cell}

The present invention relates to a method of manufacturing a hydrophilic functional film that forms a partially reduced structure by applying thermal energy to a graphene oxide film, which has physical properties of partially passing ions and an ion-containing solution, To provide a dye-sensitized solar cell having a counter electrode manufacturing method and a partially heat-reduced graphene film as a counter electrode.

The counter electrode of a dye-sensitized solar cell (DSSC) receives electrons through an external electrode and transfers electrons to iodine ions in the electrolyte through an oxidation-reduction reaction at an interface contacting the electrolyte. Play a role. Therefore, the counter electrode should have catalytic properties for the oxidation-reduction reaction and must not deteriorate by reaction with the electrolyte. In addition, the reduction of the redox couple must maintain a low voltage and have a high electrical conductivity. As a material used for such a counter electrode, there are precious metals such as platinum and silver. Among them, platinum is most widely used. However, there is a limit in increasing the surface area for catalysis of the counter electrode, which makes it difficult to commercialize dye-sensitized solar cells. There is also a need for the development of a low cost, stable catalyst material that can replace expensive platinum.

Recently, a number of studies on carbon materials have been reported as catalyst materials that can replace platinum used in the counter electrode of dye-sensitized solar cells, and in the case of using carbon nanotubes as the counter electrode, energy equivalent to platinum is used. A study on the conversion efficiency has been reported (Seung I. Cha, Journal of Materials Chemistry 2010, 20, 659-662). However, this is also low to consider commercialization, and considering the decrease in performance due to the cracking of some carbon nanotubes or the floating of carbon nanotube particles separated by the collapse, a counter electrode having more stability is required. can see.

The present invention aims to provide a durable dye-sensitized solar cell with low production cost. More specifically, graphene oxide having a novel physical property that does not dissolve in an ion-containing solution using a graphene oxide prepared from graphite by a chemical solution method and at the same time does not destroy the membrane even if the ion and the ion-containing solution permeate. It is an object of the present invention to manufacture a structure and to actively use it as a dye-sensitized solar cell catalyst electrode.

The present invention comprises the steps of (a) forming a graphene oxide film on the substrate; And (b) heat-treating the graphene oxide film at 50 to 400 ° C. to partially reduce the heat; It provides a partially heat-reduced graphene film manufacturing method comprising a.

In addition, the present invention (A) forming a graphene oxide film on the transparent conductive film; (B) heat-treating the graphene oxide film at 50 to 400 ° C. to partially heat reduction to obtain a partially heat-reduced graphene film; And (C) contacting the partially heat reduced graphene film with an ion conductive solution; It provides with a counter electrode manufacturing method of the dye-sensitized solar cell comprising a.

In addition, the present invention is coated with the working electrode and the counter electrode on the opposite surface of the transparent conductive film spaced apart, the ion conductive solution is filled in the space between the working electrode and the counter electrode is sealed, the counter electrode is partially heat It provides a dye-sensitized solar cell, characterized in that consisting of a reduced graphene film.

In the present invention, the "partially heat-reduced graphene film" is a form having intermediate physical properties in the state of pure graphene oxide and graphene which is almost heat reduced at 500 ° C. or higher, and is not reduced with the heat-reduced part inside the film. Non-oxide refers to a film in which two states of oxide coexist.

The partially heat-reduced graphene film has the following physical properties.

(1) Partially present graphene oxide has hydrophilic properties, good contact properties with electrolytes of dye-sensitized solar cells, and properties such as ion channels through which iodine ions pass.

(2) The partially heat-reduced site has the properties of graphene, which serves to prevent the graphene oxide catalyst film from melting in the electrolyte.

(3) Pure graphene, carbon nanotubes and graphite are insoluble in water, but membrane fatigue and destruction occur under conditions where ions are permeated. However, the partially heat-reduced graphene membrane does not affect the stability of the membrane even when ions are permeated.

In the present invention, using the above properties, it was possible to utilize graphene as a counter electrode of the dye-sensitized solar cell instead of platinum.

The partially heat-reduced graphene film provided by the present invention can be used as a counter electrode of a dye-sensitized solar cell because the film is not destroyed while the ions and the ion-containing solution are permeable, which can be widely supplied at low cost in place of platinum. In addition, the partially heat-reduced graphene membrane is expected to be widely applied to ion selective permeation membrane / membrane and ion channel.

FIG. 1 illustrates a process of coating a partially heat-reduced graphene oxide film on a transparent electrode and an embodiment of a dye-sensitized solar cell having a partially heat-reduced graphene oxide film as a counter electrode.
2 is a surface and cross-sectional photograph of a counter electrode formed of a graphene oxide solution by concentration, a graphene oxide solution by concentration on a glass substrate on which a FTO transparent electrode is formed, and a partially heat-reduced graphene oxide. .
FIG. 3 is a comparative example in which the counter electrode surface is not coated on the FTO transparent electrode as a control for comparing the catalytic effect of a counter electrode composed of a partially heat-reduced graphene oxide film and a comparative example coated with platinum as in the prior art It is shown.

Ⅰ. Partially heat-reduced graphene film manufacturing method

The present invention comprises the steps of (a) forming a graphene oxide film on the substrate; And (b) heat-treating the graphene oxide film at 50 to 400 ° C. to partially reduce the heat; It provides a partially heat-reduced graphene film manufacturing method comprising a.

In the step (a), the graphene oxide may be prepared by a conventional chemical solution process, and the graphene oxide may be adjusted in thickness by adjusting concentration in the manufacturing process. As a method of forming a graphene oxide film on a substrate, conventional liquid coating methods such as spin coating, dip coating, inkjet printing, and spray coating may be applied.

In the step (b), as the heat treatment method, a method such as direct heating, infrared radiation, and atmosphere heating may be used. Heat treatment in step (b) is carried out at a relatively low temperature (50 ~ 400 ℃) compared to the heat treatment temperature (500 ℃ or more) for the heat reduction, accordingly, the graphene oxide film is not completely reduced has hydrophilicity, The ion-containing solution will have the property of permeation.

The partially heat-reduced graphene film prepared by the above-described method can be used as it is, such as ion selective permeation membrane / membrane, ion channel, and the like, and specifically, as a counter electrode of a dye-sensitized solar cell. It is available.

II. Counter electrode manufacturing method of dye-sensitized solar cell and dye-sensitized solar cell

The present invention (A) forming a graphene oxide film on the transparent conductive film; (B) heat treating the graphene oxide film at 50 to 400 ° C. to obtain a partially heat-reduced graphene film; And (C) contacting the partially heat reduced graphene film with an ion conductive solution; It provides a counter electrode manufacturing method of the dye-sensitized solar cell comprising a (see Fig. 1).

At this time, the step (A) may be carried out by spin coating the coating solution diluted in distilled water with the graphene oxide prepared by the chemical solution process on a transparent conductive film, more specifically 0.5 ~ 15.0 graphene oxide The coating solution in which wt% is dispersed may be spin-coated at 2000 rpm for 30 seconds on a transparent conductive film, and then dried at room temperature. Accordingly, the thickness of the counter electrode, which is partially heat-reduced graphene film, may be variously adjusted to 10 to 300 nm according to the concentration of the graphene oxide.

Accordingly, a partially heat-reduced graphene film can be applied as a counter electrode of a dye-sensitized solar cell, and a counter electrode comprising a working electrode and a partially heat-reduced graphene film on opposite surfaces of the transparent conductive film spaced apart. Each of them is coated and filled with an ion conductive solution (electrolyte) in the space between the working electrode and the counter electrode to form a sealed dye-sensitized solar cell.

Hereinafter, the present invention will be described in detail with specific embodiments and the accompanying drawings.

In each of the following examples, the transparent conductive film was coated with a TiO ₂ paste (Ti-Nanoxide T / SP, Solaronix) on a 5 mm × 5 mm conductive glass substrate with a thickness of 15 μm using a manual screen printing apparatus, and the conductive glass substrate was coated with the conductive glass substrate. It sintered at 500 degreeC for 30 minutes.

The working electrodes of the following examples were immersed in the 5mM TiCl ₄ aqueous solution for 30 minutes at 70 ° C. by immersing the conductive glass substrate on which the transparent conductive film was formed as described above, and then sintering at 500 ° C. for 30 minutes. It was prepared by soaking for time.

The counter electrode of the following examples is a partially heat-reduced graphene film, spin-coated an aqueous solution in which graphene oxide is dispersed on the transparent conductive film and heat-treated at a relatively low temperature (50 to 400 ° C.). The graphene oxide was prepared by a chemical solution process, and an aqueous solution prepared by ultrasonic dispersion of the graphene oxide paste containing the obtained graphene solids in distilled water was spin coated on a transparent conductive film at a speed of 2000 rpm. It is.

Examples 1 to 5 are differently applied concentrations of graphene oxide solutions (GO aqueous solutions) at 0.5, 1.0, 3.0, 6.0, and 15 wt%, respectively, and the conductive glass substrate was placed on a hot plate at 250 ° C. for 2 minutes. A counter electrode having a partially thermally reduced graphene oxide film was prepared by heating.

Each of the following examples are appropriately masked film for encapsulation between the working electrode and the counter electrode prepared as described above, the electrodes face each other to face each other, inject the electrolyte and then encapsulate the unit module of the dye-sensitized solar cell It is manufactured.

Individual matters of Examples 1 to 5 are as follows.

Example 1

Example 1 was prepared 0.5wt% aqueous solution of graphene oxide (GOFⅠ) with a graphene oxide paste containing 4% of the graphene solid content, spin-coated the conductive glass substrate at a speed of 2000rpm, and then the conductive glass substrate Was placed on a hot plate and heated at 250 ° C. for 2 minutes to prepare a dye-sensitized solar cell (DSSC I) having a counter electrode having a partially heat-reduced graphene oxide layer having a thickness of about 5 nm (FIG. 2). (d))

[Example 2]

Example 2 prepared 1.0 wt% aqueous solution of graphene oxide (GOFII) from a graphene oxide paste containing 4% of graphene solids, spin-coated the conductive glass substrate at a speed of 2000 rpm, and then the conductive glass substrate. Was placed on a hot plate and heated at 250 ° C. for 2 minutes to prepare a dye-sensitized solar cell (DSSCII) having a counter electrode having a partially heat-reduced graphene oxide layer having a thickness of about 10 nm (FIG. 2). (e)).

Example 3

Example 3 prepared 3.0 wt% graphene oxide aqueous solution (GOFIII) from the graphene oxide paste containing 4% of the graphene solid content, spin-coated the conductive glass substrate at a speed of 2000 rpm, and then the conductive glass substrate. Was placed on a hot plate and heated at 250 ° C. for 2 minutes to prepare a dye-sensitized solar cell (DSSC III) having a counter electrode having a partially heat-reduced graphene oxide layer having a thickness of about 20 nm (FIG. 2). (f)).

Example 4

In Example 4, a 6.0 wt% graphene oxide aqueous solution (GOFIV) was prepared from a graphene oxide paste containing 4% of graphene solids, spin-coated the conductive glass substrate at a speed of 2000 rpm, and then the conductive glass substrate. Was placed on a hot plate and heated at 250 ° C. for 2 minutes to prepare a dye-sensitized solar cell (DSSC IV) having a counter electrode having a partially heat-reduced graphene oxide layer having a thickness of about 50 nm (see FIG. 2). (g)).

Example 5

Example 5 is to prepare a 15.0wt% aqueous solution of graphene oxide (GOF V) with a graphene oxide paste containing 4% of the graphene solid content, spin coating the conductive glass substrate at a speed of 2000rpm, and then the conductive glass substrate Was placed on a hot plate and heated at 250 ° C. for 2 minutes to prepare a counter electrode of a dye-sensitized solar cell (DSSC V) having a partially heat-reduced graphene oxide layer having a thickness of about 200 nm (see FIG. 2). (h)).

Hereinafter, as a control for comparing the catalytic effect of a counter electrode composed of a partially heat-reduced graphene oxide film, a comparative example in which the counter electrode surface is not coated on the FTO transparent electrode and a counter electrode coated with platinum as in the prior art The comparative example will be briefly described.

Comparative Example 1

Comparative Example 1 is a comparative example in which the counter electrode surface is not coated on the FTO transparent electrode. The matters related to the transparent conductive film and the working electrode are the same as in the above-described embodiment (see FIG. 3A).

Comparative Example 2

Comparative Example 2 is a comparative example having a counter electrode coated with platinum as in the related art (see FIG. 3B). A counter electrode made of platinum was prepared by spin coating a 5 mM H ₂ PtCl ₆ solution (ethanol solvent) at 1000 rpm for about 30 seconds and then annealing at 400 ° C. for 15 minutes.

[Table 1] below is a result of measuring the efficiency, the short-circuit current density, the open voltage, the filling factor of the above examples and comparative examples using a solar simulator (PEC-L11, Peccell).

Comparative Example 1 Comparative Example 2 Example 1 Example 2 Example 3 Example 4 Example 5 efficiency(%) 0.74 6.02 2.30 2.16 1.81 1.63 1.56 Short circuit current density (mA / ㎠) 10.4 12.8 11.3 12.0 10.0 10.0 10.6 Open voltage (V) 0.78 0.70 0.68 0.65 0.66 0.62 0.68 Fill factor 0.09 0.68 0.30 0.28 0.24 0.26 0.22

In the above Table 1, it can be seen that the embodiments according to the present invention are degraded as compared with Comparative Example 2, but greatly improved compared to Comparative Example 1. The present invention is a pioneering invention for presenting a new material / new structure for a counter electrode of a dye-sensitized solar cell, and the above technical effects will be sufficient.

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Claims (5)

(a) forming a graphene oxide film on the substrate; And
(b) heat treating the graphene oxide film at 50 to 400 ° C. to partially reduce the heat; Partially heat reduced graphene film manufacturing method comprising a.
(A) forming a graphene oxide film on the transparent conductive film;
(B) heat treating the graphene oxide film at 50 to 400 ° C. to obtain a partially heat-reduced graphene film; And
(C) contacting the partially heat reduced graphene film with an ion conductive solution; A counter electrode manufacturing method of a dye-sensitized solar cell comprising a.
In claim 2,
Step (A) is a counter electrode manufacturing method of a dye-sensitized solar cell, characterized in that the coating solution prepared by diluting the graphene oxide prepared in a chemical solution process by spin coating on a transparent conductive film.
4. The method of claim 3,
Step (A) is a dye-sensitized solar cell, characterized in that the coating solution is dispersed in the graphene oxide 0.5 ~ 15.0wt% spin coating at 2000rpm on a transparent conductive film for 30 seconds and then dried at room temperature Method for producing a counter electrode.
The working electrode and the counter electrode are coated on opposite surfaces of the transparent conductive film spaced apart from each other, and a space between the working electrode and the counter electrode is filled with an ion conductive solution and sealed. The counter electrode is a partially heat-reduced graphene film. Dye-sensitized solar cell, characterized in that made.

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