KR20060085108A - Electrolytic layer comprising organic sulfurs and dye sensitized solar cells using the same - Google Patents

Abstract

The present invention relates to an electrolyte layer comprising an organic sulfur-based material and a dye-sensitized solar cell having the same, and more particularly, to an electrolyte layer having an improved energy conversion efficiency by including an organic sulfur-based redox couple having a new composition, and It relates to a dye-sensitized solar cell.

The dye-sensitized solar cell according to the present invention is provided with an electrolyte layer using a compound having a cyclic disulfide group as a redox couple, thereby increasing the redox potential, so that the photoconversion is performed in comparison with a conventional iodine based electrolyte solution or acyclic disulfide based electrolyte solution. The efficiency is improved.

Description

Electrolytic layer comprising organic sulfur-based material and dye-sensitized solar cell having the same {Electrolytic layer comprising organic sulfurs and dye sensitized solar cells using the same}

1 is a view schematically showing the configuration of a dye-sensitized solar cell according to the present invention.

<Explanation of symbols for the main parts of the drawings>

10: semiconductor electrode, 11: conductive transparent substrate, 12: light absorption layer, 12a: metal oxide, 12b: dye, 13: electrolyte layer, 14: counter electrode

The present invention relates to an electrolyte layer comprising an organic sulfur-based material and a dye-sensitized solar cell having the same, and more particularly, to an electrolyte layer having an improved energy conversion efficiency by including an organic sulfur-based redox couple having a new composition, and It relates to a dye-sensitized solar cell.

Recently, various researches have been conducted to replace existing fossil fuels to solve the energy problem. In particular, extensive research has been conducted to utilize natural energy such as wind, nuclear power, and solar power to replace petroleum resources that will be exhausted within decades. Unlike other energy sources, solar cells using solar energy have unlimited resources and are environmentally friendly.Since the development of Se solar cells in 1983, silicon solar cells have been in the spotlight recently.

However, such a silicon solar cell is difficult to be commercialized because the manufacturing cost is quite expensive, and there are many difficulties in improving the battery efficiency. In order to overcome this problem, the development of dye-sensitized solar cells with significantly low manufacturing costs has been actively studied.

Unlike silicon solar cells, dye-sensitized solar cells are composed of photosensitive dye molecules capable of absorbing visible light to produce electron-hole pairs, and transition metal oxides for transferring generated electrons. Photoelectrochemical solar cell. A representative example of the dye-sensitized solar cells known to date is known in 1991 by Gratzel et al., Switzerland. The solar cell by Gratzel et al. Is composed of a semiconductor electrode composed of nanoparticle titanium dioxide (TiO ₂ ) coated with dye molecules, an opposite electrode (platinum electrode), and an electrolyte filled therebetween. This battery has been attracting attention because it has a function that can replace the conventional solar cell because the manufacturing cost per power is lower than the conventional silicon solar cell.

The structure of such a dye-sensitized solar cell is shown in FIG. Referring to FIG. 1, the dye-sensitized solar cell includes a semiconductor electrode 10, an electrolyte layer 13, and an opposite electrode 14, and the semiconductor electrode includes a conductive transparent substrate 11 and a light absorption layer 12. . In other words, the semiconductor electrode 10 and the counter electrode 14 have a structure filled with the electrolyte layer 13.

The light absorption layer 12 generally includes a metal oxide 12a and a dye 12b. The dye 12b may be represented by S, S ^* , and S ⁺ , and each represents a neutral, transition state, and an ionic state. When sunlight is absorbed, the dye molecules are excited in a ground state (S / S ⁺ ) S ^* / S ⁺ ) electron transition to form an electron-hole pair (electron-hole pair), the electron (e-) of the excited state is injected into the conduction band (CB) of the metal oxide 12a is electromotive force Will occur.

In such a conventional dye-sensitized solar cell I as oxidation-reduction couples ^- / I ₃ ^- Bar The mechanism mainly using the electrolyte layer are as follows.

In the case of using I ⁻ / I ₃ ⁻ as a redox couple, there is a problem that the open voltage (V _oc ) is small so that there is a fundamental limitation in dramatically improving the efficiency of the dye-sensitized solar cell. That is, the efficiency of the solar cell can be represented by the following Equation 1, where the decrease in the open voltage V _oc inevitably leads to a decrease in efficiency.

η _e = (V _oc I _sc FF) / (P _inc )

(Η _e represents the efficiency of the solar cell, V _oc represents the open voltage, I _sc represents the short-circuit current, FF represents the filling factor, and P _inc represents 100 mw / cm ² (1 sun))

Therefore, research on a new redox couple that increases the V _oc is in progress, and US Patent No. 4,833,048 discloses a disulfide compound, which is briefly represented by RSSR (R is an aliphatic or aromatic oil). device). Here, the SS bond is cleaved by electrolytic reduction, and forms a salt represented by cation (M ⁺ ) and RS ^- M ⁺ in the electrolyte solution. This salt returns to RSSR by electrolytic oxidation. However, such disulfide compounds are described by the inventors of U.S. Patent No. 4,833,048 by J. Electrochem. Soc., Vol. As reported by 136, No. 9, p2570-2575 (1989), there is a problem that the oxidation and reduction potential is considerably lowered. For example, in the electrolysis of [(C ₂ H ₅ ) ₂ NCSS-] ₂ , the oxidation potential and the reduction potential drop by more than 1 volt. Therefore, according to the electrode reaction theory, the electron transfer process is extremely slow, and thus, it is difficult to obtain a large current suitable for practical use, for example, a current of 1 mA / cm ² or more near room temperature, and a battery having an electrode using such a compound There is a limitation that it should be used only at a high temperature of 100 to 200 ℃ it was difficult to use.

U.S. Patent No. 5,324,599 also describes a reversible electrode material, which discloses R-S-S-R 'as an example (where R and R' are conductive polymers). Such disulfide compounds have a solubility problem that is insoluble in the electrolyte solvent.

The technical problem to be achieved by the present invention is to provide an electrolyte layer containing an organic sulfur-based material having high solar energy conversion efficiency.

Another object of the present invention is to provide a dye-sensitized solar cell including the electrolyte layer.

The present invention to achieve the above technical problem,

It provides an electrolyte layer comprising a compound of formula 1 having a cyclic disulfide group.

또는

을 나타내고,Where -X- is

or

Indicates,

R ₁ , R ₂ , R ₃ , R ₄ , R ₅ , R ₆ and R ₇ are each independently a hydrogen atom, a halogen atom, a hydroxy group, a substituted or unsubstituted alkyl group having 1 to 20 carbon atoms, a substituted or unsubstituted carbon An alkoxy group having 1 to 20 carbon atoms, a substituted or unsubstituted alkenyl group having 1 to 20 carbon atoms, a substituted or unsubstituted aryl group having 6 to 30 carbon atoms, a substituted or unsubstituted arylalkyl group having 6 to 30 carbon atoms, substituted or unsubstituted A substituted aryloxy group having 6 to 30 carbon atoms, a substituted or unsubstituted heteroaryl group having 2 to 30 carbon atoms, a substituted or unsubstituted heteroaryloxy group having 2 to 30 carbon atoms, or a substituted or unsubstituted heteroarylalkyl group Indicates.

As the compound of Formula 1, a compound of the following Formula 2a or 2b is preferable.

Wherein X represents a hydrogen atom, a halogen atom, a hydroxy group, a substituted or unsubstituted alkyl group having 1 to 20 carbon atoms, a substituted or unsubstituted alkoxy group having 1 to 20 carbon atoms, or a substituted or unsubstituted alkenyl group having 1 to 20 carbon atoms Indicates.

The present invention provides a dye-sensitized solar cell employing the electrode material in order to achieve the other technical problem.

The present invention will be described in more detail below.

The electrolyte layer including the compound of Formula 1 according to the present invention has a high redox potential and thus provides a high conversion efficiency for solar energy. For this purpose, the compound forms a redox couple as follows.

Wherein X, R ₁ , R ₂ , R ₃ , and R ₄ are as defined above.

The compound of Formula 1 is obtained by the electrolytic reduction reaction of the two electrons in the electrolyte layer is cleaved into a compound of Formula 1a, and again to form an SS bond while giving out two electrons by the oxidation reaction to formula (1) Return to the compound of. Since the bonds forming the 5-membered ring are entropy more advantageous than the molecule-to-molecular bonds, the cyclic disulfides are advantageously subjected to a redox reversible reaction when forming disulfides rather than acyclic disulfides.

The compound of Formula 1 according to the present invention is a compound having a cyclic disulfide group, and as a preferred embodiment of such a compound, compounds of the following Formulas 2a and 2b may be exemplified.                     

<Formula 2a>

Wherein X represents a hydrogen atom, a halogen atom, a hydroxy group, a substituted or unsubstituted alkyl group having 1 to 20 carbon atoms, a substituted or unsubstituted alkoxy group having 1 to 20 carbon atoms, or a substituted or unsubstituted alkenyl group having 1 to 20 carbon atoms Indicates.

<Formula 2b>

The method for preparing the compound of Formula 1 is shown in Scheme 1 below.                     

Wherein X, R ₁ , R ₂ , R ₃ , and R ₄ are as defined above.

As shown in Scheme 1, the compound of Formula 1 having a cyclic disulfide group according to the present invention reacts with the substituted amine compound of Formula 5 with substituted paraformaldehyde and thionyl chloride to obtain a compound of Formula 4, By reacting Li ₂ S to obtain a compound of formula (3) in which a chlorine atom is substituted with sulfur ions, it can be oxidized to prepare the compound of formula (1) according to the present invention.

The present invention also provides a dye-sensitized solar cell having an electrolyte layer containing the compound of Formula 1. 1 is a view schematically showing the configuration of a dye-sensitized solar cell according to the present invention. Referring to FIG. 1, the dye-sensitized solar cell according to the present invention includes a semiconductor electrode 10, a counter electrode 14, and an electrolyte layer 13 interposed therebetween. The semiconductor electrode 10 includes a conductive transparent substrate 11 and a light absorbing layer 12. As described above, the light absorbing layer 12 includes a metal oxide 12a and a dye 12b.

The transparent substrate used for the conductive transparent substrate 11 is not particularly limited as long as it has transparency, and for example, a glass substrate can be used. As a material for imparting conductivity to the transparent substrate, any material can be employed as long as it has conductivity and transparency. However, tin oxide (for example, SnO ₂ ) has a high level of conductivity, transparency, and particularly heat resistance. Etc. are suitable, and in terms of cost, indium tin oxide (ITO) is preferred.

The metal oxide 12a included in the light absorption layer 12 according to the present invention may include TiO ₂ (titanium dioxide), SnO ₂ , ZnO, WO ₃ , Nb ₂ O ₅ , TiSrO ₃ , and the like as the semiconductor fine particles. preferably the TiO ₂ of the anatase type. In addition, the kind of semiconductor is not limited to these, These can be used individually or in mixture of 2 or more types. Such semiconductor fine particles preferably have a large surface area in order for the dye adsorbed on the surface to absorb more light. For this purpose, the particle size of the semiconductor fine particles is preferably about 30 nm or less, more preferably 5 to 20 nm.

In addition, the dye 12b included with the metal oxide 12a in the light absorption layer 12 may be used without limitation as long as it is generally used in the solar cell or photovoltaic field, but ruthenium complex is preferable. However, the dye is not particularly limited as long as it has a charge separation function and exhibits an action. For example, in addition to ruthenium complexes, for example, xanthine-based pigments such as rhodamine B, rosebengal, eosin, and erythrosine, quinocyanine, Cyanine-based pigments such as cryptocyanine, basic dyes such as phenosafranin, cabrioblue, thiocin and methylene blue, porphyrin-based compounds such as chlorophyll, zinc porphyrin, magnesium porphyrin, other azo dyes, phthalocyanine compounds, Ru tris Complex compounds such as bipyridyl, anthraquinone dyes, polycyclic quinone dyes, and the like, and the like can be used alone or in combination of two or more thereof. As the ruthenium complex, RuL ₂ (SCN) ₂ , RuL ₂ (H ₂ O) ₂ , RuL ₃ , RuLL '(SCN) ₂ , 2RuL ₂ , and the like can be used (wherein L is 2,2′-bipyridyl-). 4,4'-dicarboxylate, and L 'represents a ligand having another dipyridyl group).

The thickness of the light absorption layer 12 including the metal oxide 12a and the dye 12b is 15 microns or less, preferably 5 to 15 microns. Because the light absorption layer has a large series resistance due to its structural reasons, and the increase in series resistance leads to a decrease in conversion efficiency. The film thickness is 15 microns or less, so that the series resistance is kept low while maintaining its function. Can be prevented from deteriorating.

The electrolyte layer 13 is made of an electrolyte solution and includes the light absorption layer 12 or is formed so that the electrolyte solution is infiltrated into the light absorption layer 12. Examples of the electrolyte include an acetonitrile solution, a 3-methoxy propionitrile solution, an NMP solution, and the like, including a compound of formula 1 having a cyclic disulfide group according to the present invention as a redox couple. There is no particular limitation on the shape such as gel.                     

The organosulfur material is present as a redox couple, reversibly proceeding with cyclization and acyclic in the above solution.

The counter electrode 14 can be used without limitation as long as it is a conductive material. If the conductive material is provided on the side facing the semiconductor electrode, even an insulating material can be used. However, it is preferable to use an electrochemically stable material as an electrode, and it is preferable to use platinum, gold, carbon, etc. specifically ,. In order to improve the catalytic effect of the redox, the side facing the semiconductor electrode is preferably in a fine structure, and the surface area thereof is increased. For example, it is preferable that platinum is in a platinum black state and carbon is in a porous state. The platinum black state can be formed by platinum anodization, platinum chloride treatment, or the like, and carbon in the porous state can be formed by sintering carbon fine particles or firing organic polymers.

The manufacturing method of the dye-sensitized solar cell according to the present invention having such a structure is not particularly limited, and any method known in the art can be used without limitation.

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited thereto.

Example 1

Titanium dioxide colloidal solution was prepared by hydrothermal synthesis in an autoclave where titanium isopropoxide and acetic acid were kept at 220 ° C. The solvent was evaporated until the content of the titanium dioxide in the obtained solution was 12% by weight to prepare a titanium dioxide colloidal solution having a nano-level particle size (about 5 to 30nm).

Next, hydroxy propyl cellulose (molecular weight: 80,000) was added to the metal oxide concentrated solution, followed by stirring for 24 hours to prepare a slurry for coating titanium dioxide. Subsequently, the titanium dioxide coating slurry was coated on a transparent conductive glass substrate coated with indium tin oxide (ITO) and having a transmittance of 80% by a doctor blade method, followed by heat treatment at a temperature of about 450 ° C. for 1 hour to form an organic polymer. Except for contacting and filling between the nano-particle oxides to obtain a conductive transparent substrate having a titanium dioxide layer having a thickness of about 6 microns on a surface having a thickness of 10 microns.

Subsequently, the conductive transparent substrate on which the titanium dioxide layer was formed was immersed in ruthenium dithiocyanate 2,2'-bipyridyl-4,4'-dicarboxylate ethanol solution having a concentration of 0.3 mM for 24 hours and then dried to dye. Was adsorbed onto the substrate.

Separately, a counter electrode was prepared by coating platinum on the surface of the conductive transparent glass substrate coated with ITO. Subsequently, the opposite electrode as the anode and the semiconductor electrode as the cathode were assembled. When assembling the positive electrode, the platinum layer and the light absorbing layer face each other so that the conductive surfaces of the positive electrode and the negative electrode are brought into the battery. At this time, between the anode and the cathode was placed about 40 microns thick polymer made of SURLYN (manufactured by Du Pont), the two electrodes were brought into close contact with each other at about 1 to 3 atm on a heating plate of about 100 to 140 ℃. The polymer was in close contact with the surfaces of the two electrodes by heat and pressure.                     

Next, a dye-sensitized solar cell according to the present invention was completed by filling an electrolyte solution in the space between the two electrodes through the micropores formed on the surface of the anode. As the electrolyte solution, an electrolyte solution in which 0.1 M of the compound of Formula 11 and 0.1 M thereof was dissolved in acetonitrile was used.

<Formula 11>

Example 2

Except for using the electrolyte layer using 0.1M compound 0.1M compound of Formula 12 in place of the compound of Formula 11 in the same manner as in Example 1 to prepare the desired dye-sensitized solar cell.

<Formula 12>

Comparative Example 1

In Example 1, 0.6M 1,2-dimethyl-3-octyl-imidazolium iodide (1,2-dimethyl-3-octyl-imidazolium iodide), 0.2M LiI as an electrolyte solution as in the above example 1, except for using an electrolytic solution of ^-: (4-tert- butyl-pyridin-TBP) to which I ₃ dissolved in acetonitrile ^- / I, 0.04MI ₂ and 0.2M 4-tert- butyl-pyridin- By performing the same process to prepare a dye-sensitized solar cell.

Comparative Example 2

(Please describe the example of using a conventional disulfide compound, ie, an RSSR 'type redox couple, as an electrolyte solution, and compare it with the cyclic disulfide of the present invention. It is important to demonstrate the progress of the present invention. Please.)

In Example 1, a dye-sensitized solar cell was prepared in the same manner as in Example 1, except that CH ₃ CH ₂ -SS-CH ₂ CH ₃ was used as an electrolyte solution containing a redox couple. .

Experimental Example 1:

In order to measure the light conversion efficiency of the dye-sensitized solar cells prepared in Examples 1 and 2 and Comparative Examples 1 and 2, the photovoltage and photocurrent were measured.

A xenon lamp (Oriel, 01193) was used as the light source, and the solar condition (AM 1.5) of the xenon lamp was a standard solar cell (Frunhofer Institute Solare Engeries systeme, Certificate No. C-ISE369, Type of material: Mono-). Si + KG filter). The current density (I _sc ), the voltage (V _oc ), and the fill factor (FF) calculated from the measured photocurrent voltage curves are calculated using the following equation to obtain the optical conversion efficiency (η _e ), and are shown in Table 1 below. It was. The light conversion efficiency calculation equation is as follows.

η _e = (V _oc I _sc FF) / (P _inc )

In the formula, P _inc represents 100mw / cm ² (1 sun).

division Optical conversion efficiency (%) Example 1 4.1 Example 2 4.2 Comparative Example 1 3.7 Comparative Example 2 3.5

As can be seen in Table 1, the dye-sensitized solar cell according to the present invention is provided with an electrolyte layer using a compound having a cyclic disulfide group as a redox couple, so that the redox potential is increased. It can be seen that the light conversion efficiency is improved compared to the li-type disulfide electrolyte solution.

Claims (4)

An electrolyte layer comprising a compound of formula 1 having a cyclic disulfide group: <Formula 1>

Where -X- is

or

Indicates, R ₁ , R ₂ , R ₃ , R ₄ , R ₅ , R ₆ and R ₇ are each independently a hydrogen atom, a halogen atom, a hydroxy group, a substituted or unsubstituted alkyl group having 1 to 20 carbon atoms, a substituted or unsubstituted carbon number 1-20 alkoxy group, substituted or unsubstituted alkenyl group having 1 to 20 carbon atoms, substituted or unsubstituted aryl group having 6 to 30 carbon atoms, substituted or unsubstituted arylalkyl group having 6 to 30 carbon atoms, substituted or unsubstituted Substituted aryloxy group having 6 to 30 carbon atoms, substituted or unsubstituted heteroaryl group having 2 to 30 carbon atoms, substituted or unsubstituted heteroaryloxy group having 2 to 30 carbon atoms, or substituted or unsubstituted heteroarylalkyl group. . The electrolyte layer according to claim 1, wherein the compound of Formula 1 is a compound of Formula 2a or 2b: <Formula 2a>

<Formula 2b>

Wherein X represents a hydrogen atom, a halogen atom, a hydroxy group, a substituted or unsubstituted alkyl group having 1 to 20 carbon atoms, a substituted or unsubstituted alkoxy group having 1 to 20 carbon atoms, or a substituted or unsubstituted alkenyl group having 1 to 20 carbon atoms Indicates. Conductive transparent substrate; Light absorption layer; The electrolyte layer according to claim 1 or 2; And Dye-sensitized solar cell comprising a counter electrode. The dye-sensitized solar cell of claim 3, wherein the light absorbing layer comprises a metal oxide and a dye.

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