KR20090070058A - Dye sensitized solar cells using solid-state nanocomposite electrolytes - Google Patents

Abstract

A dye sensitized solar cells using a solid-state nano-composite electrolytes are provided to improve ion conductivity and stability by using an inorganic structure of layer structure into which organic substance is inserted through ion-exchange. A solar cell is comprised of a semiconductor electrode(110), an opposite electrode(120), and a solid state nano composite electrolyte(130). The solid state nano composite electrolyte is interposed between the semiconductor electrode and the opposite electrode, and the ammonium system organic compound or an oligomer is inserted into the titania group inorganic material of the layer structure. The titania group inorganic substance is one selected from the group consisting of K2Ti4O9, na2Ti3O7, and csxTi2-x / 4O4.

Description

Solid nanocomposite electrolyte and solar cell using same {DYE SENSITIZED SOLAR CELLS USING SOLID-STATE NANOCOMPOSITE ELECTROLYTES}

The present invention relates to a solid nanocomposite electrolyte and a solar cell using the same, and more particularly, to a solid nanocomposite electrolyte having an ammonium-based organic material or oligomer inserted into a titania-based inorganic material having a layered structure and a solar cell using the same.

Dye-sensitized solar cells consist of photosensitive dye molecules capable of absorbing visible light to produce electron-hole pairs, transition metal oxides that carry the generated electrons, electrolytes, and electrodes on either side. The dye-sensitized solar cell thus constructed is cheaper in manufacturing cost per power than silicon solar cells, and has an environmentally friendly process, and thus has been in the spotlight for self-charging of the next generation power source.

FIG. 1 is an explanatory view showing the operation principle of a general dye-sensitized solar cell. The dye 12 adsorbed on the semiconductor oxide electrode 11 absorbs sunlight and is excited in a ground state (D ⁺ / D). The excited state, D ⁺ / D ^* ), forms an electron-hole pair by electron transition, and the excited state is injected into the conduction band (E _CB ) of the semiconductor oxide.

 The electrons injected into the semiconductor oxide electrode 11 are transferred to the transparent conductive substrate 13 through the interparticle interface and then moved to the counter electrode 15 coated with the platinum layer 16 through the external wire 14.

An electrolyte including an oxidation-reduction pair 17 is injected between the semiconductor oxide electrode 11 and the counter electrode 15.

The dye 12 oxidized by solar absorption receives electrons provided by the oxidation-reduction pair 17 and is reduced again. At this time, the oxidation-reduction pair 17 supplying the electrons reaches the counter electrode 15. Reduction by one electron completes the operation of the dye-sensitized solar cell.

In addition, the load L is connected to the transparent conductive substrate 13 and the counter electrode 15 in series, so that the efficiency of the battery can be known by measuring a short circuit current, an open voltage, a charge factor, and the like.

As described above, the dye molecules (D → D (+)) oxidized as a result of electron transfer by light absorption are oxidized (3I (-1) → I ₃ (-1) +2 (e) in iodine ions in the redox electrolyte. Receiving electrons provided by-) is reduced again, and I ₃ (-1) ions are reduced by electrons (e-) reaching the platinum counter electrode to complete the dye-sensitized solar cell operation process.

The photocurrent is obtained as a result of the diffusion of electrons injected into the semiconductor oxide electrode, and the photovoltage is determined by the difference between the Fermi energy of the semiconductor oxide and the oxidation-reduction potential of the electrolyte.

A representative example of dye-sensitized solar cells known to date was published in 1991 by Gratzel et al. (USP 4927721, USP 5350644), which is a solar cell composed of photosensitive dye molecules and nanoparticle titanium oxide. Compared with solar cells, the manufacturing cost is low.

Dye-sensitized nanoparticle oxide solar cells well known so far are composed of a nanoparticle oxide semiconductor anode, a platinum anode, a redox liquid electrolyte using a dye coated on the cathode and an organic solvent. However, in the dye-sensitized solar cell including the liquid electrolyte obtained from the organic solvent, there is a possibility that the electrolyte solvent is volatilized from the solar cell when the external temperature of the solar cell is increased by sunlight. Therefore, there is a problem that it is very disadvantageous for the long-term stability and practical use of the dye-sensitized solar cell due to solvent leakage.

In order to solve this problem, non-volatile and semi-solidified electrolytes have been studied. Therefore, ionic liquids having no solvent evaporation, flame retardancy, and high ionic conductivity have been spotlighted as electrolyte materials for dye-sensitized solar cells. In addition, ionic liquid-based electrolytes maintain a stable liquid phase over a wide temperature range, including room temperature, by adding a suitable gelling material to physically or chemically solidify. Representative examples of ion-gel electrolytes to date have been published in 2003 by Gratzel et al. (J. AM. CHEM. SOC. 2003, 125, 1166-1167). To prepare a semi-solid ion-gel electrolyte.

However, the inorganic particles dispersed on the electrolyte are agglomerated with each other as the outside temperature increases or as time passes, which causes long-term stability and efficiency of the dye-sensitized solar cell.

An object of the present invention is to improve the long-term stability and operating efficiency by preparing a solid nanocomposite electrolyte using a layered inorganic material and then applying it to a dye-sensitized solar cell.

In particular, long-term stability and light scattering effects are improved by preparing a solid nanocomposite electrolyte having improved dispersibility by inserting organic materials through ion exchange into a layered inorganic material.

The solar cell of the present invention for solving the above problems is a solid-state nano interposed between the semiconductor electrode, the counter electrode and the semiconductor electrode and the counter electrode, the ammonium organic material or oligomer is inserted into the titania-based inorganic material of the layer structure It comprises a composite electrolyte.

The titania-based inorganic material is formed to have a length of 100 nm to 10 μm, and may be formed of a material such as K ₂ Ti ₄ O ₉ , Na ₂ Ti ₃ O ₇ , Cs _x Ti _{2 -x / 4} O _4, and the like.

The ammonium organic material corresponds to any one of methyl ammonium, propyl ammonium and tetrabutylammonium.

The solid nanocomposite electrolyte may further include an ionic liquid and a polymer, wherein the ionic liquid is methylpropylimidazolium iodide, butylmethylimidazolium iodide, hexylmethyl imidazolium iodide. Id, imidazolium iodide and the like can be used. In addition, the polymer may be polyacrylonitrile, polyvinylidene fluoride cohexafluoropropylene, polypropylene, polyethylene oxide and the like.

The present invention includes a method of manufacturing the above-described solar cell, the method of manufacturing a solar cell according to the present invention comprises the steps of preparing a semiconductor electrode, preparing a counter electrode facing the semiconductor electrode, and the semiconductor electrode And assembling the counter electrode apart from each other and forming a solid nanocomposite electrolyte solution between the semiconductor electrode and the counter electrode.

The forming of the solid nanocomposite electrolyte solution may include preparing an inorganic material having a layered structure, hydrogenating the inorganic material having the layered structure using an ion exchange method, and performing the hydrogenated inorganic material. Inserting an organic material into the organic material, inserting an ionic liquid, an oligomer, and a polymer into an inorganic material having a layered structure into which the organic material is inserted, and using the inorganic material as a gelling material. It characterized in that it comprises a step of preparing an electrolyte.

Hereinafter, a solar cell and a method of manufacturing the same according to the present invention will be described in detail with reference to the accompanying drawings.

2 is a view schematically showing a dye-sensitized solar cell 100 including a solid nanocomposite electrolyte according to the present invention.

Referring to the drawings, the dye-sensitized solar cell according to the present invention comprises a semiconductor electrode 110 and a counter electrode 120 facing the semiconductor electrode 110. The solid nanocomposite electrolyte 130 is filled between the semiconductor electrode 110 and the counter electrode 120.

The semiconductor electrode 110 is transparent The titanium oxide blocking layer 113 is formed on the conductive substrate 111, and the semiconductor oxide electrode 115 is formed on the titanium oxide blocking layer 113.

Here, the transparent conductive substrate 111 is configured in the form of a transparent conductive thin film formed on a transparent glass substrate or a flexible (flexible) polymer substrate. The conductive thin film may be formed of indium tin oxide (ITO), SnO ₂ : F-doped (FTO), or the like, or may be formed by coating antimony tin oxide (ATO) or FTO on the ITO.

The titanium oxide blocking layer 113 is additionally formed to prevent electrons transferred to the transparent substrate from being returned to the electrolyte, and the thickness thereof is generally several tens of nm.

The semiconductor oxide electrode 115 on the transparent conductive substrate 111 is formed in a form in which the dye molecules 115b are adsorbed onto the semiconductor oxide particles 115a. The dye molecule 115b used in the semiconductor oxide electrode is preferably ruthenium-based dye or coumarin-based organic dye.

The counter electrode 120 is transparent The platinum layer 123 for the redox catalyst is formed on the conductive substrate 121. Here, the transparent conductive substrate 121 is configured in the form of a transparent conductive thin film formed on a transparent glass substrate or a flexible (flexible) polymer substrate. The conductive thin film may be formed of indium tin oxide (ITO), SnO ₂ : F-doped (FTO), or the like, or may be formed by coating antimony tin oxide (ATO) or FTO on the ITO.

The solid nanocomposite electrolyte 130 interposed between the semiconductor electrode 110 and the counter electrode 120 is The organic material is inserted into the layered inorganic material.

As the inorganic material of the layered structure, for example, a titania-based inorganic material can be used. Layered titania-based inorganic materials include K ₂ Ti ₄ O ₉ , Na ₂ Ti ₃ O ₇ , Cs _x Ti _{2 -x / 4} O ₄ , and some of the inorganic materials may be used alone or mixed as necessary. Can be used.

The layered structure of the titania-based inorganic material has a length of 100 nm to 10 μm.

As the organic material interposed between the layered inorganic materials, various organic materials may be used. Preferably, an ammonium organic material or an oligomer is preferable.

In this case, as the ammonium-based organic material may be used organic materials, such as methyl ammonium, propyl ammonium, tetrabutylammonium, may be used alone or may be used in combination as necessary.

As the oligomer, polyethylene glycol dimethyl ether, polyethylene glycol, polypropylene glycol, polypropylene glycol diamine, polyethylene glycol bis carboxymethyl ether, etc. may be used, and may be used alone or mixed as necessary. Can be used.

The solid nanocomposite electrolyte according to the invention can be used in particular in dye-sensitized solar cells.

3A to 3C are diagrams showing the crystal structure of K ₂ Ti ₄ O ₉ , which is one of the layered inorganic materials according to the exemplary embodiment of the present invention.

Figure 3a shows the crystal structure of K ₂ Ti ₄ O ₉ One layer has a size of 100nm × 100nm × 1mm, the layer itself is composed of Ti ₄ O ₉ ^{2 +} There is a K ⁺ between the layers.

3b is a structure after exchanging K ⁺ with H ⁺ through ion-exchange, and FIG. 3c is a layered inorganic material K ₂ Ti by exchanging tetrabutyl ammonium (TBA) with H ^+. ₄ O represents the tetrabutylammonium form is interposed between the crystal ₉ of the structure.

The solid nanocomposite electrolyte according to the present invention may further comprise an ionic liquid and a polymer, wherein the ionic liquid is methylpropylimidazolium iodide, butylmethylimidazolium iodide, hexylmethyl imide. It is a substance, such as dazolium iodide and imidazolium iodide, and can be used individually or in mixture as needed. The polymer is a material such as polyacrylonitrile, polyvinylidene fluoride cohexafluoropropylene, polypropylene, polyethylene oxide, and the like, and may be used alone or in combination as necessary.

The semiconductor electrode and the counter electrode may be sealed with a thermoplastic polymer 29 to prevent the electrolyte solution from leaking out.

In the solar cell according to the present invention as described above, the inorganic material of the layered structure serves as a nano channel in the electrolyte, and the positive or negative charge present in the layered structure promotes dissociation of ions in the electrolyte. Do this.

In addition, the inorganic material into which the organic material is inserted shows excellent dispersibility in the ionic liquid, and the excellent dispersibility of the inorganic material enables to improve the long-term stability of the electrolyte and the light scattering effect, thereby providing a high quality solar cell.

Figure 4 is a flow chart showing a dye-sensitized solar cell manufacturing method prepared according to the present invention.

Referring to the drawings, first, in order to prepare a semiconductor electrode, a transparent conductive substrate (ITO glass, FTO glass, or a polymer transparent substrate having a transparent conductive film such as ITO or FTO) is prepared. A barrier layer made of titanium oxide is additionally formed on the transparent substrate to prevent electrons transferred to the transparent substrate from being returned to the electrolyte. The thickness of the blocking layer is generally formed to about 100 nm or less.

Next, a semiconductor oxide electrode is formed on the transparent conductive substrate. The semiconductor oxide electrode is formed by coating a material such as titanium oxide (TiO ₂ ) paste on the transparent conductive substrate and then heat treating the same.

Next, the dye is adsorbed onto the semiconductor oxide electrode formed as described above.

In order to form a counter electrode facing the semiconductor electrode, a transparent conductive substrate is first prepared.

Next, a counter electrode is prepared by coating a platinum acting as a catalyst on the transparent conductive substrate and performing heat treatment to form a platinum layer.

The semiconductor electrode and the counter electrode prepared as described above are assembled so that the transparent conductive thin film and the platinum layer face each other and are spaced at a predetermined interval therebetween.

Next, a solid nanocomposite electrolyte solution is formed in a space spaced between the semiconductor electrode and the counter electrode, and sealed with a thermoplastic polymer 29 so that the electrolyte solution does not leak out.

Here, when the solid nanocomposite electrolyte solution is formed between the semiconductor electrode and the counter electrode, the solid nanocomposite electrolyte may be inserted between the two electrodes using a vacuum vacuum pump.

A method of manufacturing a solid nanocomposite electrolyte formed between the two electrodes (ie, the semiconductor electrode and the counter electrode) is illustrated in FIG. 5.

Referring to the drawings, a method for preparing a solid nanocomposite electrolyte according to the present invention is as follows.

First, an inorganic material having a layered structure is manufactured using a titania-based inorganic material.

The layered inorganics are then hydrogenated using an ion exchange method.

Next, an organic substance is inserted into the hydrogenated layered inorganic material. In this case, a sonication method may be used to insert the organic material into the inorganic material.

After the sonication, the inorganic material into which the organic material is inserted may be obtained by centrifugation and drying.

Next, an ionic liquid, an oligomer or a polymer is additionally mixed and inserted into the inorganic material having a layered structure in which the organic material is inserted.

Thereafter, the inorganic material is used as a gelling material to complete a solid nanocomposite electrolyte including electrolyte ions.

As described above, the dye-sensitized solar cell according to the present invention has the following advantages and effects by using a solid nanocomposite electrolyte containing a layered inorganic material.

First, by using the inorganic material of the layered structure in which the organic material is inserted as a gelling material, it is possible to improve the dispersibility in the ionic liquid, and thus to prepare a solid nanocomposite electrolyte having improved long-term stability.

Second, the layered inorganic material has a micro size, causing a light scattering effect. When applied to dye-sensitized solar cells, the current density can be increased by maximizing the light scattering effect.

Third, the layered inorganic material can improve the electrical conductivity of the electrolyte by acting as a nano channel that can easily move the electrolyte ions through the layers.

Fourth, the inorganic material of the layered structure may have a negatively charged layer and a cation exists between the layers to induce dissociation of ions, thereby improving the electrical conductivity of the electrolyte.

Hereinafter, the present invention will be described in detail in the following Examples. However, the embodiments of the present invention illustrated in the following may be modified in many different forms and the scope of the present invention is not limited or limited to the embodiments described in the following.

Example 1 Preparation of Solid Nanocomposite Electrolyte According to the Present Invention

16 g of titanium oxide (TiO ₂ ) powder and 10 g of potassium nitrate (KNO ₃ ) powder were mixed and heat-treated at 1000 ° C. for 48 hours to prepare a layered titanate (K ₂ Ti ₄ O ₉ ).

10 g of the layered titanate was added to 1 L of 2M hydrochloric acid solution and reacted at 60 ° C. and 300 rpm for 12 hours.

After completion of the reaction, 0.5 g of hydrochloric acid treated layered titanate (H ₂ Ti ₄ O ₉ ) obtained through a filter and drying was added to 6 g of an aqueous tetrabutyl ammonium solution (TBA hydroxide), followed by sonication for 1 hour. I was.

After the completion of the sonication, the titanate in which the organic material was inserted through centrifugation and drying was obtained.

The solid nanocomposite electrolyte is prepared by mixing 1 g of methyl propyl imidazolium iodide (MPII) and 1 g of titanate having the organic material inserted therein in 0.1 g of iodine (I ₂ ).

Comparative Example 1 Dye-Sensitized Solar Cell Using Ionic Liquid Electrolyte That Does Not Contain Inorganic Material

The ionic liquid electrolyte is prepared by mixing 1 g of methyl propyl imidazolium iodide (MPII) and 0.1 g of iodine (I ₂ ). In the ionic liquid electrolyte used in Example 1, only a layered inorganic material was omitted.

Example 2 Fabrication of Dye-Sensitized Solar Cell Using Solid Nanocomposite Electrolyte with Layered Inorganic Material

First, a titanium oxide (TiO ₂ ) paste (DSL, 18NR-T) was coated on a transparent conductive substrate using a doctor blade method, heat-treated at 450 ° C. for 30 minutes in an air atmosphere, and then cooled naturally to a thickness of about 12 μm. Titanium oxide (TiO ₂ ) electrodes were formed.

The titanium dioxide (TiO ₂ ) electrode was immersed in the dye solution for 24 hours to adsorb the dye molecules, and Z907 (Solaronix) / ethyl alcohol solution at 0.5 mM concentration was used in this experiment. To form a platinum layer of the counter electrode, 10 mM hexachloroplatinic acid (H ₂ PtCl _{6 ·} H ₂ O, Aldrich) / isopropyl alcohol solution was spin coated on a transparent conductive substrate (1st; 500 rpm, 5 sec; 2nd; 1000 rpm, 5 sec; 3rd; 2000 rpm, 40 sec) and heat-treated at 450 ° C. for 30 minutes in an air atmosphere, followed by natural cooling.

The electrolyte solution was prepared according to the above Examples and Comparative Examples, and a thermoplastic polymer (25 μm thick, Surlyn) was used to prevent the electrolyte solution from leaking out.

6 is a photograph showing a change in viscosity over time of the solid nanocomposite electrolyte prepared according to the present invention.

A represents an ionic liquid electrolyte, and B represents a solid nanocomposite electrolyte containing a layered inorganic material. As shown in the picture, the ionic liquid electrolyte has almost no viscosity and flows down immediately, whereas the solid nanocomposite electrolyte does not flow at all after 24 hours.

FIG. 7 shows a photocurrent-voltage characteristic curve for measuring photocurrent generated when a voltage applied to a dye-sensitized solar cell manufactured according to the present invention is changed under AM 1.5 and 100 mW / cm ² . Indicated.

 TABLE 1

Opening voltage (V) Short circuit current (mA / cm ² ) Fill factor (%) Energy conversion efficiency (%) (A) Comparative Example 1 0.637 3.0 67.6 1.30 (B) Example 1 0.633 4.5 50.7 1.43

According to FIG. 7 and Table 1, the dye-sensitized solar cell including the solid nanocomposite electrolyte according to the embodiment of the present invention exhibited a 150% improvement in short-circuit current compared to the comparative example, and as a result, the energy conversion efficiency was weak. 10% increase.

In fact, the short circuit current decreases as the viscosity of the electrolyte increases, but it can be seen that the short circuit current value is higher in the case of a solid electrolyte using a layered inorganic material as in the above embodiment.

This increases the viscosity by adding the layered inorganic material to decrease the electrical conductivity of the electrolyte, but not only improves the electrical conductivity through the nanochannel role and dissociation effect of the ions of the layered inorganic material, but also enhances the light scattering effect. This is because the current density is increased by causing it.

1 is a view schematically showing the operating principle of a typical dye-sensitized solar cell.

2 is a view schematically showing the configuration of a dye-sensitized solar cell including a solid nanocomposite electrolyte according to the present invention.

3 is a view showing a crystal structure of the layered inorganic material according to an embodiment of the present invention and X-ray diffraction diagram.

Figure 4 is a flow chart illustrating a dye-sensitized solar cell manufacturing method using a solid nanocomposite electrolyte according to an embodiment of the present invention.

5 is a flowchart illustrating a method for preparing a solid nanocomposite electrolyte according to an embodiment of the present invention.

Figure 6 is a photograph showing the difference in viscosity over time of the solid-type nanocomposite electrolyte prepared according to FIG.

Figure 7 is a photocurrent-voltage characteristic curve measured under AM 1.5, 100 mW / Cm ² condition of the dye-sensitized solar cell prepared according to FIG.

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

11: semiconductor oxide electrode 12: dye 13

15: transparent conductive substrate 14: external wire

16: platinum layer 17 for redox catalyst: redox pair

110: semiconductor electrode 111: transparent conductive substrate

113: titanium oxide blocking layer 115: semiconductor oxide electrode

120: counter electrode 121: transparent conductive substrate

123: platinum layer 130 for redox catalyst: solid nanocomposite electrolyte

Claims (13)

Semiconductor electrodes; Counter electrode; And A solid nanocomposite electrolyte interposed between the semiconductor electrode and the counter electrode, in which an ammonium organic material or oligomer is inserted into a titania-based inorganic material; Solar cells configured to include. The method of claim 1, The titania-based inorganic material is at least one selected from the group consisting of K ₂ Ti ₄ O ₉ , Na ₂ Ti ₃ O ₇ , Cs _x Ti _{2 -x / 4} O ₄ . The method of claim 1, The ammonium-based organic material is any one of methyl ammonium, propyl ammonium, tetrabutyl ammonium. The method of claim 1, The layered titania-based inorganic material has a length of 100 nm ~ 10 ㎛. The method of claim 1, The solid nanocomposite electrolyte further comprises an ionic liquid and a polymer. The method of claim 5, The ionic liquid is at least one of methyl propyl imidazolium iodide, butyl methyl imidazolium iodide, hexylmethyl imidazolium iodide, imidazolium iodide. The method of claim 5, The polymer is a solar cell, characterized in that at least any one of polyacrylonitrile, polyvinylidene fluoride cohexafluoropropylene, polypropylene, polyethylene oxide. The method of claim 1, The oligomer is at least one of polyethylene glycol dimethyl ether, polyethylene glycol, polypropylene glycol, polypropylene glycol diamine, polyethylene glycol bis carboxyl methyl ether. Solid nanocomposite electrolyte for solar cells in which an ammonium organic material or oligomer is inserted into a titania-based inorganic material having a layered structure. Preparing a semiconductor electrode; Preparing an opposing electrode facing the semiconductor electrode; Assembling the semiconductor electrode and the counter electrode apart from each other; A method of manufacturing a solar cell, comprising the step of forming a solid nanocomposite electrolyte solution according to claim 9 between the semiconductor electrode and the counter electrode. The method of claim 10, Preparing the semiconductor electrode, Forming a transparent conductive thin film on the transparent glass substrate or the flexible polymer substrate; Forming a semiconductor oxide electrode to which dye molecules are adsorbed on the transparent conductive thin film. The method of claim 10, Forming a solid nanocomposite electrolyte solution between the semiconductor electrode and the counter electrode is a solar cell manufacturing method, characterized in that for inserting the solid nanocomposite electrolyte using a vacuum vacuum pump. The method of claim 10, Forming the solid nanocomposite electrolyte solution, Preparing an inorganic material having a layered structure; Hydrogenating the layered inorganic material using an ion exchange method; Inserting an organic material into the hydrogenated inorganic material; Inserting an ionic liquid, an oligomer, and a polymer into an inorganic material having a layered structure into which the organic material is inserted; And And preparing a solid nanocomposite electrolyte including electrolyte ions using the inorganic materials as gelling materials.

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