KR100553337B1 - Copolymer containing imidazolium polymers, method for preparing the same, electrolytes for dye-sensitized solar cells containing the same and dye-sensitized solar cells - Google Patents

Abstract

 A copolymer represented by the formula (3) in which the main chain is made of oxyethylene and substituted in the side chain with a halogenated imidazolium, a preparation method thereof, an electrolyte composition for a solar cell containing the same, and a dye-sensitized solar cell comprising the same as an electrolyte.

[Formula 3]

Wherein x and y refer to the molar ratio, x + y = 1, x has a value in the range of 0.2-0.8,

n is an integer of 1-12, R ₁ and R ₂ are C _1-12 alkyl groups, X = Cl (3-1) or I (3-2).

Dye-Sensitized Solar Cell, Ionic Liquid, Imidazolium Polymer, Nonvolatile Electrolyte

Description

Copolymer containing an imidazolium group, a manufacturing method thereof, an electrolyte composition for a solar cell containing the same, and a dye-sensitized solar cell comprising the same as an electrolyte, THE SAME AND DYE-SENSITIZED SOLAR CELLS}

1 is a photocurrent-voltage characteristic of a dye-sensitized solar cell according to Example 3 using an electrolyte composition containing a polymer represented by the formula (3-2) in which the main chain is made of oxyethylene and the imidazolium iodide is substituted in the side chain. Is a graph showing

2 is a photocurrent-voltage characteristic of a dye-sensitized solar cell according to Comparative Example 1 using an electrolyte composition containing a polymer represented by the formula (3-1) in which the main chain is made of oxyethylene and substituted with chlorinated imidazolium in the side chain. Is a graph showing

The present invention relates to a copolymer containing an imidazolium group, a manufacturing method thereof, an electrolyte composition for a solar cell containing the same, and a dye-sensitized solar cell including the same as an electrolyte.

Unlike ionic salt compounds consisting of metal cations and non-metal anions, usually melting at high temperatures above 800 ° C, ionic salts that exist as liquids at temperatures below 100 ° C are called ionic liquids, especially ionic liquids that exist as liquids at room temperature. The liquid is called room temperature ionic liquid (RTIL). The ionic liquid with the organic composed of positive and negative ions, and There are imidazolium dialkylamino as cation, alkyl pyridinium, quaternary ammonium, and quaternary phosphonium anion is _{^{NO 3 -, BF 4 -,}} PF 6 - , Cl ^- is composed of a ^-, Br. Ionic liquids are non-volatile, non-toxic, non-flammable, have excellent thermal stability, ionic conductivity, polarity, solubility of inorganic and organometallic compounds, and they have unique properties as liquids over a wide temperature range. It is applied to a wide range of chemical fields such as separation and electrochemistry. In particular, room temperature ionic liquids can be used in clean solvents and electrolytes of batteries, photochemistry, electrochemistry, etc., and have no volatility. (1) chemical stability, (2) electrochemical stability with relatively wide potential window, (3) high ion conductivity, (4) low melting point, in the field of lithium secondary battery, electric double layer storage battery, photoelectrochemical solar cell, etc. 5) It is replacing the existing electrolyte with various advantages such as thermal stability. Dye-sensitized solar cell (DSSC) is a dye-sensitized solar cell (DSSC) to apply a new electrolyte in the present invention by M. Gratzel research group in Switzerland using nanocrystalline titanium dioxide particles and organic dyes A device that obtains photoenergy conversion efficiency has been published in B. O'Regan, M. Gratzel, Nature 353 , 737 (1991). This dye-sensitized solar cell has passed the excited electrons in the dye receiving light of visible light to the n-type semiconductor, titanium dioxide, and I that is included in the liquid ^electrolyte for dye through reduction-electrochemical oxidation of the ^- / I ₃ Regeneration produces current.

Conventional dye-sensitized solar cells contain a liquid electrolyte layer when forming a cell, and thus the stability of the solar cell module has been pointed out as a big problem. In particular, it is difficult to encapsulate the device and has problems such as leakage of electrolyte and electrochemical stability when used for a long time. Solutions to these problems include inorganic solid electrolytes (Langmuir 19 , 3572 (2003)), polymer solid electrolytes (Electrochemica Acta 47 , 2801 (2002)), gel electrolytes (J. Phys. Chem. B 107 , instead of liquid electrolytes). 4374 (2003)), ionic liquids (J. Am. Chem. Soc. 125, 1166 (2003)), organic hole transporters (Science 295 , 2425 (2002)), etc., have recently been actively researched and developed.

Since the electrolyte using the ionic liquid is a melting at room temperature, the viscosity is very low, and thus the non-volatile characteristics of the dye-sensitized solar cell module have many problems in the process because they are branched or flowable liquids. On the other hand, in the case of the polymer gel electrolyte containing the organic solvent, the viscosity is increased and the fluidity is low, but the long-term stability is lowered because the organic solvent is volatile. In order to develop an electrolyte using an ionic liquid and a polymer, the polymer used must be dissolved in an ionic liquid. ), Polyvinylidene fluoride (PVDF), etc. cannot be applied because they do not dissolve well in ionic liquids.

Accordingly, the inventors have invented a technique of synthesizing a copolymer having an idaethylene group having a main chain of oxyethylene and a side chain having an imidazolium group, which is soluble in an imidazolium-based ionic liquid, and makes it a nonvolatile polymer ionic gel electrolyte material.

It is an object of the present invention to provide a copolymer represented by the general formula (3), in which the main chain is made of oxyethylene, in which the imidazolium halide is substituted in the side chain, and a method for producing the same.

Still another object of the present invention is to provide a non-volatile electrolyte composition for dye-sensitized solar cells, wherein the main chain is made of oxyethylene and contains a copolymer in which the side chain is substituted with halogenated imidazolium.

It is still another object of the present invention to provide a dye-sensitized solar cell comprising a copolymer whose main chain is made of oxyethylene and substituted with a halogenated imidazolium in the side chain as an electrolyte.

As a result of intensive studies to solve the above problems in the commercial development of dye-sensitized solar cells, the present inventors have a copolymer represented by the following formula (3), the main chain is oxyethylene and imidazolium substituted in the side chain The polymer electrolyte material dissolved in the nonvolatile ionic liquid was developed.

[Formula 3]

Wherein x and y refer to the molar ratio, x + y = 1, x has a value in the range of 0.2-0.8,

n is an integer of 1-12, R ₁ and R ₂ are C _1-12 alkyl groups, X = Cl or I.

The present invention also provides a technique for producing a nonvolatile electrolyte composition for dye-sensitized solar cells, which is dissolved in an imidazole-based ionic liquid containing the copolymer up to 50% by weight.

More specifically, according to the present invention, a polymer of the formula (1) having a molecular weight of 50,000 to 800,000 g / mol, a chlorine substitution degree of 20 to 80%, and a side chain of which is substituted with a chlorinated alkyl group (molecular weight 50,000 to 800,000 g / mol) mol, chlorine degree of substitution of 20 to 80%) and a method of preparing a polymer represented by the formula (3-2) in which imidazolium iodide is substituted through a polymer reaction and an electrolyte composition of a nonvolatile dye-sensitized solar cell using the same To provide.

The present invention also provides a dye-sensitized solar cell comprising the composition as an electrolyte.

Polymers whose main chain is oxyethylene and whose side chains are chlorinated alkyl groups

Wherein x and y refer to the molar ratio, x + y = 1, x has a value in the range 0.2-0.8,

n = an integer from 1-12.

A polymer in which the imidazole is substituted in the side chain in the polymer of formula (1).

Wherein x and y refer to the molar ratio, x + y = 1, x has a value in the range 0.2-0.8,

n is an integer of 1-12, R is an alkyl group of C _1-12 .

A polymer in which the imidazolium halide is substituted in the side chain in the polymer of formula (1).

Wherein x and y refer to the molar ratio, x + y = 1, x has a value in the range 0.2-0.8,

n is an integer of 1-12, R ₁ and R ₂ are C _1-12 alkyl groups, X = Cl (3-1) or I (3-2).

[Formula 3-1]

Wherein x and y refer to the molar ratio, x + y = 1, x has a value in the range 0.2-0.8,

n is an integer of 1-12 and R ₁ and R ₂ are C _1-12 alkyl groups.

[Formula 3-2]

Wherein x and y refer to the molar ratio, x + y = 1, x has a value in the range 0.2-0.8,

n is an integer of 1-12 and R ₁ and R ₂ are C _1-12 alkyl groups.

The method for preparing a copolymer in which the imidazolium iodide of formula (3-2) is substituted in the side chain according to the present invention is prepared from the polymer of formula (1), as in Example 1 There is a method for preparing a polymer of formula (3-2) by introducing an imidazole group into the polymer to synthesize a polymer of formula (2) and reacting it with alkylimidazolide iodide. The polymer of formula (1) is reacted with 1-alkyl imidazole to synthesize a polymer of formula (3-1) in which the main chain is oxyethylene and substituted chlorinated imidazolium in the side chain, Reaction was also used together to prepare a copolymer in which the imidazolium iodide of formula (3-2) was substituted.

When applying the polymer of formula (3-2) substituted with imidazolium iodide as a solar cell electrolyte composition, titanium dioxide particles are used as electrodes and adsorbed Ru-based dyes that exhibit visible activity by receiving visible light and are developed in the present invention. The properties of the nonvolatile electrolyte composition using the polymer of Formula (3-2) and the imidazole ionic liquid are 30% when the polymer of Formula (3-2) is added in a weight ratio to the imidazole ionic liquid. In addition, the viscosity has increased by more than 40 times, and the device manufacturing processability is greatly improved. In particular, the photoelectric conversion efficiency is shown to be very excellent characteristics that are maintained as it is not reduced. In the present invention, the properties are very excellent when the imidazolium iodide is substituted in the halide imidazolium. Therefore, the dye-sensitized solar cell in an electrolyte composition according to the counter electrode, a platinum catalyst I ^- / I ₃ ^- oxidation-reduction reaction is important and this reaction iodide imidazole ryumgye electrolyte composition as in the polymer of formula (3-2) It can be seen that it is suitable.

The following examples may be modified in many different forms and should not be construed as limited to the embodiments set forth herein.

EXAMPLE

Example 1 Synthesis of Polymer of Formula (3-2) with Imidazole Iodide Substituted on Side Chain

The present Example synthesizes the polymer of formula (2) in which the main chain is oxyethylene and the imidazole is substituted in the side chain by introducing an imidazole group into the polymer of formula (1), and reacting it with alkyl iodimalium iodide to iodide Detailed synthesis method for preparing a polymer of formula (3-2) in which imidazolium is substituted. 8.0 g of polymer (Aldrich, chlorine substitution degree 66%, molecular weight 65,000 g / mol), in which the main chain of the polymer of formula (1) is oxyethylene and the side chain is substituted with chlorinated methylene group, is added to 40 mL of DMF and stirred for about 5 hours. Dissolve completely. Next, 3.7 g of NaH was added to the solution, stirred for about 30 minutes, and 10.58 g of imidazole was added thereto and reacted at room temperature. After the reaction proceeds, precipitate of the reactant is obtained in diethyl ether. The precipitated gel polymer is dissolved in a small amount of methyl alcohol and precipitated again in diethyl ether. Repeat this process several times to remove the solvent as much as possible, remove water using anhydrous magnesium sulfate, and dry under vacuum at 60 ° C. to obtain 8.8 g (72%) of the polymer of formula (2) in which the imidazole is substituted in the side chain. Get

8.0 g of the polymer of the formula (2) obtained by the above method is added to DMF, and completely dissolved. Then, 7.99 g of 1-iodopropane is added and reacted at 80 ° C. for about 24 hours. After the reaction proceeds, precipitate of the reactant is obtained in diethyl ether. The precipitated gel polymer is dissolved in a small amount of methyl alcohol and precipitated again in diethyl ether. Repeat this process several times to remove the solvent as much as possible, remove water with anhydrous magnesium sulfate, and dry under vacuum at 60 ° C. to give 11.60 g of a polymer of formula (3-2) in which imidazolium iodide is substituted in the side chain (yield). 80%). NMR and IR spectra and elemental analysis confirmed that the compound having the desired structure was obtained.

¹ H-NMR spectrum (200MHz, DMSO, ppm): 1.0 ~ 1.2 (3H, -CH ₃ ), 1.7 (2H, -CH _2- ), 3.2 ~ 3.8 (7H, -CH ₂ -,-CH ₂ O- ) 4.2-4.4 (2H, -CH ₂ N-), 7,5-7.8 (s, 2H, -CH = CH-), 10 (s, 1H).

FT-IR spectrum (cm ^-1 ): 2955, 2930 (aromatic CH stretching vibration), 1163 (CN stretching vibration), 1167 (CO stretching vibration), 1620, 1461, 1573 (aromatic C = C stretching vibration)

Example 2 Synthesis of Polymer of Formula (3-2) with Imidazole Iodide Substituted on Side Chain

This embodiment synthesizes a polymer of formula (3-1) in which the main chain is oxyethylene from the polymer of formula (1) and chlorinated imidazolium is substituted in the side chain, and from which imidazolium iodide is substituted therefrom. It is the detailed synthesis method of the polymer of 2). 8.0 g of a polymer (Aldrich, 66% chlorine substitution degree, molecular weight 65,000 g / mol) in which the main chain of the polymer of formula (1) is oxyethylene and the side chain is substituted with a chlorinated methylene group is added to 50 mL of a mixed solution of DMSO and THF. Stir for about 5 hours and dissolve completely. 10.8 g of 1-butyl imidazole was added to the completely dissolved solution and reacted at 80 ° C. for 24 hours. After the reaction proceeds, precipitate of the reactant is obtained in diethyl ether. The precipitated gel polymer is dissolved in a small amount of methyl alcohol and precipitated again in diethyl ether. Repeat this process several times to remove the solvent as much as possible, remove water using anhydrous magnesium sulfate (MgSO ₄ , anhydrous), and dry it in vacuo at 60 ° C. 12.06 g of the polymer of 1) is obtained.

3.5 g of the polymer of the formula (3-1) obtained by the above-mentioned method was dissolved by adding a small amount of methyl alcohol, and a solution of 7 g of sodium iodide (NaI) was dissolved in 10 mL of acetonitrile and 10 mL of acetone, and then stirred at 24 ° C for 24 hours. React time. The reacted solution is separated from the unreacted NaI and precipitated NaCl using a centrifuge, and the pure solution is distilled under reduced pressure to remove the solvent used. The reaction product obtained above was dissolved in methyl alcohol to obtain a precipitate in diethyl ether. The polymer of formula (3-2) in which imidazolium iodide was substituted in the side chain by drying in a vacuum oven at 60 ° C. for a long time (4.01 g, yield 85%) Got. NMR and FT-IR spectra and elemental analysis confirmed that the compound of the desired structure was obtained.

¹ H-NMR spectrum (200MHz, CDC _l3 , ppm): 0.8 ~ 1.2 (t, 3H, -CH ₃ ), 1.8 ~ 2.2 (s, 2H, -CH _2- ), 4.1 (s, 3H, -CH ₃ ), 4.3 (t, 2H, -CH _2- ), 7,5-7.8 (s, 2H, -CH = CH-), 10 (s, 1H).

FT-IR spectra (cm ⁻¹ ): 2955, 2930 (aromatic CH stretching vibration), 1163 (CN stretching vibration), 1620, 1461, 1573 (aromatic C = C stretching vibration).

Example 3 Dye-Sensitized Solar Cell Electrolyte Composition Containing Polymer of Formula (3-2) Substituted in Side Chain with Imidazolium Iodide Synthesized in Example 2

The imidazolium polymer synthesized in Example 2 is applied as a dye-sensitized solar cell electrolyte composition, and a solar cell using titanium dioxide particles is configured to measure its photoelectric conversion characteristics. Referring to the configuration of the cell of the dye-sensitized solar cell in detail, first, a conductive glass (FTO, SnO ₂ : F) consisting of a fluorine-doped tin oxide layer to be used as an electrode is prepared. Next, add 1.0 g of titanium dioxide particles (P25, Degussa) and 350 μL of 10% acetylacetone solution to the mortar and grind. If viscous occurs, add 2.5 mL of distilled water and grind finely. After adding the dispersant Triton X-l00 and mixed well to prepare a colloidal solution in which the titanium dioxide particles are sufficiently dispersed. The titanium dioxide colloidal solution thus prepared is applied to the FTO glass substrate to have a thickness of 10 μm. After drying at room temperature, a dye-sensitized solar cell electrode is prepared by sintering again at 450 ^° C. for 30 minutes in air. Dye is adsorbed onto the titanium oxide substrate of the electrode substrate prepared above to complete the lower electrode plate. In this embodiment, RuL ₂ (NCS) ₂ (L = 2.2'-bipyridyl-4.4'-dicarboxylic acid) (Solaronix's Ruthenium 535) was immersed in a 3 x 10 ^-4 molar ethanol solution using a Ru dye. After adsorption for 12 hours, washed several times with ethanol and dried. As the counter electrode of the cell, a platinum electrode is deposited on a FTO substrate having a 20 μm-thick spacer between the spacers having a thickness of 20 μm, and a lower electrode on which the dye is adsorbed is attached.

1-methyl-3-propyl imidazolium iodide (MPIm) iodide for applying the polymer of formula (3-2) synthesized in Example 2 as a dye-sensitized solar cell electrolyte composition A nonvolatile electrolyte containing (4) and iodine (I ₂ ) is prepared. In detail describing the electrolyte composition, 10, 20, 30% by weight of the polymer of the formula (3-2) synthesized in Example 2 was added to 1.6 g of MPIm and 0.25 g of iodine, and heated to 80 ^° C. Dissolve. The cell is completed by filling an electrolyte solution between the dye-adsorbed solar cell substrates.

The efficiency characteristics of the solar cell were determined by irradiating a solar simulated light source of 100 mW / cm ² using a 300 W xenon lamp equipped with an AM1.5 global filter. The photocurrent density (J _sc ) and short circuit voltage (V _oc ) From the fill factor, the energy conversion efficiency (η) is measured.

In addition, when the polymer synthesized in Example 2 is added to the electrolyte for the solar cell, the fluidity of the ionic liquid decreases as the viscosity increases, thereby greatly improving the disadvantages of the electrolyte composed of only the ionic liquid. Table 1 shows the characteristics of the dye-sensitized solar cell fabricated in this example by the above-described method. Here, the physical properties of the polymer of the formula (3-2) is 0, 10, 20, 30% by weight, respectively, were measured, and this was carried out in Examples 3-1, 3-3, 3-3, respectively. Example 3-4 is shown. As can be seen from Table 1, even if the polymer of the formula (3-2) is contained in 30% by weight, as in Example 3-4, there is no reduction in photoelectric conversion efficiency and the viscosity is 40 times the excellent properties.

A photoelectric conversion table of a dye-sensitized solar cell using a nonvolatile electrolyte containing a polymer of formula (3-2) in which imidazolium iodide is substituted in a side chain. Properties Example 3-1 Example 3-2 Example 3-3 Example 3-4 % By weight of polymer of formula (3-2) 0 10 20 30 Photocurrent Density (J _sc , mA / cm ² ) 8.22 8.59 9.07 10.37 Short circuit voltage (V _oc , V) 0.54 0.57 0.56 0.50 Filler factor 0.55 0.56 0.57 0.50 Viscosity (Pas, shear rate 100 rad / s) 0.25 1.76 4.25 10.95 Energy conversion efficiency (η,%) 2.51 2.79 2.97 2.64

Comparative Example 1. A dye-sensitized solar cell electrolyte composition containing a polymer of formula (3-1) in which chlorinated imidazolium synthesized in Example 2 is substituted in a side chain

This comparative example shows the characteristics of a dye-sensitized solar cell using an electrolyte composition prepared by using a polymer of formula (3-1) substituted with chlorinated imidazolium in the side chain instead of the polymer of formula (3-2) of Example 3. It is shown in Table 2. Here, the physical properties of the polymer of the formula (3-1) is 0, 10, 20, 30% by weight, respectively, were measured, and this was compared to Comparative Example 3-1, Comparative Example 3-2, Comparative Example 3-3, respectively Example 3-4 is shown. In the case of using the polymer of the formula (3-1), very different from Example 3, as the weight ratio of the polymer of the formula (3-1) increases, the photoelectric conversion efficiency decreases more, and thus, It can be seen that the effect on the photoelectric conversion efficiency of the electrolyte composition comprising the formula (3-2) substituted with imidazolium iodide is important.

Table of photoelectric conversion characteristics of a dye-sensitized solar cell using a nonvolatile electrolyte containing a polymer of formula (3-1) in which chlorinated imidazolium is substituted in a side chain. Properties Comparative Example 3-1 Comparative Example 3-2 Comparative Example 3-3 Comparative Example 3-4 % By weight of polymer of formula (3-1) 0 10 20 30 Photocurrent Density (J _sc , mA / cm ² ) 8.22 7.49 6.54 3.64 Short circuit voltage (V _oc , V) 0.54 0.57 0.55 0.52 Filler factor 0.55 0.58 0.54 0.55 Viscosity (Pas, shear rate 100 rad / s) 0.25 2.61 5.72 13.63 Energy conversion efficiency (η,%) 2.51 2.53 1.99 1.06

When preparing a polymer having a main chain according to the present invention made as described above having an oxyethylene and a side chain having an imidazolium halide, and using it as a non-volatile electrolyte composition of a dye-sensitized solar cell containing a weight ratio of 30%, it comprises a polymer Viscosity is increased more than 40 times compared to the non-electrolyte, which greatly improves the solar cell manufacturing process and stability. In addition, a new nonvolatile electrolyte composition has been developed in which the photoelectric conversion efficiency of the dye-sensitized solar cell is not impaired even when a polymer is included.

Claims (6)

A copolymer in which the main chain is oxyethylene and imidazolium is substituted in the side chain represented by the following formula (3);

Wherein x and y refer to the molar ratio, x + y = 1, x has a value in the range of 0.2-0.8, n is an integer of 1-12, R ₁ and R ₂ are C _1-12 alkyl groups, X = Cl (3-1) or I (3-2).  The copolymer substituted with imidazolium iodide according to claim 1, wherein X is iodine. Polymer of Formula (1)

Wherein x and y refer to the molar ratio, x + y = 1, x has a value in the range 0.2-0.8, n = an integer of 1-12; A polymer of formula (2) by introducing an imidazole group

Wherein x and y refer to the molar ratio, x + y = 1, x has a value in the range 0.2-0.8, n = 1 an integer of 1-12, R is an alkyl group of C _1-12 ; Preparing a copolymer in which the imidazolium iodide of formula (3-2) is substituted in the side chain, comprising the step of synthesizing and reacting it with alkylimidazolium iodide;

Wherein x and y refer to the molar ratio, x + y = 1, x has a value in the range 0.2-0.8, n is an integer of 1-12 and R ₁ and R ₂ are C _1-12 alkyl groups. The polymer of formula (3-1) according to claim 2, wherein the polymer of formula (1) is reacted with 1-alkyl imidazole to synthesize a polymer of formula (3-1) in which the main chain is oxyethylene and substituted chlorinated imidazolium in the side chain,

Wherein x and y refer to the molar ratio, x + y = 1, x has a value in the range 0.2-0.8, an integer of n = 1-12, R ₁ and R ₂ are C _1-12 alkyl groups; A method for producing a copolymer in which imidazolium iodide of formula (3-2) is substituted in a side chain, which comprises reacting the same with NaI in a solvent. A nonvolatile electrolyte composition for dye-sensitized solar cells containing the copolymer according to claim 2. A dye-sensitized solar cell comprising the composition of claim 5 as an electrolyte.

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