KR20110086272A - New triphenylamine derivatives and dye-sensitized solar cell comprising the same - Google Patents

Abstract

PURPOSE: A triphenylamine derivative, a producing method thereof, and a dye-sensitized solar battery containing thereof are provided to obtain the high efficiency-low cost solar battery by including plural electron-receptor functional groups. CONSTITUTION: A producing method of a triphenylamine derivative marked with chemical formula 1 comprises the following steps: reacting triphenylamine and phosphorus oxychloride to obtain a benzaldehyde derivative; and reacting the benzaldehyde derivative with 2-cyanoacetic acid. In the chemical formula 1, R1, R2, and R3 are hydrogen or 2-cyanoacrylic acid.

Description

New triphenylamine derivatives and dye-sensitized solar cell comprising the same

The present invention relates to a novel triphenylamine derivative and a dye-sensitized solar cell including the same, which can be used as a dye for a dye-sensitized solar cell because it includes a plurality of electron acceptor functional groups.

Unlike other energy sources, solar cells are endlessly resource-friendly and environmentally friendly sources. Silicon solar cells, dye-sensitized solar cells, and the like are known.

Since silicon solar cells are quite expensive to manufacture, they are difficult to be commercialized, and there are many difficulties in improving battery efficiency. In contrast, dye-sensitized solar cells have a significantly lower manufacturing cost than conventional silicon-based solar cells, and thus have the potential to replace conventional amorphous silicon solar cells. Unlike silicon solar cells, electron-holes can be absorbed by absorbing visible light. It is a photoelectrochemical solar cell whose main component is a dye molecule capable of generating a pair and a transition metal oxide that transfers generated electrons.

Ruthenium dyes are known as dyes for dye-sensitized solar cells. These ruthenium dyes are not only expensive to manufacture, but also become environmentally problematic.

Therefore, there is an urgent need to develop organic dyes which are much cheaper and have excellent photoelectric conversion efficiency and are environmentally friendly.

In order to solve the problems of the prior art, the present inventors examined the power conversion efficiency in the dye-sensitized solar cell (DSSC) using an organic dye having two or more electron acceptors of the chromophore as a photosensitizer, one electron The present invention was completed by confirming that it exhibits a high power conversion efficiency compared to the organic dye having a receptor.

Accordingly, an object of the present invention is to synthesize a compound which is an organic dye having two or more electron acceptor functional groups in a molecule, and to evaluate the performance of the synthesized compound in DSSC to provide an organic dye suitable for application for dye-sensitized solar cells. It's there.

In order to achieve the above object, the present invention provides a triphenylamine derivative represented by the following formula (1):

[Formula 1]

Wherein R ¹ , R ² and R ³ are selected from hydrogen or 2-cyanoacrylic acid, and at least one is 2-cyanoacrylic acid.

Preferably, the substituent of any one of R ¹ , R ² and R ³ is hydrogen, the other two substituents may be 2-cyanoacrylic acid, more preferably the R ¹ , R ² and R ³ is Each may be 2-cyanoacrylic acid.

In particular, the triphenylamine derivative represented by Formula 1 is 2-cyano-3- (4-diphenylamino-phenyl) -acrylic acid [2-Cyano-3- (4- (phenyl (4-vinylphenyl) amino) phenyl ) acrylic Acid; 2b] or 3- (4-{[4- (2-carboxy-2-cyano-vinyl) -phenyl] -phenyl-amino} -phenyl) -2-cyano-acrylic acid [3- (4-{[ 4- (2-Carboxy-2-cyano-vinyl) -phenyl] -phenyl-amino} -phenyl) -2-cyano-acrylic acid; 2c].

In addition, the present invention can prepare a triphenylamine derivative represented by the formula (1) in an intramolecular push-pull system using triphenylamine as the electron donor and a plurality of cyanoacetic acid as the electron acceptor. .

More specifically, the present invention comprises the steps of preparing a benzaldehyde derivative by reacting triphenylamine and phosphorus oxychloride (Phosphorus oxychloride) (Vilsmeier-Haack formylation reaction); And a triphenylamine derivative represented by Chemical Formula 1 through a process including reacting the benzaldehyde derivative with 2-cyanoacetic acid (Knoevenagel reaction).

In addition, the present invention provides an organic dye for a dye-sensitized solar cell comprising a triphenylamine derivative represented by the formula (1).

In another aspect, the present invention provides a dye-sensitized solar cell characterized in that the triphenylamine derivative represented by the formula (1) is used as the light absorption layer.

The dye-sensitized solar cell (DSSC) may include a) a cathode, b) a nanocrystalline metal oxide containing a triphenylamine derivative represented by Formula 1, c) an electrolyte, and d) an opposite electrode. The triphenylamine derivative represented by Chemical Formula 1 is adsorbed onto the nanocrystalline metal oxide and covalently bound, and the nanocrystalline metal oxide may include nanocrystalline TiO ₂ . In addition, the cathode may include fluorine-doped tin-oxide (FTO) glass, and the counter electrode may include FTO glass having thermally deposited Pt.

More specifically, the dye-sensitized solar cell comprises the steps of cleaning a glass substrate; Preparing a TiO ₂ paste; Coating and firing the TiO ₂ paste on the glass substrate; Recoating and calcining the calcined layer using TiO ₂ particles; Dipping the TiO ₂ film in an aqueous titanium tetrachloride solution; Dipping a TiO ₂ film in a solution of a triphenylamine derivative represented by Formula 1 to adsorb the dye; Assembling the dye adsorbed TiO ₂ film and the opposite electrode; And introducing an electrolyte.

As the electron acceptor of the triphenylamine derivative according to the present invention increased, the amount of dye adsorbed on the TiO ₂ surface increased in the dye-sensitized solar cell, which increased the short-circuit photocurrent density.

Among the triphenylamine derivatives according to the present invention, in particular, dye-sensitized solar cells using TPA2 as organic dyes exhibited the most excellent opto-power conversion efficiency than dye-sensitized solar cells using other dyes. That is, a maximum η value of 4.5% (Voc = 740 mV, Jsc = 8.7 mA / cm ^-2 , FF = 0.68%) under AM 1.5 irradiation (100 mW / cm ² ), while the N719 dye value was 8.3% under the same conditions Indicated.

The triphenylamine derivative according to the present invention includes a plurality of electron acceptor functional groups, and when used as a dye in a dye-sensitized solar cell, the amount of dye adsorbed on the surface of a metal oxide, for example, TiO ₂ is increased to increase the short-circuit photocurrent density. Therefore, when used as a dye for a dye-sensitized solar cell, a high efficiency and low cost solar cell can be obtained.

1 shows a process for preparing a triphenylamine derivative according to the present invention,
2 shows a spectrum according to light absorption on a solution of triphenylamine derivatives according to the present invention, and b shows a spectrum according to light absorption when adsorbed onto a TiO ₂ film of triphenylamine derivatives according to the present invention. Will,
3 is a graph showing the oxidation point being excited according to voltage and current when electrons are absorbed when light of the triphenylamine derivatives according to the present invention is absorbed,
Figure 4 shows the conversion efficiency curve as a voltage curve for the photocurrent density of the triphenylamine derivatives according to the present invention that is an organic dye for dye-sensitized solar cells,
5 is an analysis of the maximum photoelectric conversion efficiency according to the absorption wavelength of the triphenylamine derivatives according to the present invention that is an organic dye for dye-sensitized solar cells.

Hereinafter, the present invention will be described in more detail with reference to the following examples. However, the present invention is not limited by these examples.

Example 1 4-Formyltriphenylamine (1a)

Triphenylamine (40 g, 163 mmol) was dissolved in 80 mL DMF and then a few drops of POCl ₃ (76 mL, 815 mmol) were added at a temperature of 0 ° C. As the temperature rose to room temperature, the mixture turned into a bright red solution. The reaction mixture was heated at 45 ° C. for 2 hours. After cooling, the reaction mixture was poured into iced distilled water with stirring, neutralized with sodium bicarbonate and neutralized. The reaction mixture collected by extraction was recrystallized in ethanol to give a pale yellow solid (42.9 g, 96%). At this time, ¹ H NMR analysis was analyzed by Varian Mercury NMR 300Hz spectrometer.

¹ H NMR (300 MHz, CDCl ₃ ): d 9.79 (s, 1H), 7.30-7.36 (t, 4H), 7.67 (d, 2H), 7.15-7.18 (m, 6H), 7.00 (d, 2H) .

Example 2 4,4'-Diformyltriphenylamine (1b)

Triphenylamine (4.900 g, 20 mmol) and 40 mL anhydrous DMF were added to a 250-mL round bottom flask under nitrogen atmosphere. After cooling the reaction mixture to a temperature of 0 ° C., a few drops of POCl ₃ (18.0 mL, 200 mmol) were added. The reaction mixture was heated at 85 ° C. for 10 hours, and the obtained reaction mixture was poured into iced distilled water, neutralized with a 2N aqueous sodium hydroxide solution, neutralized, extracted with dichloromethane, and the solvent was removed under reduced pressure. The remaining reaction product after extraction was purified by column chromatography (silica gel, petroleum ether / ethyl acetate = 4: 1) to give the pure product (4.81g, 80%).

¹ H NMR (300 MHz, CDCl ₃ ): d 9.89 (s, 2H), 7.76-7.78 (d, 4H), 7.38-7.41 (t, 2H), 7.25-7.28 (t, 1H), 7.17-7.19 (m, 6H).

Example 3 4,4 ', 4 "-(phenylazanediyl) tribenzaldehyde [4,4', 4"-(phenyl azanediyl) tribenzaldehyde; 1c]

Triphenylamine (4.900 g, 20 mmol) and 40 mL anhydrous DMF were added to a 250-mL round bottom flask under nitrogen atmosphere. After cooling the reaction mixture to a temperature of 0 ° C., a few drops of POCl ₃ (18.0 mL, 300 mmol) were added. The reaction mixture was heated at 85 ° C. for 10 hours, and the resulting reaction mixture was poured into ice distilled water, neutralized with a 2N aqueous sodium hydroxide solution to give neutrality, extracted with dichloromethane, and the solvent was removed under reduced pressure. The remaining reaction after extraction was purified by column chromatography (silica gel, petroleum ether / ethyl acetate = 4: 1) to obtain a pure product (1.97g, 30%).

¹ H NMR (300 MHz, DMSO- d ₆ ): d 9.85 (s, 3H), 7.83-7.7.81 (d, 6H), 7.20-7.17 (d, 6H).

Example 4 2-Cyano-3- (4-diphenylamino-phenyl) -acrylic acid [2-Cyano-3- (4-diphenylamino-phenyl) -acrylic acid; 2a]

4- (diphenylamino) benzaldehyde (1 g, 3.7 mmol) and 2-cyanoacetic acid (0.47 g, 5.5 mmol) were added to 15 mL glacial acetic acid and refluxed for 3 hours in the presence of ammonium acetate (0.42 g, 5.5 mmol). . After cooling to room temperature, the reaction mixture was poured into iced distilled water. The obtained precipitate was filtered, washed with distilled water and dried under vacuum to obtain the product was purified by column chromatography (ethyl acetate / ethanol = 9: 1) to give a yellow powder of TPA1 (0.23 g, 80%).

¹ H NMR (300 MHz, DMSO- d ₆ ): d 8.13 (s, 1H), 7.90-7.93 (d, 2H), 7.40-7.43 (t, 4H), 7.20-7.27 (m, 6H), 6.84- 6.87 (d, 2 H).

Example 5 2-Cyano-3- (4-diphenylamino-phenyl) -acrylic acid [2-Cyano-3- (4- (phenyl (4-vinylphenyl) amino) phenyl) acrylic Acid; 2b]

4,4 '-(phenylazanediyl) dibenzaldehyde (0.5 g, 1.7 mmol) and 2-cyanoacetic acid (0.31 g, 3.7 mmol) are added to 15 mL glacial acetic acid and ammonium acetate (0.28 g, 3.7 mmol) is present. Under reflux for 3 hours. After cooling to room temperature, the reaction mixture was poured into iced distilled water. The obtained precipitate was filtered, washed with distilled water and dried under vacuum to obtain the product was purified by column chromatography (ethyl acetate / ethanol = 8: 2) to give the orange powder TPA2 (305 mg, 65%).

¹ H NMR (300 MHz, DMSO- d ₆ ): d8.23 (s, 2H), 8.01-8.04 (d, 4H), 7.47-7.51 (t, 2H), 7.32-7.36 (t, 1H), 7.23-7.26 (d, 2H), 7.16-7.18 (d, 4H).

Example 6 3- (4-{[4- (2-carboxy-2-cyano-vinyl) -phenyl] -phenyl-amino} -phenyl) -2-cyano-acrylic acid [3- (4- {[4- (2-Carboxy-2-cyano-vinyl) -phenyl] -phenyl-amino} -phenyl) -2-cyano-acrylic acid; 2c]

4,4 ', 4 "-(phenylazanediyl) tribenzaldehyde (0.3 g, 0.3 mmol) and 2-cyanoacetic acid (0.09 g, 1.0 mmol) are added to 15 mL glacial acetic acid and ammonium acetate (0.08 g, 1 mmol) After cooling to room temperature, the reaction mixture was poured into iced distilled water The precipitate obtained was filtered, washed with distilled water and dried under vacuum, and the resulting product was washed with distilled water and dried under vacuum. The obtained product was purified by column chromatography (ethyl acetate / ethanol = 7: 3) to obtain TPA3 (0.4g, 85%) as a dark orange powder.

¹ H NMR (300 MHz, DMSO- d ₆ ): d 7.91 (s, 3 H), 7,77-7.80 (d, 6 H), 7.01-7.04 (d, 6H).

Example 7 Fabrication and Performance Evaluation of Dye-Sensitized Solar Cell (DSSC)

Conductive glass substrates (FTO; TEC8, Pilkington, 8 Ω / cm 2, Thickness of 2.3 mm) were cleaned in ethanol using ultrasonic waves. TiO ₂ pastes were prepared using ethylcellulose (Aldrich), lauric acid (Fluka) and terpineol (Aldrich). The TiO ₂ paste prepared on the glass substrate previously cleaned using the doctor blade was coated and fired at 500 ° C. for 30 minutes. The thickness of the fired TiO ₂ paste layer was measured with an Alpha-step IQ surface profiler (KLA Tencor). In order to use another TiO ₂ paste as a scattering layer, ca. After recoating the calcined layer using 250 nm sized TiO ₂ particles, it was calcined at 500 ° C. for 30 minutes. The prepared TiO ₂ film was immersed in 0.04 M TiCl ₄ aqueous solution at 70 ° C. for 30 minutes. For dye adsorption, the heat treated TiO ₂ electrode was immersed in a dye solution (0.5 mM of dye in DMF; TPA series, N3 / N719) at 50 ° C. for 3 hours.

The Pt counter electrode was prepared by thermal reduction at 400 ° C. for 20 minutes in a thin film formed from a ₇ mM H ₂ PtCl ₆ solution dissolved in 2-propanol. A dye adsorbed TiO ₂ electrode and a Pt counter electrode were assembled using 60 μm-thick Surlyn (Dupont 1702) as a binder. The liquid electrolyte was introduced through the puncture holes on the counter electrode. The electrolyte was 3-propyl-1-methyl-imidazolysin iodide (PMII, 0.7M), lithium iodide (LiI, 0.2M), iodine dissolved in acetonitrile / valeronitrile (85:15). (I ₂ , 0.05M), t -butylpyridine (TBP, 0.5M). The active area of the dye adsorbed TiO ₂ film was evaluated by a digital microscope camera equipped with image-analysis-software (Moticam 1000).

On the other hand, the reduction properties of the three dyes according to the embodiment was evaluated using cyclic voltammetry (Model: CV-BAS-Epsilon) at a scanning speed of 100 mV / s. At this time, 0.10M tetrabutylammonium hexafluorophosphate (TBAPF ₆ ) dissolved in distilled acetonitrile was used as an electrolyte solution, and Ag / AgCl and platinum wires (0.5 mm in diameter) were used as standard electrodes. And a counter electrode.

(1) Evaluation of optical properties of organic dyes

As shown in Figure 1 and Table 1, the molar absorption coefficient was increased as the organic dye according to the present invention has a plurality of electron acceptor functional groups. The absorption wavelength of the organic dye showed a short wavelength shift on the TiO ₂ film. The short wavelength shift of the absorption wavelength is determined by the formation of H-aggregates of organic dyes on the TiO ₂ surface, and the optical and electrochemical characteristics of the organic dyes are shown in Table 1.

Dye ε _max ^a
/ M ^-1 cm ^-1 λ _max ^a
/ nm
Soln. λ _max ^a
/ nm TiO ₂ λ _max ^b
/ nm E _0-0 (eV) ^c
(abs / em) E _ox ^d
(V vs NHE) E _ox -E _0-0 ^d
(V vs NHE) HOMO (eV) LUMO
(eV) TPA1 25413 421 407 518 2.69 0.93 -1.76 -5.38 -2.69 TPA2 36099 448 433 514 2.35 1.09 -1.26 -5.57 -3.22 TPA3 41980 433 415 514 2.46 1.06 -1.40 -5.54 -3.08

In this case, λ _max and λ _max are absorbance and emission spectra measured in DMSO solution, respectively, and the emission spectra are measured at a concentration of ⁵ × 10 ⁻⁵ M at 293K. Ε _max is the molar extinction coefficient at the adsorption λ _max , E _0-0 is calculated from the junction by the tangential method of the terminal portion of the absorption spectrum, CV by the oxidation point giving the electrons of the dye as a supporting electrolyte It was measured in distilled acetonitrile containing 0.1M tetrabutylammonium hexafluorophosphate (TBAPF ₆ ). In this case, glass carbon was used as a reference electrode, Ag / Ag + titrated with Fc / Fc + as an internal standard, and Pt was used as a counter electrode. The equation for calculating the oxidation point is as follows.

[Equation 1]

HOMO (eV) = -4.8- (E _onset -E _(Ferrocene) )

(2) electrochemical properties

The LUMO level of the dye molecules, and enabling efficient injection of electrons to the conduction of the TiO ₂ film at a dye to be a large negative value than the conduction band of TiO ₂ molecular terminal band, the HOMO level ^3- I / I ^- than the reduction potential of the A positive value is known to enable the regeneration of dye molecules.

As shown in FIG. 2, the HOMO level of the organic dye according to the present invention was calculated from cyclic voltammetry (CV). TPA2 and TPA3 showed similar energy levels, such as -5.57 and -5.54 eV, respectively. The E _0-0 value was obtained from the intersection of normal UV adsorption analysis, and the LUMO level of the dye was calculated according to the following formula (E _LUMO = E _HOMO -E _0-0 ), and the results are shown in Table 1.

(3) Solar Performance of Organic Dyes

The photovoltaic performance of organic dyes and the amount of dye adsorbed on TiO ₂ surface in DSSC are shown in Table 2. Regarding the photocurrent-voltage curve is shown in FIG. 3. TPA2 and TPA3 exhibited short-circuit photocurrent densities (Jsc) of 8.7 and 8.0 mAcm ^-2 , showing better properties than TPA1 (7.1 mAcm ^-2 ). The more dyes adsorbed on the TiO ₂ surface, the higher the J _sc (short-circuit current). Therefore, it is more efficient to have more than one electron acceptor rather than one electron acceptor.

However, TPA3 showed a relatively low open-circuit voltage (Voc), which was less efficient than having two electron transporters. As a result of detecting a dye for a solar cell dye using a 55-W Xe lamp using the maximum efficiency (IPCEs) for converting photons according to the wavelength into a current, as shown in FIG. IPCE values were determined at 5 nm intervals according to the following equation.

[Equation 2]

The IPCE of organic dyes was over 70% in the analysis range of 400nm to 500nm. TPA2 at 460 nm exhibited the highest value of 83% and is related to the J _sc values shown in Table 2.

dyes Jsc
/ mAcm ^-2 Voc
/ mV FF
/% η
/% Active area / cm ² Layer thickn./μm Amount
/ 10 ^-8 mol cm ^-2 TPA1 7.1 732.7 70.62 3.7 0.421 7.46 223 TPA2 8.7 740.3 69.95 4.5 0.433 7.35 815 TPA3 8.0 630.0 65.73 3.3 0.393 7.41 554 N719 15.6 780.0 68.45 8.3 0.464 6.20 2099

Claims (6)

Triphenylamine derivative represented by the following formula (1):
[Formula 1]

Wherein R ¹ , R ² and R ³ are selected from hydrogen or 2-cyanoacrylic acid, and at least one is 2-cyanoacrylic acid. The triphenylamine derivative according to claim 1, wherein the substituent of any one of R ¹ , R ² and R ³ is hydrogen, and the other two substituents are 2-cyanoacrylic acid. The triphenylamine derivative according to claim 1, wherein R ¹ , R ² and R ³ are each 2-cyanoacrylic acid. Reacting triphenylamine with phosphorus oxychloride to prepare a benzaldehyde derivative; And
Reacting the benzaldehyde derivative with 2-cyanoacetic acid
Method for producing a triphenylamine derivative represented by the following formula (1) comprising:
[Formula 1]

Wherein R ¹ , R ² and R ³ are selected from hydrogen or 2-cyanoacrylic acid, and at least one is 2-cyanoacrylic acid. An organic dye for a dye-sensitized solar cell comprising a triphenylamine derivative represented by Formula 1 below:
[Formula 1]

Wherein R ¹ , R ² and R ³ are selected from hydrogen or 2-cyanoacrylic acid, and at least one is 2-cyanoacrylic acid. Dye-sensitized solar cell, characterized in that using the triphenylamine derivative represented by the formula (1) as a light absorption layer:
[Formula 1]

Wherein R ¹ , R ² and R ³ are selected from hydrogen or 2-cyanoacrylic acid, and at least one is 2-cyanoacrylic acid.

Images