KR101760928B1 - Organic dye having heteroleptic electron acceptors and dye-sensitized solar cell including the same - Google Patents

Abstract

본 발명에 따른 이종 전자수용체 포함 유기염료는, 이종(heteroleptic) 전자 공여체를 도입하여 흡광된 에너지를 염료분자로 전달하는 에너지 안테나(Antenna)로 사용하며, 이종(heteroleptic) 전자 수용체를 도입하여 흡광 메커니즘에 참가하는 LUMO의 수를 증가시켜 가시광선 전영역의 파장을 고르게 흡수할 수 있어 광전성능이 우수하다. The present invention provides a heterogeneous electron acceptor-containing organic dye represented by the following general formula (1).
[Chemical Formula 1]

The organic electron acceptor-containing organic dye according to the present invention is used as an energy antenna for transferring absorbed energy to a dye molecule by introducing a heteroleptic electron donor, introducing a heteroleptic electron acceptor, The number of LUMOs participating in the visible light region can be increased, and the wavelength of the entire visible light region can be uniformly absorbed, so that the photoelectric performance is excellent.

Description

TECHNICAL FIELD [0001] The present invention relates to a dye-sensitized solar cell and a dye-sensitized solar cell comprising the same,

The present invention relates to organic dyes including heterogeneous electron acceptors and dye-sensitized solar cells comprising the same.

Recently, attention has been paid to dye-sensitized solar cells (DSSCs) as a low-cost photovoltaic device. The dye-sensitized solar cell is a third-generation solar cell that converts sunlight into electricity using organic dyes and nanotechnology, unlike semiconductor solar cells that use silicon wafer substrates. It contains organic dyes that emit electrons when excited by sunlight. To generate electrons.

In the past, studies have been made to improve the stability and operational capability of the above-described dye-sensitized solar cell. Among the components of the dye-sensitized solar cell, a dye sensitizer is a dye- It is known to act as an important factor that has a considerable effect on stability and energy conversion efficiency.

Recently, it has been known that perovskite dye improves the efficiency of a dye-sensitized solar cell up to about 15%, and a zinc porphyrin dye is cobalt (II / III) tris (bis Based redox electrolyte (Co (II / III) tris (bipyridyl) -based redox electrolyte), the efficiency of the dye-sensitized solar cell is improved by more than 12%, the ruthenium polypyridyl dye is also used as an electrolyte, It is known that the efficiency of the dye-sensitized solar cell is improved by about 11% together with the cargo / triiodide mixture.

However, metal-based dyes including zinc or ruthenium complexes as described above are not environmentally friendly and are not suitable in terms of cost efficiency.

Accordingly, non-metallic organic dyes having merits of high molar extinction coefficient and simple synthesis and separation, low cost, and environmental friendliness have been attracting attention as substitutes for metal-based dyes.

For example, a number of non-metallic organic dyes such as coumarin, merocyanine, indolin, porphyrin, and fluorine based organic dyes have been developed as dyes for dye-sensitized solar cells and are known to have excellent light conversion characteristics . Donor-pi conjugated linker-acceptor (D-π-A) structures are commonly used as non-metallic organic dyes.

However, since the above-mentioned dye has a low molar extinction coefficient due to a limited absorption region, it is difficult to increase the amount of short-circuit current and thus has a disadvantage of low energy conversion efficiency.

Korean Patent Publication No. 10-2015-0066834 (Publication date: June 17, 2015) Korean Patent Laid-Open No. 10-2015-0040443 (Publication date 2014.04.15) Korean Patent Publication No. 10-2014-0059876 (Publication date: May 19, 2014) Korean Patent Publication No. 10-2011-0086272 (published on July 28, 2011)

Disclosure of Invention Technical Problem [8] Accordingly, the present invention has been made keeping in mind the above problems occurring in the prior art, and an object of the present invention is to provide a technical content of organic dyes capable of absorbing wavelengths of all RGB regions of visible light.

In order to accomplish the above-mentioned technical object, there is provided an organic dye containing a heteroleptic electron acceptor represented by the following general formula (1).

[Chemical Formula 1]

In addition, the organic dye absorbs light having a wavelength of 350 to 750 nm.

In addition, the organic dye has a light harvesting efficiency (LHE) of 0.95 or more at a wavelength of 350 to 750 nm.

Further, the organic dye is characterized in that a maximum absorption peak appears at a wavelength of 397.1 nm, 503.9 nm and 620.5 nm of an ultraviolet-visible (UV-vis) absorption spectrum.

The organic dye has a molar extinction coefficient of 1 × 10 ⁵ M ^-1 / cm or more in a light having a wavelength of 397.1 nm.

Further, the organic dye has a band gap of 1.79 eV.

The present invention also provides a photo-electrode for a dye-sensitized solar cell comprising oxide semiconductor particles in which the above-described heterogeneous electron acceptor-containing organic dye is supported.

The oxide semiconductor particles may be at least one selected from titanium oxide, tin oxide, zinc oxide, tungsten oxide, zirconium oxide, gallium oxide, indium oxide, yttrium oxide, niobium oxide, tantalum oxide and vanadium oxide .

The photoelectrode for the dye-sensitized solar cell may further comprise at least one selected from the group consisting of deoxycholic acid, a carbazole derivative, dehydrodeoxycolic acid, chenodeoxycholic acid, cholic acid methyl ester, sodium cholinic acid salt, crown ether, cyclodextrin, And at least one co-adsorbent selected from the group consisting of alumina, zirconium oxide, zirconium oxide, selenium, and polyethylene oxide.

The present invention also provides a dye-sensitized solar cell comprising the photo-electrode described above.

The organic electron acceptor-containing organic dye according to the present invention is used as an energy antenna for transferring absorbed energy to a dye molecule by introducing a heteroleptic electron donor, introducing a heteroleptic electron acceptor, The number of LUMOs participating in the visible light region can be increased, and the wavelength of the entire visible light region can be uniformly absorbed, so that the photoelectric performance is excellent.

Fig. 1 shows the results of UV-vis spectra analysis of the organic dyes according to Examples and Comparative Examples 1 to 3. Fig.
2 is a graph schematically showing the molecular energy level (MO energy level) of the organic dye according to Example (a) and Comparative Example 3 (b).
3 is a graph schematically showing the electron distribution of the molecular orbital of the organic dye according to Example (a) and Comparative Example 3 (b).
4 is a diagram schematically illustrating the intramolecular energy transfer process of an organic dye according to an embodiment.

Hereinafter, the present invention will be described in detail.

The present invention provides an organic dye comprising a heteroleptic electron acceptor represented by the following general formula (1).

[Chemical Formula 1]

The heterogeneous electron acceptor organic dyes according to the present invention include a core TPA structure in which cyanoacrylic acid and indolinum are introduced as heteroleptic electron acceptors, and a phenothiazine (PTZ) Group.

Accordingly, the organic electron acceptor-containing organic dye according to the present invention is an ADA-type organic dye introduced with a heteroleptic electron receptor and a heteroleptic electron donor, It acts as an energy antenna that transfers to the dye molecule. It introduces a heterogeneous electron acceptor and increases the number of LUMOs participating in the light absorbing mechanism, so that the light of 350 to 750 nm wavelength, that is, the light of the field of visible light, Light-harvesting efficiency (LHE) is higher than 0.95 in the above-mentioned wavelength range, and the incident photon-to-current conversion efficiency (IPCE) or light- LHE).

Particularly, the organic dye exhibits the maximum absorption peak in the light of wavelengths of 397.1 nm, 503.9 nm and 620.5 nm, and has a molar extinction coefficient of 1 × 10 ⁵ M ^-1 / cm or more in the light of 397.1 nm wavelength Exhibits excellent photoelectric performance and has a band gap of 1.79 eV, which is preferably reduced.

The present invention also provides a photoelectrode for a solar cell comprising oxide semiconductor particles in which the above-described heterogeneous electron acceptor-containing organic dye is supported.

The photoelectrode for a solar cell may be formed by coating oxide semiconductor particles on a substrate to form a thin film layer, and the organic dye may be supported on the thin film layer. In order to form the photoelectrode, Can be formed through a thin film layer forming method.

The method of supporting the organic dye on the oxide semiconductor particles formed of the thin film layer is not particularly limited. As a typical example, an organic dye may be supported on the oxide semiconductor particles by immersing a substrate having a thin film layer formed on a solution containing the organic dye to form a photoelectrode for a solar cell.

The oxide semiconductor particles may be titanium oxide, tin oxide, zinc oxide, tungsten oxide, zirconium oxide, gallium oxide, indium oxide, yttrium oxide, niobium oxide, tantalum oxide, vanadium oxide or a mixture thereof.

Further, the photoelectrode for a solar cell according to the present invention may further include a co-adsorbent to prevent binding between the organic dyes when the organic semiconductor dye is supported on the oxide semiconductor fine particles, thereby preventing aggregation on the surface of the oxide semiconductor particles Thereby preventing a decrease in photoelectric performance of the photoelectrode for the solar cell.

Examples of the above-mentioned co-adsorbent include deoxycholic acid, carbazole derivatives, dehydrodeoxycolic acid, chenodeoxycholic acid, cholic acid methyl ester, sodium cholinic acid salt, crown ether, cyclodextrin, calicaren, polyethylene oxide Or a mixture thereof.

The present invention also provides a dye-sensitized solar cell comprising the photo-electrode for a solar cell described above.

For example, the dye-sensitized solar cell includes a conductive transparent substrate, the organic dye and the oxide semiconductor particles, the photo-electrode for a solar cell including a light absorbing layer; A second electrode disposed opposite to the optical electrode on which the light absorbing layer is formed; And an electrolyte positioned in a space between the photoelectrode and the second electrode.

The absorption characteristics of photovoltaic devices such as solar cells are affected by the incident photon-to-current conversion efficiency (IPCE) or light-harvesting efficiency (LHE) depending on the absorption wavelength of the organic dye used .

Therefore, the above-described dye-sensitized solar cell can absorb light having a wavelength ranging from 350 nm to 750 nm by absorbing light having a wavelength ranging from 350 nm to 750 nm, including a photoelectrode carrying an organic dye having a high photo- Indicating the change efficiency.

Hereinafter, the present invention will be described in more detail with reference to examples. The embodiments presented are only a concrete example of the present invention and are not intended to limit the scope of the present invention.

<Examples>

The organic dyes according to the examples were prepared by the following method.

As shown in Reaction Scheme 1, cinnamyl triphenyl phosphonium bromide and N-propyl hydroxy phenothiazine were reacted with n-butyllithium (n-BuLi) ) And tetrahydrofuran (THF).

[Reaction Scheme 1]

Further, as shown in the following Reaction Scheme 2, 4-bromo phenol, 3-isopropoxy-4-methyl -3-cyclobutene-1,2-dione, triethylamine (Et ₃ N) and acetic anhydride (Ac ₂ O) were mixed to prepare a precursor. Then, benzene, Compound B was prepared by refluxing with butanol.

[Reaction Scheme 2]

Also, 2,5-dimethylthiophen-ol can be reacted with potassium tert-butoxide (tBuOK), THF and amino-diethoxyoxy And a precursor is prepared by mixing the precursor with piperidine and 3-amino-1-propanol by mixing with an amino-diethoxy-oxypotassyl-benzene. To prepare Compound (C).

[Reaction Scheme 3]

Further, Pd ₂ (dba) to the compound C, as shown in Scheme _{4, 3, S-phos,} tBuOK and after the addition of compound A by reaction, Pd ₂ (dba) ₃ in the compound C, S -phos , tBuOK and compound B were added and reacted to give phenothiazine (PTZ) to the core TPA structure in which cyanoacrylic acid and indolinum were introduced into a heteroleptic dual electron acceptor. The organic dyes introduced with this antenna were prepared.

[Reaction Scheme 4]

&Lt; Comparative Example 1 &

Pd ₂ (dba) ₃ , S-phos and tBuOK were added to Compound C prepared by using the same method as in Example and then reacted to obtain a core TPA structure in which cyanoacrylic acid was introduced 1 was prepared.

(2)

&Lt; Comparative Example 2 &

Benzene, Pd ₂ (dba) ₃ , S-phos and tBuOK were added to the compound B prepared by using the same method as in the examples, and then reacted to prepare an organic dye represented by the following formula (3).

(3)

&Lt; Comparative Example 3 &

Compound B, Pd ₂ (dba) ₃ , S-phos and tBuOK were added to Compound C prepared by using the same method as in Example, and then reacted to obtain cyanoacrylic acid and indolinium An organic dye having a core TPA structure was prepared.

[Chemical Formula 4]

Experimental Example 1: Absorption spectrum analysis of organic dyes

For the absorption spectrum analysis of the organic dyes according to Examples and Comparative Examples 1 to 3, the absorption spectrum of organic dyes in ethanol in a wavelength region of 300 to 800 nm was measured using an ultraviolet-visible spectrophotometer (UV-VIS spectrophotometer) absorption spectrum, and the results of the analysis are shown in FIG.

As shown in FIG. 1, organic dyes according to Comparative Example 1 and Comparative Example 2 were found to exhibit the lowest absorption peaks at 495 nm and 635 nm, respectively, in which HOMO? LUMO transition occurs. On the other hand, the organic dyes according to Examples and Comparative Example 3 showed three absorption peaks.

In the case of the organic dye of Comparative Example 3, the main absorption peaks of the heteroleptic electron acceptor were found at about 610 nm and 485 nm and a weak absorption peak at about 390 nm.

For the organic dyes according to the examples, a heterogeneous antenna group was introduced and the major peaks at 620 nm, 505 nm and 400 nm, respectively. The overall absorption bands of the organic dyes according to the examples were found to be stronger than those of the organic dyes according to Comparative Examples 1 to 3 and the light absorption of the organic dyes according to the Examples was the most excellent, , It can be confirmed that a molar extinction coefficient (M ^-1 / cm) at 390 nm is introduced by introducing the antenna molecule, and the light of the wavelength of the entire RGB region of visible light can be effectively absorbed, It was confirmed that the light absorbance was superior to the organic dyes according to 1 to 3.

&Lt; Experimental Example 2 > Evaluation of photoelectric performance and energy potential characteristics of organic dyes

Apart from the absorption spectrum measurement of Experimental Example 1, for each of the organic dyes according to Examples and Comparative Examples 1 to 3, the density functional theory (DFT) of the ground state ruthenium dye Time-dependent density functional theory (TD-DFT) calculations are performed to show the absorption energy, oscillator strength (f), molecular orbital (MO) contribution at wavelengths above 350 nm Table 1 shows the analysis results of the major composition and transition character on the side.

As shown in Table 1, two transitions, intramolecular charge-transfer (ICT) and π → π ^* transfer, dominated the absorption peaks shown in FIG.

It has been confirmed that the absorption peak at the long wavelength side of the organic dye according to the embodiment is dominated by ICT, and the absorption peak at the short wavelength side is dominated by the π → π ^* transition. ICT is located between the donor and the receiver, and the π → π ^* transition is located inside the double donor due to the influence of the antenna.

Further, as a result of analysis of the major composition regarding the MO contribution, the organic dye of Comparative Example 3 showed HOMO? LUMO (?) At the peaks of 610 nm and 485 nm, which are the main absorption peaks shown in the absorption spectrum of FIG. Transition, and HOMO → LUMO + 1 transition, respectively, and HOMO-1 → LUMO + 1 appeared at 390 nm.

In the case of the organic dye of the example in which the heterogeneous antenna group was introduced, three main peaks were observed. HOMO-1 - &gt; LUMO and HOMO - &gt; LUMO transition at 620 nm, which is the same as the main absorption peak shown in the absorption spectrum of FIG. And HOMO → LUMO + 1 and HOMO → LUMO + 2 metastases at 505 nm and 400 nm, respectively (Table 1). The overall absorption bands of the organic dyes of the Examples were found to be stronger than those of the other dyes, and the organic dyes of the Examples showed the highest absorption capacity.

The molecular orbital energy levels of the organic dyes according to Examples and Comparative Example 3 were analyzed. The results of the analysis are shown in FIG.

For molecular orbital energy level analysis of organic dyes, titanium dioxide (TiO ₂ ) with a conduction band (CB) of -3.44 eV was used as a semiconductor. The LUMO level of the dye molecule should be a negative value that is larger than the conduction band end of the titanium dioxide, so that efficient electron injection of the conduction path of the TiO ₂ film in the dye molecule is possible and the HOMO level is higher than the reduction potential of I ^3- / I ^- Value, it is possible to regenerate the dye molecule.

As shown in FIG. 2, the LUMO levels of the organic dyes according to Examples and Comparative Example 3 were higher than the LUMO level of titanium dioxide. Therefore, it has been confirmed that all the dyes have sufficient driving force to inject electric charges into titanium dioxide.

In the case of the organic dyes according to the embodiments, additional HOMO-1 interaction with HOMO occurs due to the introduction of the PTZ antenna moiety, so that the HOMO energy level of the organic dye according to the embodiment is higher than that of the organic dye according to Comparative Example 3 Energy level. The increase in the HOMO level of the organic dye according to the embodiment in which the hetero-charge donor is introduced can explain why the HOMO level of the organic dye according to Comparative Example 3 in which a single charge donor group is introduced is higher than that of the organic dye according to the embodiment. These results show that the energy bandgap of the organic dye according to the embodiment is reduced by the additionally introduced antenna group, and the reduction of the energy band gap of the organic dye according to the embodiment is also confirmed in the absorption spectrum shown in FIG. As can be seen, the energy band was red-shifted compared to the spectrum of the organic dye according to Comparative Example 3. [

The electron distribution and molecular structure of the organic dyes according to Examples and Comparative Examples were analyzed through the calculation of the density function function theory, and the analysis results are shown in FIG. Fig. 3 (a) shows the structure of the organic dye according to Comparative Example 3, and Fig. 3 (b) shows the structure of the organic dye according to the embodiment.

As shown in FIG. 3, the organic dyes according to Examples and Comparative Example 3 exhibited charge distributions of several boundary molecular orbits (frontier MOs).

In the HOMO and HOMO-1 of organic dyes according to Comparative Example 3, molecular orbital analysis confirmed that electrons were mainly transferred to TPA and the entire charge donor moiety. LUMO was mainly located in the fixed region of indolinium. LUMO + 1 was placed on the cyanoacrylic molecule with the phenyl linker attached.

In the case of the organic dye according to the embodiment, the structure of the molecular orbital was similar to that of the organic dye according to Comparative Example 3 due to the introduction of the heterogeneous antenna group. However, the LUMO + 2 of the organic dye according to the example was located from the PTZ antenna to the TPA donor. As shown in FIG. 1, LUMO + 2 was induced by the PTZ antenna in the organic dye according to the embodiment, and the contribution of the PTZ antenna due to the absorbance (π → π *) before the macromolecule of about 400 nm .

Intramolecular energy transfer ( E _n T ) and intramolecular charge transfer (ICT) of the prepared organic dyes were also analyzed. As a result, the antenna group of the organic dye according to the embodiment of the present invention transfers energy to the basic dye.

This E _n T occurs through the Fster energy transfer. For effective E _n T , the emission band of the antenna group must be significantly overlapped with the absorption band of the dye body.

4 is a diagram showing the intramolecular E _n T process of an organic dye according to an embodiment. As shown in Fig. 4, it was confirmed that the organic dyes according to the Examples were superior in energy absorption to organic dyes according to Comparative Example 3 in the short wavelength region (350 nm to 550 nm). In addition, the absorption spectrum of the organic dye according to the Example shows a larger area than the absorption spectrum of the organic dye according to Comparative Example 3. These facts suggest that the emission band of the PTZ antenna group in the organic dye according to the embodiment is well superimposed on the absorption band, so that the intramolecular energy transfer of the organic dye according to the embodiment is more excellent. In addition, as shown in Fig. 1, the spectrum of the organic dye according to the Example was broader than that of the organic dye according to Comparative Example 3, and exhibited a red-shifted absorption spectrum and a higher molar extinction coefficient.

The organic dyes according to the embodiments in which phenothiazine (PTZ) is introduced as an antenna group in addition to cyanoacrylate and indolinium molecules in which a heterologous electron acceptor is introduced include an emission band of the antenna group and an absorption band of the dye body , It was confirmed that the E _n T in the molecule and the photoelectric performance were excellent.

The absorption characteristics of the photoelectric converter can be evaluated by incident photon-to-current conversion efficiency (IPCE) and light harvesting efficiency (LHE) according to the absorption wavelength of the organic dye. The IPCE and the photon collection efficiency can be calculated using the following equations (1) and (2).

[Equation 1]

&Quot; (2) &quot;

Where η _inj is the quantum yield of charge injection due to charge injection and dye regeneration, η _cc is the charge collection efficiency, and A is the absorbance of the film, respectively. The absorption of the film can be represented by the oscillator strength (f) in the absorption spectrum. Assuming that η _inj and η _cc are 100%, it can be concluded that IPCE is almost equal to LHE.

The LHE values of the organic dyes according to Examples were higher than those of the organic dyes according to Comparative Example 3, and the LHE values shown in Table 1 were calculated using Equations 1 and 2, It was confirmed that the photoelectric performance of the organic dye according to the present invention is superior to other dyes.

Claims (10)

1. An organic dye comprising a heteroleptic electron acceptor represented by the following formula (1).
[Chemical Formula 1]

The method according to claim 1,
Wherein the organic dye absorbs light of a wavelength of 350 to 750 nm. The method according to claim 1,
Wherein the light harvesting efficiency (LHE) in light of a wavelength of 350 to 750 nm is 0.95 or more. The method according to claim 1,
Wherein the maximum absorption peak appears at a wavelength of 397.1 nm, 503.9 nm and 620.5 nm of an ultraviolet-visible (UV-vis) absorption spectrum. The method according to claim 1,
Wherein the molar extinction coefficient in the light having a wavelength of 397.1 nm is 1 x 10 &lt; ⁵ &gt; M &lt; ^-1 &gt; / cm or more. The method according to claim 1,
Wherein the band gap is 1.79 eV. A photoelectrode for a dye-sensitized solar cell comprising oxide semiconductor particles carrying an organic dye containing a heterologous electron acceptor according to claim 1. 8. The method of claim 7,
Wherein the oxide semiconductor particles are at least one selected from titanium oxide, tin oxide, zinc oxide, tungsten oxide, zirconium oxide, gallium oxide, indium oxide, yttrium oxide, niobium oxide, tantalum oxide and vanadium oxide Optical electrode for dye - sensitized solar cell. 8. The method of claim 7,
Wherein the compound is selected from the group consisting of deoxycholinic acid, carbazole derivatives, dehydrodeoxycolic acid, chenodeoxycholic acid, cholic acid methyl ester, sodium cholinic acid salt, crown ether, cyclodextrin, The photoelectrode for a dye-sensitized solar cell according to claim 1, further comprising a co-adsorbent. 9. A dye-sensitized solar cell comprising the photo-electrode according to claim 7.

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