KR101760493B1 - Benzobisoxazole derivatives, method of preparation thereof and organic solar cell comprising the same - Google Patents

Abstract

상기 식에서, R₁, R₅ 및 R₆는 명세서에서 정의한 바와 같다.The present invention provides a compound represented by the following general formula (1), which has an electric field transfer characteristic, a method for producing the same, and an organic solar cell comprising the same.
[Chemical Formula 1]

Wherein R ₁ , R ₅ and R ₆ are as defined in the specification.

Description

[0001] The present invention relates to benzobisoxazole derivatives, a process for their preparation, and organic solar cells comprising the same,

The present invention provides a benzobisoxazole derivative having an electric field transfer characteristic, a method for producing the same, and an organic solar battery including the same.

Researches on renewable and clean alternative energy sources such as solar energy, wind power, and hydro power are actively being conducted to solve the global environmental problems caused by the depletion of fossil energy and its use. In particular, there is a growing interest in solar cells, which are current-voltage generating cells that utilize the photovoltaic effect of absorbing light energy from sunlight to generate electrons and holes.

Dye-sensitized solar cell (DSSC) was first developed by Professor Michael Gratzel of the Lausanne University of Technology in Switzerland (1991) and introduced to Nature magazine (Vol. 353, p. 737) .

In the early dye-sensitized solar cell structure, a dye that absorbs light is adsorbed on a porous photo-electrode on a transparent electrode film through which light and electricity pass, and then another conductive glass substrate is placed on top and a simple structure .

The working principle of a dye-sensitized solar cell is as follows. When dye molecules chemically adsorbed on the surface of a porous photocathode absorb solar light, dye molecules generate electron-hole pairs, and electrons are converted into conduction tines of semiconductor oxide used as a porous photocathode Injected and transferred to the transparent conductive film to generate a current. The holes remaining in the dye molecules are transferred to the photocathode by the hole conduction or hole conductive polymer by the oxidation-reduction reaction of the liquid or solid electrolyte, and form a complete solar cell circuit, .

In this dye-sensitized solar cell structure, the transparent conductive film is mainly composed of fluorine doped tin oxide (FTO) or indium doped tin oxide (ITO), and a nanotube having a wide band gap is used as the porous photo cathode. The dyestuff is particularly well absorbed and has a lowest unoccupied molecular orbital (LUMO) energy level of the dye than the energy level of the condiction band of the photocathode material, which facilitates the separation of the exciton produced by the light, Various materials are chemically synthesized and used. The highest efficiency of liquid dye-sensitized solar cells reported so far is 11-12% for about 20 years.

Organic photovoltaics (OPVs), which have been studied extensively since mid-1990, have been used to study organic materials with electron donor (D or often called hole acceptor) characteristics and electron acceptor (A) . When a solar cell made of organic molecules absorbs light, electrons and holes are formed. This is called an exiton. The exciton moves to the DA interface to separate the charge, the electrons move to the electron acceptor, and the hole moves to the electron donor, generating a photocurrent.

Since the distance that the exciton generated from the electron donor can travel normally is very short, about 10 nm, the photoconductivity can not be accumulated thickly, and the efficiency of the photoconductivity is low due to low light absorption. In recent years, however, efficiency has greatly increased with the introduction of the so-called bulk heterojunction (BHJ) concept of increasing the surface area at the interface and the development of donor organic materials having a small band gap that is easy to absorb a wide range of solar light, Organic solar cells with efficiency over 8% have been reported (Advanced Materials, 23 (2011) 4636).

On the other hand, Prof. Mikael Gratel of the Department of Chemistry, Lausanne University of Technology, Switzerland, inventor of the dye-sensitized solar cell, reported that in 1998, instead of the liquid electrolyte, a solid-type hole transporting organic material spiro-OMeTAD (2,2 ', 7,7'-tetrakis We have reported an all-solid dye-sensitized solar cell with an efficiency of 0.74% by using N, N-di- (4-methoxyphenylamino) -9,9'-spirobifluorene. In addition, the ruthenium-based dyestuffs were produced using low-cost pure organic dyes and hole conductors such as P3HT and PEDOT, but the efficiency was still low at 2-7%.

The spiro-OMeTAD has a high hole-transporting efficiency and is widely used as a hole-transporting material of a solar cell that is recently produced. However, spiro-OMeTAD has a spiro-bifluorene core in its chemical structure. To synthesize spiro-OMeTAD, it has a complicated process. Various hole transporting organic compounds have been reported to replace this, but are still difficult to synthesize due to the complicated structure.

Accordingly, the inventors of the present invention found that benzo-bis-oxazole derivatives are easy to synthesize and have excellent hole-transporting characteristics as described in the specification of the present invention while studying the hole transporting material which can replace spiro-OMeTAD, Completed.

The present invention provides a benzobisoxazole derivative having an electric field transfer property and a process for producing the same.

The present invention also provides an organic solar cell comprising the benzobisoxazole derivative.

In order to solve the above problems, the present invention provides a compound represented by the following formula (1): < EMI ID =

[Chemical Formula 1]

In this formula,

이고, R ₁ is

ego,

p is 0 or 1,

R ₂ is hydrogen, C _{1 -10} alkyl, C _{2 -10} alkenyl, C _{2 -10} alkynyl, C _{1 -4} alkoxy, C _{1 -4} alkylthio, C _6-20 aryl, C _{5 -20} cycloalkyl , and C _{5 -20} heterocycloalkyl or NR ₃ NR _4,

R ₃ and R ₄ are aryl each is independently hydrogen, C _{1 -4} alkyl or C _{6 -20,}

이고,R ₅ and R ₆ are each independently

ego,

q is 0 or 1,

R ₇ and R ₈ are each, independently,

Hydrogen, C _{1 -10} alkyl, C _{1 -4} alkoxy, C _{1 -4} alkylthio, C ₅ or _-8 cycloalkyl or halogen,

Or phenyl or naphthyl, wherein phenyl or naphthyl is unsubstituted or substituted by 1 is C _{1 -4} alkyl, C _{1 -4} alkoxy, each independently selected from the group consisting of C _{1 -4} alkylthio, halogen one to 5 substituents, or

를 형성하고,Together with the nitrogen atom bonded to R ₇ , R ₈ and R ₇ and R ₈

Lt; / RTI >

r is an integer of 0 to 4,

Z is a bond, O, S, NR ₁₁ or CR ₁₂ R ₁₃ ,

R ₉ and R ₁₀ are each independently hydrogen, C _{1 -4} alkyl, C _{1 -4} alkoxy, C _{1 -4} alkylthio, halogen or NR ₁₄ R _15, and

R ₁₁ to R ₁₅ each independently is hydrogen, C _{1 -4} alkyl or C _{6 -20} aryl group.

The compound represented by the above formula (1) is characterized in that benzobisoxazole has a core structure and R ₅ and R ₆ are respectively substituted in the benzene ring in the middle. In particular, R ₅ and R ₆ are characterized by having a substituent containing a nitrogen atom.

The compound represented by the above formula (1) can be used as a hole transporting material, and is characterized in that it is not only effective to the effect of spiro-OMeTAD, which is a hole transporting material, but also has a simple structure and easy synthesis and is advantageous for commercial mass production.

In Formula 1, p is preferably 0, meaning that R ₁ has no phenylene structure and R ₂ has a substituent.

In addition, preferably, R ₂ is C _{1 -4} alkyl. More preferably, R ₁ is a C _{1 -4} alkyl.

Further, preferably, R ₅ and R ₆ are the same as each other.

Also preferably, q is 1, which means that in the structures of R ₅ and R ₆ , phenylene has a structure connecting NR ₇ R ₈ as a linker.

Also, preferably R ₇ and R ₈ is phenyl, said phenyl is substituted by C _{1 -4} alkoxy. More preferably, the phenyl is substituted with methoxy. Most preferably, R ₇ and R ₈ are 4-methoxyphenyl.

Representative examples of the compound represented by the formula (1) are as follows:

.

.

The present invention also provides a process for preparing a compound represented by the following general formula (1)

[Reaction Scheme 1]

In the above Reaction Scheme 1, the definitions of R ₁ , R ₅ and R ₆ are as defined above.

The step 1 is a step of reacting a compound represented by the formula (2) with ammonium hydroxide to replace a part of Br with an amino to prepare a compound represented by the formula (3). As the solvent, it is preferable to use 2-methoxyethyl acetate.

Step 2 is a step of reacting the compound represented by the formula (3) with sodium hydrosulfide to prepare a compound represented by the formula (4). As the solvent, it is preferable to use an ethanol / distilled water mixed solvent.

Step 3 is a step of reacting a compound represented by formula (4) with R ₁ -C (OEt) ₃ to prepare a compound represented by formula (5). Yttrium triflate are preferably reacted together, and as the solvent, it is preferable to use dimethylacetamide. After the reaction, it is preferable to obtain the compound represented by the general formula (5) by recrystallization with a mixed solvent of chloroform and ethanol.

Step 4 is a step of preparing a compound represented by the formula (1), and the compound to be reacted with the compound represented by the formula (5) can be appropriately selected according to the structure of R ₅ and R ₆ .

의 화합물과 반응시킨다. 이때, 톨루엔을 용매로 사용하는 것이 바람직하며, 또한 소듐 터셔리부톡사이드, 팔라듐 아세테이트 및 트리부틸포스핀을 함께 사용하는 것이 바람직하다.
First, when q is 0 in R ₅ and R ₆ , a compound represented by the formula (3) is reacted with a compound represented by NHR ₇ R _{8. When} q is 1 in R ₅ and R ₆ ,

Lt; / RTI > At this time, toluene is preferably used as a solvent, and sodium tertiary butoxide, palladium acetate and tributylphosphine are preferably used together.

When R ₅ and R ₆ are the same, it is preferable to use an excessive amount of a compound to be reacted with the compound represented by the formula (5). When R ₅ and R ₆ are different from each other, the compound represented by the formula The compound can be appropriately selected and reacted sequentially.

Also, the present invention provides a hole transport layer comprising the compound represented by the above formula (1). The present invention also provides an organic solar cell including the hole transport layer.

The organic solar battery according to the present invention may include a first electrode, a second electrode, a photoactive layer, and a hole transporting layer containing a compound represented by Formula 1.

The first electrode may be an anode, and the second electrode may be a cathode. The first electrode may be a cathode, and the second electrode may be an anode. The anode may be a transparent material having excellent conductivity, but is not limited thereto. Specifically, it may be indium tin oxide (ITO), tin oxide (SnO ₂ ), fluorine doped tin oxide (FTO), and zinc oxide (ZnO), but is not limited thereto. The cathode may be a metal having a small work function, but is not limited thereto. Specifically, it may be a metal such as lithium, magnesium, or an alloy thereof, or a multi-layered material such as Al: Li, Al: BaF ₂ , or Al: BaF ₂ : Ba.

The hole transport layer and the electron transport layer material are materials that increase the probability that electrons and holes are efficiently transferred to the photoactive layer, thereby transferring generated charges to the electrode. The hole transport layer includes the compound represented by Formula 1 according to the present invention. In addition to the hole transport layer, an electron transport layer may be further included. Examples of the material that can be used for the electron transport layer include aluminum trihydroxyquinolinate (Alq ₃ ), PBD (2- (4-bipheyl) 5-phenyl-1,3,4-oxadiazole, TPQ (1,3,4-tris [(3-phenyl-6-trifluoromethyl) qunoxaline-2-yl] benzene) and triazole derivatives.

The material used for the photoactive layer is not particularly limited as long as it is a material that generates electron-hole pairs by receiving sunlight. For example, an AMX ₃ organic hybrid organic perovskite compound (wherein A is an ammonium salt, M is a divalent metal ion, and X is a halogen ion). Examples thereof, may be _{CH 3 NH 3 PbI 3, CH} 3 NH 3 PbI (3-x) Cl x, CH 3 NH 3 PbI (3-x) for _x Br.

As an example of the method of manufacturing the organic solar cell, there is a method of manufacturing an organic solar battery, which comprises preparing a substrate, forming an anode on one region of the substrate, forming a hole transporting layer on the anode, Forming a photoactive layer on the photoactive layer, and forming a cathode on the photoactive layer. In addition, a step of forming an electron transport layer between the photoactive layer and the cathode may be added.

The compound represented by Formula 1 according to the present invention is easier to synthesize than spiro-OMeTAD because of its simple structure, and has excellent hole transporting properties, and thus can be used as a hole transporting material.

Hereinafter, preferred embodiments of the present invention will be described in order to facilitate understanding of the present invention. However, the following examples are provided only for the purpose of easier understanding of the present invention, and the present invention is not limited thereto.

Example

Step 1) Preparation of compound 3

Compound 2 (2,3,5,6-tetrabromocyclohexa-2,5-diene-1,4-dione, 43 g) was dissolved in 2-methoxyethyl acetate and stirred at 60 ° C. After cooling to room temperature, 27% ammonium hydroxide solution (43 mL) was added dropwise, followed by stirring at 80 ° C for 3 hours and then at room temperature overnight. The precipitate obtained by filtration was washed several times with distilled water, washed with acetone and dried to obtain Compound 3 (28 g).

Step 2) Preparation of compound 4

The prepared compound 3 (3.3 g) was added to a mixed solvent of ethanol and distilled water, and distilled water in which sodium hydrosulfite (4.8 g) was dissolved at 55 占 폚 was added dropwise and stirred for 1 hour. After cooling to room temperature, the precipitate was filtered, washed with distilled water and cold ethanol, and dried to obtain Compound 4 (3.1 g).

Step 3) Preparation of compound 5

Compound 4 (2.5 g) and yttrium triflate (0.13 g) prepared above were dissolved in dimethylacetamide under an argon atmosphere. The mixture was heated to 55 [deg.] C, then CH3C (OEt) 3 (1.5 g) was added over 30 minutes and stirred at 55 [deg.] C for 2 hours. After cooling to room temperature, distilled water was added, the precipitate was filtered, and washed with distilled water and cold ethanol. And recrystallized from a mixed solvent of chloroform and ethanol to obtain Compound 5 (1.4 g).

Step 4) Preparation of Compound 1

The compound 5 (5.0 g) prepared above, 4- (bis (4-methoxyphenyl) amino) phenylboronic acid (12 g), sodium tertiarybutoxy (0.30 g), palladium acetate (0.32 g), 50% tributylphosphine solution (0.79 mL) and toluene (50 mL) was refluxed under an argon atmosphere for 24 hours. After cooling to room temperature, ammonium chloride solution was added and extracted with methylene chloride. The extracted organic layer was dried over magnesium sulfate, filtered and the solvent was removed. The residue was purified by column chromatography to obtain Compound 1 (6.9 g).

¹ H NMR (CDCl ₃ , standard TMS): 7.54 (4H, d). D), 3.83 (8H, s), 2.62 (6H, s)

Experimental Example : Manufacture and Evaluation of Solar Cells

The end portion of the FTO substrate having a size of 25 mm × 25 mm was etched to partially remove the FTO. 0.1 M of _{[(CH 3) 2 CHO]} 2 Ti in the _{(C 5 H 7 O 2)} 2 (titanium diisopropoxide bis (acetylacetonate)) 1- butanol solution for 10 seconds and 2000 rpm to 700 rpm at 60-second FTO substrates 40 nm thick, and sintered at 500 ° C for 15 minutes to form a TiO ₂ layer as an N-type material.

A solution of 40 wt% of GBL was prepared by adding CH ₃ NH ₃ I (methylammonium iodide) and PbI ₂ (lead (II) iodide) to GBL (gamma-butyrolactone) at a molar ratio of 1.2: Respectively. The solution was coated on the previously prepared TiO ₂ layer at 500 rpm for 5 seconds, 1000 rpm for 40 seconds, and 5000 rpm for 30 seconds and dried at 100 ° C for 10 minutes to form a light absorbing layer.

On the light absorbing layer, a compound prepared in Example or a comparative example, spiro-OMeTAD (2,2 ', 7,7'-tetrakis (N, N-di (4-methoxyphenyl) amino) spirobifluorene), t-butylpyridine, and LiTFSI were spin-coated at 6000 rpm for 30 seconds to form a hole transporting layer. The electrode was formed by vacuum deposition of Au using a thermal evaporator.

The short-circuit current density, open-circuit voltage, performance index and power generation efficiency of the solar cell were measured. The results are shown in Table 1 below.

Hole transport layer Short circuit current density
(mA / cm 2) Open-circuit voltage (V) Performance Index (%) Power generation efficiency (%) Example 18.15 1.081 74.92 14.7 Comparative Example
(spiro-OMeTAD) 17.77 1.093 73.71 14.3

As shown in Table 1, the embodiment is characterized not only by the effect of spiro-OMeTAD, which is a hole-transferring material, but also because it is simple in structure and easy to synthesize as compared with spiro-OMeTAD.

Claims (11)

A compound represented by the following formula (1):
[Chemical Formula 1]

In this formula,
R ₁ is

ego,
p is 0 or 1,
R ₂ is hydrogen, C _1-10 alkyl, C _2-10 alkenyl, C _2-10 alkynyl, C _1-4 alkoxy, C _1-4 alkylthio, C _6-20 aryl, C _5-20 cycloalkyl , Or NR < ₃ > NR < ₄ &
R ₃ and R ₄ are each independently hydrogen, C _1-4 alkyl or C _6-20 aryl,
R ₅ and R ₆ are each independently

ego,
q is 0 or 1,
R ₇ and R ₈ are phenyl substituted with C _1-4 alkoxy.
The method according to claim 1,
and p is 0.
The method according to claim 1,
R ₂ is C _{1 -4} alkyl, compound.
The method according to claim 1,
R ₁ is C _{1 -4} alkyl, compound.
The method according to claim 1,
R ₅ and R ₆ are the same as each other.
The method according to claim 1,
and q is 1.
delete The method according to claim 1,
R < ₇ > and R < ₈ > are phenyl substituted with methoxy.
The method according to claim 1,
Wherein said compound is a compound having the structure:

.
A hole transport layer comprising a compound according to any one of claims 1 to 6, 8 and 9.
An organic solar cell comprising the hole transport layer according to claim 10.