KR101976115B1 - A compound having acryl group as an absorber, method for preparation thereof, and solar cell comprising the same - Google Patents

Abstract

The present invention relates to a compound which can be used as an absorber of a solar cell, a method for producing the same, and a solar cell comprising the compound. The compound according to the present invention can be obtained by introducing an acrylic group into an organic cation in a perovskite structure, To thereby form a bonding structure between the acrylic groups, thereby suppressing the structural collapse of the perovskite to enhance the stability against light, moisture and heat.

Description

TECHNICAL FIELD The present invention relates to a compound containing an acrylic group as an absorber, a process for preparing the same, and a solar cell comprising the same,

The present invention relates to a novel structure compound which can be used as an absorber of a solar cell, a method for producing the same, and a solar cell 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.

Of these, there is a great interest in solar cells that change electrical energy directly from sunlight. The term "solar cell" as used herein refers to a cell that generates a current-voltage by utilizing a photovoltaic effect that absorbs light energy from sunlight to generate electrons and holes.

Currently, np diode-type silicon (Si) single crystal based solar cells with a light energy conversion efficiency of more than 20% can be manufactured and used for actual solar power generation. Compound semiconductors such as gallium arsenide (GaAs) There is also solar cell using. However, since such an inorganic semiconductor-based solar cell requires a highly refined material for high efficiency, a large amount of energy is consumed for refining the raw material, and expensive process equipment is required in the process of making single crystal or thin film using raw material And the manufacturing cost of the solar cell can not be reduced.

Accordingly, in order to manufacture a solar cell at a low cost, it is necessary to drastically reduce the cost of the core material or the manufacturing process of the solar cell. As an alternative to the inorganic semiconductor-based solar cell, a dye- Solar cells are being actively studied.

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. Although the efficiency of the liquid dye-sensitized solar cell is relatively high, it is likely to be commercialized. However, there is a problem in terms of stability with time due to volatile liquid electrolyte and low cost due to use of expensive ruthenium (Ru) dye.

In order to solve this problem, a nonvolatile electrolyte using an ionic solvent, a polymer gel electrolyte, and a pure organic dyestuff have been studied in place of a volatile liquid electrolyte, but a dye sensitized with a volatile liquid electrolyte and a ruthenium dye There is a problem that the efficiency is lower than that of the solar cell.

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 migrates to the D-A interface and the charge is separated, the electrons are transferred to the electron acceptor, the holes are transferred to the electron donor, and the photocurrent is generated.

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).

Organic solar cells are easier to fabricate than existing solar cells because of their easy processability and diversity of organic materials and low unit cost. Therefore, it is possible to realize low cost manufacturing cost compared to existing solar cells. However, in the organic solar cell, the structure of the BHJ is deteriorated by moisture or oxygen in the air and the efficiency thereof is rapidly lowered, that is, there is a serious problem in the stability of the solar cell. As a method to solve this problem, it is possible to increase the stability by introducing the full sealing technology, but there is a problem that the price is increased.

As a method for solving the problems of the dye-sensitized solar cell by the liquid electrolyte, Prof. Mikael Gratzel of the Department of Chemistry, Lausanne University of Technology, Switzerland, inventor of the dye-sensitized solar cell, proposed a solid-type hole conductive organic material Spiro-OMeTAD (N, N-di-p-methoxyphenylamine) -9,9'-spirobifluorine) was used as a dye-sensitized solar cell with an efficiency of 0.74%. The efficiency was increased up to about 6% by optimization of the structure, interfacial characteristics, and hole conductivity improvement. In addition, solar cells using ruthenium-based dyes, such as P3HT and PEDOT, have been fabricated with low-cost pure organic dyes and hole conductors, but the efficiency is still low at 2-7%.

Further, research has been reported on using a quantum dot nanoparticle as a light absorber in place of a dye and using a hole-conducting inorganic or organic material in place of a liquid electrolyte. A number of solar cells using CdSe and PbS as quantum dots and conductive polymers such as Spiro-OMeTAD or P3HT as hole-conducting organic materials have been reported, but their efficiency is still very low at less than 5%. In addition, efficiency of about 6% was reported for solar cells using Sb ₂ S ₃ as a light absorbing inorganic material and PCPDTBT as a hole conductive inorganic material (Nano Letters, 11 (2011) 4789).

In addition, a 9% efficiency has been reported using a material having a hybrid organic perovskite structure instead of a pure inorganic quantum dot in place of a dye in a dye-sensitized solar cell (Scientific Reports 2, 591). In addition, although we announce solar cells using perovskite, we have yet to report new perovskite materials.

In order to improve the efficiency of the solar cell, the present inventors have conducted research to change the structure of the organic hybrid perovskite. In order to improve the stability of the organic hybrid perovskite structure, Can be usefully used as an absorber of a solar cell, thereby completing the present invention.

The present invention provides a novel structure compound which can be used as an absorber of a solar cell, and a method for producing the same.

The present invention also provides a solar cell comprising the above compound.

In order to solve the above problems, the present invention provides a compound represented by the following formula 1 or 2:

[Chemical Formula 1]

AMX ₃

In Formula 1,

A is an organic cation of R ₁ R ₂ R ₃ R ₄ N ⁺

Wherein, R _1, R _2, R ₃ and R ₄ is hydrogen, C _1-10 alkyl, or _{CH 2 = CH-COO- (C} 1-10 alkylene), each independently, provided that R _1, R _2, At least one of R ₃ and R ₄ is CH ₂ ═CH-COO- (C _1-10 alkylene)

M is a divalent metal cation,

X is the same or different halogen.

The compound represented by Formula 1 is a perovskite compound. That bears the term "perovskite (perovskite)" is, the Russian mineralogist name of Lev Perovski used in the present invention, the cation (A and M) and anion (X) a is composed of the chemical formula of AMX _3, the first Means a material having the same structure as CaTiO ₃ found in Ural acid, which is a perovskite type material. In the case of the perovskite used in the solar cell as in the present invention, the cation corresponding to A is usually monovalent ammonium ion, and thus the term "organic / inorganic hybrid" is used.

CH ₃ NH ₃ ⁺ (methylammonium) is typically known as a cation corresponding to A in the perovskite used in conventional solar cells. However, perovskite containing methylammonium is unstable to light, moisture, and heat, and therefore, when the solar cell is operated, the light conversion efficiency deteriorates over time.

In the present invention, by introducing an acrylic group into the cation corresponding to A, a bonding structure between acrylic groups is formed through heat treatment or the like to suppress the structural collapse of perovskite to enhance stability against light, moisture and heat .

Specifically, the cation corresponding to A in Formula 1 has a structure of R ₁ R ₂ R ₃ R ₄ N ⁺ , and at least one of R ₁ , R ₂ , R _3, and R ₄ is CH ₂ ═CH- COO- (C _1-10 alkylene), that is, an acrylic group. Accordingly, the intramolecular or intermolecular bonding structure can be introduced into the compound of Formula 1, thereby enhancing the stability of the compound.

Preferably, R ₁ is CH ₂ ═CH-COO- (C _1-10 alkylene) and R ₂ , R ₃ and R ₄ are each independently hydrogen or C _1-10 alkyl. That is, one substituent in the structure of R ₁ R ₂ R ₃ R ₄ N ⁺ includes an acrylic group.

Also preferably, R ₁ is CH ₂ ═CH-COO- (C _1-10 alkylene), R ₂ and R ₃ are each independently C _1-10 alkyl, and R ₄ is hydrogen. That is, in the structure of R ₁ R ₂ R ₃ R ₄ N ⁺ , one substituent includes an acrylic group, two substituents are an alkyl group, and the other substituent is hydrogen.

Also preferably, R ₁ , R ₂ , R ₃ and R ₄ are each independently hydrogen, methyl or CH ₂ ═CH-COO-CH ₂ -CH ₂ - with the proviso that R ₁ , R ₂ , R ₃ and R ₄ is at least one of _{CH 2 = CH-COO-CH} 2 -CH 2 - a.

Also preferably, M is ^{Pb 2 +, Sn 2 +,} Pd 2 +, Cu 2 +, Ge 2 +, Sr 2 +, Cd 2 +, Ca 2 +, Ni 2 +, Mn 2+, Fe 2 + , ^{2 +} is Co, Sn ^{+ 2,} Yb ^{+ 2,} or Eu ^{2 +.} More preferably, M is Sn or Pb ^{+ 2 + 2,,} and most preferably Pb ^{2 +.}

Also preferably, X is, each independently ^{Cl-a -,} Br ^-, or I. Since X may be the same or different from each other, X in the above formula (1) or (2) may contain two or three kinds of halogens.

Representative examples of the compound represented by Formula 1 is _{CH 2 = CH-COO-CH} 2 -CH 2 -N (CH 3) 2 HPbI 3.

The present invention also provides a process for preparing a compound represented by the above formula (1) In the following Reaction Scheme 1, R ₁ is CH ₂ ═CH-COO- (C _1-10 alkylene), and other compounds can also be derived from the following reaction scheme 1.

[Reaction Scheme 1]

(Wherein, in the above Reaction Scheme 1, the definitions of A, M and X are as defined above and X 'is halogen (preferably Cl)

Step 1 is a step of reacting a compound represented by the following formula (2) and a compound represented by the following formula (3) to prepare a compound represented by the following formula (4). The solvent of the reaction is preferably methylene chloride. The reaction is preferably carried out at room temperature for about 4 hours.

Step 2 is a step of reacting a compound represented by the following formula (4) with a compound represented by the following formula (5) to prepare a compound represented by the following formula (6). The solvent for the reaction is preferably ethanol. Further, it is preferable that the reaction is carried out in the presence of BHT. In addition, the reaction is preferably carried out for about 30 minutes.

Step 3 is a step of reacting a compound represented by the following formula (6) and a compound represented by the following formula (7) to prepare a compound represented by the following formula (1). The solvent for the above reaction is preferably gamma-butyrolactone, dimethylformamide, dimethylsulfoxide, N-methylpyrrolidine, or pyridine. Also, the reaction is preferably carried out at about 110 ° C for about 1 hour.

The present invention also provides a solar cell comprising the compound represented by the above formula (1).

The compound represented by Formula 1 according to the present invention plays a role of absorbing sunlight, and thus can form a light absorbing layer in a solar cell. Therefore, the solar cell used in the present invention can be constituted as follows.

A first electrode comprising a conductive transparent substrate;

An electron transport layer formed on the first electrode;

A light absorbing layer formed on the electron transporting layer and comprising a compound represented by Formula 1;

A hole transport layer formed on the light absorption layer; And

And a second electrode formed on the hole transport layer.

The solar cell may be manufactured as follows.

1) forming an electron transport layer on a first electrode comprising a conductive transparent substrate;

2) adsorbing and heat-treating the compound represented by Formula 1 on the electron transport layer to form a light absorption layer;

3) forming a hole transport layer on the light absorption layer; And

4) forming a second electrode on the hole transport layer.

The conductive transparent substrate is not particularly limited as long as it is a conductive transparent substrate ordinarily used in the field of solar cells. For example, fluorine-containing tin oxide (FTO), indium doped tin oxide (ITO), ZnO, PEDOT: PSS and the like can be used.

The electron transport layer may use a porous metal oxide, and preferably has a porous structure by metal oxide particles. Examples of the metal oxide include TiO ₂ , SnO ₂ , ZnO, Nb ₂ O ₅ , Ta ₂ O ₅ , WO ₃ , W ₂ O ₅ , In ₂ O ₃ , Ga ₂ O ₃ , Nd ₂ O ₃ , CdO can be used.

The hole transport layer may use a solid type hole transport material or a liquid electrolyte. Examples of the solid-type hole-transporting material include spiro-OMeTAD (2,2 ', 7,7'-tetrakis- (N, N-di-p- methoxyphenylamine) 9,9'- ), P3HT (poly (3-hexylthiophene)), PCPDTBT (poly [2,1,3-benzothiadiazole-4,7- (Poly (N-vinylcarbazole)), HTM-TFSI (1-hexyl-3-methyl POT (Poly (3, < / RTI > 3, < RTI ID = 4-ethylenedioxythiophene) poly (styrenesulfonate)). As the liquid electrolyte, iodine and an additive dissolved in a solvent may be used. For example, at least one additive selected from the group consisting of urea, thiourea, tert-butylpyridine, and guanidium thiotanate is added to at least one additive selected from the group consisting of ethyl acetate, acetonitrile, Methoxypropionitrile, methoxypropionitrile and the like can be used.

Is in the second electrode, ITO, FTO, ZnO-Ga 2 O 3, a glass substrate or a plastic substrate including at least one material selected from the group consisting of ZnO-Al ₂ O ₃ and tin oxide, Pt, A conductive layer containing at least one material selected from the group consisting of Au, Ni, Cu, Ag, In, Ru, Pd, Rh, Ir, Os, C and a conductive polymer may be formed.

In addition, the adsorption of the compound in the step 2 may be performed by spin-coating, dip coating, screen coating, spray coating, electrospinning, etc. for 10 seconds to 5 minutes. The solvent for dispersing the compound represented by the formula (1) is not particularly limited as far as the perovskite is easily dissolved, but gamma-butyrolactone, DMF and the like are preferable. The heat treatment temperature after adsorption is preferably 40 to 300 占 폚.

As described above, the compound according to the present invention forms a bonding structure between acrylic groups through heat treatment or the like by introducing an acrylic group into organic cations in the perovskite structure, thereby suppressing the structural collapse of perovskite And enhances stability to light, moisture and heat.

1 shows XRD data of the compound prepared in one embodiment of the present invention.
FIG. 2 shows the performance of a solar cell using the compound prepared in one embodiment of the present invention and a comparative example according to measurement time.

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 : CH ₂ = CH-COO-CH ₂ -CH ₂ - N (CH ₃ ) ₂ HPbI ₃ of  Produce

(Step 1)

Acryloyl chloride (5.0 g) and NaOH (2.2 g) were dissolved in methylene chloride, cooled to 0 캜, and 2- (dimethylamino) ethanol (5.1 g) was slowly added thereto and stirred at room temperature for 4 hours. Water was added, followed by extraction with methylene chloride. The extracted organic layer was dried with magnesium sulfate, filtered and the solvent was removed. The residue was purified by column chromatography to obtain 2- (dimethylamino) ethyl acrylate (4.0 g).

(Step 2)

2- (Dimethylamino) ethyl acrylate (4.0 g) and BHT (0.12 g) prepared in the above step 1 were dissolved in ethanol and HI (3.6 g) was slowly added thereto and stirred for 30 minutes. The solvent was removed under reduced pressure, and then washed several times with diethyl ether to obtain EADMAI (3.0 g).

¹ H NMR (CDCl _3, standard substance TMS): d 6.37 (1H, d), 6.19 (1H, dd), 6.02 (1H, d), 4.40 (2H, d), 3.47 (2H, d), 2.85 ( 6H, s)

(Step 3)

EADMAI (0.50 g) and PbI ₂ (0.85 g) prepared in the above step 2 were dissolved in dimethylformamide. The mixture was stirred at 110 DEG C for 1 hour, and then nitrogen was added thereto to remove the solvent. Thus, the title compound was prepared. XRD data of the prepared compound is shown in Fig.

Comparative Example : CH ₃ NH ₃ PbI ₃ of  Produce

A 40 wt% GBL solution was prepared by adding CH ₃ NH ₃ I (methylammonium iodide) and PbI ₂ (lead (II) iodide) at a molar ratio of 1.2: 1 to GBL (gamma-butyrolactone) at 60 ° C. The solution was slowly dried at 110 ° C to remove the solvent and the resulting crystals were washed with cold GBL, ether and GBL mixture (ether: GBL = 3: 1 (v / v)) and ether, Organic hybrid perovskite compound having the formula CH ₃ NH ₃ PbI ₃ was prepared. XRD data of the prepared compound is shown in Fig.

Experimental Example

A 25 × 25 mm FTO substrate was used and the end was etched to partially remove the FTO. TiO ₂ was used as the N-type material. A solution of 0.1 M titanium diisopropoxide bis (acetylacetonate) diluted in 1-butanol was coated at a thickness of 40 nm at 700 rpm for 10 s and at 2000 rpm for 60 s, followed by sintering at 500 ° C for 15 minutes.

The compound prepared in Examples and Comparative Examples was formed into a light absorbing layer, and was prepared as follows. First, in a comparative example, CH ₃ NH ₃ I (methylammonium iodide) and PbI ₂ (lead (II) iodide) were added at a molar ratio of 1.2: 1 to GBL (gamma-butyrolactone) % Of GBL solution was prepared. In the case of the examples, a 40 wt.% Solution of DMF was prepared by adding the compound prepared in Example at 80 DEG C to dimethylformamide in an inert condition. Each of the solutions thus prepared was coated at 500 rpm for 5 s, 1000 rpm for 40 s, and 5000 rpm for 30 s, and dried on a hot plate at 100 ° C. for 10 minutes to prepare a light absorbing layer including each of Examples and Comparative Examples .

A chlorobenzene solution in which Spiro-OMeTAD was dissolved was spin coated on the light absorption layer at 6000 rpm for 30 seconds to prepare a hole transport layer. The electrode was formed by vacuum deposition of Au with a thermal evaporator.

The performance of the solar cell was measured using each of the solar cells prepared above. The results are shown in Table 1 and FIG. 2 below. Table 1 below shows the measurement results at the time of initial measurement, and Fig. 2 shows the power generation efficiency measured over time.

Short circuit current density
(mA / cm ² ) Open-circuit voltage (V) Performance Index (%) Power generation efficiency (%) Example 14.42 1.042 74.25 11.2 Comparative Example 17.77 1.093 73.71 14.3

As shown in Table 1 and FIG. 2, in the case of the comparative example, it was confirmed that the power generation efficiency was drastically decreased with time after the first measurement, while the power generation efficiency was maintained at a high value for a long time in the embodiment.

Claims (9)

A compound represented by the following formula (1):
[Chemical Formula 1]
AMX ₃
In Formula 1,
A is an organic cation of R ₁ R ₂ R ₃ R ₄ N ⁺
Wherein, R _1, R _2, R ₃ and R ₄ is hydrogen, C _1-10 alkyl, or _{CH 2 = CH-COO- (C} 1-10 alkylene), each independently, provided that R _1, R _2, At least one of R ₃ and R ₄ is CH ₂ ═CH-COO- (C _1-10 alkylene)
M is a divalent metal cation,
X is the same or different halogen.
The method according to claim 1,
R ₁ is CH ₂ ═CH-COO- (C _1-10 alkylene)
R ₂ , R ₃ and R ₄ are each independently hydrogen or C _1-10 alkyl.
compound.
The method according to claim 1,
R ₁ is CH ₂ ═CH-COO- (C _1-10 alkylene)
R ₂ and R ₃ are each independently C _1-10 alkyl,
R < ₄ > is hydrogen.
compound.
The method according to claim 1,
R _1, R _2, R ₃ and R ₄ are each independently hydrogen, methyl, or _{CH 2 = CH-COO-CH} 2 -CH 2 - and, provided that R _1, R _2, R ₃ and R ₄ are at least one of And one is CH ₂ = CH-COO-CH ₂ -CH ₂ -.
compound.
The method according to claim 1,
M is ^{Pb 2 +, Sn 2 +,} Pd 2 +, Cu 2 +, Ge 2 +, Sr 2 +, Cd 2 +, Ca 2 +, Ni 2 +, Mn 2 +, Fe 2 +, Co 2 +, Sn ^2+, Yb ^{2 +,} or characterized in that the Eu ^{2 +,}
compound.
The method according to claim 1,
Each X is independently, Cl ^-, Br ^-, or I ^- in that, characterized in,
compound.
The method according to claim 1,
Wherein the compound is CH ₂ ═CH-COO-CH ₂ -CH ₂ -N (CH ₃ ) ₂ HPbI ₃ .
compound.
8. A solar cell comprising a compound of any one of claims 1 to 7.
9. The method of claim 8,
The solar cell has the following structure: a solar cell:
A first electrode comprising a conductive transparent substrate;
An electron transport layer formed on the first electrode;
A light absorbing layer formed on the electron transporting layer and comprising a compound represented by Formula 1;
A hole transport layer formed on the light absorption layer; And
And a second electrode formed on the hole transport layer.

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