KR20120121305A - Novel polyalkylviologen compound and Organic solar cells using the same - Google Patents

Abstract

PURPOSE: A polyalkylviologen-based compound is provided to have excellent electron insertion and transport performance and to have strong solvent resistance to organic solvent after coating, thereby capable of embodying an organic solar cell battery of a laminated type. CONSTITUTION: A polyalkylviologen-based compound is used for a water-soluble polymer interlayer material represented by chemical formula 1. In chemical formula 1, R is (CH2)x, or R is CH2CH2OCH2CH2, CH2CH2OCH2CH2OCH2CH2, or C4-12 linear alkyl group or ethylene oxide wherein x is 4, 6, 8, 10 or 12, and X is Br-, BF4-, PF6- or -phenylsulfonate anion. The number average molecular weight of the polyalkylviologen-based compound is 6,000-20,000.

Description

Novel polyalkylviologen compound and organic solar cells using the same

The present invention relates to a novel polyalkylbiologen-based compound and an organic solar cell device, and more particularly, the novel polyalkylbiologen-based compound is used as an interlayer material of an organic solar cell device because of its excellent electron transfer ability. The present invention relates to a novel polyalkylbiologen compound and an organic solar cell device using the same.

Conjugated polymers have been applied to light emitting devices, photoelectric conversion devices or thin film transistors because of their inherent optical and electrochemical properties. Π-π ^* transitions of aromatic or cyclic conjugated polymers generally exhibit absorption between 200 nm and 600 nm, and as the length of the conjugate increases, the band gap decreases, causing the absorption band to shift to longer wavelengths (red -shift) phenomenon. Using such a red-shift phenomenon, research on the electron donor polymer material of the organic solar cell having a small band gap has been actively conducted. The electron donor material mainly used in the bulk hetero-junction (BHJ) structure, which is the structure of the most common organic solar cell, has a large absorption area band and has a high overlap with solar energy. Fullerene (C ₆₀ ) based derivatives. An electron donor material is a hole mobility of the excellent PPV [poly (p -phenylenevinylene)] derivatives with electron acceptor material is C ₆₀ derivative _{PC 61 BM [(6,6) -phenyl} -C 61 -butyric acid methyl ester] Or a study using PC ₇₁ BM [(6,6) -phenyl-C ₇₁ -butyric acid methyl ester], a C ₇₀ derivative. In 1995, the AJ Heeger Group published a study on solar cells using CN-PPV with cyano groups. Sariciftci Group announced in 2001 an organic solar cell blending MDMO-PPV [poly [2-methyl-5- (3,7-dimethyloctyloxy) -p- phenylenevinylene]] with PC ₇₁ BM. [7] Research on solar cells using POPT [poly [3- (4-octylphenyl) -thiophene], a derivative based on MEH-PPV and thiophene as an electron donor, has been reported. In 2005, UCLA's Yang Group announced an efficiency of 4.4% for organic solar cells with BHJ structure (ITO / PEDOT: PSS / P3HT: PCBM / Al). In Korea, Kwang-Hee Lee's team presented the world-class research results of tandem type solar cell efficiency and V _oc of 6.6% and 1.24V, respectively, in collaboration with AJ Heeger Group. In 2009, UCLA's Yang group and Solarmer Energy jointly researched 1- (4,6-dibromothieno [3,4-b] thiophen-2-yl-2-ethylhexan-1-one [1- (4,6-dibromothieno [3,4-b] thiophen-2-yl) -2-ethylhexan-1-one] and 2,6-bistrimethyltin-4,8-didodecyloxy-benzo [1,2-b; 3,4-b] dithiophene [2,6-bis (trimethyltin) -4,8-didodecyloxy-benzo [1,2-b; 3,4-b; 4-b] dithiophene ] Of the BHJ type structure (ITO / PEDOT: PSS / PBDTTT-C: PC ₇₁ BM / Ca / Al) produced by alternating copolymerization of PBDTTT-C as an electron donor and blending PC ₇₁ BM with an electron acceptor In spite of the cell structure, not the tandem structure, the research results showed a high efficiency of 6.58%.

Recently, many research results have been published on organic solar cell research using water-soluble polymers. The general electron donor polymer and PCBM induction used in the manufacture of solar cells are very soluble in organic solvents (chloroform, chlorobenzene, dichlorobenzene, toluene, etc.) while insoluble in water or protic solvent alcohol and water. Therefore, the water-soluble polymer may be said to be a very suitable material as an interlayer material of a solar cell having a multilayer structure. Therefore, when water-soluble polymer is used as an interlayer material, ITO (electron collection electrode) as well as conventional type solar cell using ITO (Indium Tin Oxide) as a hole collection electrode and a metal electrode having a low work function as an electron collection electrode In addition, the present invention can be applied to an inverted type solar cell using a metal electrode having a high work function as the hole collection electrode. Inverted solar cells are more stable than the full-structure solar cells, and have a variety of device structure designs. Recently, research results on solar cells based on polyethylene glycol, water-soluble polyfluorene, a conjugated polymer, and ZnO, an inorganic semiconductor, have been published, and efficiency and stability are also very high. However, the solar cell using water-soluble polyfluorene is very efficient, but the synthesis process of the material is very complicated, mass production is very difficult, and it is very difficult to secure the reproducibility of the synthesized polymer properties.

The present invention is a water-soluble polymer that is a polyalkylbiologen-based compound having excellent electron transport ability to overcome the disadvantage that the synthesis of water-soluble polyfluorene-based compound is very difficult to solve the above problems, very high An object of the present invention is to provide a novel polyalkylbiologen-based compound having a Lumo energy level and excellent electron injection and transfer ability.

In another aspect, the present invention is to provide an organic solar cell device, characterized in that to improve the performance of the organic solar cell by using the polyalkylbiologen-based compound prepared above as an interlayer material of the organic solar cell device.

The present invention for solving the above problems is a polyalkylbiologen compound used in the water-soluble polymer interlayer material for an organic solar cell represented by the formula (1) as a means for solving the problem.

(Formula 1)

In the above,

R = (CH ₂ ) x, x = 4, 6, 8, 10, 12

Or R = CH ₂ CH ₂ OCH ₂ CH ₂

Or R = CH ₂ CH ₂ OCH ₂ CH ₂ OCH ₂ CH ₂

Or R is a straight chain alkyl group or ethylene oxide having 4 to 12 carbon atoms.

X = Br-, BF _4- , PF _6- , or

The polyalkylbiologen-based compound preferably has a number average molecular weight of 6,000 to 20,000.

And the present invention is a structure in which the organic solar cell device comprises an ITO / electron transport layer / active layer / hole transport layer / metal electrode,

The electron transport layer is an organic solar cell device characterized in that the polyalkylbiologen-based compound represented by the following formula (1) as an interlayer material as another means for solving the problem.

The present invention is a water-soluble polymer material, which is a polyaltyl viologen compound used as an interlayer material of an organic solar cell device, has excellent electron injection and transport ability, and has a very strong solvent resistance to an organic solvent after coating, thus forming a stacked organic solar cell. It is an advantage that the device can be implemented. In addition, the inverse structure of the solar cell device using the polyviologen-based water-soluble polymer according to the present invention has a similar efficiency to the solar cell device of the previous structure, which shows a strong acid which is the most problematic in general organic solar cells PEDOT: has the advantage of eliminating materials such as PSS.

1 is a schematic diagram of an inverted type solar cell (invert type solar cell) according to an embodiment of the present invention.
2 is a ¹ H-NMR spectrum graph of polybutylviologen dibromide (polybutylviologen dibromide, hereinafter referred to as 'PVB4') according to the present invention.
Figure 3 is a ¹ H-NMR spectrum graph of polydodecylviologen dibromide (polyvindecylviologen dibromide, 'PVB12') according to the present invention.
4 is a graph of the TGA temperature recording of Example 1 PVB4 and Example 2 PVB12 according to the present invention.
5 is a graph of UV-Vis absorption spectra of Example 1 PVB4 and Example 2 PVB12 according to the present invention.
6 is a graph of the cyclic voltammogram curves of PVB4 of Example 1 and PVB12 of Example 2 according to the present invention;
7 is a voltage-current characteristic curve graph of the solar cell device using PVB4 of Example 3 according to the present invention.
8 is a voltage-current characteristic curve graph of a solar cell device using PVB12 of Example 4 according to the present invention.

Hereinafter, with reference to the accompanying drawings, preferred embodiments of the present invention will be described in detail with reference to Figures 1 to 8, on the other hand, those skilled in the general polymer synthesis or organic solar cell device in the drawings and detailed description Illustrations and references to constructions and acts that are readily apparent are briefly or omitted.

The present invention relates to a novel polyalkylbiologen-based compound represented by the following formula (1) and an organic solar cell device using the same, and the novel polyalkylbiologen-based compound has a very good electron transfer ability, so it is an interlayer material of an organic solar cell. It is characterized by improving the performance of the organic solar cell using.

(Formula 1)

In the above,

R = (CH ₂ ) x, x = 4, 6, 8, 10, 12

Or R = CH ₂ CH ₂ OCH ₂ CH ₂

Or R = CH ₂ CH ₂ OCH ₂ CH ₂ OCH ₂ CH ₂

Or R is a straight chain alkyl group or ethylene oxide having 4 to 12 carbon atoms.

X = Br-, BF _4- , PF _6- , or

In addition, the polyalkylbiologen-based compound according to the present invention preferably has a number average molecular weight of 6,000 to 20,000. If the number average molecular weight of the polyalkylbiologen-based compound is less than 6,000, it is difficult to form a good thin film, and if it exceeds 20,000, the solubility in the solvent may be low.

Hereinafter, a method for preparing a novel polyalkylbiologen-based compound represented by Chemical Formula 1 according to the present invention will be described in detail.

The present invention is equivalent to dibromoalkane monomer equivalent to 4,4'-bipyridyl monomer, N, N, -dimethylformamide (N, N, -dimethylformamide) It is prepared by dissolving in a solvent and then reacting for 10-12 hours at a temperature of 110-130 ° C. while stirring.

The reaction solution reacted with stirring at a temperature of 110 ~ 130 ℃ in the above starts to form a yellow solid from about 2 hours after heating. After further stirring for about 10 hours, the reaction solution is cooled to room temperature. The yellow solid formed was filtered and then washed with a pure hexane solvent, washed and dried at room temperature for 24 hours at reduced pressure to prepare a novel polyalkylbiologen compound.

In the present invention, the amount of 4,4'-bipyridyl monomer and dibromoalkane monomer added to the solvent to react is 4,4'-bipyridyl (4,4). Preference is given to adding an equivalent of dibromoalkane monomer equivalent to an equivalent of -bipyridyl monomer.

In the present invention, when the 4,4'-bipyridyl (4,4, -bipyridyl) monomer and the dibromo alkane monomer is dissolved in the DMF solvent and reacted to prepare a water-soluble polymer that is a polyalkylbiologen-based compound as shown in Scheme 1 below. It is done.

(Scheme 1)

In the present invention, the reaction conditions are reacted for 10 to 12 hours at 110 ~ 130 ℃, when the reaction conditions are less than the above-defined range, the reaction rate is slow or the yield of the polyalkylbiologen-based compound may be lowered There is.

In addition, the polyalkylbiologen-based compound of the yellow solid produced through the reaction of Chemical Formula 1 is non-polar and is preferably washed with a solvent such as hexane and diethyl ether having a low boiling point.

As described above, the polyalkylbiologen-based compound according to the present invention is a water-soluble polymer material prepared by one step of polymerization, and has a high yield and very easy mass production. In addition, the synthesized polymer has a very high lumo energy level, which is excellent in electron injection and transfer ability, and has a strong solvent resistance to an organic solvent after coating, so that a stacked solar cell device can be implemented.

On the other hand, the organic solar cell device using a novel polyalkylbiologen-based compound according to the present invention is divided into a solar cell device (normal type solar cell) and inverted structure of the solar cell device (inveted solar cells) In detail, the inverse structure of the solar cell device is as follows.

As an embodiment according to the present invention, an inverted type solar cell is an ITO 20 / electron transport layer 30 / active layer 40 / on a substrate 10, as shown in FIG. 1. The hole transport layer 50 / the metal electrode 60 is a structure including.

The organic solar cell device according to the present invention having the structure as described above has a very high lumo energy level by using a polyviologen-based compound having the structure of Chemical Formula 1 as the electron transport layer 30, and thus has excellent electron injection and transfer. Have the ability. In addition, the polyviologen-based compound having a very thin film serves to increase the work function of the ITO electrode by the arrangement of the dipoles between the thin films, and thus has excellent electron injection and transfer capability.

In addition, in the organic solar cell device according to the present invention, the substrate 10, the ITO 20, the electron transport layer 30, the active layer 40 and the hole transport layer 50 and the metal electrode 60 formed on the active layer 40 Is the same material as that used in a conventional organic solar cell device, and the substrate 10 mainly uses glass or a special plastic, and the ITO 20 has a good light permeability as an anode and a hole. Indium Tin Oxide (Indium Tin Oxide) is used to receive well, the hole transport layer 50 is a layer for transferring holes generated in the active layer 30 to the indium tin oxide electrode, and mainly PEDOT, and The active layer 40 is composed of a mixture of P3HT (poly (3-hexylthiophene)) and PCBM ([6,6] -phenyl-C ₆₁ -butyric acid methyl ether), which are commonly used in organic solar cells. When light is absorbed, paired electrons in the active layer material are excited As it is), the holes and electrons separated by the active material are moved by the internal diffusion potential, so that the holes move to the anode and the electrons move to the cathode, and current flows to the outside. In the present invention, the hole transport layer 50 used tungsten oxide (WO3) instead of PEDOT having many disadvantages corresponding to the following description.

In the present invention, the metal electrode 60 is preferably selected from one or more selected from Ag, Ca, Al, Cu, Au, Ca / Ag.

As described above, the organic solar cell device according to the present invention has a very high lumo energy level by using a polybiologen-based compound having the structure of Chemical Formula 1 in the electron transport layer 30, and thus has excellent electron injection and transfer ability. It is possible to exclude materials such as PEDOT: PSS [(Poly (3,4-ethylenedioxythiophene)) :( poly (p-styrenesulfonate))], which shows strong acidity, which is the most problematic in general solar cells. The water-soluble polymer material of the rhogen-based compound has a very strong solvent resistance to the organic solvent after coating, so that the solar cell device in a laminated form can be realized.

Hereinafter, the polyalkylbiologen-based compound and the organic solar cell using the same according to the present invention will be described in detail with reference to the following examples, but the present invention is not necessarily limited to the following examples.

1. Preparation of polyalkylbiologen compounds

(Example 1)

10 mL of DMF was added to the flask, and 1 mmol of 4,4'-bipyridyl and 1 mmol of dibromobutane were added thereto to dissolve, followed by stirring at a temperature of 120 ° C. After about 2 hours a yellow solid begins to form. After further stirring for about 10 hours, the reaction solution is cooled to room temperature. The yellow solid formed was filtered using a paper filter and washed with 5 ml of pure DMF. And again washed with 20 ml of diethyl ether and then dried at room temperature, vacuum oven for 24 hours at reduced pressure to prepare a polybutylviologen dibromide (polybutylviologen dibromide, PVB4 ) compound having a number average molecular weight of 8,000 ~ 10,000.

¹ H-NMR of the PVB4 (400 MHz, CDCl3) δ 9.1 ~ 9.2 (br, 2H, Ar-H), 8.5 ~ 8.6 (br, 2H, Ar-H), 4.35 ~ 4.45 (br, 4H, CH2 ), 2.1 to 2.2 (br, 4H, CH 2).

(Example 2)

Put 10 mL of DMF into the flask, add 1 mmol of 4,4'-bipyridyl and 1.0 mmol of dibromo dodecane to dissolve it, and then stir at a temperature of 120 ° C. Let's do it. After about 2 hours a yellow solid begins to form. After further stirring for about 10 hours, the reaction solution is cooled to room temperature. The yellow solid formed was filtered using a paper filter and washed with 5 ml of pure DMF. And again washed with 20 ml of diethyl ether and then dried at room temperature, vacuum oven for 24 hours at reduced pressure to prepare a polydodecylviologen dibromide (polydodecylviologen dibromide, PVB12 ) compound having a number average molecular weight of 8,000 ~ 10,000.

¹ H-NMR of the PVB12 is (400 MHz, CDCl3) δ 9.1 ~ 9.2 (br, 2H, Ar-H), 8.5 ~ 8.6 (br, 2H, Ar-H), 4.35 ~ 4.45 (br, 4H, CH2 ), 2.0-2.1 (br, 4H, CH2), 1.1-1.4 (br, 16H, CH2).

2 and 3, which are attached to the present invention, show ¹ H-NMR spectra of PVB4 of Example 1 and PVB12 of Example 2, respectively.

And the thermogravimetric analysis (TGA) record shown in Figure 4 PVB4 and PVB12 showed a 5% weight loss at 290 ℃ and 270 ℃, respectively. Therefore, it can be seen that the water-soluble polymers are very stable at 150 ° C., which is a heat treatment temperature in a general solar cell manufacturing process.

And, FIG. 5 shows peaks in absorption at 400 nm or less, as shown in the absorption spectra of PVB4 and PVB12. The bandgap of each material, obtained from the edge of absorption, is 3.2 and 4.1 eV, respectively. 6 is a cyclic voltammetry curve of PVB4 and PVB12, in which both PVB4 and PVB12 cause a reduction reaction at a very high potential electrochemically and the Lumo energy level obtained from the electrochemically reduced peak is -4.27 eV and PVB12 in the case of PVB4. Has a very low Lumo energy level of -3.83 eV, which is very similar to the work function of ITO (-4.7 eV) and Al (-4.2 eV), making it very suitable as an electron transport material. .

2. Fabrication of Organic Solar Cell Device

(Example 3)

The organic solar cell device manufactured using PVB4, which is a sample of Example 1, was composed of GLASS (0.5 mm) / ITO (15 ohm / sq) / PVB4 (5 nm) / P3HT: PCBM (150 nm) / WO 3 (15 nm). ) / Ag (100 nm). In the above, P3HT: PCBM means an active layer and serves to convert the irradiated solar energy into electrical energy. The active layer is 15 mg of polythiophene (Rieke Metal Co.) and 15 mg of PCBM (nano-C) to 1 mL of dichlorobenzene and dissolved in a nitrogen atmosphere for 12 hours at 40 ℃. Clean ITO glass in order of ultrapure water (18 MΩcm ^-1 ), methanol, acetone and isopropyl alcohol. Ultrapure water = 2: 1, volume ratio) and dissolved in a concentration of 1 mg / mL and spin-coated at 2000 rpm. Heat treatment at 110 ℃ for 10 minutes to completely remove the solvent remaining in the thin film. The thickness of the thin film thus formed is about 5 nm. The active layer solution prepared above on the polybutylbiologen thin film was filtered through a 0.45 μm syringe filter and spin-coated at 600 rpm. After spin coating the active layer, cover it with Petri dishes and dry the active layer at room temperature for 30 minutes. The thin film thus formed has a thickness of about 150 nm. The thin film is dried and then transferred to a vacuum evaporator and then WO ³ is deposited to a thickness of 15 nm at a rate of 0.1 nm / s at 2 × 10 −6 torr. Thereafter, Ag was deposited to a thickness of 100 nm at a rate of 0.3 to 0.5 nm / s at the same pressure to fabricate an organic solar cell device. The area of the fabricated device is 12-13 mm ² .

(Example 4)

The organic solar cell device fabricated using the PVB12 sample of Example 2 is GLASS (0.5 mm) / ITO (15 ohm / sq) / PVB12 (5 nm) / P3HT: PCB (150 nm) / WO3 (15 nm ) / Ag (100 nm). In the above, P3HT: PCBM means an active layer and serves to convert the irradiated solar energy into electrical energy. In addition, the active layer was fabricated an organic solar cell device formed by the same method as in Example 3.

The device fabricated by the method of Example 3 and Example 4 was heat-treated at 140 ° C. for 10 minutes under a nitrogen atmosphere, and then the characteristics of the solar cell were evaluated. The light source used for the characteristics evaluation was equipped with a 150 W Xe lamp, a filter capable of matching AM 1.5G at the entrance of the tube, and a KG5 filter to adjust the intensity of the light source to 1.0 sun (100 mW / cm ² ). Standard Si solar cells were used.

In the present invention, Figure 7 is a voltage-current curve when the light of AM 1.5G, 1 sun conditions to the solar cell device based on PVB4, Figure 8 is AM 1.5 in the solar cell device based on PVB12 This is the voltage-current curve when G, 1 sun light is emitted. The average efficiency of the solar cell using PVB4 is 2,46%, the open voltage is 0.55 V, and the filling factor is 58.1%. The average efficiency of the solar cell using PVB12 is 2.38%, The open voltage was 0.55 V and the filling factor was 46.3%. The result is 2.7%, which is the efficiency of GLASS (0.5 mm) / ITO (15 ohm / sq) / PEDOT (40 nm) / P3HT: PCBM (150 nm) / Al (100 nm). It has the performance similar to the open voltage of 0.56V, the filling factor of 59.9%, and has the advantage of manufacturing a solar cell device excluding the PEDOT having the disadvantage of having a strong acid.

In the present invention, the average efficiency of the organic solar cell device of ITO / PEDOT: PSS (40 nm) / P3HT: PCBM (150 nm) / Al (100 nm), which is the whole structure manufactured by the control of Examples 3 and 4, was 2.67%, the open voltage was 0.57 V, and the filling factor was 57.7%, which showed no significant difference from the characteristics of the inverted device using PVB4 or PVB12.

Therefore, it can be seen that the water-soluble polyviologen in the present invention has very excellent electron transfer ability, and when using this, there is an advantage in that a solar cell excluding PEDOT: PSS having strong acidity can be manufactured.

As described above, a novel polyalkylbiologen-based compound and an organic solar cell device using the same according to a preferred embodiment of the present invention are shown in accordance with the above description and drawings, but this is merely described by way of example and the present invention. Those skilled in the art will appreciate that various changes and modifications can be made without departing from the spirit of the invention.

10: substrate 20: ITO
30: electron transport layer 40: active layer (P3HT: PCBB)
50: hole transport layer 60: metal electrode

Claims (3)

Polyalkylbiologen compounds used in the water-soluble polymer interlayer material for an organic solar cell represented by the formula (1).

(Formula 1)

In the above,
R = (CH ₂ ) x, x = 4, 6, 8, 10, 12
Or R = CH ₂ CH ₂ OCH ₂ CH ₂
Or R = CH ₂ CH ₂ OCH ₂ CH ₂ OCH ₂ CH ₂
Or R is a straight chain alkyl group or ethylene oxide having 4 to 12 carbon atoms.
X = Br-, BF _4- , PF _6- , or

The method of claim 1,
The polyalkylbiologen-based compound is a polyalkylbiologen-based compound, characterized in that the number average molecular weight of 6,000 ~ 20,000.
The organic solar cell device has a structure including ITO / electron transport layer / active layer / hole transport layer / metal electrode,
The electron transport layer is an organic solar cell device, characterized in that the polyalkylbiologen-based compound represented by the following formula (1) as an interlayer material.
(Formula 1)

In the above,
R = (CH ₂ ) x, x = 4, 6, 8, 10, 12
Or R = CH ₂ CH ₂ OCH ₂ CH ₂
Or R = CH ₂ CH ₂ OCH ₂ CH ₂ OCH ₂ CH ₂
Or R is a straight chain alkyl group or ethylene oxide having 4 to 12 carbon atoms.
X = Br-, BF _4- , PF _6- , or

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