KR20110117972A - An organic-inorganic nanocomposite, a method for preparing the same and a solar cell comprising the same - Google Patents

Abstract

The present invention is an organic-inorganic nanocomposite comprising an organic polymer and an inorganic nanostructure (nanostructure), the organic polymer is a conductive polymer containing an amine group, the inorganic nanostructure is bonded to the amine group of the conductive polymer, the conductive The present invention relates to an organic-inorganic nanocomposite having a continuous phase channel formed between a polymer and an inorganic nanostructure, a method for preparing the same, and a solar cell including the same.
In the organic-inorganic nanocomposite according to the present invention, a continuous channel is formed between the conductive polymer and the inorganic nanostructure, so that the electron and the hole can be efficiently separated by the wide junction interface, and the conductive polymer and the inorganic nanostructure Each of them is regularly aligned so that the conductivity of electrons and holes can be greatly improved. When the organic-inorganic nanocomposite according to the present invention is applied to a solar cell, a solar cell having physical stability and excellent light conversion efficiency can be expected.

Description

Organic-inorganic nanocomposite, method for preparing the same, and solar cell comprising same {An Organic-Inorganic Nanocomposite, A Method for Preparing the Same and A Solar Cell Comprising the Same}

The present invention relates to an organic-inorganic nanocomposite comprising a conductive polymer / nanostructure, and more particularly, to a nanocomposite in which a continuous phase channel is formed between a conductive polymer and an inorganic nanostructure, a manufacturing method thereof, and a solar cell including the same. will be.

Recently, as the social demand for the development of renewable energy technology increases, the industry and academia are showing great interest in the solar cell technology that converts light into electricity, and the solar cell using an inorganic semiconductor such as silicon It has been developed and is currently used for solar power generation.

However, there is a great difficulty in responding to global energy demand due to high solar cell manufacturing cost. Accordingly, interest in development of organic or organic / inorganic composite solar cells using conductive polymers, which require low-cost process cost, has recently increased.

In order to realize high photovoltaic conversion efficiency in organic or organic / inorganic hybrid solar cells, factors such as light absorption, exciton separation, and charge transfer must be optimized. Currently, the highest photoelectric conversion efficiency among solar cells using a conductive polymer is a bulk heterogeneous layer having an active layer blended with a conductive polymer and semiconductor nanostructures such as fullerene, quantum dots, nanorods and nanowires. Bulk heterojunction (BHJ) solar cells with up to 5% photoelectric conversion efficiency.

Nevertheless, BHJ solar cells have three major disadvantages.

First, organic solar cells using a conductive polymer are generally manufactured by spin coating, and the interface area of the conductive polymer donor / nano structure acceptor is non-uniform and thermodynamically unstable, and thus difficult to control.

Second, macrophase separation between the polymer and the nanostructure in the active layer during the fabrication process or during long periods of operation of the solar cell causes the interfacial region to be larger than the exciton diffusion length of the conductive polymer (about 10 nm). As a result, the efficiency of the solar cell is greatly reduced.

Third, when manufacturing a BHJ solar cell using a polymer and an inorganic nanostructure, the ligand (ligand), which is an insulating layer attached to the surface of the nanostructure, must be removed when the inorganic nanostructure is synthesized. In this case, the oxidation of the semiconductor nanostructure and the deterioration of physical properties occur during the ligand removal process.

Therefore, it is necessary to overcome the above shortcomings and to develop new technology to obtain high photoelectric conversion efficiency in organic or organic / inorganic hybrid solar cells.

Therefore, the inventors of the present application can have a wide interface between the conductive polymer donor / nanostructure acceptor and can form a channel without conducting phase separation between the conductive polymer and the nanostructure, and excellent efficiency including the same. To provide a solar cell. In addition, the present invention provides a method for manufacturing an organic-inorganic nanocomposite suitable for manufacturing a solar cell with excellent efficiency without a process of separately removing a ligand, which is an insulating layer attached to the surface of the nanostructure.

One embodiment according to the present invention is an organic-inorganic nanocomposite including an organic polymer and an inorganic nanostructure, wherein the organic polymer is a conductive polymer including an amine group, and the inorganic nanostructure is an amine group of a conductive polymer. Combined, the conductive polymer and the inorganic nanostructures relate to organic-inorganic nanocomposites in which channels in a continuous phase are formed.

One embodiment according to the present invention comprises the steps of synthesizing a conductive polymer comprising an amine group; Synthesizing inorganic nanostructures; And blending the synthesized polymer with an inorganic nanostructure in a solvent to form a continuous phase channel.

One embodiment according to the present invention is a first electrode; A second electrode; And an organic-inorganic nanocomposite as an active layer between the first electrode and the second electrode.

The organic-inorganic nanocomposite according to the present invention has a structure that is not significantly affected by the deposition process, and is thermodynamically stable. In addition, a continuous channel is formed between the conductive polymer donor / inorganic nanostructure acceptor to have a wide junction interface, so that electrons and holes are efficiently separated, and each of the conductive polymer and inorganic nanostructures is regularly aligned, The conductivity can be greatly improved. When the organic-inorganic nanocomposite according to the present invention is applied to a solar cell, a solar cell having physical stability and excellent light conversion efficiency can be expected.

Figure 1 shows the results of the analysis of the structure of the polymerized conductive polymer by ¹ H NMR;
FIG. 2 shows high-resolution transmission electron microscopy (HRTEM) images of synthesized about 2.7 nm sized CdSe quantum dots (a) and about 5 nm sized CdSe quantum dots (b);
Figure 3 shows a transmission electron microscopy (TEM) image of the nanocomposite according to an embodiment of the present invention;
4 is a graph comparing absorbance measurement results of CdSe quantum dots and nanocomposites;
5 is a TEM analysis result for confirming whether a nanocomposite has a pn diode junction according to an embodiment of the present invention; And
Figure 6 shows the results of the PL (photoluminesecence) measurement experiment for the nanocomposite according to an embodiment of the present invention.

The organic-inorganic nanocomposite according to the present invention includes a conductive polymer including an amine group as an organic polymer.

In one embodiment, the conductive polymer may include any type of polymer as long as it contains an amine group, but may be, for example, a block copolymer including a polymer containing an amine compound as a repeating unit as one block. .

The block copolymer is, for example, polymethacrylate having primary to tertiary amines in the side chain, polyacrylate having primary to tertiary amines in the side chain, and primary to tertiary in the side chain. Polystyrenes with amines, polymethacryl amides with primary to tertiary amines in the side chain, polyacryl amides with primary to tertiary amines in the side chain, aromatic amine-based polystyrene One or more selected from the group consisting of polyvinylpyridine, polyvinylpyrrolidone, and polyvinyloxazoline as a block, polyhexylthiophene (poly (3-hexylthiophene)), At least one selected from the group consisting of polyfluorene, polyparaphenylin (PPP), polyparaphenylinvinylene (PPV), polypyrrole (PPy) and polyaniline (PANI); It may comprise a different block.

The conductive polymer may be a structure controlled self-assembled polymer including nano-domains of 10 to 40 nm, and when using a self-assembled polymer having an ordered structure to form nano domains between nanostructures, the nano Continuous phase channels can be formed without phase separation from the structure.

The organic-inorganic nanocomposites according to the present invention also include inorganic nanostructures bonded to amine groups of conductive polymers.

In the organic-inorganic nanocomposite according to the present invention, since the amine group and the inorganic nanostructure of the conductive polymer are bonded by chemical coordination bonds, the insulating layer formed on the surface is generally substituted by the amine group after the inorganic nanostructure is synthesized, It was confirmed that it can be removed from the nanostructure surface.

The inorganic nanostructure may be, for example, one or more quantum dots, nanorods, tetrapods, nanowires, or the like selected from the group consisting of Group II-VI, Group IV-VI, Group IV semiconductors and metal oxides. It may be a multi-branched nanostructure. For example, the group II-VI semiconductor may be CdSe, the group IV-VI semiconductor may be PbSe, the group IV semiconductor may be Si, and the metal oxide may be, for example, ZnO or TiO ₂ .

At this time, the size of the nanostructures may be 1 to 100 nm, preferably 1 to 50 nm, any size nanostructures falling within the above range can be used. When the size of the nanostructure is greater than 100 nm, when the organic-inorganic nanocomposite including the same is applied to a solar cell or the like, since the optimal light absorption layer thickness generally used in the organic-inorganic composite solar cell is 100 to 200 nm, There is a problem in that a short circuit occurs between both electrodes or the donor / acceptor interface is significantly reduced in the nanocomposite.

The present invention is also characterized in that a continuous channel is formed between the conductive polymer and the inorganic nanostructures bonded thereto.

Conventionally, nanostructures are formed by blending nanostructures with general conductive polymers such as polyhexylthiophene (P3HT), but the polymers and nanostructures included in these nanocomposites are random in arrangement, and thus, the nanostructures are easily aggregated. . As a result, phase separation occurs, thereby reducing the conductive interface between the conductive polymer and the nanostructure, and when applied to the solar cell, it is difficult to efficiently separate excitons and difficult to conduct free electrons and holes to the electrode even when separated.

However, the present invention includes a conductive polymer including an amine group and an inorganic nanostructure bonded thereto, whereby the conductive polymer donor and the inorganic nanostructure acceptor are regularly arranged to form a continuous channel, and thus, the continuous electron / hole channel is formed. Can be formed. Through this, the organic-inorganic nanocomposite according to the present invention has a conductive polymer donor- in which the conductive polymer and the inorganic nanostructure are arranged in a nano-domain of 10 nm or less by a self-assembly method. It was confirmed that the nanostructure acceptor may have a pn diode junction.

In this case, the weight ratio of the conductive polymer and the inorganic nanostructure in the nanocomposite may be, for example, 10: 1 to 1:10, specifically 1: 1 to 10. The weight ratio of the conductive polymer and the inorganic nanostructure may be effectively applied to the present invention in any ratio included in the above weight ratio range, and even if the content of the conductive polymer is small, sufficient channel formation in the continuous phase is possible.

The present invention also comprises the steps of synthesizing a conductive polymer comprising an amine group; Synthesizing inorganic nanostructures; And blending the synthesized polymer and the inorganic nanostructure in a solvent to form a channel in a continuous phase.

In general, when preparing organic-inorganic nanocomposites by synthesizing nanostructures, a process of removing an organic molecular layer (ligand), which is an insulating layer on the surface of nanostructures, is required. However, this process is very complicated, causing oxidation of the nanostructure, and thus there is a problem that the physical properties are lowered.

However, the manufacturing method of the organic-inorganic nanocomposite according to the present invention is that the insulating layer on the surface of the nanostructure is replaced by the amine group of the conductive polymer, so that a separate process of removing the insulating layer and annealing of the nanocomposite are required. Not. Therefore, the nanocomposite production efficiency is excellent, and the nanocomposite in which the desired channel is formed can be manufactured without fear of oxidation and physical property degradation of the nanostructure.

The configuration, structure, and properties of the conductive polymer and the inorganic nanostructures used in each step included in the method of manufacturing a nanocomposite according to the present invention are as described above. As the solvent used in the blending step, a conventional organic solvent may be used. For example, toluene or chlorobenzene may be used, but is not limited thereto.

Moreover, the present invention provides a light emitting device comprising: a first electrode; A second electrode; And an organic-inorganic nanocomposite as an active layer between the first electrode and the second electrode.

In the solar cell according to the present invention, an organic-inorganic nanocomposite in which a continuous phase channel is formed between a conductive polymer and an inorganic nanostructure is applied to an active layer. It can exhibit excellent efficiency.

Hereinafter, the present invention will be described in more detail based on the following Examples and Experimental Examples, but the scope of the present invention is not limited thereto.

[Manufacturing Example]

1. Preparation of polythiophene-block copolymer-polydimethylaminoethyl methacrylate polymer

(1) Preparation of poly (3-hexylthiophene) having an allyl group at the terminal

The 2,5-dibromo-3-hexylthiophene monomer was dissolved in dehydrated and degassed THF, and then reacted with t-Butyl-MgCl dissolved in dimethyl ether at 2.0 M concentration for 2 hours at room temperature under argon atmosphere. . Thereafter, 0.03 equivalents of Ni (dppp) Cl ₂ , which is a catalyst and an initiator, was added, and the reaction was performed at room temperature for about 10 minutes to polymerize poly (3-hexylthiophene: P3HT). In order to replace the allyl group at the terminal of the polymerized poly (3-hexylthiophene), about 0.3 equivalents of the Grignard reagent allylmagnesium bromide (Allyl-MgBr) was added thereto, followed by reaction for about 2 minutes, and then methanol was added. To terminate the polymerization. Synthesized poly (3-hexylthiophene) (P3HT) was precipitated in methanol, extracted using a glass filter, purified by solvent extraction using pentane to remove polymers of low molecular weight, and an allyl group was introduced at the terminal. Prepared P3HT.

(2) Formation of poly (3-hexylthiophene) having a hydroxyl group introduced at the terminal

In order to introduce a hydroxyl group into the terminal of P3HT whose terminal is substituted with an allyl group, P3HT having an allyl group is dissolved in dehydrated and degassed THF, and then sufficiently dissolved. Reaction was carried out for 24 hours. After 2mL of 6M NaOH solution was added and reacted for 15 minutes, the temperature was dropped to room temperature. When the temperature drops to room temperature, 2mL of 33% water-soluble H ₂ O ₂ was added, and the temperature was raised to 40 ° C. for 12 hours. After the reaction was completed, the product was precipitated in a solution mixed with methanol and heavy water, extracted using a glass filter, and then the unreacted material was removed by solvent extraction using methanol.

(3) Preparation of poly (3-alkylthiophene) having ECPA introduced at the end

In order to introduce an ECPA group at the terminal of the poly (3-alkylthiophene), poly (3-alkylthiophene) having a hydroxyl group at the terminal is sufficiently dissolved in dehydrated and degassed methylene chloride (MC), and then argon is sufficiently dissolved. TEA was added under an atmosphere and reacted at 40 ° C. for about 15 minutes. After the reaction, ECPA was injected drop by drop, and reacted at 40 ° C. for 12 hours to prepare poly (3-hexylthiophene) having an ECPA group introduced at the terminal. Then, precipitated in methanol, extracted using a glass filter, washed with cold methanol (Cold MeOH) and purified using a solvent extraction method using methanol.

(4) Preparation of polythiophene-block copolymer-polydimethylaminoethyl methacrylate polymer using poly (3-hexylthiophene) macro initiator

N, N-dimethylaminoethyl methacrylate, RuCl ₂ (PPh ₃ ) _3, and tributylamine were added to the poly (3-hexylthiophene) macro initiator, and dissolved with toluene, and then the temperature was about 80 ° C. The polythiophene-block copolymer-polydimethylaminoethyl methacrylate polymer was polymerized in the maintained oil bath, and the structure of the polymerized polymer was analyzed by ¹ H NMR.

Referring to FIG. 1, the peak (a) of P3HT-b-PDMAEMA was detected at 7.0 ppm, the first CH ₂ (C) of the hexyl group located at the third position of P3HT appears at 2.8 ppm, and the rest was 2.6-0.4 ppm. It appeared to appear in between. In addition, the peak of CH ₂ at position (b) of PDMAEMA appears at 4.1 ppm, CH ₂ (d) near the amine group appears at 2.6 ppm and CH ₃ at position (e) appears at 2.3 ppm, (g), (h) peak was confirmed to come out at 2.6 ~ 0.4ppm.

2. Synthesis of Nanostructures

(1) Synthesis of CdSe quantum dots (QDs) with a diameter of 5 nm

a. A reaction solution consisting of 0.5 mmol of CdO, 5 mmol of oleic acid and 20 mL of 1-octadecene was placed in a 100 mL 3-neck flask and heated to 180 ° C. to give a colorless, transparent Cd precursors were synthesized.

b. A Se precursor consisting of 1 mmol of Se powder, 4 mmol of trioctylphosphine (TOP) and 6 mL of 1-octadecene was synthesized.

c. The Cd precursor solution was heated to 300 ° C. at a rate of 10 ° C./min, and then the Se precursor was injected at this temperature.

d. After quantum dots were grown by reacting at 260 ° C. for 50 minutes, the mixture was cooled to room temperature.

e. Excess acetone was injected into the synthesized quantum dot solution, and then centrifuged at 4000 rpm for 10 min to obtain precipitated quantum dot powder. The high-resolution transmission electron microscopy (HRTEM) image thereof is shown in FIG. Shown in

(2) Synthesis of CdSe Quantum Dots with Diameter of 2.7 nm

a. A reaction solution consisting of 0.5 mmol of CdO, 2.5 mmol of oleic acid, and 10 mL of 1-octadecene was placed in a 100 mL 3-neck flask and heated to 180 ° C. to give colorless, Transparent Cd precursors were synthesized.

b. A Se precursor consisting of 0.15 mmol of Se powder, 0.2 mmol of TOP (trioctylphosphine) and 1 mL of 1-octadecene was synthesized.

c. The Cd precursor solution was heated to 300 ° C. at a rate of 10 ° C./min and then the Se precursors were injected at this temperature.

d. After quantum dots were grown by reacting at 260 ° C for 10 minutes, the mixture was cooled to room temperature.

e. Excess acetone was injected into the synthesized quantum dot solution, and then centrifuged at 4000 rpm for 10 min to obtain precipitated quantum dot powder, and its HRTEM image is shown in FIG. 2 (b).

3.P3HT- b -Synthesis of PDMAEMA / CdSe Quantum Dot Nanocomposites

The desired concentration of P3HT- b -PDMAEMA solution and CdSe quantum dot solution was mixed (blending) and then stirred with a magnetic stirrer for 6 hours. The solvent used at this time is toluene or chlorobenzene. Transmission electron microscopy (TEM) images of the prepared P3HT- b- PDMAEMA / 5nm CdSe quantum dots (weight ratio 1: 1) nanocomposites are shown in FIG. 3.

Example 1

For comparison of the shapes, CdSe quantum dots and P3HT polymer were mixed and dissolved in a toluene solvent.

1 mg of P3HT- b- PDMAEMA and 0.1 mg of CdSe QD (10: 1 wt / wt) were dissolved in 10 mL of toluene, followed by stirring for 6 hours using a magnetic stirrer at room temperature. Thereafter, all of the toluene solvents were removed under vacuum to obtain a nanocomposite in a solid state, and the block copolymer was not dissolved but again dissolved using hexane, which can dissolve only quantum dots surrounded by an oleic acid ligand (insulation layer). As a result, it was found that the CdSe quantum dots were not dissolved in hexane, and the nanocomposite was insoluble in hexane.

Through this, the oleic acid ligand attached to the CdSe quantum dot surface is substituted by chemical bonding with the amine ligand of PDMAEMA, which is a linker portion of the block copolymer polymer, so that the quantum dot surface is not dissolved in hexane while forming a nanocomposite surrounded by the block copolymer. I could see that.

In addition, referring to FIG. 4, the nanocomposite including P3HT- b- PDMAEMA and CdSe QD (10: 1 wt / wt) has a maximum absorption peak at 506 nm with a shorter wavelength than 533 nm showing the maximum absorption peak of CdSe quantum dots. It can be seen that through this, the oleic acid ligand attached to the CdSe quantum dot surface is substituted by the amine group of PDMAEMA is removed from the quantum dot surface, it can be confirmed that the CdSe quantum dot surface is etched (etched).

[Example 2]

Polymer donor / nanostructure acceptor in which P3HT- b- PDMAEMA and CdSe quantum dots are arranged in nano-domains of 10 nm or less by self-assembly in nanocomposites TEM analysis was performed to determine whether the pn diode junction was. The nanocomposite used at this time was mixed with P3HT- b -PDMAEMA and CdSe QD in a weight ratio of 1: 1.

As shown in the TEM image of FIG. 5, it can be seen that the CdSe quantum dots dispersed in the P3HT- b- PDMAEMA matrix form a nano network with a regular average spacing of less than 2 nm. In addition, unlike the case of mixing pure P3HT polymer and CdSe quantum dots whose surface is substituted with pyridine, macrophase separation through aggregation of quantum dots does not occur in the polymer matrix, and P3HT- b- PDMAEMA It can be seen that a continuous channel is formed between the CdSe quantum dots. Through this, it was confirmed that the nanocomposite may have a pn diode junction of the polymer donor / nanostructure acceptor.

Example 3

In order to know the applicability of the nanocomposite to the solar cell active layer, a PL (photoluminesecence) measurement experiment was conducted, and the results are shown in FIG. 6. The nanocomposite used at this time is a nanocomposite in which 10 wt%, 30 wt%, 50 wt%, 70 wt% and 90 wt% of CdSe quantum points are added in the nanocomposite, respectively.

At the same optical density, as shown in FIG. 6, as the content of CdSe quantum dots increases, the PL due to the P3HT- b -PDMAEMA matrix decreases nonlinearly, and as the content of CdSe quantum dots increases, the PL intensity of the quantum dots increases. Should increase, but does not increase and decreases continuously. In addition, a large PL decrease was observed as 70 wt% of CdSe quantum dots entered, and a significant decrease in both PL of the polymer and the CdSe quantum dots was observed.

This is because the continuous channel is formed between the quantum dots and the polymer to optimize the network, and the interface between the quantum dots and the polymer is greatly increased, and the conductivity of the electrons separated at the interface is greatly increased, thereby increasing the lifetime of the separated charges. I think it's the cause. Therefore, the synthesized nanocomposite is considered to be applicable to the active layer of the nano solar cell.

Those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims.

Claims (12)

An organic-inorganic nanocomposite comprising an organic polymer and an inorganic nanostructure,
The organic polymer is a conductive polymer containing an amine group,
The inorganic nanostructure is bonded to the amine group of the conductive polymer,
An organic-inorganic nanocomposite having a continuous channel formed between the conductive polymer and the inorganic nanostructure. The method of claim 1,
The conductive polymer is an organic-inorganic nanocomposite, characterized in that the block copolymer comprising a polymer having an amine compound as a repeating unit as one block. The method of claim 2,
The polymer using the amine compound as a repeating unit is a polymethacrylate having primary to tertiary amines in the side chain, polyacrylate having primary to tertiary amines in the side chain, and primary in the side chain. Polystyrene having a secondary to tertiary amine, polymethacryl amide having a primary to tertiary amine in the side chain, polyacrylamide having a primary to tertiary amine in the side chain, and an aromatic amine Organic-inorganic nanocomposites comprising at least one selected from the group consisting of polyvinylpyridine, polyvinylpyrrolidone, and polyvinyloxazoline. The method of claim 2,
The block copolymer is polyhexylthiophene (poly (3-hexylthiophene)), polyfluorene (polyfluorene), polyparaphenylin (PPP), polyparaphenylin vinylene (PPV), polypyrrole (PPy) and polyaniline ( Organic-inorganic nanocomposite further comprising as a block one or more polymers selected from the group consisting of PANI). The method of claim 1,
The conductive polymer is an organic-inorganic nanocomposite that is a structure controlled self-assembled polymer including nano-domains of 10 nm to 40 nm. The method of claim 1,
The inorganic nanostructure may be one or more quantum dots, nanorods, tetrapods, nanowires, or multibranches selected from the group consisting of group II-VI, group IV-VI, group IV semiconductors and metal oxides. Organic-inorganic nanocomposites that are multi-branched nanostructures. The method of claim 1,
The inorganic nanostructure is an organic-inorganic nanocomposite, characterized in that having a size of 1 to 100 nm. The method of claim 1,
The inorganic nanostructure is an organic-inorganic nanocomposite, characterized in that coupled by chemical coordination bond with the amine group of the conductive polymer. The method of claim 1,
The conductive polymer and the inorganic nanostructures are organic-inorganic nanocomposites having a weight ratio of 10: 1 to 1:10. The method of claim 1,
The conductive polymer and the inorganic nanostructure have a pn diode junction of a conductive polymer donor-nanostructure acceptor arranged in a nano-domain by a self-assembly method. Organic-inorganic nanocomposites. Synthesizing a conductive polymer including an amine group;
Synthesizing inorganic nanostructures; And
11. A method for producing an organic-inorganic nanocomposite according to any one of claims 1 to 10, comprising blending the synthesized polymer and an inorganic nanostructure in a solvent to form a continuous phase channel. A first electrode;
Second electrode; And
The solar cell comprising the organic-inorganic nanocomposite according to any one of claims 1 to 10 as an active layer between the first electrode and the second electrode.

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