WO2020085572A1 - Novel polymer and organic electronic device employing same - Google Patents

Abstract

The present invention relates to a novel polymer and an organic electronic device including same, and more specifically, to: a novel polymer having improved solubility as well as improved electron transfer properties; and an organic electronic device having excellent efficiency due to employing the novel polymer.

Description

Novel polymer and organic electronic device employing the same

The present invention relates to a novel polymer and an organic electronic device employing the same.

The organic electronic device is an electronic device using an organic semiconductor material, and requires exchange of holes and electrons between the electrode and the organic semiconductor material. Organic electronic devices can be roughly divided into two types according to the operating principle.

First, excitons are formed in the organic layer by photons introduced into the device from an external light source, and the excitons are separated into electrons and holes, and the electrons and holes are transferred to different electrodes to be used as a current source (voltage source). It is a form of electronic device. The second is an electronic device in which holes and electrons are injected into a layer of an organic semiconductor material forming an interface with an electrode by applying voltage or current to two or more electrodes, and operated by the injected electrons and holes.

Examples of organic electronic devices include organic solar cells, organic light emitting devices, organic photoreceptors, and organic transistors, all of which are electron / hole injection materials, electron / hole extraction materials, electron / hole transport materials or light emitting materials for driving devices. need. Hereinafter, an organic solar cell will be mainly described in detail, but in the organic electronic devices, electron / hole injection material, electron / hole extraction material, electron / hole transport material, or light-emitting material all work on a similar principle.

There are two types of polymer solar cells (PSC): polymer-fullerene derivative solar cells (fullerene PSC) and polymer-polymer solar cells (all-PSC). The existing fullerene PSC is 11%. Although it has a high degree of power conversion efficiency, it has a disadvantage that it is difficult to obtain a high voltage value because it is expensive to synthesize, difficult to purify, and difficult to control the energy level. On the other hand, all-PSC has excellent mechanical stability and heat durability compared to the existing fullerene PSC, but has a limitation that the power conversion efficiency is remarkably low at 4%.

On the other hand, all-PSCs capable of introducing a photoactive layer composed of a blend of two components of a conjugated polymer and a receiving polymer into a solution process have superior properties of fullerene PSCs, that is, improved light absorption and chemical structure. Due to its various variability and properties such as energy level, it has received considerable attention. Moreover, all-PSC has improved stability against thermal and mechanical stress compared to fullerene PSC.

Recently, research has been focused on improving the power conversion efficiency (PCE) of the all-PSC. However, examples of high performance all-PSCs are rare.

The performance of all-PSCs includes (i) poorly aligned polymer receiving to produce low electron mobility, (ii) insufficient charge dissociation at the donor / receiver (D / A) interface, and (iii) energetically preferred polymers. -Unoptimized bulk-heterojunction (BHJ) blend morphology due to polymer-demixing, (iv) low short-circuit current density, mainly caused by the relatively low light absorption coefficient of the polymer receiver ( J _sc ) and filling rate (FF) were often limited.

Moreover, despite the great potential of the all-PSC for the production of a high open-circuit voltage (V _OC), and it is difficult to the all-PSC with the highest open-circuit voltage (V _OC), because of the limited choice of implementation given polymer.

In the case of the polymer solar cell, the improvement of efficiency is prominent due to the new device configuration and the change of process conditions, so the donor material and charge mobility with low bandgap are still good to replace the existing material. The development of new acceptor materials continues to require research and development.

The object of the present invention is BDT (benzo [1,2-b: 4,5-b '] dithiophene) -DTBDD (1,3-bis (thiophen-2-yl) -4H, 8H-benzo [1,2- c: 4,5-c '] dithiophene-4,8-dione) It is to provide a polymer that improves solubility and improves electron transport properties by introducing an alkylthio group to the backbone.

Another object of the present invention is to provide an organic electronic device having excellent efficiency by employing the polymer of the present invention.

Another object of the present invention is to provide an organic solar cell having excellent photoelectric conversion efficiency as the polymer of the present invention is employed in a photoactive layer.

In order to achieve the above-mentioned object, a polymer comprising a repeating unit represented by Formula 1 below is provided.

[Formula 1]

[In the formula 1,

R ₁ to R ₄ are each independently C ₁ -C ₃₀ alkyl;

X ₁ to X ₄ are each independently O, S or Se;

Y ₁ and Y ₂ are each independently O, S or Se.]

In the polymer according to an embodiment of the present invention, X ₁ to X ₄ are the same as each other, and may be O or S.

In the polymer according to an embodiment of the present invention, R ₁ to R ₄ are each independently C ₆ -C ₃₀ alkyl, X ₁ to X ₄ are the same as each other, O or S, Y ₁ and Y ₂ may be each independently O or S.

The polymer according to an embodiment of the present invention may be more preferably represented by the following formula (2).

[Formula 2]

[In the formula 2,

R ₁ to R ₄ are each independently crushed C ₆ -C ₃₀ alkyl.]

In order to realize the above object, an organic electronic device including the polymer according to an embodiment of the present invention is provided.

The organic electronic device according to an embodiment of the present invention may be an organic light emitting device, an organic thin film transistor, an organic photosensor or an organic solar cell, and preferably an organic solar cell.

In the organic electronic device according to an embodiment of the present invention, the polymer may be included in the photoactive layer of the organic solar cell.

In the organic electronic device according to an embodiment of the present invention, the polymer may be included in the photoactive layer of the organic solar cell as an electron donor.

The polymer of the present invention is a benzo [1,2-b: 4,5-b '] dithiophene (benzo [1,2-b: 4,5-) in which a 5-membered heteroaromatic ring substituted with alkylthio is introduced into the side chain. b '] dithiophene (BDT) -derived electron donor unit and alkylthio substituted 1,3-bis (thiophen-2-yl) -4H, 8H-benzo [1,2-c: 4,5-c '] Dithiophene-4,8-dione (1,3-bis (thiophen-2-yl) -4H, 8H-benzo [1,2-c: 4,5-c'] dithiophene-4,8-dione , DTBDD) is a copolymer of electron acceptor units, which not only has excellent oxidation stability and thermal stability, but also has high intermolecular interaction, showing remarkability in hole and electron mobility, and extended pi-pie stacking (π- πstacking) to show a low band gap.

In addition, the polymer of the present invention can have improved solubility in organic solvents due to the alkylthio groups introduced into the main chain and side chains of the repeating unit, and thus is applicable not only to vacuum deposition but also to solution processes such as spin coating and printing, as well as electron mobility. Because it has high and shows excellent electrical properties, the organic electronic device including the polymer of the present invention has excellent short-circuit current (J _sc ) and fill factor (FF) properties.

In addition, the polymer of the present invention can effectively absorb light in the visible ray region emitted from the sun and transfer electrons generated by the absorbed energy more efficiently, and the organic electronic device employing the polymer of the present invention has high efficiency. Indicates.

The novel polymer according to the present invention and the organic electronic device employing the same will be described below, but unless otherwise defined in the technical terms and scientific terms used at this time, those skilled in the art to which the present invention pertains will usually Descriptions of well-known functions and configurations that have an understanding meaning and may unnecessarily obscure the subject matter of the present invention are omitted in the following description.

"Alkyl" as described herein includes both straight chain or pulverized forms.

The present invention BDT (benzo [1,2-b: 4,5-b '] dithiophene) -DTBDD (1,3-bis (thiophen-2-yl) -4H, 8H-benzo [1,2-c: 4,5-c '] dithiophene-4,8-dione) by providing an alkylthio group in the backbone to improve solubility and to provide a polymer with improved electron transport properties, the polymer of the present invention is represented by the following formula (1) It may include a repeating unit.

[Formula 1]

[In the formula 1,

R ₁ to R ₄ are each independently C ₁ -C ₃₀ alkyl;

X ₁ to X ₄ are each independently O, S or Se;

Y ₁ and Y ₂ are each independently O, S or Se.]

The polymer according to the present invention is BDT (benzo [1,2-b: 4,5-b '] dithiophene) -DTBDD (1,3-bis (thiophen-2-yl) -4H, 8H-benzo [1,2 -c: 4,5-c '] dithiophene-4,8-dione) structure having a backbone, a thiophene substituted with an alkylthio group as a side chain in the BDT of the backbone, and an alkylthio group substituted in DTBDD of the backbone Furnace, by inducing delocalization of electrons, it is possible to appropriately adjust the band gap, HOMO, and LUMO values of the polymer, and has improved electron density through high interaction between molecules.

In addition, as described above, the polymer according to the present invention has high hole and electron mobility as it has a repeating unit of a specific structure, and has high solubility in a common organic solvent. Moreover, it is possible to impart more advantage to the solution process because it satisfies the viscosity range favorable to the solution process with high solubility in a conventional organic solvent.

In addition, the polymer of the present invention exhibits excellent charge generation ability and effective exciton dissociation to improve short-circuit current density and charge rate, and exhibits an excellent balance between hole and charge mobility.

The polymer of the present invention is a new p-type material capable of efficiently absorbing light in the visible region emitted from the sun and delivering holes generated when the photovoltaic element receives light, has excellent hole mobility, and is an organic solar cell As an electron donor, it has excellent electrical properties.

In the polymer according to an embodiment of the present invention, in terms of having high solubility and excellent electron transport properties, X ₁ to X ₄ are the same as each other, and may be O or S.

In the polymer according to an embodiment of the present invention, in terms of having high solubility and excellent electron transport properties, more preferably, R ₁ to R ₄ are each independently C ₆ -C ₃₀ alkyl, and X ₁ to X ₄ are the same as each other, O or S, and Y ₁ and Y ₂ may each independently be O or S.

The polymer according to an embodiment of the present invention may be more preferably represented by the following formula (2).

[Formula 2]

[In the formula 2,

R ₁ to R ₄ are each independently crushed C ₆ -C ₃₀ alkyl.]

In the polymer according to an embodiment of the present invention, in terms of having high charge mobility and high solubility in an organic solvent together with high electron density, R ₁ to R ₄ are each independently C ₆ -C ₃₀ alkyl It may be, preferably may be pulverized C ₆ -C ₃₀ alkyl, more preferably

It may be, wherein a is an integer from 1 to 5, R may be C ₃ -C ₂₅ alkyl of the branched chain and preferably C ₅ -C ₂₀ alkyl of the branched chain. When having the alkyl group of the branched chain as described above, high solubility in an organic solvent can be realized, and by controlling the morphology of the polymer, the crystallinity of the repeating unit is increased to impart better charge mobility. . In particular, as the a value increases in R ₁ to R ₄ , characteristics of the organic solar cell device may be further improved due to an increase in crystallinity and an increase in mobility.

The polymer according to an embodiment of the present invention may be included in an organic electronic device, and among them, it is used as an electron donor material in a photoactive layer of an organic solar cell and has improved short circuit current (J _SC ) and open voltage (V _OC ). It is possible to provide a highly efficient organic solar cell.

The polymer according to an embodiment of the present invention can be prepared as in the following reaction scheme, but can be prepared through a conventional organic synthesis method, and the organic solvent used therein is not limited, and the reaction time and temperature are also invented. Of course, changes can be made without departing from the core. In addition, it is needless to say that synthesis is possible in a manner that can be recognized by those skilled in the art.

[Scheme 1]

In addition, the present invention provides an organic electronic device comprising the polymer of the present invention.

The organic electronic device according to an embodiment of the present invention is not limited as long as it is a device in which the polymer of the present invention can be used. In one non-limiting example, the organic electronic device is an organic solar cell, an organic thin film transistor, an organic memory, or an organic. A photoreceptor, an organic optical sensor, and the like, preferably an organic solar cell or an organic thin film transistor.

The organic electronic device according to an embodiment of the present invention may be an organic solar cell, and the polymer may be included in the photoactive layer of the organic solar cell.

More specifically, the polymer of the present invention is used as an electron donor in the photoactive layer of an organic solar cell, and the organic solar cell employing it has improved photoelectric conversion efficiency.

Hereinafter, an organic solar cell according to an aspect of the present invention will be described, but this is for example, and is not limited thereto.

The polymer of the present invention has excellent electron transport properties and can be used as an electron donor material in a photoactive layer of an organic solar cell, thereby realizing high efficiency.

The organic solar cell according to an embodiment of the present invention may include a substrate, a first electrode, a photoactive layer, and a second electrode, and of course, may further include a hole transport layer, an electron transport layer, and the like.

In addition, the organic solar cell according to an embodiment of the present invention may be an inverted type organic solar cell.

In addition to the glass and quartz plates, the substrate is PET (polyethylene terephthalate), PEN (polyethylene naphthelate), PP (polyperopylene), PI (polyimide), PC (polycarbornate), PS (polystylene), POM (polyoxyethlene), AS resin (acrylonitrile styrene) copolymer), ABS resin (acrylonitrile butadiene styrene copolymer) and TAC (Triacetyl cellulose).

In addition, the first electrode is formed by applying a transparent electrode material to one surface of the substrate or coated in a film form using sputtering, E-Beam, thermal evaporation, spin coating, screen printing, inkjet printing, doctor blade or gravure printing. do. The first electrode is a part that functions as an anode. As a material having a larger work function than the second electrode described later, any material having transparency and conductivity may be used. For example, ITO (indium tin oxide), gold, silver, fluorine doped tin oxide (FTO), aluminum doped zinc oxide (aluminium doped zink oxide, AZO), IZO (indium zink oxide) ), ZnO-Ga ₂ O ₃ , ZnO-Al ₂ O ₃ and ATO (antimony tin oxide, SnO ₂ -Sb ₂ O ₃ ), and the like, preferably ITO.

A hole transport layer may be inserted between the first electrode and the photoactive layer, and the hole transport layer may be formed through a method such as spin coating or dip coating. As a material for forming the hole transport layer, it is preferable to use a conductive polymer PEDOT: PSS (poly (3,4-ethylenedioxythiophene): polystyrene sulfonate), which transfers electrons to an indium tin oxide (ITO) layer as an anode. It helps to transport the hole smoothly while preventing it from being done.

An electron transport layer may be inserted between the second electrode and the photoactive layer, and the electron transport layer is a metal oxide layer including a metal oxide, but the metal oxide is not limited thereto, titanium dioxide (TiO ₂ ), tin dioxide It may be formed of nanoparticle oxides such as (SnO ₂ ), zinc oxide (ZnO).

The photoactive layer may include an electron donor electron donor and an electron acceptor. At this time, the polymer can be used as an electron donor of the photoactive layer to realize improved external quantum efficiency. At this time, the electron donor and the electron acceptor of the photoactive layer constitute a bulk heterojunction (BHJ). Bulk heterojunction means that each compound corresponding to an electron donor and an electron acceptor in the photoactive layer is mixed with each other.

The photoactive layer may include the polymer as an electron donor of the photoactive layer, and constitute a bulk heterojunction together with the electron acceptor.

In addition, the photoactive layer may include the polymer according to the present invention as an electron donor, and the compounding amount thereof may be appropriately adjusted according to the application. In addition, the polymer may include a solvent and an electron acceptor. Examples of the electron acceptor include C60, C70, [60] Phenyl C ₆₁ -butyric acid methyl ester (PCBM), [70] PCBM (Phenyl C ₇₁ -butyric acid methyl ester), [60] ICBA (Indene-C ₆₀ Bis-Adduct), [60] PCBCR (phenyl-C ₆₁ -butyric acid cholestryl ester), [70] PCBCR (phenyl-C ₇₁ -butyric acid cholestryl ester), perylene, PBI (polybenzimidazole), PTCBI (3,4,9,10-perylene-tetracarboxylic bis-benzimidazole), P (NDI2HD-Se), etc. may be used, but is not limited thereto.

In this case, when the polymer according to the present invention is included as an electron donor of the photoactive layer, it is possible to effectively compensate for the relatively low light absorption coefficient of the electron acceptor, thereby simultaneously improving the short circuit current density ( J _sc ) and the filling factor (FF). .

In addition, the photoactive layer may further include additional additives in order to realize excellently improved efficiency by controlling the morphology and crystallinity of the active layer. Examples of the additives are 1,8-diiodooctane (DIO: 1,8-diiodooctane), 1-chloronaphthalene (1-CN: 1-chloronaphthalene), diphenyl ether (DPE: diphenylether), octanediol (octane dithiol) and tetrabromothiophene, and the like, and may be appropriately combined according to the use. Preferably, the polymer according to the present invention realizes significantly improved crystallinity when used in combination with 1,8-diiodooctane, which improves short-circuit current density ( J _sc ) and fill rate (FF) as well as significantly External quantum efficiency can be implemented.

The polymer may be used by dissolving in a solvent, and the solvent may be used as acetone, methanol, THF, toluene, xylene, tetralin, chloroform, chlorobenzene, dichlorobenzene, or a mixed solvent thereof, but is not limited thereto. . The polymer is preferably introduced into the photoactive layer with a thickness of 60 to 120 nm, but is not limited thereto. In addition, the photoactive layer comprising the polymer according to the present invention is good in energy conversion efficiency due to an increase in short circuit current density and open circuit voltage due to high electron density.

The organic solar cell may further include an electron transport layer. The electron transport layer may be prepared by adding a surfactant to improve the morphology of the electron transport layer. At this time, the electron transport layer may be prepared by dissolving a water-soluble polymer having an electrophilic function in water, ethanol or a mixed solvent thereof, adding a surfactant to the polymer solution, and filtering to form a thin film. have. At this time, poly [9,9-bis (6'-diethanolamino) hexyl) -fluorene] is preferable as the water-soluble polymer having the electrophilic functional group, and the surfactant is 2,4,7,9- It is preferably tetramethyl-5-dekin-4,7-diol, but is not limited thereto. In addition, the solution of the water-soluble polymer and the surfactant is preferably 2 to 20 nm coated by a method such as spin coating to heat treatment. At this time, in addition to the spin coating method, the electron transport layer may apply methods such as dip coating, screen printing, inkjet printing, gravure printing, spray coating, doctor blade or brush painting, and the present invention is not limited thereto.

In addition, the second electrode may be deposited using a thermal evaporator in the state where the electron transport layer is introduced. The electrode materials that can be used are lithium fluoride / aluminum, lithium fluoride / calcium / aluminum, aluminum / calcium, barium fluoride / aluminum, barium fluoride / barium / aluminum, barium / aluminum, aluminum, gold, silver, magnesium: silver and lithium : It can be selected from aluminum, and preferably, an electrode made of silver, aluminum, aluminum / calcium or barium fluoride / barium / aluminum is used.

In general organic solar cells, electrons are cathodes, and holes are discharged to anodes. Inverted organic solar cells, on the contrary, electrons are anodes, and holes are cathodes. , The present invention includes all of them.

Hereinafter, the present invention will be described in detail by examples. However, the following examples are only for illustrating the present invention, and the contents of the present invention are not limited by the following examples. At this time, unless there is another definition in the technical terminology and scientific terminology used, it has a meaning that a person with ordinary knowledge in the technical field to which this invention belongs generally understands. In addition, repeated description of the same technical configuration and operation as the prior art will be omitted.

[Physical property evaluation method]

^{The 1} H NMR spectrum was measured with a Varian Mercury Plus 300 MHz and Bruker FT NMR spectroscopy system, and the ultraviolet absorption spectrum was measured with a UV-1800 spectrophotometer (Shimadzu Scientific Instruments). In order to obtain the HOMO level of the material, cyclic current-voltage analysis (Cyclic Voltammetry, CV) was measured using a CHI 600C electrochemical analyzer, and the JV curve of the solar cell was used with a 1Kw solar simulator (Newport 91192). Was measured. IPCE characteristics were measured by Solar cell response / Quantum efficiency / IPCE Measurement system (PV Measurements. Inc.).

M _n and PDI values were measured under an o-DCB (o-dichlorobenzene) solvent at 80 mL at a rate of 1 mL / min using a GPC consisting of a Waters 1515 Isocratic HPLC pump, a temperature control module and a Waters 2414 differential refractive detector. Molecular weights were calibrated using polystyrene standards.

[Example 1] Preparation of polymer 1

Step 1: Preparation of Compound A

Thiophene (3 g, 35.7 mmol) was added to THF (20 mL), dissolved, and the temperature was lowered to -78 ° C, and 2.5M n-Butyllithium (14.3 mL, 35.7 mmol) was slowly dropped for 2 hours. It was stirred. After further stirring at room temperature for 30 minutes, the temperature was lowered to 0 ° C, sulfur (1.14 g, 35.7 mmol) was added, and the mixture was stirred for 2 hours. And 2-Ethylhexyl bromide (6.89 g, 35.7 mmol) was slowly dropped and stirred at room temperature for 12 hours. Distilled water (40 mL) was added to the reaction mixture to terminate the reaction. After extracting with ethyl acetate (EA), the organic layer was washed with water, dried over MgSO _4, and the solvent was removed using a rotary evaporator. Then, it was purified by column chromatography (n-Hexane) to obtain Compound A as a liquid (yield = 42%).

¹ H NMR (CD ₂ Cl ₂ , 300 MHz), δ (ppm): 6.96 (s, 2 H), 2.84 (m, 4 H), 1.56-1.29 (m, 18 H), 0.95-0.86 (m, 12 H).

Step 2: Preparation of compound B

After dissolving 2,5-Dibromo-3,4-thiophenedicarboxylic acid (6 g, 18.2 mmol) and DMF (2 drop) in 1,2-Dichloroethane (40 mL), Oxalyl chloride (14 mL, 163.7 mmol) was slowly dropped. The mixture was dropped and stirred at room temperature for 12 hours. The solvent was removed using a rotary evaporator to obtain crude 2,5-dibromothiophene-3,4-dicarbonyl dichloride, which was subjected to the next reaction without purification.

After dissolving crude 2,5-dibromothiophene-3,4-dicarbonyl dichloride (6.7 g, 18.2 mmol) and compound A (6.8 g, 18.2 mmol) in 1,2-Dichloroethane (40 mL), AlCl ₃ (9.7 g, 72.7 mmol) Slowly dropped, stirred at 0 ° C. for 30 minutes, and then stirred at room temperature for 3 hours. Distilled water (80 mL) and HCl (20 mL) were added to the reaction mixture to terminate the reaction. After extracting with dichloromethane (MC), the organic layer was washed with water, dried over MgSO _4, and the solvent was removed using a rotary evaporator. Then, it was purified by column chromatography (n-Hexane / dichloromethane = 8/1) to obtain Compound B as a solid (yield = 42%).

¹ H NMR (CD ₂ Cl ₂ , 300 MHz), δ (ppm): 3.12 (m, 4 H), 1.88-1.80 (m, 2 H), 1.60-1.51 (m, 8 H), 1.41-1.35 ( m, 8 H), 1.02-0.93 (m, 12 H).

Step 3: Preparation of compound C

2- (2-ethylhexylthio) thiophene (8.8 g, 31 mmol) was added to THF (60 mL), melted, the temperature was lowered to -78 ° C, and 2.5M n-Butyllithium (13.6 mL, 34 mmol) was slowly dropped. (dropping) and stirred at room temperature for 2 hours. Then, 4,8-Dihydrobenzo [1,2-b: 4,5-b '] dithiophen-4,8-dione (1.7 g, 7.8 mmol) was added thereto, and the temperature was raised to 50 ° C and stirred for 2 hours. After lowering the temperature to room temperature, SnCl ₂ · 2H ₂ O (13.6 g, 60.7 mmol) in 10% hydrochloric acid (30 mL) was added to the reaction solution and stirred for 2 hours to terminate the reaction. After extraction with diethyl ether (Ether), the organic layer was washed with water, dried over MgSO _4, and the solvent was removed using a rotary evaporator. Then, it was purified by column chromatography (n-hexane) to obtain compound C as a liquid (yield = 50%).

¹ H NMR (CD ₂ Cl ₂ , 300 MHz), δ (ppm): 7.65 (d, 2 H), 7.56 (d, 2 H), 7.38 (d, 2 H), 2.99 (m, 4 H), 1.73-1.64 (m, 2H), 1.57-1.30 (m, 16 H), 0.97-0.92 (m, 12 H).

Step 4: Preparation of compound D

Compound C (16.5 g, 25.7 mmol) was added to THF (250 mL), dissolved, and the temperature was lowered to -70 ° C to slowly drop 2.5M n-Butyllithium (25.6 mL, 64 mmol) at 40 ° C. Stir for 3 hours. Carbon tetrabromide (21 g, 64 mmol) was added to THF (35 mL) and dissolved, and then the temperature was lowered to -70 ° C and dropped slowly. After stirring for 30 minutes, the temperature was gradually raised to room temperature. Distilled water (500 mL) was added to the reaction mixture to terminate the reaction. After extracting with dichloromethane (MC), the organic layer was washed with water, dried over MgSO _4, and the solvent was removed using a rotary evaporator. Then, it was purified by column chromatography (n-Hexane) to obtain Compound D as a solid (yield = 78%).

¹ H NMR (CD ₂ Cl ₂ , 300 MHz), δ (ppm): 7.62 (s, 2 H), 7.31 (d, 2 H), 7.25 (d, 2 H), 2.99 (m, 4 H), 1.72-1.61 (m, 2 H), 1.58-1.33 (m, 16 H), 0.97-0.93 (m, 12 H).

Step 5: Preparation of compound E

Compound D (8.1 g, 10.1 mmol) and 2- (Tributylstannyl) thiophene (11.3 g, 30.3 mmol) were dissolved in toluene (150 mL) and DMF (20 mL), followed by nitrogen substitution. After adding Pd (PPh ₃ ) ₄ (1.2 g, 1 mmol), the mixture was stirred at 100 ° C. for 6 hours. After filtering by lowering the temperature to room temperature, distilled water (300 mL) was added to the obtained filtrate to terminate the reaction. After extracting with dichloromethane (MC), the organic layer was washed with water, dried over MgSO _4, and the solvent was removed using a rotary evaporator. Then, it was purified by column chromatography (n-Hexane / dichloromethane = 6/1) to obtain Compound E as a solid (yield = 69%).

¹ H NMR (CD ₂ Cl ₂ , 300 MHz), δ (ppm): 7.66 (s, 2 H), 7.41-7.35 (m, 6 H), 7.30 (d, 2 H), 3.02 (m, 4 H ), 1.74-1.68 (m, 2 H), 1.60-1.33 (m, 16 H), 1.00-0.92 (m, 12 H).

Step 6: Preparation of compound F

Compound E (4.5 g, 5.6 mmol) was added to THF (120 mL), dissolved, and then the temperature was lowered to -78 ° C to slowly drop 2.5M n-Butyllithium (6.0 mL, 15 mmol) at 40 ° C. Stir for 3 hours. After lowering to -78 ° C and slowly dropping Trimethyltin chloride (3.3 g, 16.7 mmol), the temperature was gradually raised to room temperature and stirred for 12 hours. Distilled water (200 mL) was added to the reaction mixture to terminate the reaction. After extraction with diethyl ether (Ether), the organic layer was washed with water, dried over MgSO _4, and the solvent was removed using a rotary evaporator. Then, recrystallization (Ether: Hexane) purification gave compound F as a solid (yield = 51%).

¹ H NMR (CD ₂ Cl ₂ , 300 MHz), δ (ppm): 7.43 (s, 2 H), 7.23-7.18 (m, 4 H), 7.08 (d, 2 H), 6.97 (m, 2 H ), 2.80 (m, 4 H), 1.52-1.46 (m, 2 H), 1.38-1.12 (m, 16 H), 0.79-0.71 (m, 12 H), 0.31-0.12 (m, 18 H).

Step 7: Preparation of polymer 1

The polymer 1 may be polymerized through a Stille coupling reaction.

Compound B (0.5 g, 0.44 mmol) and compound F (0.294 g, 0.44 mmol) were dissolved in toluene (0.5 mL) and DMF (9.5 mL), followed by nitrogen substitution. Pd (PPh ₃ ) ₄ (5 mg, 0.0044 mmol) was added thereto and refluxed at 100 ° C. for 3 hours. The reaction mixture was slowly added to methanol (500 mL) to form a precipitate and the resulting solid was filtered. The filtered solid was purified in the order of methanol, hexane, dioxane, and chloroform through soxlet. The obtained liquid was precipitated again in methanol, filtered through a filter and dried to obtain polymer 1 in a solid form (yield = 44%).

¹ H NMR (CD ₂ Cl ₂ , 300 MHz), δ (ppm): 7.78-7.17 (m, 7 H), 7.42 (m, 2 H), 7.17 (m, 3 H), 2.96 (m, 8 H ), 1.47-1.18 (m, 36 H), 0.87 (m, 24 H).

Weight average molecular weight (Mw): 160,269 g / mol

Number average molecular weight (Mn): 111,815 g / mol

PDI (polydispersity index): 1.43

T _{d, 5%} (℃): 350 ℃

The light absorption region of the polymer 1 prepared in Example 1 was measured in a solution state and a film state, and the results are shown in Table 1 below.

	Polymer 1 (Example 1)
Solution λ max (nm)	554, 464 (s)
Film λ max (nm)	567, 468 (s)
UV max (100 ℃) (nm)	572, 472 (s)
E g (eV)	1.80
E HOMO (eV)	-5.36
E LUMO (eV)	-3.56

[Example 2] Organic solar cell fabrication

To investigate the photovoltaic properties of the organic solar cell device produced using the polymer 1 prepared in Example 1 as a new electron donor [ITO / PEDOT: PSS / polymer 1 + PC ₇₀ BM / Al] structure organic solar cell device Was produced.

The glass substrate coated with ITO (Indium Tin Oxide) was washed three times with acetone and isopropyl alcohol (IPA), and then dried in an oven at 130 ° C. for 5 hours. The cleaned ITO glass substrate was treated with UV-Ozone for 30 minutes. After the PEDOT-PSS (Baytron P TP AI 4083, Bayer AG) layer was spin coated to a thickness of 40 nm, annealing was performed at 120 ° C for 60 minutes. Using the polymer 1 prepared in Example 1, the PCBM derivative (PC ₇₀ BM) was dissolved in chlorobenzene at a weight ratio of 1: 1 (wt: wt) and stirred at 60 ° C. for 12 hours, followed by 0.45 μm (PTFE ) Filtered through a syringe filter to prepare an organic semiconductor solution. The organic semiconductor solution was spin coated on the PEDOT-PSS layer to prepare a photoactive layer with a thickness of 93 nm. Thereafter, aluminum (Al) was deposited to a thickness of 100 nm in a high vacuum (10 ^-6 torr) to produce an organic solar cell.

The current density-voltage (JV) characteristic of the organic solar cell produced by the above method was measured under illumination simulating sunlight as 100 mW / ㎠ (AM1.5G) by an Oriel 1000W solar simulator, and V _OC (open circuit voltage) ), J _SC (short-circuit current density), FF (fill factor) and photovoltaic parameters of power conversion efficiency (PCE) were confirmed.

[Comparative Examples 1 and 2] Production of organic solar cells

An organic solar cell was prepared in the same manner as in Comparative Example C1 and C2, respectively, instead of Polymer 1 prepared in Example 1 used for the photoactive layer in Example 2, and the properties were compared.

Comparative polymer C1:

(Mw: 432,000 g / mol; Mn: 181,000 g / mol; PDI: 2.38; T _{d, 5%} (° C): 377 ° C)

Comparative polymer C2:

(Mw: 541,000 g / mol; Mn: 216,000 g / mol; PDI: 2.51; T _{d, 5%} (° C): 427 ° C)

V _oc (V) and J _sc (mA / cm ² ) each represent a voltage value when the current is 0 and a current value when the voltage is 0, in the current-voltage curve of the fabricated device.

In addition, the fill factor (FF) is calculated from Equation 1 below.

[Equation 1]

FF = V _mpp ㆍ J _mpp / V _oc ㆍ J _sc

(In the above Equation 1, V _mpp and J _mpp each represents the voltage and current value at the point indicating the maximum power when measuring the current-voltage of the fabricated device, V _oc (V) and J _sc (mA / cm ² ) Each represents the voltage value when the current is 0 and the current value when the voltage is 0 in the current-voltage curve of the fabricated device.)

Furthermore, the photoelectric conversion efficiency (%) is calculated from Equation 2 below.

[Equation 2]

Photoelectric conversion efficiency (%) = 100 × FF × V _oc ㆍ J _sc / P _in

(In Equation 2, FF, V _oc and J _sc are as defined in Equation 1, and P _in represents the total energy of light incident on the device.)

It has been confirmed that the organic solar cell employing the polymer of the present invention can realize remarkable power conversion efficiency by simultaneously realizing the improvement of the short-circuit current density, charging rate and open-voltage value.

As described above, although the embodiments of the present invention have been described in detail, those of ordinary skill in the art to which the present invention pertains, without departing from the technical spirit of the present invention as defined in the appended claims The present invention may be implemented in various ways. Therefore, changes in the embodiments of the present invention will not be able to escape the technology of the present invention.

Claims (7)

1. A polymer comprising a repeating unit represented by Formula 1 below:

   [Formula 1]

   

   [In the formula 1,

   R ₁ to R ₄ are each independently C ₁ -C ₃₀ alkyl;

   X ₁ to X ₄ are each independently O, S or Se;

   Y ₁ and Y ₂ are each independently O, S or Se.]
2. According to claim 1,

   The X ₁ to X ₄ are the same as each other, O or S, a polymer.
3. According to claim 1,

   R ₁ to R ₄ are each independently C ₆ -C ₃₀ alkyl, X ₁ to X ₄ are the same as each other, O or S, and Y ₁ and Y ₂ are each independently O or S, a polymer.
4. According to claim 1,

   A polymer comprising a repeating unit represented by Formula 2 below:

   [Formula 2]

   

   [In the above formula 2, R ₁ to R ₄ are each independently crushed C ₆ -C ₃₀ alkyl.]
5. An organic electronic device comprising the polymer according to any one of claims 1 to 4.
6. The method of claim 5,

   The organic electronic device is an organic solar cell, an organic thin film transistor, an organic memory, an organic photoreceptor or an organic photosensor, an organic electronic device.
7. The method of claim 6,

   The polymer is included in the photoactive layer of the organic solar cell as an electron donor, an organic electronic device.