KR101504864B1 - Conjugated side-chain incorporated conjugated polymers and organic optoelectronic devices - Google Patents

Abstract

The present invention relates to a polymer material having a conjugated side chain introduced thereto, which can improve efficiency of an organic photoelectronic device. Provided is a polymer introducing a benzodithiophen conjugated dithienylene (DTE) side chain group. According to the present invention, the polymer material shows absorption wavelength in wide UV-visible ray region and low band. The photoelectronic device including a photoactivated layer containing the materials has excellent energy conversion efficiency. Accordingly, the polymer provided in the present invention can be utilized for manufacturing various types of organic photoelectornic devices.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a polymer having conjugated side chains and conjugated side-chain incorporated conjugated polymers and organic optoelectronic devices,

The present invention relates to a polymer having conjugated side chains introduced therein and an optoelectronic device having increased energy conversion efficiency using the conjugated side chain.

Concerns about depletion of fossil fuels, warming due to their abuse, safety concerns with climate change and nuclear energy have raised the need for photovoltaic power generation, which is sustainable energy, higher than ever. The average energy delivered by the sun to the Earth on average is 105 TW, a fraction of which is well above the 20 TW expected to be required by the entire 2020 region.

Of course, not all energy from the sun can be exploited, but because of its relatively sub-regional characteristics and inherent eco-friendliness, photovoltaics has always been regarded as one of the most attractive renewable energy sources.

Organic semiconductors constituting organic solar cells can be implemented at a relatively low temperature and process relative to other semiconductor technologies, which is advantageous in that they can be compatible with low-cost glass or various plastic substrates, which can be a problem in high temperature processing. In particular, when a plastic substrate is used, roll-to-roll and printing processes can be applied. In this case, it is expected to realize an ultra-low-cost solar cell technology by realizing high production per unit time. The efficiency of the organic solar cell has been steadily developed since Kodak's Tang realized about 1% of the efficiency using the multilayer thin film of the low-molecular semiconductor layer using the vacuum deposition in the middle of 1980's. In particular, researches related to organic solar cells have increased rapidly since 2000, and polymer solar cells capable of introducing a photoactive layer by a solution process introduced a bulk heterojunction concept with PCBM in the early stage of PPV polymer in 2000, And the use of P3HT as a photoactive layer has generally resulted in an efficiency of 4-6%. These results indicate that attempts to develop new materials and device structures by attracting attention from academia and industry have been in full swing since 2005 .

Polymer Solar Cell Efficiency The efficiency of solar cells using new polymers other than PPV and P3HT, which could not reach the range of 1-2% until 2005, will increase dramatically in Polyera in early 2012 Respectively. In addition, recent theoretical predictions that the energy conversion efficiency of 10% or more based on the single layer structure is possible by well controlling the energy level and the photoelectric property of the organic semiconductor brightens the practical use of the organic thin film solar cell, .

On the other hand, an organic solar cell using an organic semiconductor such as a conjugated polymer has a problem that its photoelectric conversion efficiency is lower than that of a conventional solar cell using an inorganic semiconductor, and thus has not yet been put to practical use. There are three main reasons for the low photoelectric conversion efficiency of an organic solar cell using a conventional conjugated polymer. The first is that the absorption efficiency of solar light is low. Second, in the case of organic semiconductors, the binding energy of excitons generated by sunlight is large, so that it is difficult to separate electrons and holes. Third, traps for capturing carriers (electrons and holes) are likely to be formed, so that the generated carriers are easily trapped by the traps and the carrier mobility is low. That is, the semiconductor material generally requires high mobility of the carrier of the material. The conjugated polymer has a problem that the mobility of the charge carrier is lower than that of the conventional inorganic crystal semiconductor or amorphous silicon. For this reason, it is necessary to use a means of absorbing a lot of sunlight and separating generated electrons and holes from the excitons well, and a carrier trapping due to carrier scattering or trapping between the non-crystalline region of the conjugated polymer or the conjugated polymer chain, Is a very important factor for practical use of the organic semiconductor solar cell.

Furthermore, as a method of improving the photoelectric conversion efficiency, a bulk heterojunction type in which an electron-accepting organic material (n-type organic semiconductor) and an electron-donating organic material (p-type organic semiconductor) are mixed and the junction surface contributing to photoelectric conversion is increased It has been developed. Among them, a photoelectric conversion device using a conjugated polymer as an electron donating organic material (p-type organic semiconductor) and a semiconductor polymer having an n-type semiconductor property and a fullerene derivative such as C60 as an electron-accepting organic material has been reported .

Currently, the biggest problem of polymer solar cells is the photoelectric conversion efficiency, which is significantly lower than that of inorganic structures such as silicon and CIGS. Therefore, it is necessary to develop a photoelectric conversion device using an organic semiconductor having a high photoelectric conversion efficiency.

Korea Patent Publication No. 2013-0092162

Accordingly, an object of the present invention is to provide a polymer (polymer) into which a conjugated side chain is introduced to improve photoelectric conversion efficiency.

It is another object of the present invention to provide an organic photonic device including a polymer having a conjugated side chain introduced therein according to the present invention.

In order to accomplish the above object, the present invention provides a polymer having a conjugated side chain introduced therein.

According to an embodiment of the present invention, the polymer may have a number average molecular weight of 40,000 to 140,000.

According to an embodiment of the present invention, the polymer may have an absorption wavelength of 300 to 750 nm in the ultraviolet and visible light regions.

According to an embodiment of the present invention, the polymer may have an energy band gap of 1.80 to 1.90 eV.

The present invention also provides an organic photonic device comprising the polymer according to the present invention.

According to an embodiment of the present invention, the organic photonic device of the present invention may be an organic photovoltaic cell, an organic memory, an organic light emitting diode, an organic sensor, an organic thin film transistor, an organic light emitting diode (OLED), a polymeric light emitting diode (PLED) An organic integrated circuit (O-IC), an organic field effect transistor (OFET), or an organic electroluminescent display.

According to an embodiment of the present invention, the organic optical device includes a laminate structure of indium tin oxide (ITO) / PEDOT: PSS / photoactive layer / LiF / Al, and the photoactive layer includes the polymer according to the present invention .

According to an embodiment of the present invention, the organic optical device may have an energy conversion efficiency (PCE) of 5.0 to 6.0%.

The present invention relates to a polymer material into which a conjugated side chain is introduced to improve the efficiency of an organic solar device, and a polymer polymer having a conjugated dithienylene (DTE) side chain group introduced into benzodiothiophene is provided. The polymer material according to the present invention exhibited absorption wavelengths in a wide range of ultraviolet-visible light, exhibited a low band gap, and organic light-emitting devices including a photoactive layer containing these materials showed excellent energy conversion efficiency. Therefore, the polymer provided by the present invention has an effect that it can be utilized for manufacturing various kinds of organic optical devices.

FIG. 1 shows a specific result of thermal characteristics of polymers according to an embodiment of the present invention through TGA.
FIG. 2 shows the results of analyzing ultraviolet-visible light absorption spectra of the polymers according to an embodiment of the present invention in a solution state and a film state, respectively.
FIG. 3 is a graph showing the ultraviolet-visible light absorption spectra of the polymers according to an embodiment of the present invention in terms of optical absorption coefficient.
FIG. 4 shows the results of analyzing the current-voltage characteristics of the solar cell device according to the blend ratios of these polymers and PCBM for each of the polymers P1 and P2 produced in one embodiment of the present invention.
FIG. 5 is a graph showing the AFM height images of a polymer device preannealing a solar cell device manufactured using the polymers P1 and P2 produced in an embodiment of the present invention at 100.degree. PCBM (1: 1), (d) P2 / PCBM (1: 1) Shows P2 / PCBM (1: 1) + DIO.

Unless defined otherwise, all technical terms used in the present invention have the following definitions and are consistent with the meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. Also, preferred methods or samples are described in this specification, but similar or equivalent ones are also included in the scope of the present invention. The contents of all publications referred to herein are incorporated herein by reference.

The term "alkyl" includes both branched and straight-chain saturated aliphatic hydrocarbon groups. Unless otherwise indicated, the term includes annular airways. Examples of the alkyl group include methyl, ethyl, propyl, isopropyl, isobutyl, sec-butyl, tert-butyl, pentyl, isopentyl, neopentyl, cyclopentyl, hexyl, cyclohexyl, isohexyl and the like. The term "alkyl" also includes both substituted and unsubstituted hydrocarbon groups. In some embodiments, the alkyl group may be monosubstituted, disubstituted and trisubstituted. Other saturated alkyl groups are formed from one or more of the substituents described herein. The term includes heteroalkyl groups. The heteroalkyl group may have from 1 to 20 carbon atoms.

The term "polymer" means an oligomer, a homopolymer, and a copolymer having two or more different repeating units.

The term "about" is used herein to refer to a reference quantity, a level, a value, a number, a frequency, a percent, a dimension, a size, a quantity, a weight, or a length of 30, 25, 20, 25, 10, 9, 8, 7, Level, value, number, frequency, percent, dimension, size, quantity, weight or length of a variable, such as 4, 3, 2 or 1%.

Throughout this specification, the words "comprises" and "comprising ", unless the context requires otherwise, include the steps or components, or groups of steps or elements, Steps, or groups of elements are not excluded.

Hereinafter, the present invention will be described in detail.

The present invention solves the problem that an organic solar cell using an organic semiconductor such as a conjugated polymer is low in photoelectric conversion efficiency compared with a solar cell using a conventional inorganic semiconductor, and is a material capable of producing an organic solar cell having excellent photoelectric conversion efficiency The present invention provides a polymer having a conjugated side chain introduced therein.

The conjugate side chain introduced polymer of the present invention is a polymer having the following structural formula,

R is an alkyl group having 1 to 30 carbon atoms, m is an integer of 1 to 5, 1 is an integer of 0 to 5, and Y is S, O, Se or Te.

In the above formulas, A may be any of compounds having the following structural formulas, wherein Z is S, O, or Se; R ²¹ to R ³⁷ independently of one another are hydrogen, halogen, (C 1 -C 30) alkyl, (C 1 -C 30) alkoxy, (C 1 -C 30) alkoxycarbonyl or (C 6 -C 30) ; The alkyl group, alkoxy, alkoxycarbonyl, and aralkyl of R ²¹ to R ³⁷ are independently selected from the group consisting of (C 1 -C 30) alkyl, (C 2 -C 30) alkenyl, (C 2 -C 30) alkynyl, A halogen atom, a cyano group, a nitro group, a trifluoromethyl group, and a silyl group; R ⁴¹ to R ⁴⁶ are hydrogen or a (C 1 -C 30) alkyl group; and k may be an integer of 1 to 2.

That is, in order to improve the efficiency of the organic solar cell, the present invention provides a novel benzodiaphthoene (benzo [1,2-b: 4,5-b '] dithiophene) -based alkyldithienylethylene group Dithienyl thieno [3,4-c] pyrrole-4,6-dione dithiophene) copolymers were synthesized and their characteristics were analyzed.

The method for producing the copolymer synthesized in the present invention, that is, the polymer into which the conjugated side chain is introduced, is described in detail in the following examples.

The present inventors have analyzed the physical properties and thermal properties of polymers having a conjugated side chain introduced thereto. The thermal characteristics of the polymers were analyzed by TGA analysis. As a result, the decomposition temperatures of the polymers of the present invention were thermally (See Fig. 1). In addition, the polymers synthesized in the present invention show high solubility in organic solvents such as chloroform, toluene, and chlorobenzene.

The number average molecular weight of the polymer according to the present invention is preferably 40,000 to 140,000. If the number average molecular weight is less than 40,000, the polymer may cause thin film formation and crystallization during device operation, There is a problem that solubility and processability become difficult.

In addition, the optical characteristics and electrical characteristics of the polymer according to the present invention were analyzed. The polymer of the present invention exhibited absorption wavelengths of 300 to 750 nm in the ultraviolet and visible regions, and had a low energy band gap of 1.80 to 1.90 eV It is characterized by excellent energy efficiency.

In general, the short-circuit current is the primary requirement when considering the mechanism of the organic solar cell, how much it absorbs the photons coming from the sun. Since the solar spectrum has more photons distributed toward the longer wavelength side, the polymer having a role of absorbing the light in the organic solar cell also has a theoretically lower band gap, which is more efficient in terms of efficiency.

Furthermore, the present invention can provide an organic photonic device including the polymer according to the present invention.

The organic light-emitting device of the present invention may include, but not limited to, an organic solar cell, an organic memory, an organic light emitting diode, an organic sensor, an organic thin film transistor, an organic light emitting diode (OLED), a polymer light emitting diode (PLED) IC), an organic field effect transistor (OFET), or an organic electroluminescent display.

The organic photonic device may be formed of ITO (indium tin oxide) / PEDOT: PSS [poly (3,4-

ethylenedioxythiophene: polystyrenesulfonate] / photoactive layer / LiF / Al, and the photoactive layer may include the polymer according to the present invention.

More specifically, among organic photonic devices, an organic solar cell (organic thin film solar cell) basically includes a metal / organic semiconductor (photoactive layer) / metal structure, and a transparent electrode having a high work function such as ITO (indium tin oxide) Is used as the anode, and Al or Ca having a low work function is used as the cathode material. The photoactive layer is a two-layer structure (D / A bi-layer structure) of electron donor (D) and electron acceptor (A) or a bulk-double junction (D + A bulk-heterojunction blend, BHJ) structure can be used. The organic semiconductors used as the photoactive layer include organic monomers and polymers. In the case of the organic monomers, the donor layer and the acceptor layer are successively formed by heating in vacuum, In the case of a polymer, a solution in which an electron donor and an electron acceptor are dissolved can be prepared by forming a film using a wet process such as spin coating, inkjet printing, or screen printing.

In the present invention, an organic thin film solar cell was manufactured using the polymer of the present invention in one embodiment, and it was fabricated with a sandwich structure of ITO / PEDOT: PSS / photoactive layer / LiF / Al. Specifically, ITO-coated glass substrates were sonicated in a detergent and wiped with distilled water, acetone, and 2-propanol. PEDOT: PSS (Baytron P) To a thickness of 40 nm. The mixture was heated on a heater at 110 ° C for about 10 minutes, and the photoactive layer was spin-coated with a mixed solution filtered with a 0.45 μm PP syringe filter. Finally, fabrication of the device was completed by depositing a 150 nm cathode on the photoactive layer under a vacuum of 10 ^-6 torr. The polymer of the present invention was mixed with PC ₇₁ BM using chloroform and included in the photoactive layer.

In addition, the organic optical device of the present invention has an excellent energy conversion efficiency. According to an embodiment of the present invention, it is confirmed that the organic optical device has an energy conversion efficiency (PCE) of 5.0 to 6.0%.

In conclusion, the present invention relates to benzo [1,2-b: 4,5-biphenyl-4,4'-dicarboxylic anhydride] containing a new p-type material alkyl dithienylethylene (DTE) b] dithiophene (BDT) -based electron acceptor substance and dithienyl thieno [3,4-c] pyrrole-4,6-dione (DTTPD) The new polymers were synthesized. Benzodiothiophene (BDT), which is used as a p-type material, is a well-known planar structure. It has a well-stacked π-π between molecules, allowing electrons to flow smoothly and have high charge mobility. By introducing a conjugated diethylenethene (DTE) side chain structure into BDT, a unit of such p-type material, the effective conjugation length can be increased and the inter-molecule pi-pi stacking can be improved. Through the introduction of the conjugated diethylethylene (DTE) side chain structure, the maximum wavelength of the ultraviolet-visible light absorption spectrum shifted to the long wavelength region, and the absorption band of the broader region was observed, thus exhibiting a lower HOMO energy level. It can be seen that large V _OC and J _sc can be expected by having a low band gap material as a photoactive layer of an organic solar cell.

Also, dithienyl thieno [3,4-c] pyrrole-4,6-dione (DTTPD)), a well-known n-type monomer, was used. The characteristics of the optical and electrical characteristics and the characteristics of the organic thin film solar cell were analyzed through the following examples and experimental examples.

Hereinafter, the present invention will be described in more detail with reference to Examples. It will be apparent to those skilled in the art that these embodiments are merely illustrative of the present invention and that the scope of the present invention is not limited to these embodiments.

<Preparation of Reagents and Devices>

In the examples of the present invention, the reagents used in the synthesis of the polymer were those purchased from Aldrich. The solvents used in the reaction were Aldrich and purified gold products, and the solvents used in the extraction were purified purified gold products. The catalyst was a STREAM product. ¹ H and ¹³ C NMR spectra were measured with BRUCKER ULTRASHIELD 300 and elemental analysis was measured with CE instrument EA 1110 and EA 1112. Ultraviolet-visible light absorption spectra were obtained using HP 8435 UV-VIS-NIR spectrometer. The cyclic voltammetry (CV) was measured at a scan rate of 50 mV / s using an AUTOLAB / PG-STAT12 model system and 0.1 M tetrabytylammonium tetrafluoroborate (n-Bu ₄ NBF ₄ ) was used as the electrolyte. GPC (gel permeation chromatography) was measured with Viscotek T60A Instrument using polystyrene as a reference and TGA (thermal gravimetric analysis) with TA Q100 under nitrogen. The JV characteristics of Photovoltaic were measured at 100 mW / cm ² (AM 1.5 G) with a Newport (USA) 300 W solar simulator. Standard PV reference cells were 22 monocrystalline silicon solar cells (calibrated at NREL, Colorado, USA). The film thickness was measured using a KLA Tencor Alpha-step 500 surface profilometer with an accuracy of 1 nm.

< Example  1>

Synthesis of S-series monomers

The present inventors prepared S-based monomers through the following reaction formula.

&Lt; 1-1 > Synthesis of Compound 1 Monomer

(5.0 g, 0.059 mol) of thiophene and 60 mL of THF were placed in a 500 mL reaction flask which had been dehydrated and filled with nitrogen, and n-BuLi (n-buthyllithium) , 0.071 mol) dropwise over 30 minutes. After stirring for 10 minutes at low temperature, 2-ethylhexyl bromide (9.3 mL, 0.049 mol) was added, and then the temperature was slowly maintained at 80 ° C and then stirred for 24 hours. After removal of the solvent, the reaction mixture was extracted with water and hexane, and water was removed using anhydrous MgSO ₄ . After removing the solvent by using a rotary evaporator, 5.5 g (49%) of a pure colorless liquid was obtained by distillation under reduced pressure. NMR analysis results of the compound obtained by the production were as follows.

_{^{1 H NMR (CDCl 3, 300}} MHz, ppm): δ 7.06 (s, 1H), 7.04 (d, 1H), 6.80 (d, 1H), 2.74 (d, 2H), 1.56 (m, 1H), 1.28 -1.27 (m, 8H), 0.88 (t, 6H). ¹³ C NMR (CDCl ₃ , 75 MHz, ppm):? 111.00, 14.32, 23.22, 25.71, 29.07, 32.56, 34.02, 41.67, 76.80, 77.22, 77.65, 123.07, 125.11, 126.67, 144.41.

&Lt; 1-2 > Synthesis of Compound 2 Monomer

Dimethylformamide (11.0 mL, 0.140 mol) was added to a 500-mL reaction flask which had been dehydrated and charged with nitrogen, and phosphoryl chloride (8.5 mL, 0.089 mol) was added slowly at 0 ° C. Compound 1 (4.0 g, 0.018 mol) was added to the above container, and the mixture was reacted for 2 hours while maintaining the temperature at 85 ° C. After completion of the reaction, the reaction mixture was cooled to room temperature and sodium bicarbonate was added thereto to adjust the pH to 5 It was adjusted accordingly. The solvent was then removed, extracted with water and chloroform, and water was removed using anhydrous MgSO ₄ . After removing the solvent using a rotary evaporator, 4.0 g (89%) of a transparent liquid was obtained by distillation under reduced pressure. NMR analysis results of the obtained compound are as follows. _{^{1 H NMR (CDCl 3, 300}} MHz, ppm): δ 9.81 (s, 1H), 7.60 (d, 1H), 6.89 (d, 1H), 2.79 (d, 2H), 1.32 (m, 1H), 1.29 -1.27 (m, 8H), 0.89 (t, 6H). ¹³ C NMR (CDCl ₃ , 75 MHz, ppm):? 10.88, 14.20, 23.04, 25.65, 28.89, 32.46, 34.93, 41.57, 76.81, 77.23, 77.65, 126.95, 137.09, 141.92, 156.64, 182.70. Mass (FAB); (m / z): 225 (M ^&lt; ^{+ &} gt ^; ). Anal. Calcd. _{for C 13 H 20 OS: C} , 69.59; H, 8.98; O, 7.13; S, 14.29. Found: C, 69.97H, 8.83S, 13.94.

<1-3> Synthesis of Compound 4 Monomer

(3.0 g, 0.011 mol), Compound 3 (diethyl (thiophen-2-yl) methylphosphonate) (3.3 g, 0.014 mol) and THF (30.0 mL) were placed in a 250 mL reaction flask and stirred at room temperature. And maintained for about 30 minutes. After that, potassium-tert-butoxide (14.2 ml, 0.014 mol) was added, and the reaction was terminated after stirring for about 1 hour. After that, acetic acid was added dropwise, extracted with ethyl acetate and water, and water was removed using anhydrous MgSO ₄ . The solvent was removed using a rotary evaporator, and 3.5 g (91%) of a pale yellow liquid was obtained by silica gel chromatography using a developing solvent of hexane. The NMR analysis of the obtained compound was as follows.

_{^{1 H NMR (CDCl 3, 300}} MHz, ppm): δ 7.13 (d, 1H), 7.00-6.88 (m, 4H), 6.82 (d, 1H), 6.62 (d, 1H), 2.71 (d, 2H) , 1.59-1.50 (m, 1H), 1.29-1.28 (m, 8H), 0.88 (t, 6H). _{^{13 C NMR (CDCl 3, 75}} MHz, ppm): δ 11.04, 14.35, 23.20, 25.71, 29.07, 32.57, 34.54, 41.56, 76.81, 77.23, 77.65, 120.34, 122.17, 124.02, 125.67, 125.90, 126.28, 127.76, 140.33, 142.90, 144.26. Mass (FAB); (m / z): 304 (M ^&lt; ^{+ &} gt ^; ). Anal. Calcd. _{for C 18 H 24 S 2:} C, 71.00; H, 7.94; S, 21.06. Found: C, 70.15H, 8.14S, 20.84.

<1-4> Synthesis of Compound 5 Monomer

Compound (4) (3.0 g, 9.00 mmol) and 25 mL of solvent THF were added to a 100 mL reaction flask which had been dehydrated and charged with nitrogen, and the temperature was maintained at -40 ° C. After about 30 minutes, Lithium diisopropylamide (4.8 mL, 9.62 mmol) was slowly added dropwise and maintained at low temperature for 30 minutes, then slowly warmed to 0 ° C and BDT (0.66 g, 3.00 mmol) was added. The temperature was raised to 50 캜, stirred for 2 h, and then cooled to 0 캜. After sufficient cooling, SnCl ₂ / HCl (4.5 g / 10.0 mL) was added dropwise and stirred at ambient temperature for 10 minutes. The reaction mixture was extracted with water and chloroform, and water was removed using anhydrous MgSO ₄ . The solvent was removed using a rotary evaporator, and 0.76 g (30%) of pure yellow solid was obtained through silica gel chromatography using a developing solvent of hexane: chloroform = 4: 1. NMR analysis results are as follows. _{^{1 H NMR (CDCl 3, 300}} MHz, ppm): δ 7.70 (d, 2H), 7.58 (d, 2H), 7.35 (d, 2H), 7.14 (d, 2H), 7.04 (d, 2H), 6.95 2H), 6.88 (d, 2H), 2.75 (d, 4H), 1.54 (m, 2H), 1.34 (m, 18H), 0.89 (t, 12H). ¹³ C NMR (CDCl ₃ , 75 MHz, ppm):? 8.04, 0.22, 11.09, 14.37, 23.22, 25.78, 29.12, 32.63, 34.64, 41.63, 120.30, 122.61, 126.04, 126.55, 128.97, 131.15, 137.57, 140.42, 143.14, 143.69, 144.64. Mass (FAB); (m / z): 794 (M ^&lt; ^{+ &} gt ^; ). Anal. Calcd. for C ₄₆ H ₅₀ S ₆ : C, 69.47; H, 6.34; S, 24.19. Found: C, 69.78H, 6.25S, 23.74.

&Lt; 1-5 > Synthesis of Compound 6 Monomer

Compound 5 (0.7 g, 0.820 mmol) and 20 mL of THF were added to a 100 mL reaction flask which had been dehydrated and charged with nitrogen and kept at -60 캜 for 30 minutes. Lithium diisopropylamide (0.94 mL, 1.89 mmol) was slowly added dropwise thereto, stirred for 30 minutes, further cooled to -78 ° C, and Me ₃ SnCl (2.05 mL, 2.05 mmol) was added thereto and slowly warmed. After the temperature was raised to room temperature, the mixture was stirred for 4 hours, then extracted with water and chloroform, and water was removed using anhydrous MgSO ₄ . The solvent was removed using a rotary evaporator, followed by reprecipitation with methanol and chloroform to obtain 0.82 g (85%) of yellow solid. _{^{1 H NMR (CDCl 3, 300}} MHz, ppm): δ 7.70 (s, 2H), 7.39 (d, 2H), 7.14 (d, 2H), 7.02 (d, 2H), 6.97 (d, 2H), 6.88 (d, 2H), 6.65 (d, 2H), 2.76 (d, 4H), 1.31 (m, 16H), 0.90 (t, 12H), 0.41 (t, 18H). ¹³ C NMR (CDCl ₃ , 75 MHz, ppm):? 11.08, 14.37, 23.22, 25.78, 29.12, 32.63, 34.64, 41.63, 76.81, 77.23, 77.65, 120.29, 122.35, 122.60, 126.04, 126.21, 126.55, 128.97, 131.14, 137.56, 138.98, 140.42, 143.13, 143.54, 143.69, 144.63. Mass (FAB); (m / z): 1120 (M ^&lt; ^{+ &} gt ^; ). Anal. Calcd. for C ₅₂ H ₆₆ S ₆ Sn ₂ : C, 55.72; H, 5.93; S, 17.16; Sn, 21.18. Found: C, 57.14H, 6.07S, 16.31.

<1-6> Synthesis of Compound 7 Monomer

Compound 7 shown in the above reaction formula was used as a monomer for synthesizing the polymer of the following preparation example and compound 7 was obtained by the same method as the compound described in the above reaction formula, Were synthesized.

< Example  2 to 3>

Synthesis of polymers using S-series monomers

The polymer was synthesized through the following reaction using the S-series monomer prepared in Example 1.

< Example  2 of P2  Polymer synthesis>

 To a 100 mL reaction flask filled with nitrogen was added Compound 6 (0.3 g, 0.255 mmol) and 1,3-bis (5-bromothiophen-2-yl) -5- (2-

(Pph ₃ ) ₄ (8.8 mg, 7.6410 ^-3 mmol) and 11 mL of a 10: 1 toluene / DMF solvent were added to a solution of [3,4-c] pyrrole-4,6- . Then, the mixture was heated at 60 DEG C while stirring for 8 hours, then poured into 10% aqueous HCl solution and stirred for 30 minutes. Then, it was filtered under reduced pressure, and then subjected to vacuum filtration using chloroform and methanol, followed by soxhlet purification in the order of methanol, acetone, and chloroform. The solvent was removed using a rotary evaporator, and then redeposited using methanol to obtain 0.32 g (98%) of a dark blue solid. Anal. Calcd. for (C ₇₈ H ₉₁ NO ₂ S ₉ ) _n : C, 68.73; H, 6.73; N, 1.03; O, 2.35; S, 21.17. Found: C, 68.60H, 6.75; N, 1.01; S, 20.91.

< Example  3 of P3  Polymer synthesis>

(0.25 g, 0.223 mmol) and 1- (4,6-Dibromo-3-fluorothieno [3,4-b] thiophen-2-yl) -2-ethylhexan-

1-one (0.098 g, 0.223 mmol), Pd (pph ₃ ) ₄ (15 mg, 13.3810 ^-3 mmol) and toluene / DMF in a ratio of 10: 1. Then, the mixture was stirred for 24 hours while being heated to 110 ° C., and the mixture was poured into a 10% aqueous solution of HCl for 10 minutes. The mixture was then subjected to filtration under reduced pressure, followed by vacuum filtration using methanol and chloroform. The solvent was removed using a rotary evaporator, and then reprecipitated with methanol to obtain 0.21 g (88%) of a dark blue solid.

< Comparative Example  1>

P1  Polymer synthesis

(0.2 g, 0.264 mmol) and 1,3-bis (5-bromothiophen-2-yl) -5- (2-octyldodecyl) -5H-thieno [3,4-c ] pyrrole-4,6-dione (0.215 g, 0.277 mmol) was added to a solution of tetrakistriphynylphosphine palladium (0) Pd (PPh ₃ ) ₄ (9.0 mg, 7.9410 ^-3 mmol) in toluene / DMF Respectively. Then, the mixture was heated to 60 DEG C while stirring for 5 hours, then poured into 10% aqueous HCl solution and stirred for 30 minutes. The mixture was filtered under reduced pressure, filtered through chloroform and methanol under reduced pressure, and subjected to soxhlet purification in the order of methanol, acetone, and chloroform. The solvent was removed by using a rotary evaporator, and then reprecipitated with methanol to obtain 0.18 g (62%) of a dark blue solid. Analytical results of the obtained solid are as follows.

Anal. Calcd. for (C ₆₃ H ₈₉ NO ₄ S ₅ ) _n : C, 69.76; H, 8.27; N, 1.29; O, 5.90; S, 14.78. Found: C, 68.79; H, 7.96; N, 1.33; S, 15.32.,

< Example  4>

Se Synthesis of monomers

The present inventors prepared Se-based monomers through the following reaction formula.

&Lt; 4-1 > Synthesis of Compound 8 Monomer

Dimethylformamide (DMF) (22.91 mL, 0.296 mol) was added to a 500 mL reaction flask filled with nitrogen and the temperature was reduced to 0 ° C. After stirring for 30 minutes, 13.9 mL of POCl ₃ (99%, 0.148 mol) And kept for 30 minutes. Selenophene (10.0 g, 0.074 mol) was slowly added dropwise thereto, and the temperature was raised to room temperature. The reaction was then allowed to proceed at room temperature for 24 hours. Aqueous NaHCO ₃ And water were alternately extracted with chloroform and water was removed using anhydrous MgSO ₄ . The solvent was removed using Reducing vacuum distillation and 10.70 g (88%) of a colorless liquid was obtained. _{^{1 H NMR (CDCl 3, 300}} MHz, ppm): δ 9.70 (s, 1H), 7.83 (s, 1H), 7.28 (s, 1H), 2.86 (d, 2H), 1.60 (m, 1H), 1.29 (m, 8 H), 0.89 (t, 6 H)

<4-2> Synthesis of Compound 9 Monomer

Add 10 g of selenophene (95%, 0.073 mol) and 100 mL of THF to a 500 mL reaction flask with water removed and nitrogen purged to -78 ° C. After the low-temperature condition is maintained sufficiently, 67.9 mL of n-BuLi (1M in THF) is slowly added dropwise. After stirring for 10 minutes, add 20.4 mL of 2-ethylhexylbromide (95%, 0.110 mol) and raise the temperature to 50 ° C. After stirring for 24 hours, the mixture was extracted with ethyl acetate and water, and water was removed using anhydrous MgSO ₄ . And distilled under reduced pressure to obtain 7.75 g (44%) of a colorless liquid. _{^{1 H NMR (CDCl 3, 300}} MHz, ppm): δ 7.72 (d, 1H), 7.04 (t, 1H), 6.84 (d, 1H), 2.75 (d, 2H), 1.45 (m, 1H), 1.25 (m, 8 H), 0.82 (t, 6 H). ¹³ C NMR (CDCl ₃ , 75 MHz, ppm):? 152.00, 129.07, 128.36, 127.41, 42.44, 36.68, 32.53, 29.07, 25.67, 23.21, 14.33, 11.01. Mass (FAB); (m / z): 244 (M ^&lt; ^{+ &} gt ^; ). Anal. Calcd. for C ₁₂ H ₂₀ Se: C, 59.25; H, 8.29; Se, 32.46. Found: C, 54.69; H, 7.80.

<4-3> Synthesis of Compound 10 Monomer

Add a solution of compound 9 (8.0 g, 0.033 mol) and 20 mL of 1.4-dioxane in a 250 mL reaction flask which has been freed from moisture and charged with nitrogen and maintain the temperature at 10 ° C. Add 6.5 mL of HCl (37%, 0.079 mol) and drop the temperature to 0 ° C. Add 1.35 g of paraformaldehyde (95%, 0.043 mol) and let the temperature rise to room temperature. After stirring for 1 hour, add 1.35g of paraformaldehyde (95%, 0.043mol) and 6.5mL of HCl (37%, 0.079mol) once more at room temperature. The temperature was raised to 40 ° C and stirred for 4 hours. Add 1.35 g of paraformaldehyde (95%, 0.043 mol) and 6.5 mL of HCl (37%, 0.079 mol) once more. After stirring for 1 hour, the mixture is extracted with ethyl acetate using NaHCO ₃ and water, and water is removed using anhydrous MgSO ₄ . The solvent is removed with a rotary evaporator and the following reaction is sent in situ. _{^{1 H NMR (CDCl 3, 300}} MHz, ppm): δ 7.01 (d, 1H), 6.72 (d, 1H), 4.79 (s, 2H), 2.78 (d, 2H), 1.54 (m, 1H), 1.29 (m, 8 H), 0.88 (t, 6 H).

<4-4> Synthesis of Compound 11 Monomer

Add 5.8 mL of triethyl phosphite (98%, 0.033 mol) to 8.8 g of compound 10 (0.030 mol) in a 50 mL round bottom flask. The temperature is raised to 160 ° C and after 6 hours, 5.8 mL of triethyl phosphite (98%, 0.033 mol) is added. After stirring for 6 hours, add 5.8 mL of triethyl phosphite (98%, 0.033 mol) and stir for 24 h. And distilled to obtain 6.5 g (55%) of a colorless liquid. _{^{1 H NMR (CDCl 3, 300}} MHz, ppm): δ 6.88 (d, 1H), 6.73 (d, 1H), 4.10 (m, 4H), 3.41 (d, 2H), 2.75 (d, 2H), 1.50 (m, 1H), 1.34-1.25 (m, 14H), 0.89 (t, 6H) 3.08 (s, 6H). ¹³ C NMR (CDCl ₃ , 75 MHz, ppm):? 144.05, 129.85, 127.08, 125.07, 62.53, 41.46, 34.11, 32.43, 28.95, 27.31, 25.59, 23.10, 16.52, 14.22, 10.93. Anal. Calcd. for C ₁₇ H ₃₁ O ₃ PSe : C, 51.91; H, 7.94; O, 12.20; P, 7.87; Se, 20.07. Found: C, 57.87; H, 8.80; O, 4.35.

<4-5> Synthesis of Compound 12 Monomer

Add 2.1 g of compound 8 (0.013 mol) and 6.2 g of compound 11 (0.016 mol) into a 100 mL reaction flask which is freed from moisture and charged with nitrogen. Add 30 mL of THF and lower the temperature to 0 ° C. Add 15.8 mL of t-BuOK (1M in solution) slowly and raise the temperature to room temperature. After stirring for 2 hours, the mixture was extracted with hexane and water, and water was removed using anhydrous MgSO ₄ . The solvent was removed using a rotary evaporator, and 4.6 g (88%) of a pure colorless liquid was obtained by silica gel chromatography using a developing solvent of hexane: ethyl acetate = 10: 1. _{^{1 H NMR (CDCl 3, 300}} MHz, ppm): δ 7.80 (d, 1H), 7.18 (m, 1H), 7.13 (m, 1H), 6.95 (m, 1H), 6.89 (s, 1H), 6.87 (s, 1H), 6.76 (d, 1H), 2.78 (d, 2H), 1.31 (m, 1H), 1.31-1.26 (m, 8H), 0.91 (t, 6H). ¹³ C NMR (CDCl ₃ , 75 MHz, ppm):? 151.13, 148.83, 146.25, 130.26, 128.91, 128.58, 128.47, 128.16, 125.80, 124.03, 42.21, 37.16, 32.49, 29.02, 25.66, 23.16, 14.33, 11.02. Mass (FAB); (m / z): 399 (M ^&lt; ^{+ &} gt ^; ). Anal. Calcd. for C ₁₈ H ₂₄ Se ₂ : C, 54.28; H, 6.07; Se, 39.65. Found: C, 55.30; H, 6.13.

<4-6> Synthesis of Compound 13 Monomer

Add a solution of compound 12 (2.3 g, 6.91 mmol) and 20 mL of THF into a 100 mL reaction flask that is free of water and charged with nitrogen and lower the temperature to 0 ° C. 4.8 mL of lithium diisopropylamide (2M in THF, 9.66 mmol) is slowly added dropwise, and the mixture is stirred for 1 hour. 4.8-dihydrobenzo [1,2-b: 4,5-b '] dithiophen-4,8-dione, BDT (2.76 mmol, 0.62 g) was added and the temperature was raised to 50 ° C. After stirring for 2 hours and lowering the temperature to 0 ℃ SnCl _{2 ·} 2H ₂ gives into the O / HCl (6.24g / 20mL) . After stirring for 10 minutes, the mixture was extracted with chloroform and water, and water was removed using anhydrous MgSO ₄ . The solvent was removed using a rotary evaporator, and 1.78 g (80%) of a yellow solid was obtained by silica gel chromatography using a developing solvent of hexane: chloroform = 4: 1. _{^{1 H NMR (CDCl 3, 300}} MHz, ppm): δ 7.69 (d, 2H), 7.49 (s, 2H), 7.48 (s, 2H), 7.26 (d, 2H), 7.01 (d, 2H), 6.97 (d, 2H), 6.94 (d, 2H), 6.81 (d, 2H), 2.80 (d, 4H), 1.54 (m, 2H), 1.31 (m, 16H), 0.90 ¹³ C NMR (CDCl ₃ , 75 MHz, ppm):? 151.77, 150.46,146.27,142.79,136.49,131.54,129.38,128.91,128.36,128.01,126.42,124.18,123.95,123.62,42.36,37.32,32.61,19.13, 25.77, 23.23, 14.37, 11.09. Mass (FAB); (m / z): 984 (M ^&lt; ^{+ &} gt ^; ). Anal. Calcd. for C ₄₆ H ₅₀ S ₂ Se ₄ : C, 56.21; H, 5.13; S, 6.52; Se, 32.13 Found: C, 56.49; H, 5.16; S, 5.06.

<4-7> Synthesis of Compound 14 Monomer

Compound (13) (1.5 g, 1.88 mmol) is added to a 100 mL reaction flask which is freed from moisture and charged with nitrogen, charged with nitrogen, 30 mL of THF in which moisture is removed, and the mixture is stirred at -40 ° C for 30 minutes. Allow the LDA (2M in THF) (3.01mL, 4.71mmol) slowly after the low temperature condition is maintained. trimethyltin chloride (6.51 mL, 5.09 mmol) was added, and the mixture was stirred for 10 minutes. The temperature is raised to room temperature. After stirring for 2 hours, the mixture was extracted with water and chloroform, and water was removed using anhydrous MgSO ₄ . The solvent was removed using a rotary evaporator, and the residue was reprecipitated with chloroform and methanol to obtain 1.66 g (80%) of a yellow solid. The NMR analysis results of the obtained compound are as follows. _{^{1 H NMR (CDCl 3, 300}} MHz, ppm): δ 7.72 (s, 2H), 7.50 (d, 2H), 7.28 (d, 2H), 7.01 (d, 2H), 6.98 (d, 2H), 6.95 (d, 2H), 6.80 (d, 2H), 2.80 (d, 4H), 1.32 (m, 16H), 0.90 (t, 12H), 0.41 (s, 18H). ¹³ C NMR (CDCl ₃ , 75 MHz, ppm):? 151.42, 149.90, 146.20, 143.61, 137.09, 131.19,129.03,128.82,128.16,122.02,123.92,42.16,37.13,32.41,28.93,25.59,23.03,14.18, 10.90. Mass (FAB); (m / z): 1308 (M ^&lt; ^{+ &} gt ^; ). Anal. Calcd. for C ₅₂ H ₆₆ S ₂ Se ₄ Sn ₂ : C, 48.22; H, 5.08; S, 4.90; Se, 24.14; Sn, 18.14. Found: C, 48.22; H, 5.14; S, 5.00.

< Example  5 to 6>

Se Synthesis of Polymers Using Monomers

Polymers of P4 and P5 were synthesized by the following reaction formula using the Se system monomers prepared in Example 4, respectively.

<Synthesis of P4 Polymer of Example 5>

(0.25 g, 0.191 mmol) and 1,3-bis (5-bromothiophen-2-yl) -5- (2-octyldodecyl) -5H-thieno [3,4-c ] pyrrole-4,6-dione (0.13 g, 0.181 mmol) was added and tetrakis (triphynylphosphine) palladium (0) Pd (PPh ₃ ) ₄ (6.62 mg, 5.7310 ^-3 mmol) was added. Then, 11 mL of nitrogen-treated anhydrous toluene: DMF = 10: 1 was added, and the mixture was stirred for 10 hours while being heated to 100 ° C., and then poured into 10% aqueous HCl solution and stirred for 30 minutes. The mixture was filtered under reduced pressure, filtered through chloroform and methanol, and purified by soxhlet in the order of methanol, acetone, hexane and chloroform. The solvent was removed using a rotary evaporator, and then reprecipitated with methanol to obtain 0.23 g (77%) of a dark black solid P1. Anal. Calcd. for (C ₇₉ H ₉₃ NO ₂ S ₅ Se ₄ ) _n : C, 60.64; H, 5.99; N, 0.90; O, 2.04; S, 10.25; Se, 20.18. Found: C, 60.17; H, 6.15; N, 0.83; S, 9.18.

< Example  6 of P5  Polymer synthesis>

To a 100 mL reaction flask filled with nitrogen was added compound 14 (0.25 g, 0.191 mmol) and 3,6-bis (5-bromo-2-thienyl) -2,5-bis (2- hexyldecyl) 3,4-c] pyrrole-1,4-dione (0.16 g, 0.181 mmol) was added and tetrakis (triphynylphosphine) palladium (0) Pd (PPh ₃ ) ₄ (6.62 mg, 5.7310 ^-3 mmol) was added. Then, 11 mL of nitrogen-treated anhydrous toluene: DMF = 10: 1 was added, and the mixture was heated to 100 ° C. and stirred for 7 hours. The mixture was then poured into 10% aqueous HCl solution and stirred for 30 minutes. The mixture was filtered under reduced pressure, filtered through chloroform and methanol, and purified by soxhlet in the order of methanol, acetone, hexane and chloroform. The solvent was removed using a rotary evaporator, and then reprecipitated with methanol to obtain 0.27 g (83%) of a dark black solid P2. Anal. Calcd. for (C ₉₂ H ₁₂₀ N ₂ O ₂ S ₄ Se ₄ ) _n : C, 63.87; H, 6.99; N, 1.62; O, 1.85; S, 7.41; Se, 18.26. Found: C, 63.42; H, 6.84; N, 1.52; S, 7.29.

< Experimental Example  1>

Molecular weight and thermal characterization of polymers according to the present invention

The present inventors analyzed the molecular weight and thermal properties of the five polymers (P1, P2, P3, P4, P5) prepared in the above examples.

Polydispersity indices (PDI) were measured by GPC using polystyrene as a standard and chloroform as a solvent. The results are shown in Table 1 (molecular weight of the polymer and ultraviolet-visible light maximum Absorption wavelength results). In addition, the synthesized polymers showed high solubility in common organic solvents such as chloroform, toluene, and chlorobenzene. In addition, the thermal properties of the polymers were measured using TGA, and it was confirmed that the polymers measured by TGA were thermally stable at a decomposition temperature (T _d ) of 300 ° C. or higher (see FIG. 1 Reference).

< Experimental Example  2>

Analysis of visible light absorption wavelength and electrical characteristics of polymer according to the present invention

Ultraviolet-visible light absorption spectra of the polymers prepared in the above examples were analyzed. For this purpose, 0.5 wt% solution was prepared by using chloroform in all the polymers, and the solution was filtered with a 0.45 μm polypropylene (PP) syringe filter Respectively. Spin-coated at 1000 rpm, and then measured through ultraviolet-visible light absorption spectra in a solution state and a thin film state.

The results of the analysis are shown in FIG. 2. Polymer P1 showed absorption peaks at 430, 530 and 591 nm in the solution state, 428, 531 and 591 nm in the thin film state, and polymer P2 at 389, 570 and 612 nm in the solution state 410, 569, and 613 nm, respectively. The absorption peak at 400 nm, which is short wavelength, is the absorption peak due to the benzodiethiophene unit, and the absorption peak at 530-590 nm, which is the long wavelength, is the effect of intramolecular charge transfer (ICT) between the electron acceptor substance and electron donor substance It is expected to be due to peaks. It was observed that the maximum absorption wavelength of the short wavelength region shifted to the long wavelength region of about 40 nm between the two polymers in the solution and the thin film state because of the increase of the effective conjugation length by the side chain of dithienylene (DTE). In addition, the intensity of absorption in the 350-450 nm region of the short wavelength region was also found to increase with increasing conjugation side chain to benzodiethiophene, resulting in an increase in inter-molecule π-π interaction and an increase in effective conjugation length (See FIG. 3). 3, it can be seen that the absorption coefficient of P2 (7.5 x 10 ⁴ cm ^-1 ) is twice as large as that of P1 (3.7 x 10 ⁴ cm ^-1 ) in the absorption coefficient graph. This is probably due to the increase in the chromophore density by the DTE side chain group introduced into BDT. Both P1 and P2 showed absorption in the region of 300-750 nm.

The inventors of the present invention performed a cyclic voltammetric (CV) analysis to confirm that the polymers prepared in the present invention have a low energy band gap. As a result, the polymer P2 of the present invention has an energy band of 1.84Eg (eV) While the polymer P1 exhibited a higher energy band gap of 1.91Eg (eV) than P2.

The HOMO value of each of the P1 and P2 polymers was measured by cyclic voltammetry. The electrolyte solution was a solution of 0.1 M tetrabutylammonium tetrafluoroborate (n-Bu ₄ NBF ₄ ) dissolved in acetonitrile, As a counter electrode, Ag / Ag ⁺ As a reference electrode, ferrocene was used as a reference material. The HOMO value was calculated using the following equation.

E _HOMO (eV) = - (4.8 + E _onset ) + (E _{onset of} ferrocene)

As a result of the analysis, the HOMO value of the polymer was -5.55 eV for the polymer and -5.63 eV for the P2, and the LUMO value of the polymer calculated using the optical bandgap of the UV-visible was P1 - 3.63 eV, and P2 was -3.68 eV. In the organic thin-film solar cell, V _oc is determined by the difference between the HOMO value of the polymer and the LUMO value of the electron acceptor PCBM, so that the V _{oc of} P2 is larger than P1.

Also, the charge mobility of P1 and P2 was measured. In order to achieve this, the gate electrode of aluminum (1500 Å), insulator SiO ₂ (3000 Å) and gold (1200 Å) (OTFT) was fabricated, and a device having a channel length (L) of 12 μm and a channel width (W) of 120 μm was used. The substrate was treated with OTS-8 (octyltrichlorosilane) solution and MNB (2-mercapto-5-nitrogenzinidazole) solution to reduce contact resistance. The organic semiconductor thin film was prepared with 1 wt% polymer solution under nitrogen using chloroform and spin coated at 1000 rpm for 30 seconds. The coated substrate was heat-treated at 100 ° C for 5 minutes under nitrogen, and the P-type TFT performance was measured. In order to measure the performance of each polymer as an organic thin film transistor, the drain voltage was fixed at -60 V and the transfer curve was drawn by varying the gate voltage. Through this, the charge carrier mobility and on / off ratio ratio.

As a result of this charge mobility analysis, P1 has a charge mobility of 7.7 x 10 ^-5 , while P2 has a charge mobility of 1.8 x 10 ^-3 cm ² V ^-1 s ^-1 . Therefore, P2 shows more charge mobility than P1.

Optical and electrical properties of polymer Polymer Solution
(? _max , nm) Film
(? _max , nm) Eg
(eV) E _HOMO
(eV) E _LUMO
(eV) Mobility
(cm ² / Vs) P1 430, 530, 591 428, 531, 591 1.91 5.55 3.64 7.7 x 10 ^-5 P2 389, 570, 612 410, 569, 613 1.84 5.63 3.68 1.8 x 10 ^-3

< Experimental Example  3>

Analysis of solar cell characteristics

The present inventors analyzed the characteristics of a solar cell fabricated and fabricated with organic thin film solar cell elements P1 and P2 among the polymers prepared in the above examples. First, in order to manufacture a solar cell device, each of the polymers (P1 and P2) and PC ₇₁ BM were mixed using chloroform. The concentration was adjusted to 2.0 wt%. Polymer solar cell devices were fabricated with a typical sandwich structure of ITO / PEDOT: PSS / photoactive layer / LiF / Al. The ITO coated glass substrate was sonicated in a detergent and wiped with distilled water, acetone, and 2-propanol. PEDOT: The PSS (Baytron P) layer was exposed to ozone for 10 minutes and then spin-coated to a thickness of 40 nm. And then heated on a heater at 110 ° C for 10 minutes. The photoactive layer was spin-coated with a mixed solution filtered with a 0.45 μm PP syringe filter. Finally, fabrication of the device was completed by depositing a 150 nm cathode on the photoactive layer under a vacuum of 10 ^-6 torr. All of this was done under a nitrogen atmosphere.

The characteristics of the organic thin film solar cell for the polymer are shown in Table 2 below, and the IV curve is shown in FIG. The maximum PCE value of P2 polymer was obtained when 3% 1,8-diiodooctane (DIO) additive was added at 1: 1 mixing ratio of polymer and PCBM. In this case, the P1 element has a V _oc of 0.84 V, a J _sc of 5.96 mA / cm ² , a FF of 0.60 and an energy conversion efficiency of 3.03%. In the case of the P2 element, V _oc is 0.87 V and J _sc is 10.90 mA / cm ² , FF was 0.63, and the energy conversion efficiency was 6.04%. In the case of V _oc , P2 has a larger V _oc value, which is considered to be due to its lower HOMO value than alkoxy polymer. In J _sc value, the value of P2 is about twice as large as that of P1, which is expected to have a large value of the charge mobility of P2 and the effect of the optical properties of the polymer. By introducing DTE side chains into BDT, the degree of absorption in the short wavelength region was increased, which would have contributed to the improvement of J _sc and PCE values in organic solar cell characteristics of P2 polymer.

In addition, the morphology of the photoactive layer is very important for the efficiency of the organic solar cell, and in some cases, the characteristics of the device depend greatly on the morphology. AFM (atomic force microscopy) was measured to observe the surface morphology of the photoactive layer after the fabrication of the device. FIG. 5 shows the AFM height image of the device of the polymer pre-annealed at 100 ° C. The difference in AFM image between the case with and without DIO additive was remarkable in both polymers. In the case of the additive in the two polymers, it can be seen that the polymer and PCBM are evenly dispersed, which increases the area of the interface where the polymer and PCBM can meet, thereby allowing the charge separation and charge transfer to take place effectively. Therefore, it was found that the J _sc of the DIO additive was significantly increased.

From the above results, the present inventors have found that the introduction of the side chain conjugate substituent influences the optical characteristics, the control of the HOMO energy level, and the charge mobility in the ultraviolet-visible light region, (BDT) family of benzo [1,2-b: 4,5-b '] dithiophene (BDT) Could know.

The present invention has been described with reference to the preferred embodiments. It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims. Therefore, the disclosed embodiments should be considered in an illustrative rather than a restrictive sense. The scope of the present invention is defined by the appended claims rather than by the foregoing description, and all differences within the scope of equivalents thereof should be construed as being included in the present invention.

Claims (8)

A polymer having the following structural formula introduced with a conjugated side chain;

R is an alkyl group having 1 to 30 carbon atoms, m is an integer of 1 to 5, 1 is an integer of 0 to 5, and Y is S, O, Se or Te. The method according to claim 1,
A is a polymer selected from the group consisting of compounds having the following structural formulas;

Wherein Z is S, O or Se;
R ²¹ to R ³⁷ independently of one another are hydrogen, halogen, (C 1 -C 30) alkyl, (C 1 -C 30) alkoxy, (C 1 -C 30) alkoxycarbonyl or (C 6 -C 30) ;
The alkyl group, alkoxy, alkoxycarbonyl, and aralkyl of R ²¹ to R ³⁷ are independently selected from the group consisting of (C 1 -C 30) alkyl, (C 2 -C 30) alkenyl, (C 2 -C 30) alkynyl, A halogen atom, a cyano group, a nitro group, a trifluoromethyl group, and a silyl group;
R ⁴¹ to R ⁴⁶ are hydrogen or a (C 1 -C 30) alkyl group; k is an integer of 1 to 2; The method according to claim 1,
Wherein the polymer has a number average molecular weight of 40,000 to 140,000. The method according to claim 1,
Wherein the polymer has an absorption wavelength of 300 to 750 nm in the ultraviolet and visible light regions. The method according to claim 1,
Wherein the polymer has an energy band gap of 1.80 to 1.90 eV. An organic photonic device comprising the polymer according to any one of claims 1 to 5. The method according to claim 6,
The organic photonic device may be an organic solar cell, an organic memory, an organic light emitting diode, an organic sensor, an organic thin film transistor, an organic light emitting diode (OLED), a polymeric light emitting diode (PLED), an organic integrated circuit (O- A transistor (OFET) or an organic electroluminescent display. The method according to claim 6,
Wherein the organic photonic device comprises a layered structure of indium tin oxide (ITO) / PEDOT: PSS / photoactive layer / LiF / Al, and the photoactive layer comprises the polymer of claim 1.

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