Conductive polymers, the organic photovoltaic cell comprising the same, and the synthesis thereof

Abstract

The present invention relates to a conductive polymer, the organic photovoltaic cell comprising the same, and the synthesis method of the same. The novel polymer, according to the present invention, displays more excellent optical properties and higher photoelectric conversion efficiency than the conventional RRa (regiorandom) polymer due to its symmetrical structure of quaterthiophene and benzothiadiazole substituted with fluorine.

Claims

1. A method for preparing the polymer represented by formula 1, which comprises the following steps: (a) producing the compound represented by formula 2 having a symmetrical structure by reacting a quaterthiophene derivative and a benzothiadiazole derivative with the substitution of bromine and fluorine in the presence of a palladium catalyst; (b) producing the compound represented by formula 3 by reacting the compound represented by formula 2 with a brominating agent; and (c) reacting the compound represented by formula 3 with a bithiophene derivative in the presence of a palladium catalyst: ##STR00026## wherein R is independently C.sub.1?C.sub.30 straight or branched alkyl, C.sub.1?C.sub.30 straight or branched alkoxy, or C.sub.6?C.sub.30 aryl, wherein the alkyl, alkoxy, and aryl can be substituted with one or more C.sub.1?C.sub.10 alkyl, hydroxyl, amino, or carboxy, and the alkyl, alkoxy, and aryl can independently contain one or more hetero atoms, X is independently H or F, N is an integer of 1?500.

2. The method for preparing the polymer represented by formula 1 according to claim 1, wherein the R in the formulas above is independently selected from the group consisting of ethylhexyl, butyloctyl, hexyldecyl, and octyldodecyl.

3. The method for preparing the polymer represented by formula 1 according to claim 1, wherein the palladium catalyst is selected from the group consisting of PdCl2, Pd(OAc)2, Pd(CH3CN)2Cl2, Pd(PhCN)2Cl2, Pd2(dba)3, and Pd(PPh3)4.

4. The method for preparing the polymer represented by formula 1 according to claim 1, wherein the quaterthiophene derivative is (3,3-bis(2-octyldodecyl)-[2,2:5,2:5,2-quaterthiophene]-5,5-yl)bis(trimethylstannane) or (3,4-difluoro-3,3-bis(2-octyldodecyl)-[2,2:5,2: 5,2-quaterthiophene]-5,5-diyl)bis(trimethylstannane).

5. The method for preparing the polymer represented by formula 1 according to claim 1, wherein the benzothiadiazole derivative with the substitution of bromine and fluorine is 4-bromo-5-fluoro-7-(4-(2-octyldodecyl)thiophene-2-yl)benzo[c][1,2,5]thiadiazole.

6. The method for preparing the polymer represented by formula 1 according to claim 1, wherein the bithiophene derivative is 5,5-bis(trimethylstannyl)-2,2-bithiophene or (3,3-difluoro-[2,2-bithiophene]-5,5-diyl)bis(trimethyl stannane).

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The application of the preferred embodiments of the present invention is best understood with reference to the accompanying drawings, wherein:

(2) FIG. 1 presents the UV-vis absorption spectra of the polymer compound of the invention (RR PfBT4T-OD) in solution and on film.

(3) FIG. 2 presents the UV-vis absorption spectra of the polymer compound of the invention (RR-PfBTff4T-OD) in solution and on film.

(4) FIG. 3 presents the cyclic voltammetry of the polymer of the invention (RR PfBT4T-OD).

(5) FIG. 4 presents the cyclic voltammetry of the polymer of the invention (RR-PfBTff4T-OD).

(6) FIG. 5 is a graph illustrating the current density-voltage curve of the organic photovoltaic cell comprising the polymer compound of the invention (RR PfBT4T-OD).

(7) FIG. 6 is a graph illustrating the current density-voltage curve of the organic photovoltaic cell comprising the polymer compound of the invention (RR-PfBTff4T-OD).

DESCRIPTION OF THE PREFERRED EMBODIMENTS

(8) Hereinafter, the present invention is described in detail.

(9) The present invention relates to the polymer compound represented by formula 1 below.

(10) ##STR00004##

(11) In formula 1, R is independently C.sub.1?C.sub.30 straight or branched alkyl, C.sub.1?C.sub.30 straight or branched alkoxy, or C.sub.6?C.sub.30 aryl, wherein the alkyl, alkoxy, and aryl can be substituted with one or more C.sub.1?C.sub.10 alkyl, hydroxyl, amino, or carboxy, and the alkyl, alkoxy, and aryl can independently contain one or more hetero atoms,

(12) X is independently H or F,

(13) N is an integer of 1?500.

(14) In a preferred embodiment of the present invention, R of formula 1 can be the one selected from the group consisting of ethylhexyl, butyloctyl, hexyldecyl, and octyldodecyl, and preferably is octyldodecyl.

(15) As confirmed in the experimental example which would be described hereinafter to explain the polymer compound of the invention, the polymer compound of the invention can be used as an optoelectronic device material applicable to organic photovoltaic cell, organic photovoltaic device, display device such as OLED, OTFE, photodetector, organic/inorganic hybrid solar cell, etc, due to the excellent optical properties and high photoelectric conversion efficiency and more preferably used as an electron donor material for the photoactive layer of an organic photovoltaic cell. In a preferred embodiment of the present invention, the display device contains the first electrode, the second electrode, the hole transport layer placed in between the first electrode and the second electrode, and the photoelectric layer comprising an emitting layer. Herein, the photoelectric layer can contain the conductive polymer compound of an example of the invention. In an example of the invention, the photodetector includes a substrate, an electrode disposed on the substrate, and a light receiving layer connected to the electrode. The light receiving layer can contain the conductive polymer of an example of the invention.

(16) The present invention also relates to an organic photovoltaic cell comprising the polymer compound above.

(17) Particularly, the present invention relates to an organic photovoltaic cell comprising a cathode and an anode opposite to each other; and at least one photoactive layer in between the anode and the cathode, wherein the photoactive layer contains the polymer compound represented by formula 1 as an electron donor and an electron acceptor.

(18) In a preferred embodiment of the present invention, the electron acceptor can be one or more materials selected from the group consisting of fullerene (C60), fullerene derivative, perylene, perylene derivative, and semiconductor nanoparticle.

(19) The fullerene derivative can be [6,6]-phenyl-C61-butyric acid methyl ether (PCBM) or [6,6]-phenyl-C71-butyric acid methyl ether (PC71BM). The perylene derivative is 3,4,9,10-perylenetetracarboxylic bisbenzimidazole (PTCBI). The semiconductor nanoparticle can be selected from the group consisting of ZnO, TiO2, CdS, CdSe, and ZnSe.

(20) In another preferred embodiment of the present invention, the organic photovoltaic cell can additionally include a hole transport layer in between the photoactive layer and the anode.

(21) The hole transport layer can be one or more compounds selected from the group consisting of low molecular weight compounds and polymers containing PEDOT:PSS [poly(3,4-ethylenedioxythiophene):poly(4-styrene sulfonate)], G-PEDOT [poly(3,4-ethylenedioxythiophene):poly(4-styrene sulfonate):polyglycol(glycerol)], PANI:PSS [polyaniline:poly(4-styrene sulfonate)], PANI:CSA (polyaniline:camphor sulfonic acid), PDBT [poly(4,4-dimethoxy bithiophene)], and arylamine group, and low molecular weight compounds and polymers containing aromatic amine group.

(22) In another preferred embodiment of the present invention, the organic photovoltaic cell can additionally include a electron transport layer in between the photoactive layer and the cathode.

(23) The electron transport layer can be one or more materials selected from the group consisting of ZnO nanoparticle, Doped-ZnO (ZnO:Al, ZnO:B, ZnO:Ga, ZnO:N, etc.) nanoparticle, SnO2 nanoparticle, ITO nanoparticle, and TiO2 nanoparticle in metal oxide sol (or solution), and titanium(diisoproxide)bis(2,4-pentadionate) solution semiconductor nanoparticle in TiOx (1<x<2) sol or Cs2CO3 solution.

(24) In the meantime, a typical organic photovoltaic cell can be composed of a substrate, an anode (transparent electrode) layer, a hole transport layer, a photoactive layer, an electron transfer layer and a cathode. Hereinafter, the organic photovoltaic cell composed of a substrate, an anode, a hole transport layer, a photoactive layer, an electron transfer layer and a cathode, wherein the photoactive layer contains the polymer compound of the invention represented by formula 1 is described in more detail.

(25) The substrate to be placed on the light incidence surface side of the photovoltaic cell has to have light transmittance, which can be colorless and transparent or with some color. For example, such transparent glass substrates as soda-lime glass and alkali-free glass, or plastic films prepared with polyester, polyamide, or epoxy resin can be used. As the transparent electrode, any transparent material is usable as long as it has an electrical conductivity, which is preferably exemplified by single or complex metal oxide of indium (In), tin (Sn), gallium (Ga), zinc (Zn), and aluminum (Al) such as In2O3, ITO (indium-tin oxide), IGZO (indium-galliumzincoxide), ZnO, AZO (Aluminum-zinc oxide; ZnO:Al), SnO2, FTO (Fluorine-dopedtin oxide; SnO2:F), and ATO (Aluminum-tin oxide; SnO2:Al). Such transparent electrode can be formed by DC sputtering or chemical vapor deposition (CVD), atomic layer deposition (ALD), sol-gel coating, or electroplating. The electrode formed on the substrate may be immersed in acetone, alcohol, water or a mixed solution thereof, followed by ultrasonic cleaning.

(26) As a material for the hole transport layer, a compound that has excellent characteristics of transporting holes, blocking electrons, and forming a thin film is preferred. Particularly, low molecular weight compounds and polymers containing PEDOT:PSS [poly(3,4-ethylenedioxythiophene):poly(4-styrene sulfonate)], G-PEDOT [poly(3,4-ethylenedioxythiophene):poly(4-styrene sulfonate):polyglycol(glycerol)], PANI:PSS [polyaniline:poly(4-styrene sulfonate)], PANI:CSA (polyaniline:camphor sulfonic acid), PDBT [poly(4,4-dimethoxy bithiophene)], and arylamine group, and low molecular weight compounds and polymers containing aromatic amine group are preferred, but not always limited thereto. A method for forming the hole transport layer is exemplified by spin coating, spray coating, screen printing, bar coating, doctor blade coating, and vacuum thermal evaporation. The thickness of the hole transport layer is preferably 5?300 nm.

(27) The photoactive layer is formed with the conductive polymer containing the polymer compound represented by formula 1 as an electron donor and an electron acceptor. The electron acceptor herein can be fullerene (C60), fullerene derivative such as [6,6]-phenyl-C61-butyric acid methyl ether (PCBM) or [6,6]-phenyl-C71-butyric acid methyl ether (PC71BM), perylene, perylene derivative such as 3,4,9,10-perylenetetracarboxylic bisbenzimidazole (PTCBI), or semiconductor nanoparticle such as ZnO, TiO2, CdS, CdSe, or ZnSe. At this time, the size of the nanoparticle is preferably 1?100 nm, but not always limited thereto. The photoactive layer is formed by using the polymer compound represented by formula 1 and the electron acceptor mixture solution. At this time, polar solvents such as chloroform, chlorobenzene, 1,2-dichlorobenzene, 1,2,4-trichlorobenzene, and toluene can be used as a solvent. The method for forming the photoactive layer is exemplified by spin coating, spray coating, and screen printing, etc.

(28) The pattern of the electron transport layer can be formed by inkjet method, offset printing, or gravure printing using a metal precursor sol (or solution). Or, a n-type metal oxide nanoparticle is first prepared, which is then spread in a dispersive medium together with an additive, resulting in the formula form of ink, slurry, or paste, with which the pattern can be formed by one of the methods above. The metal oxide sol (or solution) and the metal oxide nanoparticle can be exemplified by ZnO nanoparticle, Doped-ZnO (ZnO:Al, ZnO:B, ZnO:Ga, ZnO:N, etc.) nanoparticle, SnO2 nanoparticle, ITO nanoparticle, TiO2 nanoparticle, TiOx (1<x<2) sol, Cs2CO3 solution, and titanium(diisoproxide)bis(2,4-pentadionate) solution. The electron transport layer can be formed with organic materials. The coating above can be achieved by spin coating, spray coating, screen printing, bar coating, doctor blade coating, flexography, and gravure printing. When a material to form the electron transport layer is a low molecule organic material, it is not necessarily dissolved in a solvent but can proceed to vacuum thermal evaporation.

(29) The cathode is an electrode to collect electrons that are generated in the photoactive layer efficiently. It is preferable to use an electrode material made of a metal having a small work function, an alloy, a conductive compound, or a mixture thereof. The material for the cathode, therefore, is exemplified by alkali metals, alkali metal halides, alkali metal oxides, rare earths and alloys of these with other metals such as sodium-potassium alloys, magnesium-silver mixtures, aluminum-lithium alloys, and aluminum-lithium fluorine double layer. A film can be generated with the electrode material by sputtering or vacuum evaporation, but not always limited thereto.

(30) The present invention also relates to a method for preparing the polymer compound represented by formula 1.

(31) Particularly, the method for preparing the polymer compound represented by formula 1 of the invention comprises the following steps: (a) producing the compound represented by formula 2 below having a symmetrical structure by reacting a quaterthiophene derivative and a benzothiadiazole derivative with the substitution of bromine and fluorine in the presence of a palladium catalyst; (b) producing the compound represented by formula 3 below by reacting the compound represented by formula 2 with a brominating agent; and (c) reacting the compound represented by formula 3 with a bithiophene derivative in the presence of a palladium catalyst.

(32) ##STR00005##

(33) Wherein, R is independently C.sub.1?C.sub.30 straight or branched alkyl, C.sub.1?C.sub.30 straight or branched alkoxy, or C.sub.6?C.sub.30 aryl, wherein the alkyl, alkoxy, and aryl can be substituted with one or more C.sub.1?C.sub.10 alkyl, hydroxyl, amino, or carboxy, and the alkyl, alkoxy, and aryl can independently contain one or more hetero atoms,

(34) X is independently H or F,

(35) N is an integer of 1?500.

(36) In a preferred embodiment of the present invention, R of formula 1 can be the one selected from the group consisting of ethylhexyl, butyloctyl, hexyldecyl, and octyldodecyl, and preferably is octyldodecyl.

(37) In a preferred embodiment of the present invention, the palladium catalyst is selected from the group consisting of PdCl2, Pd(OAc)2, Pd(CH3CN)2Cl2, Pd(PhCN)2Cl2, Pd2(dba)3, and Pd(PPh3)4.

(38) In a preferred embodiment of the present invention, the quaterthiophene derivative compound can be (3,3-bis(2-octyldodecyl)-[2,2:5,2:5,2-quaterthiophene]-5,5-yl)bis(trimethylstannane) or (3,4-difluoro-3,3-bis(2-octyldodecyl)-[2,2:5,2:5,2-quaterthiophene]-5,5-diyl)bis(trimethylstannane). The benzothiadiazole derivative compound substituted with bromine and fluorine can be 4-bromo-5-fluoro-7-(4-(2-octyldodecyl)thiophene-2-yl)benzo[c][1,2,5]thiadiazole.

(39) In a preferred embodiment of the present invention, the bithiophene derivative compound can be 5,5-bis(trimethylstannyl)-2,2-bithiophene or (3,3-difluoro-[2,2-bithiophene]-5,5-diyl)bis(trimethylstannane).

(40) In the meantime, the polymer compound represented by formula 1 can be prepared by the process of reaction formula 1 below in example 1 or by the process of reaction formula 2 in example 2 which will be illustrated hereinafter.

(41) ##STR00006## ##STR00007##

(42) As shown in reaction formula 1 above, N-bromosuccinimide (NBS), chloroform, and acetic acid were added to 3-(2-octyldodecyl)thiophene (1) compound, resulting in the synthesis of 2-bromo-3-(2-octyldodecyl)thiophene (2) compound. To the compound (2) were added 5,5-bis(trimethylstannyl)-2,2-bithiophene, palladium catalyst (Pd2(dba)3), P(o-tolyl)3, and tetrahydrofuran (THF) solvent, leading to the synthesis of 3,3-bis(2-octyldodecyl)-2,2:5,2:5,2-quaterthiophene (3) compound. The compound (3) was dissolved in tetrahydrofuran (THF) solvent, to which n-BuLi and trimethyltin chloride were added stepwise, followed by reaction to synthesize (3,3-bis(2-octyldodecyl)-[2,2:5,2:5,2-quaterthiophene]-5,5-diyl)bis(trimethylstannane) (4) compound. In the mean time, 3-(2-octyldodecyl)thiophene was dissolved in tetrahydrofuran (THF) solvent, to which n-BuLi and trimethyltin chloride were added stepwise, leading to the reaction to synthesize tributyl(4-(2-octyldodecyl)thiophene-2-yl)stannane (5) compound, and then 4,7-dibromo-5-fluorobenzo[c][1,2,5]thiadiazole, a palladium catalyst, and toluene were added to the compound (5), followed by reaction to synthesize 4-bromo-5-fluoro-7-(4-(2-octyldodecyl)thiophene-2-yl)benzo[c][1,2,5]thiadiazole (6) compound. Then, a palladium catalyst (Pd2(dba)3), P(o-tolyl)3, and tetrahydrofuran (THF) solvent were added to the (3,3-bis(2-octyldodecyl)-[2,2:5,2:5,2-quaterthiophene]-5,5-diyl)bis(trimethylstannane) (4) compound and the 4-bromo-5-fluoro-7-(4-(2-octyldodecyl)thiophene-2-yl)benzo[c][1,2,5]thiadiazole (6) compound, followed by reaction to synthesize 7,7-(3,3-bis(2-octyldodecyl)-[2,2:5,2:5,2-quaterthiophene]-5,5-diyl)bis(6-fluoro-4-(4-(2-octyldodecyl)thiophene-2-yl)benzo[c][1,2,5]thiadiazole) (7) compound. To the compound (7) were added a brominating agent (N-bromosuccinimide: NBS), chloroform, and acetic acid, leading to the reaction to introduce a bromine group to the compound (7). The brominated 7,7-(3,3-bis(2-octyldodecyl)-[2,2:5,2:5,2-quaterthiophene]-5,5-diyl)bis(4-(5-bromo-4-(2-octyldodecyl)thiophene-2-yl)-6-fluorobenzo[c][1,2,5]thiadiazole) compound (7) was added with 5,5-bis(trimethylstannyl)-2,2-bithiophene, a palladium catalyst (Pd2(dba)3), P(o-tolyl)3, and chlorobenzene solvent, leading to the final reaction to synthesize the polymer compound of the present invention which was RRPfBT4T-OD represented by formula 1.

(43) ##STR00008## ##STR00009##

(44) As shown in reaction formula 2, N-bromosuccinimide (NBS), chloroform, and acetic acid were added to 3-(2-octyldodecyl)thiophene (1) compound, followed by reaction to synthesize 2-bromo-3-(2-octyldodecyl)thiophene (2) compound. The compound (2) was added with (3,3-difluoro-[2,2-bithiophene]-5,5-diyl)bis(trimethylstannane), a palladium catalyst (Pd2(dba)3), P(o-tolyl)3, and tetrahydrofuran (THF) solvent, followed by reaction to synthesize 3,4-difluoro-3,3-bis(2-octyldodecyl)-2,2:5,2:5,2-quaterthiophene (3) compound. The compound (3) was dissolved in tetrahydrofuran (THF) solvent, to which n-BuLi and trimethyltin chloride were added stepwise, followed by reaction to synthesize (3,4-difluoro-3,3-bis(2-octyldodecyl)-[2,2:5,2:5,2-quaterthiophene]-5,5-diyl)bis(trimethylstannane) (4) compound. In the meantime, 3-(2-octyldodecyl)thiophene was dissolved in tetrahydrofuran (THF) solvent, to which n-BuLi and trimethyltin chloride were added stepwise, followed by reaction to synthesize tributyl(4-(2-octyldodecyl)thiophene-2-yl)stannane (5) compound. The compound (5) was added with 4,7-dibromo-5-fluorobenzo[c][1,2,5]thiadiazole, a palladium catalyst, and toluene, followed by reaction to synthesize 4-bromo-5-fluoro-7-(4-(2-octyldodecyl)thiophene-2-yl)benzo[c][1,2,5]thiadiazole (6) compound. A palladium catalyst (Pd2(dba)3), P(o-tolyl)3, tetrahydrofuran (THF) solvent were added to the (3,4-difluoro-3,3-bis(2-octyldodecyl)-[2,2:5,2:5,2-quaterthiophene]-5,5-diyl)bis(trimethylstannane) (4) compound and the 4-bromo-5-fluoro-7-(4-(2-octyldodecyl)thiophene-2-yl)benzo[c][1,2,5]thiadiazole (6) compound synthesized above, followed by reaction to synthesize 7,7-(3,4-difluoro-3,3-bis(2-octyldodecyl)-[2,2:5,2:5,2-quaterthiophene]-5,5-diyl)bis(6-fluoro-4-(4-(2-octyldodecyl)thiophene-2-yl)benzo[c][1,2,5]thiadiazole) (7) compound. To the compound (7) were added a brominating agent (N-bromosuccinimide: NBS), chloroform, and acetic acid, leading to the reaction to introduce a bromine group to the compound (7). As a result, 7,7-(3,4-difluoro-3,3-bis(2-octyldodecyl)-[2,2:5,2:5,2-quarter thiophene]-5,5-diyl)bis(4-(5-bromo-4-(2-octyldodecyl)thiophene-2-yl)-6-fluorobenzo[c][1,2,5]thiadiazole) (8) compound was synthesized. The compound (8) was added with (3,3-difluoro-[2,2-bithiophene]-5,5-diyl)bis(trimethylstannane), a palladium catalyst (Pd2(dba)3), P(o-tolyl)3, and chlorobenzene solvent, leading to the final reaction to synthesize the polymer compound of the present invention which was RR PfBTff4TOD represented by formula 2.

(45) Practical and presently preferred embodiments of the present invention are illustrative as shown in the following Examples.

(46) However, it will be appreciated that those skilled in the art, on consideration of this disclosure, may make modifications and improvements within the spirit and scope of the present invention.

Example 1: Synthesis of RR-PFBT4T-OD Polymer

<1-1> Synthesis of 2-bromo-3-(2-octyldodecyl)thiophene

(47) ##STR00010##

(48) 3-(2-Octyldodecyl)thiophene (2.00 g, 5.48 mmol), NBS (N-bromosuccinimide, 1.07 g, 6.03 mmol), chloroform (20 ml), and acetic acid (20 ml) were added in a 100 ml flask equipped with a nitrogen purge tube, followed by reaction at room temperature for one day. The reactant was extracted with distilled water and MC. Then, moisture in the organic layer was dried over anhydrous sodium sulfate. The solid impurities were removed by filtration under reduced pressure. The remaining solvent was eliminated by evaporation, and the residue was separated by column chromatography (hexane). As a result, 2.21 g of the target compound was obtained as clear transparent oil (yield: 91.2%).

(49) .sup.1H NMR (400 MHz, CDCl3) ? (ppm): 7.11 (d, 1H), 6.74 (d, 2H), 2.48 (d, 2H), 1.25 (m, 33H), 0.88 (m, 6H).

<1-2> Synthesis of 3,3-bis(2-octyldodecyl)-2,2:5,2:5,2-quaterthiophene

(50) ##STR00011##

(51) 2-Bromo-3-(2-octyldodecyl)thiophene (2.21 g, 5.00 mmol) synthesized in Example <1-1> was mixed with 5,5-bis(trimethylstannyl)-2,2-bithiophene (1.11 g, 2.27 mmol), Pd2(dba)3 (0.08 g, 0.09 mmol), P(o-tolyl)3 (0.05 g, 0.18 mmol), and THF (tetrahydrofuran, 20 ml) in a 100 ml flask equipped with a reflux condenser, followed by reflux stirring in an oil bath at 70? C. The reactant was cooled down at room temperature, followed by extraction several times with diethyl ether. Then, moisture in the organic layer was dried over anhydrous sodium sulfate. The solid impurities were removed by filtration under reduced pressure. The remaining solvent was eliminated by evaporation, and the residue was separated by column chromatography (hexane). As a result, 1.11 g of the target compound was obtained as transparent yellow oil (yield: 55.4%).

(52) .sup.1H NMR (400 MHz, CDCl3) ? (ppm): 7.17 (d, 2H), 7.10 (d, 2H), 7.00 (d, 2H), 6.90 (d, 2H), 2.71 (d, 4H), 1.68 (m, 2H), 1.22 (m, 64H), 0.88 (m, 12H)

<1-3> Synthesis of (3,3-bis(2-octyldodecyl)-[2,2:5,2:5,2-quaterthiophene]-5,5-diyl)bis(trimethylstannane)

(53) ##STR00012##

(54) After eliminating moisture through frame dry, 3,3-Bis(2-octyldodecyl)-2,2:5,2:5,2-quaterthiophene (1.10 g, 1.24 mmol) synthesized in Example <1-2> and 15 ml of anhydrous THF (tetrahydrofuran) were loaded in a 100 ml flask equipped with a nitrogen purge tube, whose temperature was adjusted to be ?78? C. with acetone and dry ice. 2.5 M n-BuLi (3.1 mmol, 1.24 ml) was slowly added thereto little by little, followed by reaction at ?78? C. for 30 minutes. Then, the reaction was induced again at room temperature for 30 minutes. The temperature was dropped down again to ?78? C., to which 1 M trimethyltin chloride (3.1 mmol, 3.1 ml) was added, followed by reaction at room temperature for one day. Extraction was performed by using distilled water and diethyl ether. Then, moisture in the organic layer was dried over anhydrous sodium sulfate. The solid impurities were removed by filtration under reduced pressure. The remaining solvent was eliminated by evaporation. As a result, the target compound was obtained as transparent brown oil (0.98 g, yield: 64.9%).

(55) .sup.1H NMR (400 MHz, CDCl3) ? (ppm): 7.08 (d, 2H), 6.99 (d, 2H), 6.94 (s, 2H), 6.90 (d, 1H), 2.72 (d, 4H), 1.70 (m, 2H), 1.22 (m, 64H), 0.88 (m, 12H), 0.37 (s, 18H)

<1-4> Synthesis of tributyl(4-(2-octyldodecyl)thiophene-2-yl)stannane

(56) ##STR00013##

(57) After eliminating moisture through frame dry, 3-(2-octyldodecyl)thiophene (2.00 g, 5.48 mmol) and 15 ml of anhydrous THF (tetrahydrofuran) were loaded in a 100 ml flask equipped with a nitrogen purge tube, whose temperature was adjusted to be ?78? C. with acetone and dry ice. 2.5 M n-BuLi (13.7 mmol, 5.48 ml) was slowly added thereto little by little, followed by reaction at ?78? C. for 30 minutes. Then, the reaction was induced again at room temperature for 30 minutes. The temperature was dropped down again to ?78? C., to which tributyltin chloride (13.7 mmol, 4.45 g) was added, followed by reaction at room temperature for one day. Extraction was performed by using distilled water and diethyl ether. Then, moisture in the organic layer was dried over anhydrous sodium sulfate. The solid impurities were removed by filtration under reduced pressure. The remaining solvent was eliminated by evaporation. As a result, the target compound was obtained as transparent brown oil (3.14 g, yield: 87.7%). The reaction was carried out without any purification process.

<1-5> Synthesis of 4-bromo-5-fluoro-7-(4-(2-octyldodecyl)thiophene-2-yl)benzo[c][1,2,5]thiadiazole

(58) ##STR00014##

(59) Tributyl(4-(2-octyldodecyl)thiophen-2-yl)stannane (3.14 g, 4.80 mmol) synthesized in Example <1-4> was mixed with 4,7-dibromo-5-fluorobenzo[c][1,2,5]thiadiazole (1.79 g, 5.76 mmol), Pd(PPh3)4 (0.27 g, 0.24 mmol), and toluene (15 ml) in a 100 ml flask equipped with a reflux condenser, followed by reflux stirring in an oil bath for 16 hours. The reactant was cooled down at room temperature, followed by extraction several times with MC. Then, moisture in the organic layer was dried over anhydrous sodium sulfate. The solid impurities were removed by filtration under reduced pressure. The remaining solvent was eliminated by evaporation, and the residue was separated by column chromatography (hexane). As a result, 1.66 g of the target compound was obtained as transparent yellow oil (yield: 58.5%).

(60) .sup.1HNMR (400 MHz, CDCl3) ? (ppm): 7.97 (s, 1H), 7.70 (d, 1H), 7.11 (s, 1H), 2.64 (d, 2H), 1.71 (m, 1H), 1.30 (m, 32H), 0.89 (m, 6H)

<1-6> Synthesis of 7,7-(3,3-bis(2-octyldodecyl)-[2,2:5,2:5,2-quaterthiophene]-5,5-diyl)bis(6-fluoro-4-(4-(2-octyldodecyl)thiophene-2-yl)benzo[c][1,2,5]thiadiazole)

(61) ##STR00015##

(62) (3,3-Bis(2-octyldodecyl)-[2,2:5,2:5,2-quaterthiophene]-5,5-diyl)bis(trimethylstannane) (0.98 g, 0.81 mmol) synthesized in Example <1-3>, 4-Bromo-5-fluoro-7-(4-(2-octyldodecyl)thiophen-2-yl)benzo[c][1,2,5]thiadiazole (1.06 g, 1.78 mmol) synthesized in Example <1-5>, Pd2(dba)3 (0.016 mmol, 0.02 mmol), P(o-tolyl)3 (0.06 mmol, 0.02 g), and 15 ml of THF (tetrahydrofuran) were added in a 100 ml flask equipped with a reflux condenser, followed by reflux stirring in an oil bath for 16 hours. The reactant was cooled down at room temperature, followed by extraction several times with distilled water and MC (methylene chloride). Then, moisture in the organic layer was dried over anhydrous sodium sulfate. The solid impurities were removed by filtration under reduced pressure. The remaining solvent was eliminated by evaporation, and the residue was separated by column chromatography (MC:HEX=1:20). As a result, 0.46 g of the target compound was obtained as a red solid (yield: 30.1%).

(63) .sup.1H NMR (400 MHz, CDCl3) ? (ppm): 8.10 (s, 2H), 7.96 (s, 2H), 7.75 (d, 2H), 7.18 (s, 4H), 7.07 (s, 2H), 2.84 (d, 4H), 2.63 (d, 4H), 1.83 (m, 2H), 1.69 (m, 2H), 1.24 (m, 128H), 0.86 (m, 24H)

<1-7> Synthesis of 7,7-(3,3-bis(2-octyldodecyl)-[2,2:5,2:5,2-quaterthiophene]-5,5-diyl)bis(4-(5-bromo-4-(2-octyldodecyl)thiophene-2-yl)-6-fluorobenzo[c][1,2,5]thiadiazole)

(64) ##STR00016##

(65) 7,7-(3,3-Bis(2-octyldodecyl)-[2,2:5,2:5,2-quaterthiophene]-5,5-diyl)bis(6-fluoro-4-(4-(2-octyldodecyl)thiophen-2-yl)benzo[c][1,2,5]thiadiazole) (0.46 g, 0.24 mmol) synthesized in Example <1-6>, NBS (N-bromosuccinimide) (0.093 g, 0.52 mmol), 10 ml of chloroform, and 10 ml of acetic acid were added in a 100 ml flask equipped with a nitrogen purge tube, followed by reaction at room temperature. Extraction was performed several times by using distilled water and MC (methylene chloride). Then, moisture in the organic layer was dried over anhydrous sodium sulfate. The solid impurities were removed by filtration under reduced pressure. The remaining solvent was eliminated by evaporation, and the residue was separated by column chromatography (MC:HEX=1:25). As a result, 0.37 g of the target compound was obtained as a purple solid (yield: 75.2%).

(66) .sup.1HNMR (400 MHz, CDCl3) ? (ppm): 8.10 (s, 2H), 7.72 (s, 2H), 7.65 (d, 2H), 7.17 (s, 4H), 2.83 (d, 4H), 2.56 (d, 4H), 1.83 (m, 2H), 1.75 (m, 2H), 1.24 (m, 128H), 0.86 (m, 24H)

<1-8> Synthesis of RR-PfBT4T-OD

(67) ##STR00017##

(68) 7,7-(3,3-bis(2-octyldodecyl)-[2,2:5,2:5,2-quaterthiophene]-5,5-diyl)bis(4-(5-bromo-4-(2-octyldodecyl)thiophen-2-yl)-6-fluorobenzo[c][1,2,5]thiadiazole) compound synthesized in Example <1-7>(223 mg, 1.07 mmol), 5,5-bis(trimethylstannyl)-2,2-bithiophene (52.6 mg, 1.07 mmol), Pd2(dba)3 (2 mg, 0.0021 mmol), P(o-tolyl)3 (3.5 mg, 0.0087 mmol), and 0.25 ml of chlorobenzene were loaded in a microwave-dedicated glass beaker, followed by reaction at 160? C. for 3 hours using a microwave device. Upon completion of the reaction, the reactant was precipitated by using methanol. Impurities and oligomers were removed by Soxhlet extraction using hexene and methanol. The polymer was extracted by using chloroform. As a result, 141 mg of the target compound was obtained as a dark blue solid (yield: 61.6%).

(69) The final polymer synthesized by the process above according to the present invention is referred as RR-PfBT4T-OD.

Example 2: Synthesis of PfBT4ffT-OD Polymer

<2-1> Synthesis of 2-bromo-3-(2-octyldodecyl)thiophene

(70) ##STR00018##

(71) 3-(2-Octyldodecyl)thiophene (4.00 g, 10.97 mmol), NBS (N-bromosuccinimide, 2.14 g, 12.06 mmol), chloroform (25 ml), and acetic acid (25 ml) were added in a 100 ml flask equipped with a nitrogen purge tube, followed by reaction at room temperature for one day. The reactant was extracted with distilled water and MC (methylene chloride). Then, moisture in the organic layer was dried over anhydrous sodium sulfate. The solid impurities were removed by filtration under reduced pressure. The remaining solvent was eliminated by evaporation, and the residue was separated by column chromatography (hexane). As a result, 4.51 g of the target compound was obtained as clear transparent oil (yield: 92.6%).

(72) .sup.1H NMR (400 MHz, CDCl3) ? (ppm): 7.11 (d, 1H), 6.74 (d, 2H), 2.48 (d, 2H), 1.25 (m, 33H), 0.88 (m, 6H).

<2-2> Synthesis of 3,4-difluoro-3,3-bis(2-octyldodecyl)-2,2:5,2:5,2-quaterthiophene

(73) ##STR00019##

(74) 2-Bromo-3-(2-octyldodecyl)thiophene (2.51 g, 5.66 mmol) synthesized in Example <2-1> was mixed with (3,3-difluoro-[2,2-bithiophene]-5,5-diyl)bis(trimethylstannane) (1.36 g, 2.57 mmol), Pd2(dba)3 (0.051 g, 0.055 mmol), P(o-tolyl)3 (0.062 g, 0.20 mmol), and THF (tetrahydrofuran, 20 ml) in a 100 ml flask equipped with a reflux condenser, followed by reflux stirring in an oil bath at 70? C. The reactant was cooled down at room temperature, followed by extraction several times with diethyl ether. Then, moisture in the organic layer was dried over anhydrous sodium sulfate. The solid impurities were removed by filtration under reduced pressure. The remaining solvent was eliminated by evaporation, and the residue was separated by column chromatography (hexane). As a result, 1.33 g of the target compound was obtained as transparent yellow oil (yield: 55.6%).

(75) 1H NMR (400 MHz, CDCl3) ? (ppm): 7.21 (d, 2H), 6.91 (d, 2H), 6.87 (s, 2H), 2.71 (d, 4H), 1.68 (m, 2H), 1.23 (m, 64H), 0.88 (m, 12H).

<2-3> Synthesis of (3,4-difluoro-3,3-bis(2-octyldodecyl)-[2,2:5,2:5,2-quaterthiophene]-5,5-diyl)bis(trimethylstannane)

(76) ##STR00020##

(77) After eliminating moisture through frame dry, 3,4-difluoro-3,3-bis(2-octyldodecyl)-2,2:5,2:5,2-quaterthiophene (1.33 g, 1.43 mmol) synthesized in Example <2-2> and 15 ml of anhydrous THF (tetrahydrofuran) were loaded in a 100 ml flask equipped with a nitrogen purge tube, whose temperature was adjusted to be ?78? C. with acetone and dry ice. 2.5 M n-BuLi (3.29 mmol, 1.32 ml) was slowly added thereto little by little, followed by reaction at ?78? C. for 30 minutes. Then, the reaction was induced again at room temperature for 30 minutes. The temperature was dropped down again to ?78? C., to which 1 M trimethyltin chloride (3.29 mmol, 3.29 ml) was added, followed by reaction at room temperature for one day. Extraction was performed by using distilled water and diethyl ether. Then, moisture in the organic layer was dried over anhydrous sodium sulfate. The solid impurities were removed by filtration under reduced pressure. The remaining solvent was eliminated by evaporation. As a result, the target compound was obtained as transparent brown oil (1.10 g, yield: 61.3%).

(78) 1H NMR (400 MHz, CDCl3) ?(ppm): 6.95 (s, 2H), 6.85 (s, 2H) 2.71 (d, 2H), 2.72 (d, 4H), 1.68 (m, 2H), 1.23 (m, 64H), 0.88 (m, 12H).

<2-4> Synthesis of tributyl(4-(2-octyldodecyl)thiophene-2-yl)stannane

(79) ##STR00021##

(80) After eliminating moisture through frame dry, 3-(2-octyldodecyl)thiophene (2.00 g, 5.48 mmol) and 15 ml of anhydrous THF (tetrahydrofuran) were loaded in a 100 ml flask equipped with a nitrogen purge tube, whose temperature was adjusted to be ?78? C. with acetone and dry ice. 2.5 M n-BuLi (13.7 mmol, 5.48 ml) was slowly added thereto little by little, followed by reaction at ?78? C. for 30 minutes. Then, the reaction was induced again at room temperature for 30 minutes. The temperature was dropped down again to ?78? C., to which tributyltin chloride (13.7 mmol, 4.45 g) was added, followed by reaction at room temperature for one day. Extraction was performed by using distilled water and diethyl ether. Then, moisture in the organic layer was dried over anhydrous sodium sulfate. The solid impurities were removed by filtration under reduced pressure. The remaining solvent was eliminated by evaporation. As a result, the target compound was obtained as transparent brown oil (3.14 g, yield: 87.7%). The reaction was carried out without any purification process.

<2-5> Synthesis of 4-bromo-5-fluoro-7-(4-(2-octyldodecyl)thiophene-2-yl)benzo[c][1,2,5]thiadiazole

(81) ##STR00022##

(82) Tributyl(4-(2-octyldodecyl)thiophen-2-yl)stannane (3.14 g, 4.80 mmol) synthesized in Example <2-4> was mixed with 4,7-dibromo-5-fluorobenzo[c][1,2,5]thiadiazole (1.72 g, 5.52 mmol), Pd(PPh3)4 (0.27 g, 0.23 mmol), and toluene (15 ml) in a 100 ml flask equipped with a reflux condenser, followed by reflux stirring in an oil bath for 16 hours. The reactant was cooled down at room temperature, followed by extraction several times with MC. Then, moisture in the organic layer was dried over anhydrous sodium sulfate. The solid impurities were removed by filtration under reduced pressure. The remaining solvent was eliminated by evaporation, and the residue was separated by column chromatography (hexane). As a result, 1.66 g of the target compound was obtained as transparent yellow oil (yield: 58.5%).

(83) 1H NMR (400 MHz, CDCl3) ? (ppm): 7.97 (s, 1H), 7.70 (d, 1H), 7.11 (s, 1H), 2.64 (d, 2H), 1.71 (m, 1H), 1.30 (m, 32H), 0.89 (m, 6H)

<2-6> Synthesis of 7,7-(3,4-difluoro-3,3-bis(2-octyldodecyl)-[2,2:5,2:5,2-quaterthiophene]-5,5-diyl)bis(6-fluoro-4-(4-(2-octyldodecyl)thiophene-2-yl)benzo[c][1,2,5]thiadiazole)

(84) ##STR00023##

(85) (3,4-difluoro-3,3-bis(2-octyldodecyl)-[2,2:5,2:5,2-quaterthiophene]-5,5-diyl)bis(trimethylstannane) (1.10 g, 0.88 mmol) synthesized in Example <2-3>, 4-Bromo-5-fluoro-7-(4-(2-octyldodecyl)thiophen-2-yl) benzo[c][1,2,5]thiadiazole (1.20 g, 2.02 mmol) synthesized in Example <2-5>, Pd2(dba)3 (0.016 mmol, 0.017 mmol), P(o-tolyl)3 (0.07 mmol, 0.021 g), and 15 ml of THF (tetrahydrofuran) were added in a 100 ml flask equipped with a reflux condenser, followed by reflux stirring in an oil bath for 16 hours. The reactant was cooled down at room temperature, followed by extraction several times with distilled water and MC (methylene chloride). Then, moisture in the organic layer was dried over anhydrous sodium sulfate. The solid impurities were removed by filtration under reduced pressure. The remaining solvent was eliminated by evaporation, and the residue was separated by column chromatography (MC:HEX=1:20). As a result, 0.61 g of the target compound was obtained as a red solid (yield: 35.4%).

(86) 1H NMR (400 MHz, CDCl3) ?(ppm): 8.07 (s, 2H), 7.93 (s, 2H), 7.77 (d, 2H), 7.05 (s, 2H), 7.01 (s, 2H), 2.82 (d, 4H), 2.61 (d, 4H), 1.83 (m, 2H), 1.69 (m, 2H), 1.25 (m, 128H), 0.86 (m, 24H)

<2-7> Synthesis of 7,7-(3,4-difluoro-3,3-bis(2-octyldodecyl)-[2,2:5,2:5,2-quarter thiophene]-5,5-diyl)bis(4-(5-bromo-4-(2-octyldodecyl)thiophene-2-yl)-6-fluorobenzo[c][1,2,5]thiadiazole)

(87) ##STR00024##

(88) 7,7-(3,4-difluoro-3,3-bis(2-octyldodecyl)-[2,2:5,2:5,2-quaterthiophene]-5,5-diyl)bis(6-fluoro-4-(4-(2-octyldodecyl)thiophen-2-yl)benzo[c][1,2,5]thiadiazole) (0.61 g, 0.31 mmol) synthesized in Example <2-6>, NBS (N-bromosuccinimide) (0.12 g, 0.68 mmol), 10 ml of chloroform, and 10 ml of acetic acid were added in a 100 ml flask equipped with a nitrogen purge tube, followed by reaction at room temperature. Extraction was performed several times by using distilled water and MC (methylene chloride). Then, moisture in the organic layer was dried over anhydrous sodium sulfate. The solid impurities were removed by filtration under reduced pressure. The remaining solvent was eliminated by evaporation, and the residue was separated by column chromatography (MC:HEX=1:25). As a result, 0.51 g of the target compound was obtained as a purple solid (yield: 77.7%).

(89) 1H NMR (400 MHz, CDCl3) ?(ppm): 8.06 (s, 2H), 7.69 (s, 2H), 7.60 (d, 2H), 7.00 (s, 2H), 2.81 (d, 4H), 2.54 (d, 4H), 1.83 (m, 2H), 1.75 (m, 2H), 1.24 (m, 128H), 0.86 (m, 24H)

<2-8> Synthesis of RR PfBTff4T-OD

(90) ##STR00025##

(91) 7,7-(3,4-difluoro-3,3-bis(2-octyldodecyl)-[2,2:5,2:5,2-quaterthiophene]-5,5-diyl)bis(4-(5-bromo-4-(2-octyldodecyl)thiophen-2-yl)-6-fluorobenzo[c][1,2,5]thiadiazole) (204 mg, 0.096 mmol) synthesized in Example <2-7>, (3,3-difluoro-[2,2-bithiophene]-5,5-diyl)bis(trimethylstannane) (50 mg, 0.096 mmol), Pd2(dba)3 (2 mg, 0.002 mmol), P(o-tolyl)3 (2.4 mg, 0.008 mmol), and 0.25 ml of chlorobenzene were loaded in a microwave-dedicated glass beaker, followed by reaction at 160? C. for 3 hours using a microwave device. Upon completion of the reaction, the reactant was precipitated by using methanol. Impurities and oligomers were removed by Soxhlet extraction using hexene and methanol. The polymer was extracted by using chloroform. As a result, 151 mg of the target compound was obtained as a dark blue solid (yield: 71.9%).

(92) The final polymer synthesized by the process above according to the present invention is referred as RR PfBTff4T-OD.

Example 3: Construction of an Organic Photovoltaic Cell Comprising RR-PfBT4T-OD, the Polymer Compound of the Invention

(93) A solar cell was constructed by using RR-PfBT4T-OD, the conductive polymer prepared in Example 1 according to the present invention, as follows.

(94) The glass substrate coated with ITO was washed by ultrasonic cleaning with acetone, distilled water, and isopropyl alcohol in that order for 10 minutes each, followed by drying. The dried ITO substrate was placed in an UV ozone chamber and treated therein for 20 minutes. The substrate was coated with ZnO by sol-gel method, followed by heat-treatment at 200? C. for 1 hour. The heat-treated substrate was cooled fully. The substrate was coated via spin coating (800 rpm) with a mixed solution prepared by mixing 0.4 ml of a mixture of chlorobenzene and 1,8-diiodooctane (97:3) and a mixture of PfBT4T-OD, the polymer obtained in Example 1 (3.2 mg), and (6,6)-phenyl-C71-butylic acid methyl ester (PC71BM) (4.8 mg) (1:1.5). Then, 10 nm of moly oxide (MoO.sub.3) and silver (Ag) electrode were deposited thereon at the thickness of 100 nm. As a result, a solar cell having the structure of ITO/ZnO/PfBT4T-OD:PC71BM(1:1.5)/MoO3/Ag was obtained.

Example 4: Construction of an Organic Photovoltaic Cell Comprising RR PfBTff4T-OD, the Polymer Compound of the Invention

(95) A solar cell was constructed by using RR PfBTff4T-OD, the conductive polymer prepared in Example 2 according to the present invention, as follows.

(96) The glass substrate coated with ITO was washed by ultrasonic cleaning with acetone, distilled water, and isopropyl alcohol in that order for 10 minutes each, followed by drying. The dried ITO substrate was placed in an UV ozone chamber and treated therein for 20 minutes. The substrate was coated with ZnO by sol-gel method, followed by heat-treatment at 200? C. for 1 hour. The heat-treated substrate was cooled fully. The substrate was coated via spin coating (800 rpm) with a mixed solution prepared by mixing 0.4 ml of a mixture of xylene and diphenyl ether (97:3) and a mixture of RR PfBTff4T-OD, the polymer obtained in Example 2 (2.4 mg), and (6,6)-phenyl-C71-butylic acid methyl ester (PC71BM) (4.8 mg) (1:1.5). Then, 10 nm of moly oxide (MoO.sub.3) and silver (Ag) electrode were deposited thereon at the thickness of 100 nm. As a result, a solar cell having the structure of ITO/ZnO/PfBTff4T-OD:PC71BM(1:1.5)/MoO3/Ag was obtained.

Experimental Example 1: Measurement of Optical Band Gap of the Polymer Compound of the Invention

<1-1> Measurement of Optical Band Gap of the Conductive Polymer RR-PfBT4T-OD

(97) The following experiment was performed to measure the optical band gap of the conductive polymer of the present invention.

(98) Absorbance was measured using a spectrophotometer (UV-vis spectrometer). Absorbance in the liquid phase was measured in chloroform solution and absorbance in the solid phase (film) was measured after the polymer dissolved in chloroform was coated on the glass substrate by spin coating. Each graph was normalized and plotted

(99) As shown in FIG. 1, the polymer compound RR-PfBT4T-OD of the present invention demonstrated the maximum absorption at 580 nm in the chloroform solvent, while it displayed the maximum absorption on the solid film at 640?720 nm. The optical band gap of the conductive polymer of Example 1 of the invention was 1.58 eV on the film and 1.62 eV in the solution, suggesting that the optical band gap of the conductive polymer according to the present invention was reduced on the film by inter-polymer chain packing.

(100) TABLE-US-00001 TABLE 1 Optical properties of RR-PfBT4T-OD E.sub.g on film (eV) E.sub.g in solution (eV) 1.58 1.62

<1-2> Measurement of optical Band Gap of the Conductive Polymer RR PfBTff4T-OD

(101) The following experiment was performed by the same manner as described in Experimental Example <1-1>.

(102) As shown in FIG. 2, the polymer compound RR PfBTff4T-OD of the present invention showed the maximum absorption at 700 nm in the chloroform solvent and on the film. The optical band gap of the conductive polymer of Example 2 of the invention was 1.59 eV on the film and 1.64 eV in the solution, suggesting that the optical band gap of the conductive polymer according to the present invention was reduced on the film by inter-polymer chain packing.

(103) TABLE-US-00002 TABLE 2 Optical properties of RR-PfBTff4T-OD E.sub.g on film (eV) E.sub.g in solution (eV) 1.59 1.64

Experimental Example 2: Evaluation of Electrochemical Characteristics of the Polymer Compound of the Present Invention

<2-1> Evaluation of Electrochemical Characteristics of the Conductive Polymer Compound RR-PfBT4T-OD

(104) Cyclic voltammetry was performed to evaluate the electrochemical characteristics of the conductive polymer of the present invention.

(105) Silver and silver univalent cations were used as the standard electrode. Glassy carbon was used as the working electrode and Pt wire was used as the counter electrode. Cyclic voltammetry was measured using ferrocene as the standard. The measurement was achieved by making the ferrocene as the standard. At this time, 0.1 M tetrabutyl ammonium hexafluorophosphate was used as the electrolyte for the sample.

(106) As a result, as shown in FIG. 3 and Table 3, HOMO and LUMO energy values of the compound were calculated as 5.45 eV and ?3.68 eV respectively and the band gap was 1.77 eV.

(107) TABLE-US-00003 TABLE 3 Electrochemical characteristics of RR-PfBT4T-OD E.sub.ox (V) E.sub.ox (V) HOMO (eV) LUMO (eV) Eg.sup.CV (eV) 1.07 ?0.70 ?5.45 ?3.68 1.77

<2-2> Evaluation of Electrochemical Characteristics of the Conductive Polymer Compound RR-PfBTff4T-OD

(108) The following experiment was performed by the same manner as described in Experimental Example <2-1>.

(109) As a result, as shown in FIG. 4 and Table 4, HOMO and LUMO energy values of the compound were calculated as 5.23 eV and 3.32 eV respectively and the band gap was 1.91 eV.

(110) TABLE-US-00004 TABLE 4 Electrochemical characteristics of RR-PfBTff4T-OD E(V) E.sub.ox(V) HOMO (eV) LUMO (eV) Eg.sup.CV (eV) 0.85 ?1.08 5.23 3.32 1.91

Experimental Example 3: Evaluation of the Characteristics of the Organic Photovoltaic Cell Comprising the Polymer of the Present Invention

(111) The following experiment was performed to investigate the characteristics of the organic photovoltaic cell comprising the conductive polymer of the present invention.

(112) Particularly among the electrochemical properties, fill factor and energy conversion efficiency of each organic photovoltaic cell prepared in Example 3 and Example 4 were calculated by mathematical formula 1 and mathematical formula 2 below.

(113) The results of the organic photovoltaic cell device (ITO/ZnO/PfBTff4T-OD:PC71BM(1:1.5)/MoO3/Ag) prepared in Example 3 are shown in Table 5 and FIG. 5. The results of the organic photovoltaic cell device (ITO/ZnO/PfBTff4TOD:PC71BM(1:1.5)/MoO3/Ag) prepared in Example 4 are shown in Table 6 and FIG. 6.
Fill factor (FF)=(Vmp?Imp)/(Voc?Isc)[Mathematical Formula 1]

(114) Wherein, V.sub.mp indicates the voltage value at the maximum power point, and I.sub.mp indicates the current value at the maximum power point. V.sub.oc is the photo open voltage and I.sub.sc is the photo short circuit current.
Energy conversion efficiency (PCE,%)=feel factor?[(Jsc?Voc)/100][Mathematical Formula 2]

(115) Wherein, J.sub.sc is the photo short circuit current density and Voc is the photo open voltage.

(116) TABLE-US-00005 TABLE 5 Characteristics of the RR PfBT4T-OD polymer based organic photovoltaic cell RR PfBT4T-OD:PC.sub.71BM V.sub.oc (V) J.sub.sc (mA/cm.sup.2) FF (%) PCE (%) 1:1.6 0.65 12.89 69.59 5.85

(117) As shown in Table 5, V.sub.oc of the organic photovoltaic cell of the invention was 0.65 and J.sub.sc was 12.89, while fill factor was 69.59%. From the result of the current density-voltage measurement, the energy conversion rate of the polymer of the invention was as excellent as 5.85%.

(118) TABLE-US-00006 TABLE 6 Characteristics of the RR PfBTff4T-OD polymer based organic photovoltaic cell V.sub.oc (V) J.sub.sc (mA/cm.sup.2) FF (%) PCE (%) 15 mg/ml 1:1.5 0.77 16.04 58.12 7.16

(119) As shown in Table 6, V.sub.oc of the organic photovoltaic cell of the invention was 0.67 and J.sub.sc was 16.04, while fill factor was 58.12%. From the result of the current density-voltage measurement, the energy conversion rate of the polymer of the invention was as excellent as 7.16%.

(120) The results above indicate that the conductive polymer compound of the present invention is suitable as a polymer for the organic photovoltaic cell which is particularly excellent in photon absorptiveness and hole mobility.

(121) As explained hereinbefore, the conductive polymer of the present invention not only is useful as a low band gap electron donor for an organic photovoltaic cell but also displays improved high photon absorptiveness, so that it can be used as a material for an organic optoelectronic device applicable to various fields of OPD, OTFT, OLED, and organic photovoltaic cells. In particular, the conductive polymer can be effectively used for the organic photovoltaic cell with improved energy conversion efficiency.

(122) Those skilled in the art will appreciate that the conceptions and specific embodiments disclosed in the foregoing description may be readily utilized as a basis for modifying or designing other embodiments for carrying out the same purposes of the present invention. Those skilled in the art will also appreciate that such equivalent embodiments do not depart from the spirit and scope of the invention as set forth in the appended Claims.

BRIEF DESCRIPTION OF THE MARK OF DRAWINGS

(123) HOMO: highest occupied molecular orbital

(124) LUMO: lowest unoccupied molecular orbital

(125) Band gap: space between HOMO and LUMO

(126) Voc: voltage at both ends of the photovoltaic system as not being loaded (open) at a specific temperature and sunlight intensity.

(127) Jsc: output current of the photovoltaic system such as solar cell or module in the short circuit conditions at a specific temperature and sunlight intensity. In some case, the short circuit current per unit area is called Jsc.

(128) FF: ratio of the maximum output to open-circuit voltage X short-circuit current, which is an index indicating the quality of the current-voltage characteristic curve (I-V curve). FF depends on the internal series, parallel resistance and diode quality factor.

(129) PCE: result of the multiplication of the area (solar cell area A) generating the maximum power (Pmax) of the solar cell by the incidence irradiance (E) measured under the prescribed test conditions, which is presented as percentage (%).