KR101743252B1 - Diketopyrrolopyrrole-based terpolymer for active layer of polymer solar cell or transistor and manufacturing method of the same - Google Patents

Abstract

The present invention relates to a ternary copolymer comprising a diketopyrrolopyrrole compound, selenophene and thiophene and a process for their synthesis.
According to the present invention, novel tertiary copolymers containing two different electron-rich units of diketopyrrolopyrrole-based compounds and selenophene (Se) and thiophene (Th) and a method of synthesizing them have been confirmed. By adjusting the crystallinity of the polymer by appropriately adjusting the content of selenophene and thiophene, it is possible to optimize the BHJ blend shape and exhibit high telephone mobility, thereby improving the performance of organic electronic materials such as solar cells and transistors.

Description

TECHNICAL FIELD The present invention relates to a diketopyrrolopyrrole-based terpolymer for an active layer of a polymer solar cell or a transistor and a method for manufacturing the same.

TECHNICAL FIELD The present invention relates to a low-band-gap polymer for an active layer of a solar cell or a transistor, and more specifically, to a ternary copolymer for an active layer in which polymer properties are optimized by adjusting the proportion of constituent components so as to achieve balance between crystallinity and solubility, .

Electron rich units (D) - Electron-deficient units (A) Alternating low bandgap polymers have been developed for single polymer solar cells (PSCs) The power conversion efficiency (PSE) power conversion efficiency (PCE) of PSCs has been enhanced to 8 - 9%. However, in order to achieve PSCs with a theoretical PCEs of more than 10% for commercialization, further development of conjugated polymers is essential. In order to design a high-efficiency electron donor, several important properties of the polymer, including light absorption capacity, energy level, charge mobility, and solubility, must be simultaneously considered and optimized (Zhou, H. et al. et al ., Macromolecules 2012, 45, 607; Lee, W. et al ., Macromolecules 2014, 47, 1604; Ye, L. et al ., Acc. Chem. Res 2014, 47, 1595; Li et al ., Chem. Rev. 2009, 109, 5868, Li, Y.-J. et al ., Mater. Today 2014, 17, 11; Facchetti, A. Chem. Y. Acc. Chem. Res., 2012, 45, 723, Bundgaard, E. et al ., Sol . Recently, random terpolymers composed of three different units in a conjugated backbone are promising candidates as efficient electron donors. This is because adding the third component to the DA alternating polymer can bring synergy effects to the various important properties mentioned above (Kang, TE et al ., Macromolecules 2013, 46, 6806; Chao, YIH et al . , Adv. Mater . 2014, 26, 5205; Kang, TE et al ., J. Mater. Chem. A 2014, 2, 15252; Chang, W.-H. et al ., Adv. Energy Mater. , DOI: 10.1002 / aenm.201300864; Jiang, J.-M. et al ., Polym. Chem., 2013, 4, 5321; Jung, JW et al ., Energy Environ. L. et al. Chem. Mater. 2013, 25, 4874).

Of the various properties of the low bandgap polymers, crystallinity and solubility of the active layer determine the electrical properties and processability of the PSCs, which is a very important parameter that greatly affects the efficiency of the PSCs. Diketopyrrolopyrrole (DPP) -based alternating polymers have attracted considerable attention due to their high charge transport ability in organic field-effect transistors (OFETs) and PSCs, and their excellent crystalline properties resulting in high performance Kim, J.-H. et al, J. Mater Chem A 2014, 2, 6348;... Ye, L. et al, Adv Mater 2012, 24, 6335;... Meager, I. et al,. J. Am. Chem. Soc . 2013, 135, 11537; Yiu, AT et al ., J. Am. Chem. Soc . 2012,134, 2180; Liu, F. et al ., J. Am. Li, W. et al ., Adv. Mater . 2014, 26, 1565, Hendriks, K.H. et al ., J. Am. Chem. Soc ., 2013, 135, et al, J. Am Chem Soc 2014 , 136, 11128;.... Lee, J. et al, J. Am Chem Soc 2013, 135, 9540;..... Kang, I. et al, J. Am. Chem. Soc ., 2013, 135, 14896; Gao, J. et al ., Adv . Even though the high crystalline properties of the low band gap polymer significantly improve the charge carrier mobility due to the formation of highly aligned molecular packing between the conjugated backbones of the polymer, the properties are typically characterized by solubility in various organic solvents (Xiao, S. et al ., Adv. Funct. Mater . 2010, 20, 635; Cho, H.-H. et al . , Macromolecules 2012, 45, 6415; Beaujuge, PM et al ., J. Am. Chem. Soc . 2011, 133, 2000; Liu, J. et al ., Adv . Recently, Janssen et al. Reported a correlation between a fibril (fibril) width and its photovoltaic performance of the DPP based polymer (Li, W. et al, J. Am Chem Soc 2013, 135, 18942;.... Li, W. et al ., Adv. Materials 2014, 26, 1565). The aggregation properties through the fixed conjugated backbone of the DPP-based polymer and its π-π stacking resulted in the formation of a fibrillar structure which is highly favorable for charge transport capability. However, at the same time, such aggregation tends to cause strong phase separation in BHJ (Bulk Heterojunction) films with fullerene acceptors (Chen, W. et al ., Energy Environ. Li, Y. et al ., Energy Environ. Sci ., 2013, 6, 1684). For example, if a DPP polymer with too high crystallinity produces a fibril that is significantly larger than ~ 10 nm, the exciton dissociation into the free charge becomes worse and limits the performance of the PSCs (Li , W. et al ., Adv. Mater . 2014, 26, 1565). Thus, determining the optimum crystallinity of the conjugated polymer is very important to optimize the BHJ blend form and to produce high efficiency PSCs.

The phase separation behavior of the conjugated polymer donor and fullerene acceptor blend has been intensively studied with regard to structural modifications of conjugated materials, such as changes in side chain length and conjugation length on the conjugated polymer (Cho, C.-H. et al . , Chem Commun 2011, 47, 3577 ;.. Kim, K.-H. et al, Chem Mater 2012, 24, 2373;...... Lei, T. et al, Chem Mater 2014, 26, 594; Mei, J. et al, Chem Mater 2014, 26, 604;... Son, HJ et al, J. Am Chem Soc 2011, 133, 1885;...... Ren, G. et al, Chem Mater , 2010, 22, 2020). Even minor variations in the chemical structure of the DA alternating polymer can significantly alter its surface energy and interchain interactions, leading to a significant impact on the shape of the BHJ blend and the PSC performance (Cho, H.-H. et al ., Macromolecules 2012, 45, 6415 ; Kim, K.-H. et al, Chem Mater 2012, 24, 2373;....... Son, HJ et al, J. Am Chem Soc 2011, 133, 1885 ; Stuart, AC et al, J. Am Chem Soc 2013, 135, 1806;....... Cho, C.-H. et al, J. Mater Chem 2012, 22, 14236). Compared with the DA alternating copolymer process, the ternary copolymer process can provide an opportunity to optimize polymer properties by achieving a sophisticated balance between competitive effects, i.e., the crystallinity and solubility of the polymer (Kang, TE et al ., J. Mater Chem A 2014, 2, 15252; Chang, W.-H. et al, Adv Energy Mater 2014, 4, DOI:..... 10.1002 / aenm.201300864; Fang, L. et al. , Chem. Mater . 2013, 25, 4874). For example, in a ternary copolymer process, the careful selection of a relatively planar third component with controlled ratios can improve the pi-pi interaction of the polymer, while still retaining excellent solubility , J.-H. et al ., Macromolecules 2012, 45, 8628). These random terpolymers have higher PCEs than their parent alternating copolymers due to their improved hole mobility and optimized BHJ morphology. However, successful examples of highly efficient random terpolymers for OTFTs and PSCs are limited (Kang, TE et al ., J. Mater. Chem . A 2014, 2, 15252). Also, the comparison of random terpolymers having different compositions with their parent polymers was very limited (Kang, TE et al ., Macromolecules 2013, 46, 6806; Nielsen, CB et al ., Chem. Commun . ); These studies are important in understanding the compositional effects of random terpolymers on device performance, with regard to their structural, electrical, and morphological properties.

Accordingly, the present inventors describe the synthesis of a series of novel low band gap random terpolymers (PDPP2T-Se-Th) exhibiting different crystalline behaviors. The present inventors have also conducted a systematic study of their structural, optical and electrical properties and have investigated their properties in PSCs and OFETs. A monomer (DPP2T) consisting of strong electron-withdrawing DPP units capped with thiophene is copolymerized with two different electron rich monomers, selenophene (Se) and thiophene (Th) (Se / Th = 0/100 (PDPP2T-Th100, P1 ), 10/90 (PDPP2T-Se10-Th90, P2 ), 30 / 70 (PDPP2T-Se30-Th70, P3 ), 50/50 (PDPP2T-Se50-Th50, P4 ), and 100/0 mol% (PDPP2T-Se100, P5 ). Since the isolated electron pair of selenium atoms migrates easily, a quinoidal structure is produced predominantly from the aromatic structure (Patra, A. et al ., J. Mater. Chem . 2010, 20, 422; Wijsboom, YH et al . al ., Angew. Chem . Int. Ed., 2009, 48, 5443). Thus, the incorporation of selenophene into the terpolymer can improve the intermolecular interactions and molecular alignment of the terpolymer, which can be achieved by differential scanning calorimetry (DSC) and grazing angle incidence X- incidence X-ray scattering (GIXS) measurements. The present inventors have found that by using a third component of selenophene in which only one atom is different from the thiophene unit of the parent polymer, it is possible to control the crystallinity of the DPP-based copolymer through the randomen terpolymer process, But only minimal impact on other characteristics.

Thus, the present random terpolymer system is ideal for studying the effect of crystallinity of random terpolymers on the performance of organic electronic devices.

Accordingly, the present invention provides a novel diketopyrrolopyrrole-based terpolymer having optimized crystallinity by including two different electron-rich units of selenophene (Se) and thiophene (Th) in an appropriate ratio and a method for synthesizing the same .

Another object of the present invention is to provide a polymer solar cell or a transistor including the above-mentioned terpolymer as an active layer.

In order to accomplish the above object, the present invention provides a terpolymer composed of a diketopyrrolopyrrole (DPP) -based compound and an aromatic ring compound.

In the present invention, the diketopyrrolopyrrole compound generally represents a compound having a structure represented by the following general formula (1), and is widely used in pigments, solar cells, organic thin film transistors and the like.

In the present invention, the aromatic ring compound means a compound having a ring-shaped atomic arrangement in the molecule, and the carbon ring compound in which the atom constituting the ring is composed only of carbon and the heterocyclic compound . There is a heterocyclic compound in which a single ring compound consisting of only one ring and two or more rings are fused to form a ring.

In one embodiment of the present invention, the aromatic ring compound is selected from the group consisting of selenophene, thiophene, furan, phenyl, naphthalene, anthracene, thianothiophene thienothiophene, and pyrene, preferably, selenophene and thiophene. In the present invention, the selenophene and thiophene may be contained in a molar ratio of 0.1-1.0.

In the present invention, the selenophene is a colorless liquid which is easily dissolved in ether, acetone, benzene, etc., but is not soluble in ethanol and does not dissolve in water. Thiophene is not soluble in water but is mixed with a solvent such as benzene, ether, It is a liquid with incense similar to that of colorless benzene mixed with selenophene and thiophene. It is widely used for synthesis of polymers for use in solar cells and transistors. In the present invention, a monomer (DPP2T) consisting of a strong electron-withdrawing DPP unit capped with thiophene is copolymerized with two different electron rich monomers, selenophene (Se) and thiophene (Th) To produce a series of novel random terpolymers with various Se / Th ratios in the backbone.

In the present invention, the terpolymer refers to a polymer synthesized from three kinds of monomers, and may be referred to as a terpolymer or a terpolymer. Compared to alternating polymers of electron-rich units (D) -electronic deficiency units (A) in polymers applied to solar cells or transistors, ternary copolymers can optimize polymer properties by balancing the crystallinity and solubility of the polymer ( Examples 3 to 5).

In one embodiment of the present invention, the diketopyrrolopyrrole compound may be represented by the following general formula (2).

In one embodiment of the present invention, the terpolymer may be used as an active layer of a solar cell or a transistor.

In the present invention, the solar cell is a semiconductor device that converts solar energy into electric energy, and includes inorganic solar cells, organic monomolecular solar cells, and polymer solar cells (PSCs) Polymer solar cells have attracted attention due to disadvantages of process, low power efficiency of organic monomolecular solar cell, and the like. In order to improve the power conversion efficiency (PCE) of a polymer solar cell, a new polymer in a battery has been required to be developed. Accordingly, a novel polymer capable of improving the performance of the battery has been synthesized.

In the present invention, the transistor means a semiconductor device that performs amplification and switching. In recent years, an organic field-effect transistor (OFET) using an organic semiconductor technology is mainly used for a channel of a transistor . New materials have been actively developed to improve the efficiency, including various molecules with various directions and bonding materials as the active layer and small molecules such as rubrene, tetracene, pentacene, TCMQ and various polymers. have.

In the present invention, the active layer is an organic layer positioned between a cathode and an anode in a solar cell and absorbing light to form electrons and holes. The active layer includes an electron donor material (D) And an electron acceptor material (A) which receives the electrons and transfers them to the electrodes. (D / A bi-layer), bulk heterojunction (BHJ, D + A blend), mixed structure (D / (D + A) / A) formed by two electron donors and electron acceptors, .

The present invention also provides a polymer solar cell comprising a ternary copolymer composed of a diketopyrrolopyrrole compound, selenophene and thiophene as an active layer.

The present invention also provides an organic field effect transistor comprising a ternary copolymer composed of a diketopyrrolopyrrole compound, selenophene and thiophene as an active layer.

The present invention also relates to a process for the preparation of a compound of formula (I), which comprises a) degassing a mixture of diketopyrrolopyrrole compounds, thiophene and selenophene; b) reacting the degassed mixture of step a) in a microwave reactor and cooling the mixture to room temperature to prepare a gel; c) diluting and refluxing the gel of step b); And d) extracting and refining the refluxed gel of step c).

In one embodiment of the present invention, the degassing in the step a) is performed by firstly degassing by adding argon, then adding triphenylphosphine and tris (dibenzylideneacetone) It can be done. Specifically, a solution of dry toluene and dry DMF added to the three monomers is degassed with argon, and triphenylphosphine and tris (dibenzylideneacetone) dipalladium are added and then sealed and further degassed .

In one embodiment of the present invention, the extraction in step d) may be a soxhlet extraction with methanol, acetone, hexane, dichloromethane, chloroform and chlorobenzene.

In the present invention, the Soxhlet extraction is a quantitative method used for biocomponent analysis, food analysis, and feed analysis, using a Soxhlet extractor used for extracting non-volatile components in a solid using a volatile solvent Lt; / RTI >

According to the present invention, novel tertiary copolymers containing two different electron-rich units of diketopyrrolopyrrole-based compounds and selenophene (Se) and thiophene (Th) and a method of synthesizing them have been confirmed. By adjusting the crystallinity of the polymer by appropriately adjusting the content of selenophene and thiophene, it is possible to optimize the BHJ blend shape and exhibit high telephone mobility, thereby improving the performance of organic electronic materials such as solar cells and transistors.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagram showing the synthesis scheme and chemical structure of a DPP random terpolymer of the present invention having Se and Th units of different compositions. FIG.
Fig. 2 shows UV-visible absorption spectra of (a) diluted chlorobenzene and (b) thin film of the PDPP2T-Se-Th terpolymer of the present invention; DSC (c) heating and (d) cooling thermogram.
3 is a cyclic voltammogram of the PDPP2T-Se-Th terpolymer according to the present invention.
Fig. 4 is a graph showing the device performance of PDPP2T-Se-Th PSCs and OFETs according to the present invention depending on the Se content and showing the PCE values (left side, blue line) and electron mobility (right side, red line) of PSCs to be.
5 is a graph of transfer characteristics of OFETs with a P1 - P5 membrane prepared by solution shear and annealed at 200 < 0 > C. (FIG. 5) and an electron-enhanced operation (below FIG. 5) with V _DS = -100 V and +100 V, respectively.
FIG. 6 shows the output characteristics of OFETs with P1 - P5 films annealed at 200 DEG C, which are graphs for the hole-enhancing operation (FIG. 6) and the electron-enhancing operation (FIG. 6 below), respectively.
7 is a graph showing optimized JV characteristics (FIG. 7 a) and EQE spectrum (FIG. 7 b) of PSCs of the BHJ inverse structure PDPP2T-Se-Th ternary copolymer system according to the present invention.
8 shows the UV-visible absorption spectrum of a PDPP2T-Se-Th: PC ₇₁ BM film under optimized PSC device conditions according to the present invention.
Figure 9 relates to a GIXS pattern of an optimized active layer based on PDPP2T-Se-Th terpolymer blended with PC ₇₁ BM in accordance with the present invention.
Figure 10 relates to the GIXS pattern of the out-of-plane (Figure 10a) and in-plane (Figure 10b) PDPP2T-Se-Th: PC ₇₁ BM films under optimized PSC devices according to the present invention.
11 relates to a GIXS pattern of a polymer ( P1 - P5 ) film according to the present invention.
Figure 12 relates to the GIXS pattern out of plane (Figure 12a) and in plane (Figure 12b) of a polymer ( P1 - P5 ) film according to the present invention.
Figure 13 relates to a TEM image (reference bar 200 nm) of a blended film of P1 - P5 and PC ₇₁ BM under optimized conditions for a PSC device according to the present invention.

Hereinafter, the present invention will be described in detail with reference to examples. However, these examples are intended to further illustrate the present invention, and the scope of the present invention is not limited to these examples.

Example 1 Synthesis of Polymer

In the present invention, two parental alternating copolymers PDPP2TT100 ( P1 ) and PDPP2T-Se100 (Pd ₂ ) were obtained through steel coupling using Pd ₂ (dba) ₃ (2 mol%) and PPh ₃ P5 ), and PDPP2T-Se-Th (see Fig. 1). All reactions were carried out under an argon atmosphere and the 2,5-bis (2-hexyldecyl) -3,6-bis (5-bromothiophen-2-yl) pyrrolo [ Pyrrol-l, 4-dione and PC ₇₁ BM were purchased from SunaTch and Nano-C Inc. Respectively, and used as such without purification. Unless otherwise stated, all chemicals were purchased from Aldrich and used as such.

1.1 Preparation of 2,5-bis (trimethylstannyl) selenophene

n-BuLi (10.5 mL of a 2.5 M solution in hexane, 26.3 mmol) was added dropwise to a solution of celenophene (1.5 g, 11.5 mmol) in THF (40 mL) at -78 <0> C. After stirring at -78 ° C for 30 minutes, the reaction mixture was gradually warmed to room temperature and stirred for an additional 2 hours. Trimethyltin chloride (26.9 mL of a 1 M solution in THF) was added slowly and then stirred overnight at room temperature. The mixture was poured into ice / water and the product was extracted with ether. The organic layer was washed several times with water, dried with MgSO _4, the solvent was removed by rotary evaporation. Recrystallization from ethanol provided the desired product as white crystals (3.9 g, 8.63 mmol, yield 75%).

^{The 1} H-NMR spectrum was measured on a Liquid 400 NB NMR instrument with CDCl ₃ as the solvent. The peak was provided in ppm against CDCl ₃ (7.26 ppm). The measurement results are as follows. ¹ H-NMR (400 MHz, CDCl ₃ , TMS):? (Ppm) 7.65 (s, 2H, -Th), 0.34 (s, 18H, -CH ₃ ).

1.2 General Polymerization Procedure by Steel Coupling Reaction

All polymers were synthesized by microwave-assisted Stille coupling reaction. Three monomers were weighed and added to a microwave vial equipped with a magnetic stirrer. Dry toluene and dry DMF were added and the solution was degassed with argon for 20 minutes. Triphenylphosphine (PPh ₃ , 8 mol%) and tris (dibenzylideneacetone) dipalladium (Pd ₂ (dba) ₃ , 2 mol%) were added and then sealed with a cap. The mixture was degassed for an additional 20 minutes, after which the vial was placed in a microwave reactor and stirred at 150 &lt; 0 &gt; C for 3 hours. The trimethylstannyl- and bromo-terminal groups of the polymer were then reacted with 2-bromothiophene (0.2 mL) and 2- (tributylstannyl) thiophene (0.25 mL) in a microwave reactor at 150 & Capped. After cooling to room temperature, the obtained gel was diluted with chloroform and refluxed with ethylenediaminetetraacetic acid (EDTA, 300 mg) in water at 110 ° C for 1 hour. The organic layer was washed with water, and dried with MgSO _4. The solvent was removed in vacuo and precipitated with methanol, and the resulting solid was subsequently purified via Soxhlet extraction with methanol, acetone, hexane, dichloromethane, chloroform and chlorobenzene (if necessary). The filtrate from each fraction was concentrated under reduced pressure and precipitated with cold methanol. The polymer was dried under vacuum for 24 hours.

1.3 PDPP2T-Th100 ( P1 ) Polymerization

3,4-c] pyrrole-1,4-dione (200.0 mg, 1.0 (2-hexyldecyl) -3,6-bis A mixture of Pd ₂ (dba) ₃ (4.0 mg) and a mixture of 2,5-bis (trimethylstannyl) thiophene (90.35 mg, 1.0 eq), PPh ₃ (4.6 mg) (0.3 mL), thus synthesizing P1 according to the procedure described above (chloroform fraction: 147 mg, yield 80%). Was measured with a GPC equipped with a Waters 1515 isocratic HPLC pump, a temperature control module and a Waters 2414 refractometer at a molecular weight of 80 캜 (flow rate: 1 mL / min). As a result of GPC, M _n is 78.4 K, M _w is 270 K, and PDI is 3.45. The elemental analysis (Elem. Anal. Calcd.) Is as follows: C, 72.41; H, 8.78; N, 3.38; S, 11.58; O, 3.86. Results: C, 72.43; H, 8.85; N, 3.38; S, 11.07.

1.4 PDPP2T-Se10-Th90 ( P2 ) Polymerization

3,4-c] pyrrol-l, 4-dione (300.0 mg, 1.0 (2-hexyldecyl) -3,6-bis eq), 2,5-bis (trimethylstannyl) thiophene (122.1 mg, 0.9 eq), 2,5-bis (trimethylstannyl) selenophene (15.12 mg, 0.1 eq), PPh ₃ The mixture and Pd ₂ (dba) ₃ (6.1 mg) were added to toluene (2.5 mL) and DMF (0.3 mL) to synthesize P2 according to the procedure described above (chloroform fraction: 162 mg, yield 60%). As a result of GPC, M _n is 164K, M _w is 698K and PDI is 4.25. The elemental analysis calculations are as follows: C, 71.99; H, 8.73; N, 3.36; S, 11.13; O, 3.84; Se, 0.96. Results: C, 71.62; H, 8.81; N, 3.30; S, 10.84.

1.5 PDPP2T-Se30-Th70 ( P3 ) Polymerization

3,4-c] pyrrole-1,4-dione (400.0 mg, 1.0 (2-hexyldecyl) -3,6-bis eq), 2,5-bis (trimethylstannyl) thiophene (126.5 mg, 0.7 eq), 2,5-bis (trimethylstannyl) selenophene (60.4 mg, 0.3 eq), PPh ₃ And Pd ₂ (dba) ₃ (8.1 mg) were added to toluene (3.0 mL) and DMF (0.3 mL) to synthesize P3 according to the procedure described above (chloroform fraction: 307 mg, yield 83%). As a result of GPC, M _n is 119K, M _w is 531K and PDI is 4.45. The elemental analysis calculations are as follows: C, 71.18; H, 8.63; N, 3.32; S, 10.24; O, 3.79; Se, 2.84. Results: C, 71.40; H, 8.68; N, 3.33; S, 10.26.

1.6 PDPP2T-Se50-Th50 ( P4 ) Polymerization

3,4-c] pyrrole-1,4-dione (400.0 mg, 1.0 (2-hexyldecyl) -3,6-bis eq), 2,5-bis (trimethylstannyl) thiophene (90.35 mg, 0.5 eq), 2,5-bis (trimethylstannyl) selenophene (100.7 mg, 0.5 eq), PPh ₃ P4 was synthesized according to the procedure described above by adding the mixture and Pd ₂ (dba) ₃ (8.1 mg) to toluene (3.0 mL) and DMF (0.3 mL) (chloroform fraction 252 mg, yield 67%). As a result of GPC, M _n is 86.3K, M _w is 387K and PDI is 4.48. The elemental analysis calculations are as follows: C, 70.37; H, 8.53; N, 3.28; S, 9.37; O, 3.75; Se, 4.69. Results: C, 70.55; H, 8.56; N, 3.30; S, 9.32.

1.7 PDPP2T-Se100 ( P5 ) Polymerization

3,4-c] pyrrole-1,4-dione (400.0 mg, 1.0 (2-hexyldecyl) -3,6-bis eq), 2,5-bis (trimethylstannyl) selenophene (201.4 mg, 1.0 eq), PPh ₃ (9.3 mg) and Pd ₂ (dba) ₃ (8.1 mg) were dissolved in toluene (0.3 mL) to synthesize P5 according to the procedure described above (chloroform fraction: 200 mg, yield 52%). As a result of GPC, M _n is 22.7 K, M _w is 93.4 K and PDI is 4.12. The elemental analysis calculations are as follows: C, 68.45; H, 8.30; N, 3.19; S, 7.30; O, 3.65; Se, 9.12. Results: C, 67.82; H, 8.25; N, 3.16; S, 7.32.

&Lt; Example 2 > Production of PSC device

In order to evaluate the effect of the structural change of the random terpolymer on the performance of the organic electronic device, the present inventors have used bottom-gate, top-contact OFET and inverted-type PSC Device.

2.1 Manufacture and measurement of OFET device

PDPP2T-Se-Th ternary copolymer system OFETs were fabricated into a massively n-doped Si wafer (<0.004 Ω cm) covered with a 300 nm thick SiO ₂ dielectric (C _i = 10 nF cm ^-2 ). The SiO ₂ / Si wafer was treated with n-octadecyltrimethoxysilane (OTS) in solution phase. A 3 mM OTS solution in trichlorethylene (TCE) was spun onto a UV / ozone treated SiO ₂ / Si wafer after being washed with a pyran solution (7: 3 volume ratio of H ₂ SO ₄ and H ₂ O ₂ mixture) Coated. The wafer was then exposed to ammonia vapor in a vacuum desiccator at room temperature for 12 hours. Thereafter, the substrate was washed with toluene, acetone, isopropyl alcohol, then was dried with N ₂ flow (N ₂ blowing). A solution-shearing thin film of the terpolymer was deposited on an OTS-treated SiO ₂ / Si substrate using a chlorobenzene solution (2 mg mL ^-1 ). In the solution shear stage, the shear rate was optimized to 0.12 mm s ^-1 . Then, it was annealed on a hot plate at 200 ℃ for 10 minutes under N ₂ atmosphere terpolymer film (annealed). A 40 nm gold electrode was evaporated to the semiconductor layer through a shadow mask. The current-voltage (IV) characteristics of the device were measured using a Keithley 4200 semiconductor parametric analyzer in a N ₂ filled glove box. The field effect mobility was calculated as saturation using the following equation.

In Equation 1, I _D is a drain current, and, W and L are the width and length of each of the semiconductor channel, μ is the mobility, and, C _i is a power failure per unit area of the gate dielectric capacity (capacitance), V _G, and V _T are the gate voltage and the threshold voltage, respectively.

2.2 Manufacture of inverse structured PSCs

In order to investigate the photovoltaic properties of the PDPP2T-Se-Th terpolymer of the inverse-structured polymer solar cell, a bulk heterojunction (BHJ) photovoltaic cell was fabricated using ITO / ZnO / terpolymer: PC ₇₁ BM / MoO ₃ / Ag . (Zn (O ₂ CCH ₃ ) _2. (H ₂ O) ₂ , 99.9%) was added under vigorous stirring for more than 24 hours for the hydrolysis reaction and aging, using the sol-gel procedure of the ZnO sol- , 1 g) and ethanolamine (HOCH ₂ CH ₂ NH ₂ , 99.5%, 0.28 g) in anhydrous 2-methoxyethanol (CH ₃ OCH ₂ CH ₂ OH,> 99.8%, 10 mL). A ZnO thin film having a thickness of about 40 nm was prepared by spin-coating a sol-gel precursor solution at 4000 rpm on top of the ITO substrate. The membrane was heated at 200 &lt; 0 &gt; C for 1 hour in air. After application of the ZnO layer, all subsequent procedures were performed in a glove box under an N ₂ atmosphere. Each active blending solution (terpolymer: PC ₇₁ BM = 1: 2 w / w, polymer concentration = 5 mg / mL) was then spin cast on the ITO / ZnO substrate at 1200 rpm for 90 seconds. The thickness of the optimized active layer was 130 nm ( P1 ), 135 nm ( P2 ), 130 nm ( P3 ), 150 nm ( P4 ) and 120 nm ( P5 ). Finally, to complete the _{device, 7 nm MoO 3/100 nm} Ag film electrode and the top was thermally evaporated under vacuum (less than 10 ^-6 Torr). The active area of the fabricated device was 0.09 cm &lt; ^{2 &} gt ;. The retrostructured PSC devices were characterized by an air mass (AM) 1.5G filter using a solar simulator (Newport Oriel Solar Simulators). The intensity of the solar simulator was carefully tuned using an AIST-certified silicon photodiode. The current-voltage behavior was measured using a Keithley 2400 SMU.

&Lt; Example 3 > Properties of synthesized polymer

In the present invention, a representative DPP low bandgap polymer ( P1 ), which provided superior performance in PSCs and OFETs, was selected as the control polymer (Ye, L. et al ., Adv. Mater . 2012, 24, 6335; Bijleveld, JC et al ., J. Am. Chem. Soc. 2009, 131, 16616). In addition, the embodiment different molar feed ratio of Se to the Th monomer as in the first (10, 30, and 50 mol% Se) is a used during the copolymerization, PDPP2T-Se10-Th90 (P2 ), PDPP2T-Se30-Th70 (P3 ) And PDPP2T-Se50-Th50 ( P4 ) were synthesized. The following experiment was conducted to confirm the properties of the synthesized polymer.

3.1 Measurement of Se / Th ratio of terpolymer

The actual Se / Th ratio in the terpolymer was determined by elemental analysis (see Table 1 below). Elemental analysis was performed with the Thermo Scientific Flash 2000 series.

The results showed excellent agreement with the Se / Th mol feed ratio. P1 - P5 weight average molecular weight (M _w), number average molecular weight (M _n), and the polydispersity (polydispersity index; PDI) is o - gel permeation at 80 ℃ using dichlorobenzene as the eluent chromatography (gel permeation chromatography (GPC)). All polymers had high M _w values in excess of 100 kg / mol. However, the inventors have noted that the M _w value of P5 was measured to a small extent due to low solubility and strong aggregation under GPC measurement conditions. The properties of the polymers are summarized in Table 2 below.

3.2 Optical characterization

The optical and electrochemical properties of conjugated polymers are important in determining performance in organic electronic devices such as OFETs and PSCs. Figure 2 shows the absorption spectra of all polymers in the form of thin films in dilute chlorobenzene solution and UV-vis absorption spectra were measured at room temperature using a UV-1800 spectrophotometer (Shimadzu Scientific Instruments). The absorption properties of the polymer are summarized in Table 2 above. All random terpolymers exhibited similar absorption characteristics between 400 and 1000 nm. The optical bandgap (E _g ^opt ) of all P1 - P5 polymers had a similar value of 1.32-1.35 eV based on the onset of light absorption. The maximum absorption peak (λ _max ) was slightly red shifted from P1 to P5 as the Se content was increased. In addition, all the polymers exhibited the maximum absorption peak shifted red in the thin film compared to the solution, but the degree of red-shifting decreased gradually from P1 to P5 .

These results were caused by the promoted intermolecular interactions through the pi-orbital overlap between Se units in the polymer backbone (Nguyen, T.-Q. et al ., J. Chem. Phys . 1999, 110, 4068) , From which it was confirmed that the optical absorption coefficient of five different polymers was improved as the Se content in the polymer main chain was increased.

3.3 Electrochemical Characterization

The ionization potential and electron affinity of the terpolymer were measured using cyclic voltammetry (CV) (Bredas, J.-L. Mater. Horiz. 2014, 1, 17). The electrochemical cyclic voltammetry (CV) (CHI 600C electrochemical analyzer) was carried out in anhydrous acetonitrile containing 0.1 M tetrabutylammonium hexafluorophosphate (Bu ₄ NPF ₆ ) using a Pt disturbing electrode, Pt counter electrode and Ag wire - a quasi-reference electrode at a potential scan rate of 50 mV / s. For electrochemical measurements, the polymer membrane was coated from a chloroform solution at a concentration of approximately 1 mg / mL.

The results are summarized in Table 2 above and its CV curves are shown in FIG. The ionization potential and electron affinity were measured from the oxidation initiation potential (E _ox ^on ) and the reduction initiating potential (E _red ^on ) for the ferrocene standard, respectively.

As a result, as the Se content increased, the ionization potential gradually increased from -5.23 ( P1 ) to -5.15 eV ( P5 ), indicating that the electrons in Se units were more abundant and increased molecular interactions (Chen, H.-Y. et al. J. Mater. Chem. 2012, 22, 21549). However, the optical and electrochemical properties of the five polymers were not significantly different. The use of Se units instead of Th units minimized changes in the optical and electrochemical properties of the polymer merely that the sulfur atom was replaced by a selenium atom.

3.4 Identification of thermal mobility

Next, the effect on the thermal behavior of the Se content in the polymer was investigated using differential scanning calorimetry. Differential Scanning Calorimetry (DSC) analysis was performed on a TA Instruments DSC Q200. The sample (~5 mg) was heated from 25 to 350 ° C at a scan rate of 10 ° C min ^-1 under N ₂ atmosphere. A heating and cooling thermogram of the PDPP2T-Se-Th terpolymer is shown in Figures 2 (c) and 2 (d), respectively, and its thermal properties are summarized in Table 2 above. During the heating process, the P1 copolymer exhibited a melting endothermic peak (T _m ) at 295.9 ° C and the T _m values of P2 , P3 , P4 and P5 gradually increased to 302.0 ° C, 306.9 ° C, 310.8 ° C and 322.1 ° C, respectively Respectively. In the cooling cycle, the same tendency was observed in the crystallization temperature (T _c) of a random terpolymer, which was 235.9 (P1), 268.9 (P2 ), 273.5 (P3), 274.8 (P4), and 281.1 ℃ (P5) . This strong trend of increasing T _m and T _c values indicates that incorporation into the terpolymer of Se can induce strong interchain interactions and lead to the formation of highly ordered structures of ternary copolymers with reduced chain mobility It is possible to cause it.

With respect to these results, the relative crystallinity of the terpolymer was quantitatively compared by measuring the heat of crystallization (ΔH _c ) (Causin, V. et al ., Macromolecules 2005, 38, 409; Kim, HJ et al ., Macromolecules 2013, 46, 8472; Woo, CH et al ., J. Am. Chem. Soc . 2008, 130, 1632). The ΔH _c value of the terpolymer increased markedly from 5.8 ( P1 ) to 16.2 J / g ( P5 ) as the Se content increased, indicating a significant increase in crystallinity. The crystallinity of the terpolymer Significant differences in behavior can affect not only electrical properties (i.e., charge mobility) but also solubility in solvents and miscibility with fullerene acceptors (Xiao, S. et al ., Adv. Funct. Mater . 2010, 20, 635; Cho, H.-H. et al, Macromolecules 2012, 45, 6415;. Beaujuge, PM et al, J. Am Chem Soc 2011, 133, 20009;.... Liu, J. et al ., Adv. Materials , 2012, 24, 538).

<Example 4> Performance measurement of PCS device

In order to evaluate the effect of the structural change of the random terpolymer on the performance of the organic electronic device, in the present invention, a bottom-gate, top-contact OFET, and inverse- an inverted-type PSC device was fabricated. The following experiment was carried out to confirm the properties of the fabricated device.

Figure 4 shows the performance of PDPP2T-Se-Th PSCs and OFETs as a function of Se content; PCE values (left, blue lines) for PCs and electron mobility (right, red lines) at OFETs. Interestingly, the performance of OFETs and PSCs exhibited different trends as a function of Se content and therefore as a function of the crystallinity of the PDPP2T-Se-Th terpolymer. The μ _e value of OFETs increased gradually as Se content increased from P1 to P5 . On the other hand, different trends of PCE values of PSCs were confirmed and it was shown that the highest PCE value (7.2%) was obtained in P2 system PSCs. The causes of these different trends in OFETs and PSCs will be discussed below.

4.1 Electrical Characteristics of OFET and PDPP2T-Se-Th PSCs

The electrical performance of the OFETs is summarized in Table 3 below and its transmission power characteristics are disclosed in Figures 5 and 6, respectively.

The transfer curves of FIG. 5 exhibited rather nonlinear behavior, and the mobility described above may potentially lead to some problems, such as charge scattering induced at high gate voltages, contact resistance, gate leakage, bias stress ) Can be measured over a full range of gate voltage sweeps. P1 consisting solely of DPP2T and Th groups exhibited a maximum μ _e value of 2.11 cm ² V ^-1 s ^-1 . The μ _e value gradually increased from 2.11 ( P1 ) to 2.48 ( P4 ) cm ² V ^-1 s ^-1 with higher Se content ( P2 : 2.12 and P3 : 2.39 cm ² V ^-1 s ^-1 ). Finally, P5 consisting solely of DPP2T and Se showed the highest μ _e value of 5.54 cm ² V ^-1 s ^-1 among the five polymers. Although all of the polymers used in this study exhibited bipolar properties, the balance between hole and electron mobility was improved as Se content increased, mainly due to the improved electron mobility. Insertion of Se atoms into the π-conjugated backbone is known to provide a number of advantages: (i) interchain-charge transport can be facilitated by intermolecular Se: Se contact, (ii) oligo- and Polyselenophene improves resistance to twisting along the main chain due to its quinone type nature (Lee, J. et al ., J. Am. Chem. Soc ., 2012, 134, 2071). Due to these properties, P5 system OFETs exhibited very high hole and electron mobility (4.72 and 5.54 cm ² V ^-1 s ^-1 , respectively) with well-balanced bipolarity.

Thus, it was confirmed that the improvement in the charge transport capability, together with the higher Se content, was closely related to the more fixed characteristics of the polymer and the stronger crystalline behavior.

On the other hand, PSC devices based on PDPP2T-Se-Th terpolymer showed very different tendencies from those of OFET as a function of Se content. The PSC device was prepared in a reverse configuration (ITO / ZnO / terpolymer: phenyl-C ₇₁ -butyric acid methyl ester (PC ₇₁ BM) / MoO ₃ / Ag), optimal donor: acceptor weight ratio 1: 2, 3 volume% 1,8-diiodooctane (DIO) was used as a solvent additive. The current-voltage (IV) characteristics of the inverse-structured PSC device are shown in FIG. 7 (a) and the results are summarized in Table 4 below.

Table 4 relates to the best performance of the element P1-P5 ^a base station optimized structure of the PSCs, ^a value in parentheses is the average of the elements of more than 12 with an active area of 0.09 cm ^2. Detailed mean values and standard deviations are shown in Table 5 below. ( ^b / ^b ) = 1: 2, 1,8-diiodooctane (3 vol%) as an additive, and the mixing ratio of ^c solvent o- DCB / CF , And the mixing ratio of the ^d solvent o- DCB / CF (v / v) = 3: 1.

As a result, the open-circuit voltage (V _oc ) of the random terpolymer is P1 (0.68 V)> P2 (0.67 V) P3 (0.67 V)> P4 (0.66 V)> P5 ), Respectively. The change in V _oc of PSCs was consistent with the tendency of the ionization potential of the terpolymer. Because, V _oc is typically because it is proportional to the difference between the electron affinity of the ionization potential and the acceptor of the polymer also (Kim, K.-H. et al, Chem Mater 2011, 23, 5090;... Chen, H.-Y. et al, Nat Photonics 2009, 3, 649;...... Price, SC et al, J. Am Chem Soc 2011, 133, 4625). However, the PCE values of the random terpolymers are 5 to 7% nonlinear in order of P2 (7.20%)> P3 (6.91%)> P1 (6.79%)> P4 (6.76%)> P5 . Among all the terpolymers, P2 : PC ₇₁ BM showed the highest PCE value (V _OC = 0.67 V; J _SC = 16.22 mA cm ^-2 ; and FF = 0.66) of 7.20%. However, the P5 polymer that produced the best OTFT device had the lowest PCE value of 5.59% (V _OC = 0.65 V; J _SC = 13.44 mA cm ^-2 ; and FF = 0.64). This PCE trend as a function of Se content was mainly due to the change in J _sc and FF values.

4.2 Measurement of external quantum efficiency spectrum

External quantum efficiencies (EQEs) were measured for random tri-co-polymer PSC devices under optimized device conditions (Figure 7b). The wavelength range of the EQE spectrum of the PSC device was in good agreement with the UV-visible absorption range of the terpolymer / PC ₇₁ BM blend film (see FIG. 8). Except for P5 (~ 39%), the maximum EQEs of PSC devices exceeded 50% at 560 nm. In particular, the EQE value of the P2 : PC ₇₁ BM device was greater than P1 : PC ₇₁ BM over the entire range of 400 to 900 nm. The measured J _sc value for the PSC element was well matched (within 2% error) with the integrated J _sc value obtained from the EQE spectrum.

Example 5 GIXS Analysis of Ternary Copolymer

5.1 GIXS Analysis

In order to further investigate the change in the crystalline behavior of the ternary copolymer as a function of the Se content in relation to the change in PSC performance, the crystallographic behavior and microstructure of the polymer of the blend membrane Respectively. (GIXS) measurements were performed at Beamline 3C of the Pohang Accelerator Laboratory (Korea) and GIXS samples were prepared by spin coating on PEDOT: PSS / Si substrates with optimized active layer conditions. At this time, an X-ray having a wavelength of 1.1179 A was used. The incident angle (~ 0.12 °) was chosen for complete transmission of the X-ray into the film.

As a result, the GIXS image of the optimized active layer is shown in FIG. 9, and its line profile in the out-of-plane (q _z ) and in-plane (q _xy ) . All the terpolymers exhibited a distinct (100) reflection peak in the in-plane direction, which represented a nearly identical lamella spacing (d ¹⁰⁰ ) of approximately 2.0 nm (q _xy ? 0.314 A ^-1 ) 6).

Also, the (010) reflection peaks from the pi-pi stack of all the polymers appeared in the out-of-plane direction with a domain spacing (d ⁰¹⁰ ) of about 0.36 nm (q _z ? 1.728 A ^-1 ) quot; face-on "molecular alignment (Guo, X. et al ., Nat. Photonics 2013, 7, 825; Tumbleston, JR et al ., Nat. Photonics 2014, 8, C. et al ., J. Am. Chem. Soc . 2010, 132, 7595). Interestingly, (010) reflection peaks from the pi-pi stack were more prominent from P1 to P5 as Se content increased. Further, the correlation of the polymer within the optimized active length (L _c) by using the Scherrer equation was calculated from the reflection GIXS (Erb, T. et al, Adv Funct Mater 2005, 15, 1193;.... Chen, MS et al ., Chem. Mater . 2013, 25, 4088, Rivnay, J. et al ., Chem Rev. 2012, 112, 5488). The L _c value provides a measure of the distance over which the crystalline array is held. In polymer membranes, the reduction in chain position and rotation variability corresponds to a narrow peak width and larger L _c value (hen, MS et al ., Chem. Mater . 2013, 25, 4088; Rivnay, J. et al . , Chem. Rev. 2012, 112, 5488). Table 6 above shows the lamellar (L _c ¹⁰⁰ ) and pi-pi stack (L _c ⁰¹⁰ ) correlation lengths of five different polymers in the optimized active layer and Table 7 below shows the corresponding full-width at half-maximum ; fwhm) values.

As Se content increased, the L _c ¹⁰⁰ value gradually increased from 8.97 ( P1 ) to 12.82 nm ( P5 ). An equally increasing tendency of L _c ⁰¹⁰ values for the pi-pi stack was observed for higher Se content. In particular, P5 based showed the longest L _c value of ⁰¹⁰ (2.02 nm) for the π-π stacking of the film series, which is two times the value of L _c ⁰¹⁰ (1.18 nm) obtained for the P1-based film. We also performed GIXS measurements to investigate the microstructure and crystalline behavior of the pristine P1 - P5 polymer in the membrane, and the results show that the crystalline behavior of the terpolymer increases as the Se content increases (Detailed data are shown in Figures 11 and 12 and Table 8 below).

From the above results it can be clearly seen that higher Se content leads to excellent ability to charge transfer by allowing the polymer backbone to form a crystalline structure with better alignment. However, from the combined results of the DSC and GIXS measurements, the differences in the fine pattern of the improved polymer packing structure due to incorporation of Se units were not directly related to the trend of photovoltaic performance. Therefore, the BHJ form of the active layer blended with PC ₇₁ BM is another important problem.

5.2 TEM measurement

The effect of the random terpolymer on the non-linear trend of photovoltaic performance was confirmed by determining the macroscopic problem of the blend form of the active layer optimized by TEM measurement (tertiary copolymer: PC ₇₁ BM) (see FIG. 13). TEM measurements were performed with JEM-3011 JEOL Ltd. The optimized active layer was spin cast onto the PEDOT: PSS / Si substrate, after which the thin film was floated on the air / water interface and transferred to the TEM grid.

As a result, the TEM image clearly indicated that the Se content in the polymer significantly affected the fibril formation of the polymer in the active layer. For example, P5 with a higher Se content has the most pronounced fibrillar structure in the active layer, which is due to the tendency of the polymer chains to aggregate. Lowering the Se content inhibited the formation of the fibril structure of the polymer in the active layer, which showed a less pronounced fibril structure. In addition, the inventors have noted that the tendency of the degree of fibril formation of the polymer is very consistent with the L _c value obtained from the GIXS data. Even if it is very advanced fibril castle structure of the polymer in the active layer is very advantageous to improve the charge transport through the fibrils, which PC ₇₁ BM in the active layer, which can prevent the efficiency of exciton dissociation in the polymer / PC ₇₁ BM interface Leading to severe phase separation from the domain. Recently, Janssen et al. Studied a series of DPP-based alternating copolymers and found a strong correlation between the width of the polymer fibrils and the EQE of the conversion of photons to electrons (Li, W. et al ., J. Am. Chem. Soc ., 2013, 135, 18942). Typically, the exciton diffusion length for the conjugated polymer is a few nanometers, and thus polymers with broader fibrils can exert a negative effect on the efficiency of the exciton diffusion to the interface with the fullerene acceptor . Thus, P2 and P3 polymers with relatively low Se content developed an appropriate fibril structure for efficient exciton diffusion to the PC ₇₁ BM interface, resulting in better exciton dissociation in other polymers. As a result, the incorporation of Se units into the DPP-based terpolymer resulted in (1) improved charge mobility and (2) an efficient means of optimizing the BHJ form, resulting in optimal performance of the PSCs.

That is, a novel PDPP2T-Se-Th random terpolymer containing two different electron rich units of Se and Th was synthesized to control the crystalline behavior of the low band gap polymer (see Example 1). Through a change in the relative composition of Se and Th in the polymer, we were able to successfully fine-tune the crystallinity and telephone transport capability and demonstrate the advantages of the random terpolymer process with respect to the performance of OFETs and PSCs .

Specifically, increasing the Se content led to a significant increase in T _c and T _m values as well as crystallinity (see Example 3). This change in crystallinity of the polymer was a major factor in determining OFET and PSC performance (see Example 4), although the energy level and light absorption capacity were slightly different from each other. The improved crystallinity of the random terpolymer improved hole and electron mobility in the OFET device in the order of P1 , P2 , P3 , P4 and P5 , and P5 system OFETs had very high hole and electron mobility (4.72 and 5.54 cm ² V ^-1 s ^-1 ). On the other hand, PCE values of PSCs were observed to be different. This is because the shape of the polymer: PCBM BHJ film in the PSCs strongly depends on the Se content, and as the Se content increases, the polymer has an increased size range and phase separation. Thus, the best performance of the PSC device was obtained for P2 polymer (PCE: 7.2%) with optimum Se content and showed synergistic effects of optimized BHJ morphology and high charge mobility. This discovery suggests that optimization of the crystallinity of the polymer is an essential consideration for designing high-efficiency materials for organic electronic devices (e.g., OFETs or PSCs). In addition, it has been confirmed that the random terpolymer method is particularly effective in optimizing the characteristics of the polymer and maximizing the performance of the organic electronic device.

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 (10)

(DPP) -based compound and an aromatic cyclic compound comprising selenophene and thiophene, wherein the cyclic compound is a cyclopentadienyl compound,
The selenophene and the thiophene are contained at a molar ratio of 0.1-0.5,
A ternary copolymer represented by the following formula:
[Chemical Formula]

delete delete delete The terpolymer of claim 1, wherein the terpolymer is an active layer of a solar cell or a transistor. A polymer solar cell (PSCs) comprising the terpolymer of claim 1 as an active layer. An organic field-effect transistor (OFET) comprising the ternary copolymer of claim 1 as an active layer. A method for synthesizing a terpolymer comprising the steps of:
a) degassing a mixture of diketopyrrolopyrrole compounds, thiophene and selenophene;
b) reacting the degassed mixture of step a) in a microwave reactor and cooling the mixture to room temperature to prepare a gel;
c) diluting and refluxing the gel of step b); And
d) extracting and purifying the refluxed gel of step c). The method according to claim 8, wherein the degassing in step a) is performed by firstly degassing with addition of argon, followed by second degassing by adding triphenylphosphine and tris (dibenzylideneacetone) dipalladium Lt; / RTI &gt; 9. A method according to claim 8, wherein the extraction in step d) is soxhletextracted with methanol, acetone, hexane, dichloromethane, chloroform and chlorobenzene.

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