KR101443295B1 - Novel ambipolar organic semiconductor compounds possible to change dominant polarity and organic thin-film transistor device comprising the same - Google Patents

Abstract

The present invention relates to an ambipolar semiconductor compound capable of simultaneously forming p-type and n-type semiconductors, and is characterized by being represented by the following Chemical Formula 1, wherein the thermally removable functional group is removed by a subsequent heat treatment, The p-type and n-type semiconductor characteristics can be realized at the same time using the bipolar semiconductor compound according to the present invention, Can be produced. In addition, a display excellent in impact resistance and flexible characteristics can be realized at lower cost by solving electron and hole mobility generated in a thin film transistor or the like made of an organic material in the related art.
[Chemical Formula 1]

Description

TECHNICAL FIELD The present invention relates to a novel bipolar organic semiconductor compound capable of converting a polarity and an organic thin film transistor including the same,

[0001] The present invention relates to a novel polymer semiconductor compound capable of converting a polarity and an organic semiconductor thin film device including the same, and more particularly, to an organic semiconductor thin film device capable of simultaneously converting p-type and n-type semiconductors, 0001] The present invention relates to an ambipolar semiconductor compound and an organic semiconductor thin film transistor including the same.

BACKGROUND OF THE INVENTION Organic field effect transistors (OFETs) are an important element in relation to large flexible electronic devices at very low cost such as radio frequency identification (RFID) tags, smart cards and organic active matrix displays, Research is being conducted in earnest all over the world. Organic electronics industry is not only simple and cost-effective to manufacture compared to inorganic electronics industry, but also has the advantage of being able to make an electronic circuit board that can be folded or folded without being broken easily by impact. And the development of organic transistors capable of meeting these needs is emerging as an important research area.

Organic semiconductor materials that determine the characteristics of an organic thin film transistor are largely divided into a unipolar semiconductor and a bipolar semiconductor. An electronic circuit made of a unipolar semiconductor has a disadvantage in that it has high power loss, low driving speed and stability. Such drawbacks can be solved by putting a p-type and n-type semiconductors, which are unipolar semiconductors, into a complementary circuit, Cost was raised as a problem.

On the other hand, bipolar semiconductors utilize both electrons and holes as driving charges, and the manufacturing process is simpler than that of unipolar semiconductors, so that electronic circuits can be fabricated by a single pattern process. However, in bipolar semiconductors, There is a problem that imbalance occurs.

SUMMARY OF THE INVENTION The present invention provides a bipolar polymer semiconductor compound capable of eliminating an imbalance in the mobility of electrons and holes in an ambipolar polymer semiconductor and adjusting the polarity of the main carrier by a simple heat treatment without further processing will be.

The present invention also provides an organic semiconductor thin film including the polymer semiconductor compound and an element such as an organic field effect transistor (OFET), an organic light emitting diode (OLED), and an organic solar cell.

In order to solve the above problems, the present invention provides a polymeric organic semiconductor compound represented by the following formula (1).

[Chemical Formula 1]

In the above formula (1)

Wherein R ₁ is an alkoxycarbonyl group having 1 to 10 carbon atoms, R ₂ is an alkyl group having 1 to 40 carbon atoms, and Ar is an aryl group having 6 to 30 carbon atoms.

In the polymer compound represented by Formula 1, R ₁ is a functional group that is thermally removed by heat treatment.

According to one embodiment of the present invention, the compound represented by Formula 1 may be a polymeric organic semiconductor compound represented by Formula 2 below.

(2)

The present invention also provides an ambipolar organic semiconductor thin film comprising a plurality of polymeric organic semiconductor compounds represented by the above formula (1).

The organic semiconductor thin film is characterized in that the arrangement of adjacent polymers is represented by the following structural formula 1, and the main electrode is a p-type semiconductor at room temperature.

[Structural formula 1]

In the above formula 1,

Wherein R ₁ is an alkoxycarbonyl group having 1 to 10 carbon atoms, R ₂ is an alkyl group having 1 to 40 carbon atoms, and Ar is an aryl group having 6 to 30 carbon atoms.

According to an embodiment of the present invention, the organic semiconductor thin film may be manufactured by a drop-casting method or a solution shearing method on a substrate, preferably by a solution shearing method.

In addition, the bipolar organic semiconductor thin film may be an n-type semiconductor with a main electrode by heat treatment.

As described in the later-described embodiments, when a bipolar organic semiconductor thin film (BOC-PTDPP) represented by the above formula (1) is incorporated into a transistor using a solution front-end process, it exhibits a p-type superiority property, And electron mobility of about 1.32 × 10 ^-2 cm ² V ^-1 s ^-1 and 2.63 × 10 ^-3 cm ² V ^-1 s ^-1 , which is about one order higher than the mobility of the thin film produced by drop casting Size.

In addition, the lead polarity of the charge carriers are negative in turn into the amount after thermal decomposition of the t-BOC group from 150-250 ℃, the film is excellent electromigration prepared by subsequent heat treatment solution shear Process (μ _e = 4.60 × 10 ^{- 2} cm ² V ^-1 s ^-1 ), whereas the hole mobility decreases by a first order magnitude ( μ _e = 4.30 × 10 ^-3 cm ² V ^-1 s ^-1 ). An inverter configured with a combination of two identical bipolar organic semiconductor thin films exhibits a gain of about 10.

In this solution process, a method of selectively controlling the dominant polarity of charge carriers in bipolar OFETs was first identified in the present invention.

In addition, the present invention provides a bipolar organic semiconductor thin film characterized in that a bipolar organic semiconductor thin film is thermally treated to form hydrogen bonds between neighboring polymers in a network structure, and the arrangement of adjacent polymers is represented by the following structural formula 2.

[Structural formula 2]

In the above formula 2,

Wherein R ₁ is an alkoxycarbonyl group having 1 to 10 carbon atoms, R ₂ is an alkyl group having 1 to 40 carbon atoms, and Ar is an aryl group having 6 to 30 carbon atoms.

Wherein the positive electrode of the bipolar organic semiconductor thin film is an n-type semiconductor.

The present invention also provides a method of manufacturing the organic semiconductor thin film and a transistor (OFET) including the organic semiconductor thin film, an organic light emitting diode (OLED), an organic solar cell, and the like.

The "unipolar semiconductor" described in the specification of the present invention is a semiconductor in which a current flows through only one of two carriers such as an electron and a hole and is classified into a p-type semiconductor and an n-type semiconductor , "Bipolar semiconductor" refers to a semiconductor that uses both electrons and holes as a carrier to contribute to the flow of current.

The term "p-type semiconductor" refers to a semiconductor in which a semiconductor in which a hole is used as a carrier for transferring charges, that is, a hole in which a positive charge moves, , "n-type semiconductor" refers to a semiconductor in which electrons having a negative charge are moved by a carrier in which electrons having a negative charge are transferred, and carriers are electrons.

The term "bipolar" refers to a polarity of a charge carrier in a bipolar semiconductor. When a hole in a carrier inside a bipolar semiconductor is more dominant than an electron, And the polarity becomes the p-type, and the opposite polarity becomes the n-type.

By using the bipolar semiconductor compound according to the present invention, p-type and n-type semiconductor characteristics can be realized at the same time, and an electronic circuit can be manufactured by a relatively simple solution process.

In addition, the problem of unevenness of electron and hole mobility generated in a thin film transistor or the like made of an organic material in the past can be solved, and a display excellent in impact resistance and flexibility can be realized at a lower cost.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1A is a schematic diagram of a bipolar polymeric compound comprising a thermally removable functional group (t-BOC) according to the present invention and a control scheme of the polarity through heat treatment. The intermolecular distance and the charge transfer characteristics are changed by inducing intermolecular hydrogen bonding through heat treatment, so that the bipolar polymer semiconductor having a pore type is converted into an n type bipolar polymer semiconductor.
1B is a conceptual diagram showing a technique for solution shearing.
FIG. 1C is a schematic diagram showing the main polarity transformation of the organic thin film transistor according to the present invention manufactured through a solution process. As the thermally removable functional group is removed by the heat treatment, the energy level changes and the polarity conversion of the organic thin film transistor appears.
FIG. 2A shows the TGA results of the t-BOC-protected DPP precursor at a heating rate of N ₂ , 10 ° C / min and FIG. 2b shows the TGA results of the UV-vis-NIR after pyrolysis at 200 ° C. of the t- Absorption spectrum.
FIG. 3A shows TGA of BOC-PTDPP at a heating rate of N ₂ , 10 ° C./min. FIG. 3B shows UV-vis-NIR absorption spectrum of BOC-PTDPP in a thin film before and after pyrolysis at 200 ° C.
Figure 4 shows the FT-IR spectrum of the (4a) drop-cast film of (4a) solution-shear thin film of BOC-PTDPP before and after pyrolysis at 200 ° C It is a guideline.
5 is a cyclic voltammogram of BOC-PTDPP thin film on a glassy carbon (GC) electrode at (a) and (b) before and after pyrolysis at 200 ° C (room temperature, 0.1 M n-Bu ₄ NPF ₆ Acetonitrile solution).
FIG. 6 shows the XRD results obtained from the drop cast BOC-PTDPP films before (above) and after (below) pyrolysis at 200.degree.
FIG. 7 is a top view of the geometry and charge density isomorphism and the PTDPP polymer at the HOMO and LUMO levels through DFT calculation ((a) t-BOC group presence, (b) t-BOC group member).
FIG. 8 is a tapping mode AFM image of a drop-cast film, (c) and (d) solution-shear film of BOC-PTDPP, (a) and (c) b) and (d) are after pyrolysis.
9 is a BOC-PTDPP bipolar transistor operating in (a) hole-enhancement and (b) electron-enhancement modes prior to pyrolysis, which is a transport and output characteristic of an OFET device based on a solution-sheared BOC- PTDPP thin film, The characteristics of the PTDPP bipolar transistor after pyrolysis are (c) the hole-enhancement and (d) the result of the thin film obtained in electron-enhanced mode (| V _DS | = 100 V).
10 shows the inverter characteristics of the bipolar BOC-PTDPP in air. When the supply bias is constant, the gain of the inverter is about 10 (V _DD = 100 V)

Hereinafter, the present invention will be described in more detail.

Among the organic semiconductor materials, the polymer semiconductor has the greatest significance because the solution process can be performed, and the manufacturing cost of the organic electronic device can be greatly reduced. In order to enable a solution process, it is common to introduce a long alkyl chain into the polymer backbone as a solubilizing group. However, the alkyl chain introduced in this case acts as an element that hinders dense molecular alignment and packing of the conjugated structure polymer semiconductor, which adversely affects the charge transfer characteristics.

Accordingly, one aspect of the present invention is to solve the above-mentioned problems by introducing a functional group that minimizes the influence on the molecular packing by mixing the alkyl chain and the thermally removable functional groups at a certain ratio, And a polymer organic semiconductor compound represented by the following formula

[Chemical Formula 1]

In the above formula (1)

Wherein R ₁ is an alkoxycarbonyl group having 1 to 10 carbon atoms, R ₂ is an alkyl group having 1 to 40 carbon atoms, and Ar is an aryl group having 6 to 30 carbon atoms.

In addition, a new functional group capable of inducing intermolecular hydrogen bonding is generated in the place where the functional group (R ₁ ) is removed by a simple heat treatment, thereby increasing the intermolecular interaction and reducing the distance between the polymer chains, have.

The hydrogen bonds induced through the heat treatment were confirmed by Fourier transform infrared spectroscopy in the following Examples. In the infrared spectroscopy spectrum after the heat treatment, the C = O bond peak due to the ester group in the thermally removable functional group disappeared and the NH bond peak in the polymer backbone .

In order to estimate the distribution of electrons in the polymer due to the thermally removable functional group and the change of the energy, numerical simulation was performed using the density function function theory calculation. As a result of the removal of the thermally removable functional group, a more planarized molecular structure was induced, and it was confirmed that the energy levels were changed as electrons became more delocalized.

Especially, it was confirmed that the mobility of the bipolar polymer was easily changed according to the heat treatment. That is, as shown in FIG. 1A, the hole mobility prevailed before the heat treatment, and the p-type was the polarity. However, after the heat treatment, the electron mobility prevailed and the n-type became the polarity. After the heat treatment, the bipolar charge transfer characteristics may be controlled depending on the chemical structure and ratio of the thermally removable functional groups.

Another aspect of the present invention relates to a thin film of an ambipolar organic semiconductor comprising a plurality of polymeric organic semiconductor compounds represented by the formula (1).

At room temperature, packing arrangements between adjacent polymers are represented by the following structural formula 1, and the pores are p-type semiconductors.

When the subsequent heat treatment process is performed, the thermally removable functional group R ₁ is removed, and hydrogen bonds are formed between the adjacent polymers to form a network structure, and the arrangement with the adjacent polymer is represented by the following formula (2) .

[Structural formula 1]

[Structural formula 2]

In the above-mentioned structural formulas 1 and 2,

은 수소결합(hydrogen-bonding)을 나타낸다.
Wherein R ₁ is an alkoxycarbonyl group having 1 to 10 carbon atoms, R ₂ is an alkyl group having 1 to 40 carbon atoms, Ar is an aryl group having 6 to 30 carbon atoms,

Represents hydrogen bonding.

More specific details of the present invention will be described in detail in the following examples. 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. It will be clear to those who have knowledge.

<Examples>

&Lt; Materials and devices used in the above-mentioned embodiments according to the present invention are as follows:

(1) Materials were purchased from Aldrich or Acros and used without further purification. Solvents are ACS grade unless otherwise noted. Anhydrous THF was obtained by distillation from sodium / benzophenone prior to use, and anhydrous toluene was used as is.

Dihydropyrrolo [3,4-c] pyrrole-1,4-dione (DTDPP), 2-decyltetradecylbromide, 1,4-dioxole 3,4-c] pyrrole-2,5-dicarboxylic acid di-tert-butyl ester and 3,6-bis- (5-bromothiophen-2-yl) -Yl) -1,4-dioxopyrrolo [3,4-c] pyrrole-2,5-dicarboxylic acid di-tert-butyl ester was prepared by a known method.

(2) ¹ H NMR and ¹³ C NMR spectra were recorded on a VNMRS 600 (Varian, USA) spectrometer using solvent CDCl ₃ and internal standard tetramethylsilane (TMS) and MALDI MS spectra were recorded on an Ultraflex III (Bruker, Germany) &Lt; / RTI &gt; Thermogravimetric analysis (TGA) was performed on a Q200 (TA Instrument, USA) while heating from 50 ° C to 800 ° C at a heating rate of 10 ° C / min.

FT-IR spectra were also recorded on 670-IR / 620-IR Imaging (Varian, USA) and UV-vis-NIR spectra were obtained on a Cary 5000 (Varian, USA) spectrometer. Atomic Force Microscopy (AFM) images were obtained using an Agilent 5500 (Agilent, USA). X-ray diffraction (XRD) analysis was performed on a D / MAZX 2500V / PC (Rigaku, Japan). The number average (Mn) molecular weight and weight average (Mw) molecular weight and polydispersity index (PDI) of the polymer product were determined by gel permeation chromatography (GPC) with an Agilent 1200 HPLC Chemstation using a series of It was determined at 308 K using monodispersed polystyrene.

The cyclic voltammetry (CV) measurement was also carried out in a 0.1 M tetra-n-butylammonium hexafluorophosphate (n-Bu ₄ NPF ₆ ) acetonitrile solution at a scan rate of 100 mV / s under argon in Solartron SI 1287 The measurement was carried out at room temperature using an electrode cell. A silver wire, a platinum wire, and a glass carbon disk were used as the reference electrode, the counter electrode, and the working electrode, respectively. The Ag / Ag ⁺ reference electrode used a ferrocene / ferrocenium redox couple as an external standard, and calibration was performed with the oxidation potential set to 4.8 eV for the zero vacuum level. The HOMO energy level is given by the equation HOMO (eV) = - (E _ox ^onset - E _ferrocene ^onset + 4.8). The LUMO level of the polymer is given by the equation LUMO (eV) = - (E _red ^onset - E _ferrocene ^onset + 4.8).

Synthesis Example 1 Synthesis of [Formula 2] (hereinafter, also referred to as 'BOC-PTDPP' or 'BOC protected PTDPP')

4-dione-5 ', 5'-dideoxy-5'-dicyclohexylcarbodiimide according to the following [synthesis route] 5'-dicyclene-3,6-dithien-2-yl-2,5-di (2-decyltetradecanyl) -pyrrolo [3,4-c] pyrrole-1,4- diyl] was synthesized.

[Synthetic route]

(2)

(I) di-tert-butyl dicarbonate, dimethylaminopyridine (DAMP), THF, Ar atmosphere, 24 h, 85%

(Ii) 2-decyltetradecyl bromide, K ₂ CO ₃ , DMF, 120 ° C., Ar atmosphere, 24 h, 55%

(Iii) NBS, chloroform, dark, Ar atmosphere, 48h, 75%

(Iv) LDA, 2-isopropoxy-4,4,5,5-tetramethyl-1,3,2-dioxaborolane, THF,

(V) Pd ₂ (dba) ₃ / P- (o-Tol) ₃ , K ₃ PO ₄ , toluene / H ₂ O, 95 ° C, 48 h, 75%.

(1) (3,6-Di (2- (4,4,5,5-tetramethyl- [1,3,2] dioxaborolan-2-yl) thien-5-yl) -decyltetradecyl) -pyrrolo [3,4-c] pyrrole-1,4-dione (3,6-di (2- (4,4,5,5-tetramethyl- [ Pyran-2-yl) thien-5-yl) -2,5-di

3,4-c] pyrrole-l, 4,4-d] pyrimidin-2-yl) -2,5-di (2-decyltetradecyl) pyrrole dissolved in THF -Dione (1 g, 1.0 mmol) and 2-isopropyl-4,4,5,5-tetramethyl-1,3,2-dioxoborane (0.42 g, 0.46 mL, 2.5 mmol) Isopropylamide (LDA) solution (1.28 mL, 2.5 mmol) was added slowly (over 5 min).

The resulting mixture was stirred at 0 &lt; 0 &gt; C for 1 h and then quenched with water (200 mL). The compound was extracted in CHCl ₃ , washed and dried over MgSO ₄ , then the solvent was evaporated under reduced pressure and washed three times with methanol (200 mL).

Separation yield = 1.0 g (79%)

Viscous viscous oil

¹ H NMR (CDCl ₃ , 600 MHz):? Ppm 8.91 (d, J = 3.17,2H), 7.71 (d, J = 3.17,2H), 4.05 (m, 4H) s, 24H), 1.27-1.20 (m, 80H), 0.87-0.86 (m, 12H).

^{13 C} NMR (CDCl ₃ , 150 MHz):? Ppm 161.71, 140.48, 137.62, 136.11, 135.63, 108.70, 84.55, 46.24, 37.77, 31.91, 31.27, 30.01, 29.80, 29.68, 29.66, 29.64, 29.62, 29.57, 29.35, 29.33, 26.32, 24.75, 22.67, 14.10.

MALDI-TOFMS (m / z) 1225.68 (M &lt; + &gt;).

Analytical theoretical amount of C ₇₄ H ₁₂₆ B ₂ N ₂ O ₆ S ₂ : C, 72.52; H, 10.36, N, 2.29 ydslnal: C, 72.40; H, 10.59, N, 2.57.

(2) Poly [3,6-dithien-2-yl-2,5-di (t-butoxycarbonyl) -pyrrolo [3,4-c] pyrrole-1,4-dione 5 ', 5 " 3,4-c] pyrrole-1,4-dione-5 ', 5 &apos; ' -diyl] (poly (3,6-dithien-2- Pyrrole [3,4-c] -pyrrole-1, 4-dione-5 ', 5 "-diyl (3-methyl- 3,4-c] pyrrole-l, 4-dione-5 &apos;, 5 & Diyl]) (BOC-PTDPP)

A mixture of the above-mentioned three compounds (104 mg, 0.16 mmol), the above 4 compounds (200 mg, 0.16 mmol) and tris (dibenzylideneacetone) dipalladium (0) (10 mg, 0.011 mmol) Were placed together in a Schlenk flask. To this solution was added tri (o-tolyl) phosphine (5 mg, 0.016 mmol) and K ₃ PO ₄ (220 mg) dissolved in toluene (5 mL) with demineralized water (1 mL) Heated at 95 &lt; 0 &gt; C for 48 h with vigorous stirring and then poured into a mixture of methanol (300 mL) and water (100 mL). The resulting solids were filtered off and the lower molecular weight fraction was removed from this material by sequestering with methanol (1 d), acetone (1 d) and hexane (1 d). The residue was extracted with chloroform, precipitated again in methanol and dried in vacuo to give a dark purple product.

Separation yield of polymer BOC-PTDPP = 150 mg (75%)

GPC analysis Mn = 13,520 kg / mol, Mw = 48,360 kg / mol and PDI = 3.58 (for PS standard materials)

_{^{1 HNMR (CDCl 3, 600 MHz}} ): δ ppm 8.96-8.91 (br, 2H), 8.37-8.33 (br, 2H), 7.63-7.07 (br, 4H), 4.03-3.93 (br, 4H), 2.94- 1.20 (t, 94H), 0.85-0.84 (br, 12H)

Analytical theoretical amount of C ₈₈ H ₁₃₀ N ₄ O ₈ S ₄ : C, 70.45; H, 8.73 N, 3.73; H, 9.00, N, 3.51

The polymer compound represented by formula (2) according to an embodiment of the present invention is synthesized by the above-described [synthesis route].

As shown in the above synthetic route, DPP (diketopyrrolopyrrole) precursor [1] protected with t-BOC (tert-butoxycarbonyl) as a monomer for metal (Ni or Pd) catalytic cross-linking polymerization is di- Dicarbonate, which was then converted to the brominated DPP [3] (yield 75%).

Next, to ensure solution processability of the DPP-based polymer, 2-decyl-1-tetradecyl was substituted for a long branched alkyl side chain with nitrogen atoms in the DPP molecular structure. This is accomplished by the reaction of a lithium substitution reaction (LDA) followed by 2-isopropoxy-4,4,5,5-tetramethyl-1,3,2-dioxaborolane to give the corresponding diboride ester comonomer [4 ] (79%).

Then, a soluble DPP-containing polymer [BOC-PTDPP] having a thermally removable solubilizer according to the present invention was synthesized by Suzuki coupling polymerization between a bis-borylated monomer and a bis-brominated monomer.

The methanol and acetone were successively used to remove the impurities and undesired low molecular weight oligomers by the Soxhlet extraction method. The dark colored solid was obtained in high yield (75%) and according to size exclusion chromatography (PS standard) The number average molecular weight (Mn) was 13,520 g / mol and the polydispersity index (PDI) was 3.56. In addition, BOC-PTDPP is characterized in that it can be easily dissolved in a common organic solvent (THF, chloroform, toluene, etc.) at room temperature due to long branching side chain substitution.

Experimental Example 1. Investigation according to thermogravimetric analysis (TGA) and UV-vis spectral change

As shown in FIG. 2A, the DPP (diketopyrrolopyrrole) precursor t-BOC (tert-butoxycarbonyl) protected [1] has a pyrolysis reaction at about 180 ° C., , Which corresponds exactly to the loss of the t-BOC group (Fig. 2a).

The chloroform solution containing the polymer compound represented by the formula 2 was spin-cast to produce a uniform thin film colored in an orange color. The film was subjected to heat treatment at 200 ° C for 5 minutes to obtain a polycrystalline red film (Fig. 2B). The change in photophysical properties is due to the NH-O hydrogen bonding effect of DPP.

3, the pyrolysis of t-BOC groups in BOC-PTDPP also started to occur at about 180 ° C., but the UV-vis spectrum of the film before and after the heat treatment was almost the same in shape and absorbance , And broadband around 800 nm. This result is due to the presence of a long branched alkyl side chain on one comonomer besides the t-BOC group in the polymer backbone. However, it can be seen that after the post-processing step, the final film becomes completely insoluble and strong intramolecular π-π interactions occur in a closely packed planar DPP system.

In order to confirm whether the intermolecular interaction successfully formed the hydrogen-bonded network structure, the BOC-PTDPP film of the drop casting method and the solution shear method was subjected to heat treatment at 200 ° C. for 30 minutes before and after Fourier transform infrared (FT-IR) spectroscopy (Figure 4 below). FT-IR spectrum obtained after the heat treatment as well as the disappearance of the carbamate loss of C = O stretching vibration band at 1749 cm ^-1 of the protecting group, 3436 cm ^- reveals that lead to the appearance of the NH band close to ¹ (FIG. 4a). υ _{c = o} (amide) appears to have moved towards lower energy after heat treatment (about 23 cm ^-1 as), which is a sign of a hydrogen bond (C = OHN) formed along the polymer backbone (Fig. 4b). In addition, heat treated solution shear polymer films have more migration of υ _{c = o} (amide) than drop cast films, which means stronger intermolecular interaction by shear force.

Experimental Example 2: Electrochemical Properties

The highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) energy levels of BOC-PTDPP were confirmed before and after the heat treatment by cyclic voltammetry (CV).

Tetra -n- butylammonium hexafluorophosphate _{(n-Bu 4 NPF 6)} (0.1 M) supporting electrolyte, a polymer film coated with glassy carbon (GC) working electrode, a counter electrode, a platinum wire auxiliary electrode, Ag wire reference electrode, Was performed at a scan rate of 100 mV / s using Fc / Fc ⁺ as an external reference.

The cyclic voltammetry graph of the BOC-PTDPP film before and after the heat treatment at 200 ° C for 5 minutes is shown in FIG. 5 and the CV data (E _ox ^onset / E _red ^onset , HOMO and LUMO energy levels, E _g ^ec ) Table 1].

Both the t-BOC-protected polymer and the deprotected polymer exhibit reversible p-doping / dedoping (oxidation / re-circulation) processes at both positivities, and n-doping / ) Process is also clearly reversible.

Experimental E _{HOMO / LUMO} = - [E _red ^onset -E _ferrocene ^onset + 4.8 eV], the HOMO and LUMO energy levels are estimated to be 5.31 and -3.79 eV for BOC-PTDPP, and after heat treatment, the polymer has a slightly lower bandgap (E _g ^ec ) 5.41 eV) and LUMO (-3.83 eV). The molecular energy level, especially the LUMO level, corresponds to the energy category (-3.1 to -3.8 eV) in which the bipolar behavior of the OFET is experimentally observed when gold electrodes are used.

[Table 1]

EXPERIMENTAL EXAMPLE 3 X-ray Diffraction (XRD) Analysis

X-ray diffraction (XRD) analysis was performed on the BOC-PTDPP thin films to further confirm the molecular dense structure of the polymer thin films due to pyrolysis.

The thin film prior to the heat treatment shown in FIG. 6A shows a sharp first order diffraction peak at 2? = 3.96 °, which corresponds to a d (001) -interval of 22.29 Å resulting from the orderly interlayer deposition of the polymer. In addition, a small secondary peak (002) is observed at 2? = 7.80 °, suggesting that the thin film before heat treatment is a laminate structure having a relatively long order.

When thermally decomposed by heat treatment at 200 ° C for 30 minutes, the deprotected polymer exhibits a first order diffraction peak at 2θ = 4.26 °, corresponding to a d (001) - interval of 20.72 Å. A slightly reduced d (001) - spacing means that the π-plane distance is shortened, which means that it is advantageous for charge transport compared to the molecular packing of the thin film before annealing. In addition, an additional broad peak is observed at about 2 &amp;thetas; = 21.30 DEG, which corresponds to a d-spacing of about 4.20 ANGSTROM (Fig. 6B). The presence of such a small d-spacing value indicates that there is a strong intermolecular interaction force between the fused ring moiety (DPP) and the thiophene moiety including the deprotected PTDPP backbone.

Experimental Example 4. DFT Calculation

By using the Gaussian 03 package, you can perform DFT calculations according to the nonlinear Hybrid Becke 3-variable Lee-Yang-Parr (B3LYP) function and 6-31G * basic settings, and optimize the geometry of BOC-PTDPP using the same method The HOMO and LUMO levels were confirmed.

In order to identify the different molecular structures of the polymers, we used a Gaussian 03 package for BOC-PTDPP and deprotected PTDPP and used molecular simulations with chain length n = 1 according to Density Functional Theory (DFT) in B3LYP / 6-31G * (Fig. 7).

The back angle between DPP and thiophene is sensitive to the substituents on the N-atom in DPP units. Therefore, the back angle of BOC-PTDPP is 18 °, but in the case of deprotected PTDPP, a fully planar three-dimensional structure is observed. This means that the deprotected PTDPP can be easily deposited through the pi-pi interactions of the molecular layers. The calculated results were in good agreement with the XRD analysis results. The HOMO and LUMO trajectories of the deprotected PTDPP are better delocalized because there is no substituent in the DPP unit. In particular, the LUMO trajectory of the deprotected PTDPP is much more delocalized than BOC-PTDPP, which means that n-channel behavior can be promoted after pyrolysis. It can therefore be clearly seen that the t-BOC groups on the DPP can be used as tuning means to control the twist angle and thereby control the electronic and optical properties of the polymer.

Experimental Example 5. Thin Film Morphology Analysis

BOC-PTDPP film morphology was confirmed by tapping mode atomic force microscope (AFM) in order to confirm the effect of thermally removable t-BOC group on the polymer semiconductor thin film prepared by solution process before and after heat treatment.

As shown in FIG. 8, the drop-cast thin film before heat treatment shows a uniform surface with very fine grains.

It can be observed that the polymer thin film heat-treated at 200 ° C still consists of grains of a small clustered non-fibrillar structure, but pinhole-type voids due to evaporation of the t-BOC groups on the surface during heat treatment are produced with a small density . On the other hand, when solution shear technology is applied, the BOC-PTDPP film reveals a completely different shape in which arrays of unidirectional valleys are observed. This means that solution shear may also affect the molecular densification and orientation of the polymer chains. The thin film morphology is the result of a combination of solution shear technique and hydrogen bonding effect on the deprotected PTDPP, and aligned grains with elongated orientation in the polymer film will be a very effective pathway for charge carrier transport.

&Lt; Example 1 > Organic field effect transistor (OFET)

A highly n-doped silicon wafer (< 0.004 ohm cm) thermally grown a 300 nm thick SiO ₂ layer (C _i = 10 nF cm ^-2 ) was used as the OFET substrate. SiO ₂ The surface was treated with n-octadecyltrimethoxysilane (OTS) in solution and the SiO ₂ / Si wafer was irradiated with a Piranha solution (7: 3 mixture of H ₂ SO ₄ and H ₂ O ₂ in volume ratio) After the plasma treatment, 3 mM OTS dissolved in trichlorethylene was spin-coated on the cleaned wafer for 30 seconds at 3000 rpm. Next, the wafer was placed in a desiccator and exposed to ammonia vapor for about 12 hours. The wafers were sequentially washed with toluene, acetone and isopropyl alcohol and then dried under a stream of nitrogen. The contact angle of DI water to OTS-treated wafers was 104 ° or more.

For drop casting, BOC-PTDPP was dissolved in chlorobenzene (2 mg / mL) and the solution (about 80 μL) was drop cast onto an OTS-treated SiO ₂ / Si substrate.

In addition, in the solution shear method, a BOC-PTDPP solution (about 50 ㎕) was placed on an OTS-treated SiO ₂ / Si substrate placed on a preheated hot plate at 80 캜.

Next, another OTS-treated substrate was placed as a shear tool on the substrate on which the solution was placed and moved at a shear rate of 0.12 mms &lt; ^-1 &gt; using a digital syringe pump. To completely remove residual solvent molecules, a solution-processed polymer thin film (about 50 nm) was placed in a vacuum oven set at 100 ° C for 12 hours, and then heat-treated for 30 minutes on a hot plate set at 200 ° C under a nitrogen atmosphere to remove To obtain a PTDPP film.

Next, a gold electrode (about 40 nm) was thermally evaporated on a polymer thin film using a shadow mask to form a source electrode and a drain electrode having a channel length L of 50 占 and a channel width W of 1000 .

Experimental Example 6 Characterization of Organic Field Effect Transistor

Using the Keithley 4200 semiconductor variable analyzer, the transport and output characteristics of the OFET were recorded in a glove box filled with N ₂ . The field effect mobility in the saturation region was calculated by the following equation (1).

_{I DS = 1/2 (W} / L) μC i (V G -V T) 2 Formula (1)

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

An OFET device based on BOC-PTDPP thin films was fabricated in a top-contact bottom-gate geometry on a nioctadecyltrimethoxysilane (OTS) treated SiO ₂ / Si substrate in a drop cast or solution shear mode. The OFET characteristics of the BOC-PTDPP thin films are summarized in Table 2 below. Figure 9 illustrates typical bipolar characteristics of OFET based on solution sheared BOC-PTDPP films with gold electrodes.

[Table 2]

The p-type and n-type characteristics of bipolar BOC-PTDPP OFET were measured at V _DS = -100 V and +100 V, respectively.

V-type transport characteristics are clearly observed in the hole-increasing (V _DS = -100 V) and electron-increasing (V _DS = 100 V) mode operation. This is consistent with what was predicted from the experimental LUMO window (-3.1 to -3.8 eV) for gold-contact bipolar organic semiconductors. BOC-PTDPP exhibits a maximum hole and electron mobility of 1.32 × 10 ^-2 and 2.63 × 10 ^-3 cm ² V ^-1 s ^-1 , respectively. The hole mobility in BOC-PTDPP is about one order of magnitude higher than the electron mobility.

In general, the densely packed polymer p-plane backbone after heat treatment promotes the charge transport of both holes and electrons, whereas the hole and electron mobility is changed after pyrolysis of the t-BOC group at 200 ° C, The hole mobility is 4.30 × 10 ^-3 cm ² V ^-1 s ^-1 and the electron mobility is 4.60 × 10 ^-2 cm ² V ^-1 s ^-1 . That is, after thermal decomposition of the t-BOC group, the electron mobility increases while the hole mobility decreases by about one order of magnitude.

The reversal of the dominant polarity in bipolar PTDPP OFET can result from several factors. First, as can be seen from the DFT calculation, the LUMO trajectory of the deprotected PTDPP is much more delocalized than BOC-PTDPP, which is advantageous for n-channel conduction. On the other hand, the increase of delimitation of the HOMO orbit is not as high as the LUMO orbit. Second, the downward movement of HOMO-LUMO energy level in BOC-PTDPP after annealing can reduce the injection barrier of electrons and increase the injection barrier of holes relatively. Third, the elimination of unconjugated t-BOC groups, which can act as an electron trap, promotes electron transport.

The polymer shear BOC-PTDPP thin film exhibits about one order of magnitude greater mobility than drop-cast films. This is a synergistic result of the effect of the alignment of the solution shear and the result of lattice deformation, and the effect of efficient charge transport by forming a hydrogen-bonded network structure along the polymer backbone with the deprotected PTDPP polymer thin film. The reversal characteristics of the dominant polarity by pyrolysis are observed in the BOC-PTDPP OFET with aluminum electrode.

Two identical bipolar transistors were applied to the CMOS inverter and a common gate was used as the input voltage (V _IN ). The inverter characteristics were verified under unoptimized conditions, but showed a maximum gain of about 10 (Fig. 10), which is comparable to the newer CMOS-type inverters based on two-component organic semiconductors. A device based on a thermally deprotected material will be able to achieve better operational stability over a longer period of time, thus successful implementation of the inverter using BOC-PTDPP means that the polymeric compound according to the present invention is also easy in the CMOS form.

As described above, the polymer semiconductor compound according to the present invention is a thermally decomposable polymer (BOC-PTDPP) having a narrow bandgap based on t-butoxycarbonyl (t-BOC) and diketopyrrolopyrrole (DPP) to be.

In addition, BOC-PTDPP is soluble in organic solvents and can be conveniently prepared as a film, and the BOC-PTDPP film is converted directly into the deprotected PTDPP film using t-BOC pyrolysis at about 200 ° C. The deprotected PTDPP film has a hydrogen-bonded network structure, as evidenced by FT-IR spectrum change and XRD analysis.

In addition, solution shear techniques are used to form highly ordered BOC-PTDPP films with well aligned interactions. The p-type conduction-dominant bipolar performance is confirmed by solution shear BOC-PTDPP ( μ _e = 1.32 × 10 ^-2 cm ² V ^-1 s ^-1 ; μ _e = 2.63 × 10 ^-3 cm ² V ^-1 s ^{- 1} ). After pyrolysis at 200 ° C, the dominant polarity of bipolar OFET is converted to n-type ( μ _e = 4.30 × 10 ^-3 cm ² V ^-1 s ^-1 ; μ _e = 4.60 × 10 ^-2 cm ² V ^-1 s ^-1 ). This is due to the much more deliberate LUMO trajectory, lower electron injection barrier and removal of the t-BOC groups which can act as electron traps. An inverter configured by combining two identical BOC-PTDPP OFETs exhibits a gain of about 10. The thermally decomposable DPP-containing bipolar polymer will have potential utility in the manufacture of low-cost OFET circuits and arrays using high throughput, roll-to-roll techniques suitable for a wide range of practical electronic applications when used in conjunction with solution shear methods.

Claims (13)

A polymeric organic semiconductor compound represented by the following Chemical Formula 1:
[Chemical Formula 1]

In the above formula (1)
Wherein R ₁ is an alkoxycarbonyl group having 1 to 10 carbon atoms, R ₂ is an alkyl group having 1 to 40 carbon atoms, and Ar is an aryl group having 6 to 30 carbon atoms. The method according to claim 1,
Wherein R &lt; _{1 &gt;} is a functional group thermally removed by heat treatment. The method according to claim 1,
Wherein the polymer organic semiconductor compound has a number average molecular weight of 12,000-15,000 kg / mol and a weight average molecular weight of 40,000-55,000 kg / mol. The method according to claim 1,
The polymer organic semiconductor compound represented by the formula (1) is represented by the following formula (2): &lt; EMI ID =
(2)

1. An ambipolar organic semiconductor thin film comprising a plurality of polymeric organic semiconductor compounds represented by the following Chemical Formula 1,
Wherein the arrangement of the adjacent polymers is represented by the following structural formula 1:
[Chemical Formula 1]

In the above formula (1)
Wherein R ₁ is an alkoxycarbonyl group having 1 to 10 carbon atoms, R ₂ is an alkyl group having 1 to 40 carbon atoms, and Ar is an aryl group having 6 to 30 carbon atoms.
[Structural formula 1]

In the above formula 1,
Wherein R ₁ is an alkoxycarbonyl group having 1 to 10 carbon atoms, R ₂ is an alkyl group having 1 to 40 carbon atoms, and Ar is an aryl group having 6 to 30 carbon atoms. 6. The method of claim 5,
Wherein the amorphous organic semiconductor thin film is a p-type semiconductor. 6. The method of claim 5,
Wherein the bipolar organic semiconductor thin film is made of an n-type semiconductor by a heat treatment. The bipolar organic semiconductor thin film according to claim 5, wherein the bipolar organic semiconductor thin film is formed by hydrogen bonding between the adjacent polymers by the heat treatment and the arrangement of adjacent polymers is represented by the following formula 2:
[Structural formula 2]

In the above formula 2,
Wherein R ₁ is an alkoxycarbonyl group having 1 to 10 carbon atoms, R ₂ is an alkyl group having 1 to 40 carbon atoms, and Ar is an aryl group having 6 to 30 carbon atoms. 9. The method of claim 8,
Wherein the positive electrode of the bipolar organic semiconductor thin film is an n-type semiconductor. An organic field effect transistor (OFET) comprising an organic semiconductor thin film according to claim 5 and an organic semiconductor thin film according to claim 8. An organic light emitting diode (OLED) comprising an organic semiconductor thin film according to claim 5 and an organic semiconductor thin film according to claim 8. An organic solar cell comprising the organic semiconductor thin film according to claim 5 and the organic semiconductor thin film according to claim 8. (a) an organic semiconductor composition in which a polymeric organic semiconductor compound represented by the following formula (1) is dissolved or dispersed in a solvent on an SiO ₂ / Si substrate treated with n-octadecyltrimethoxysilane (OTS) Type semiconductor thin film;
(b) an organic semiconducting compound represented by the following formula (1) is dissolved or dispersed in a solvent on an SiO ₂ / Si substrate treated with n-octadecyltrimethoxysilane (OTS) Forming a thin film, and then performing heat treatment at 150-250 占 폚 to form an n-type semiconductor thin film; And
(c) forming a source electrode and a drain electrode on the p-type semiconductor thin film and the n-type semiconductor thin film,
[Chemical Formula 1]

In the above formula (1)
Wherein R ₁ is an alkoxycarbonyl group having 1 to 10 carbon atoms, R ₂ is an alkyl group having 1 to 40 carbon atoms, and Ar is an aryl group having 6 to 30 carbon atoms.

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