KR20200089058A - Composition comprising water for bi-phasic dip-coating techniques and method for forming semiconducting polymer thin films using thereof - Google Patents

Abstract

The present invention relates to a bi-phasic dip-coating composition and a method of forming a semiconductor polymer thin film using the same. More specifically, the present invention relates to a bi-phasic dip-coating composition comprising water as the bottom phase, and a conductive polymer solution as the top phase, the composition capable of forming a thin film that is uniform with high crystallinity via solvent interactions; a method of forming a semiconductor polymer thin film which may be adopted in a device to dramatically increase the electrical performance thereof; a semiconductor polymer thin film formed thereby; and field-effect transistors (FETs) comprising the same.

Description

Composition for two-phase deep coating containing water and a method for forming a polymer thin film using the same{COMPOSITION COMPRISING WATER FOR BI-PHASIC DIP-COATING TECHNIQUES AND METHOD FOR FORMING SEMICONDUCTING POLYMER THIN FILMS USING THEREOF}

The present invention relates to a bi-phasic dip coating composition and a method of forming a semiconductor polymer thin film using the same, more specifically, water as a bottom phase; And a two-phase deep coating composition comprising a conductive polymer solution as a top phase. A uniform and highly crystalline thin film can be obtained by solvent interaction, and the electrical performance of the device employing this is greatly improved. It relates to a method of forming a semiconductor polymer thin film, a semiconductor polymer thin film formed therethrough, and field effect transistors (FETs) including the same.

Organic electronic devices are new technologies expected in a variety of applications, such as disposable electronic devices, wearable electronic devices, and multifunctional sensors. One of the advantages of organic semiconductors is solution processability, which is compatible with the manufacture of large area flexible substrates. Various solution deposition methods are available to produce organic semiconductor thin film transistors (TFTs) with uniform, smooth, and high conductivity with desirable organic crystal structures that provide high charge mobility.

The successful commercialization of organic electronic devices with the improvement of the field effect mobility of organic semiconductors requires the removal of hazardous halogenated and/or aromatic solvents in TFT manufacturing. Most organic semiconductors are treated using environmentally toxic halogenated solvents with a rigid π-conjugated semiconductor structure as a solvent. The environmental impact of halogenated solvents is an important issue when manufacturing large area organic semiconductor coatings. Manufacturing of highly mobile TFT devices using environmentally friendly non-halogenated solvents remains a challenging and urgent task in this field.

Various solution processing methods have been developed for the preparation of large area coatings. Of these, deep-coating is widely used for academic research and industrial production. The method not only provides fine control over the conjugated polymer crystallization process that enables efficient charge carrier transport, but is also advantageous for producing uniform and smooth films on flexible substrates of various curves. However, the dip-coating process is not easily bulked up because a large amount of polymer solution is required to fill the dip-coated reservoir. To overcome this problem, a new two-phase deep-coating method was developed using a reusable inert liquid support phase (most of the system) and a phase separated solvent system that floats the solution to be supported on the support. In this configuration, the volume of the polymer solution can be greatly minimized.

Hye Su Kim, Jin Yeong Na, Yeong Don Park. Polym. Kor. (2014) 38, 188.

The two-phase dip-coating process requires the selection of a pair of solvents capable of forming a stable two-phase state. Typically, two-phase systems can be made using low density floating solvents and high density bottom support solvents; However, most solvents capable of dissolving the π-conjugated polymer have a high density exceeding 1.1 g cm ^-3 , making it difficult to find a suitable solvent base. In order to reduce the environmental impact of the dip-coating process, it is important to find a green solvent capable of forming a stable two-phase state with an organic semiconductor solution. Here, we report a new two-phase dip coating method using water as a reusable bottom phase solvent. The inventors have systematically studied the formation of a two-phase solution system by changing solvent properties, including solubility parameters and surface tension. In order to obtain a high crystalline polymer film, a high boiling point solvent additive was added to control the evaporation rate of the solvent, which had a great effect on the polymer crystallization process. The two-phase system of the solvent mixture produced a uniform and smooth deep-coated film containing a high crystalline conjugated polymer phase for use in thin film transistor devices.

In order to achieve the above technical problem, the present invention is water in the lower phase (bottom phase); And it provides a composition for a two-phase deep coating comprising a conductive polymer solution as a top phase (top phase).

The solvent of the conductive polymer solution has a boiling point of 50 to 200°C, and the crystallinity of the polymer film increases as the boiling point increases. The solvent evaporation rate is the most important factor in controlling the crystallinity of the polymer film produced by dip coating, and the high boiling point solvent can promote crystallization between polymer chains by extending the solvent evaporation time. . Therefore, when the boiling point of the solvent is 50° C. or less, the evaporation time of the solvent is short, so that the crystals of the film are not sufficiently formed, and when it exceeds 200° C., a dewetting problem is caused and the film formation is poor.

In another embodiment, a composition for two-phase deep coating in which a solvent additive is floated on the conductive polymer solution and a mixture solution in which a solvent additive is mixed in the conductive polymer solution are located. The solvent additive helps to maintain uniform and pinhole-free film coverage while controlling the solvent evaporation rate.

Preferably, the solvent additive is characterized by reducing the evaporation rate of the conductive polymer solvent.

An important solvent mixing factor to be considered when selecting the solvent additive is the Hansen solubility parameter (HSP), and the difference between the solvent of the conductive polymer solution and the Hansen solubility parameter (HSP) of the solvent additive is preferably 2.0 MPa ^1/2 or less. When the Hansen solubility parameter difference is more than 2.0 MPa ^1/2 , the solvent additive is prevented from diffusing into the conductive polymer solution in the floating method, and as a result, the crystallization of the polymer is prevented to form a non-uniform film. In addition, when the difference in the Hansen solubility parameter in the mixing method exceeds 2.0 MPa ^1/2 , there is a disadvantage that the aggregated DCB is diffused in a solution state to form a non-uniform film.

Preferably, the solvent of the conductive polymer solution is chloroform (CF), the solvent additive is either chlorobenzene (CB) or dichlorobenzene (DCB), and the water is deionized water (DI water).

In addition, the conductive polymers are polyacetylene (PA), polythiophene (PT), poly(3-alkyl)thiophene (P3AT), polypyrrole (PPY), polyyi Polyisothianapthelene (PITN), polyethylene dioxythiophene (PEDOT), polyparaphenylene vinylene (PPV), poly(2,5-dialkoxy)paraphenylene vinylene (poly(2 ,5-dialkoxy)paraphenylene vinylene), polyparaphenylene (PPP), perylene tetracarboxylic diimide (PTCDI), polyparaphenylene sulphide (PPS), polyheptadiyne : PHT), poly(3-hexyl)thiophene (poly(3-hexyl)thiophene: P3HT), polyaniline (PANI) and one or more selected from the group consisting of derivatives thereof, preferably The conductive polymer is poly(3-hexyl)thiophene (P3HT).

According to another embodiment of the present invention, 1) placing the water in the bottom phase (bottom phase); 2) preparing a two-phase dip coating solution by dropping a conductive polymer solution onto water as a top phase; 3) immersing the substrate in the two-phase deep coating solution; And 4) recovering the substrate.

The dropping step is preferably a dropwise dropping method in which a polythiophene solution is added at once and gradually added dropwise to the interface so that the interface is stably maintained, rather than mixing the interface between the solvents.

In addition, after the step 2), it may further include a step of dropping and floating a solvent additive on the conductive polymer solution.

In addition, in step 2), a step of mixing the conductive polymer solution with a solvent additive before dropping may be further included.

According to another embodiment of the present invention, a semiconductor polymer thin film formed according to the method as described above, and field-effect transistors (Field-Effect Transistors; FETs) including the same are provided.

The solvent additive evaporation rate of the present invention and the miscibility between the additive and the main solvent influenced film formation and polymer crystallization during the dip-coating process, and a high crystalline thin film can be produced with a small polymer solution, and the uniformity of the thin film surface In addition to the performance, it is possible to greatly improve the molecular alignment, crystallinity, charge carrier transport (charge mobility) and performance of polymer FETs in thin films. Therefore, the two-phase deep coating method of the present invention may provide important advantages for the design and development of a robust and effective organic electronic device for a wide range of commercial applications.

1 shows (a) surface tension and density of various solvents; (b) is a schematic diagram illustrating a two phase dip-coating process; (c) CF (top)/THF (bottom), (d) CF (top)/DMF (bottom) and (e) CF (top)/deionized water (bottom).
Figure 2 (a) normalized UV-vis absorption spectrum of P3HT film prepared from CF, CB and DCB; (b) Schematic of the solvent addition process: floating method and mixing method; Standardized UV-vis absorption spectrum of P3HT thin films prepared from different solvent addition processes: (c) floating and (d) mixing method in a fixed amount of 5-10 vol% of added solvent; (e) It is a diagram showing the ratio of the intensity of the peak of (0-0) and the peak of (0-1). The inset shows the change in free exciton bandwidth W calculated from the UV-vis absorption spectrum of a deep-coated P3HT thin film.
3 is a photograph of a P3HT film deep-coated on a silicon substrate treated with OTS in a uniform solvent; (a) A photograph of a P3HT film dip-coated with CF, CB and DCB and mixed solvents prepared using different solvent addition processes; (b) Floating and (c) mixing methods. It is an optical microscopic image of a P3HT film dip-coated from a two-phase solvent for two different solvent addition methods using solvent additives CF:CB and CF:DCB; (d) floating method and (e) mixing method.
4 is a tapping-mode AFM phase image of a P3HT film obtained from a two-phase P3HT solution; (a) AFM phase image of film treated with CF, CB and DCB solvents. AFM phase images of films processed from CF:CB and CF:DCB solvent mixtures prepared using different solvent addition methods; (b) floating method and (c) mixing method.
Figure 5 shows a plot of gate voltage versus drain current at linear (left axis) and log (right axis) scales of deep-coated P3HT films from solvent mixtures CF:CB and CF:DCB (fixed drain voltage -80V); (a) floating method and (b) mixing method. (c) It is a graph showing the average field effect mobility of a dip-coated P3HT film from various solvent mixtures using various solvent addition methods.
6 is a schematic diagram illustrating a method in which a solvent addition method (floating and mixing) induces solvent mixing and aggregation in a solution state.

Hereinafter, the present invention will be described in more detail through examples and experimental examples. However, these examples are only for the understanding of the present invention, and the scope of the present invention is not limited to these examples in any sense.

Example

Poly(3-hexylthiophene) (P3HT, MW = 69 kDa, regioregularity=96%, PDI=2.0-2.3) was purchased from Rieke Metals, Inc. P3HT was dissolved in chloroform (CF), chlorobenzene (CB) and dichlorobenzene (DCB) at a concentration of 7 mg mL ^-1 and stirred at 50 DEG C for 3 hours. A highly doped n-type silicon wafer covered with a 300 nm thick thermally grown silicon dioxide (SiO ₂ ) layer was heated at 70° C. for 30 minutes to remove organic contaminants (3% of 98% sulfuric acid and 35% hydrogen peroxide). :2 volume mixture). Octyltrichlorosilane (OTS) was coated by immersing the Si/SiO ₂ substrate in toluene containing OTS reagent for 30 minutes at room temperature. The OTS treated substrates were sonicated in toluene and ethanol for 3 minutes each and dried under vacuum before use. A support solvent was formed using a 3 mL glass vial filled with 2.5 mL deionized (DI) water, and 0.07 mL of a P3HT solution was carefully dropped onto the DI water surface using a syringe. The OTS-treated Si/SiO ₂ substrate was dip-coated at a dip of 5 mm s ^-1 and withdrawal rate. The P3HT film was heat treated at 80°C for 30 minutes and kept in a vacuum for 2 hours to evaporate deionized water (DI) and organic solvent prior to electrical characterization. The top gate organic TFT device was fabricated by evaporating the gold electrode. Gold source and drain electrodes were patterned using a shadow mask with a 1000 μm channel width and a 100 μm channel length. UV-vis absorption measurement was performed using a P3HT film prepared on a cleaned glass substrate.

Experimental condition

The UV-vis absorbance spectrum was recorded using a UV-vis spectrophotometer (Thermo Scientific, Genesys 10S). The morphology of the film was observed using an atomic force microscope (AFM) (Multimode 8, Bruker) and an optical microscope (OM; OLYMPUS BX51). Electrical properties of the P3HT film were measured at room temperature and vacuum using a semiconductor analyzer (Keithley 4200-SCS). Field effect mobility was calculated in the saturation region.

Experimental Example

1. Formation of a biphasic system

We chose poly(3-hexylthiophene) (P3HT) as a conjugated polymer, one of the best studied model systems for film formation and crystallization. For deposition, a biphasic deposition coating method was used, including a top phase polymer solution in which the organic semiconductor was dissolved and a bottom phase solvent filled most of the dip-coated vessel volume. The top and bottom solvent properties were different to understand the properties contributing to the formation of a stable two-phase state.

Most solvents that dissolve conjugated polymers used in organic electronics are high density chlorinated solvents exceeding 1.1 g cm ^-3 (CF = 1.48 g cm ^-3 , CB = 1.11 g cm ^-3 , 1.2-DCB = 1.30 g cm ^-3 ). Therefore, the candidate material for the lower phase solvent was significantly limited to a solvent having a density higher than that of the upper phase solution.

In the present invention, the inventors investigated other solvent properties, including surface tension, γ, to identify floor-phase green solvents suitable for use in stable two-phase systems. Surface tension can be defined as the properties of a liquid surface that can resist the outer surface. The surface tension depends on the cohesive nature of the solvent molecule. Even if the solvent density of the upper phase solution is higher than the lower phase solvent density, a sufficiently high surface tension in the lower phase solvent can help to form a two phase solution.

The present inventors compared two other organic solvents having a lower surface tension than water to water, and observed which solvent can form a two-phase solution state.

Figure 1 shows that despite the fact that the density of water (1 g cm ^-3 ) is lower than that of polymer-dissolved solvent (1.48 g cm ^-3 ), only DI water is a two-phase solution with P3HT in CF solution It shows forming a structure. Tetrahydrofuran (THF) and dimethylformamide (DMF) having densities similar to deionized water exhibited a collapsed two-phase state due to insufficient surface tension.

2. Secondary solvent addition process

During the dip-coating process, the solvent properties of the upper phase solution greatly influenced the film formation and crystallization behavior of the conjugated polymer. The solvent evaporation rate is one of the most important factors controlling the crystallinity of the polymer film produced by dip coating. High boiling point solvents can promote crystallization between polymer chains by extending the solvent evaporation time. In the present invention, three different solvents of CF, CB, and DCB were tested with the upper phase solvent having different boiling points of 61 to 180°C.

The UV-vis spectrum of the deep-coated coating film formed from the P3HT-water two-phase system was compared (FIG. 2). The absorption spectrum of the P3HT thin film prepared from CF, CB and DCB showed absorption peaks of the P3HT thin film at 560 and 608 nm due to the intermolecular interaction (FIG. 2A). The ratio of the intensity of the (0-0) peak of the (0-1) peak at A _0-0 /A _0-1 at 560 nm and the intensity of the peak at 608 nm correlates with crystallinity in the P3HT film.

2E shows that A _0-0 /A _0-1 increases from 0.65 to 0.82 as the boiling point of the solvent increases. Although the DCB-treated P3HT film showed the highest crystallinity, if the solvent evaporation rate is too low, the film thickness and dewetting behavior due to solution agglomeration may be reduced. The present inventors put a high boiling point of 1,2,4-trichlorobenzene at a high boiling point of 214°C in a biphasic dip-coating system, causing excessively high boiling point dewetting problems and poor film formation. Confirmed that.

In order to reliably produce P3HT films, the inventors have added solvent additives to the polymer solution to control the rate of solvent evaporation while maintaining uniform and pinhole-free film coverage. Numerous studies have reported that solution processes using solvent additives can perform better than systems prepared without solvent additives.

The inventor tested solvent additives in a two-phase dip-coating method in two ways (FIG. 2b): 1) floating the solvent additive on a polymer-dissolved top-phase solution (floating method); And 2) mixing the solvent additive with the polymer-dissolved solution (mixing method) before forming the two-phase system.

(1) Floating method

The inventors used CB and DCB as solvent additives and CF as the polymer-dissolved host solvent. First, the present inventor used CB as a solvent additive to the P3HT-CF solution using a floating method. The absorption spectrum of the deep-coated P3HT film from CF:CB showed a strongly increased intermolecular peak at 560 and 608 nm compared to the homogeneous solvent, deep-coated film from CF (FIG. 2C).

Even if a small amount of CB (5 vol%) was added, the absorption spectrum showed a significant increase in A _0-0 /A _0-1 and reached saturation. Beyond the saturation point, the CF:CB (CB 10 vol%) system provided spectra similar to distinct (0-0) and (0-1) peak absorption compared to those obtained from CF:CB (5 vol%); However, the absorption spectrum obtained from the CF:DCB solvent mixture shows lower intensity at the (0-0) absorption peak than that obtained from CF:CB, indicating that the CF:DCB film has a lower crystallinity than the CF:CB film. Indicates.

The absorption spectrum of the CF:DCB film showed a strong dependence of the A _0-0 /A _0-1 peak ratio on the volume ratio of DCB to CB (FIG. 2e). The present inventor differs from the CF:CB and CF:DCB systems in that the miscibility of the main solvent and the additive solvent affects the method in which the solvent additive diffuses into the host solution and the solute to promote solute crystallization in the solution state. ). The present inventors have similar Hansen solubility parameters of CB and CF, so that the floating solvent additive CB is mixed with the polymer-dissolved solution CF, lowering the evaporation rate during film formation and improving the crystallinity of the resulting P3HT film. I confirmed that I can do it. DCB solvent additives with Hansen solubility parameters lower than CF inefficiently diffuse into the P3HT solution and do not help P3HT crystallization compared to the CF:CB system. The difference between CB and DCB additive properties showed that the good miscibility between solvent and additive is important to induce P3HT crystallization in using the solvent additive floating method.

(2) Mixing method

The effect of the solvent additive mixing method on P3HT crystallization was further studied by adding the solvent additive CB or DCB to the polymer solution P3HT/CF before forming the two-phase solution. The P3HT film processed from the solvent additive mixed solution showed a larger intermolecular (0-0) peak compared to the P3HT film processed using the solvent additive floating solution. In both the CF:CB and CF:DCB systems, mixing the solvent additive with the P3HT solution using 5 vol% solvent additive provided a higher A _0-0 /A _0-1 and saturation trend. The A _0-0 /A _0-1 peak ratio of the absorption spectrum obtained from CF:DCB showed a much lower dependence on the solvent additive volume ratio than the ratio obtained from the CF:DCB floating solution. Premixing the DCB solvent additive has been shown to form a better mixed phase than the solvent additive floating method (FIG. 2E ). These results strongly influenced the method used to incorporate the solvent additive into the P3HT solution and the P3HT crystallization behavior and the resulting film morphology.

3. Film morphology

The film coverage of the substrate was investigated by obtaining a picture of a deep-coated P3HT film from a two-phase solution on an OTS treated silicon substrate (FIG. 3). The rate of solvent evaporation of the polymer-dissolved top-phase solution greatly influenced the resulting film coverage. The lower the solvent evaporation rate, the lower the film coverage. The inventors have found that a solvent with a higher boiling point (CB or DCB) produces non-uniform film coverage with a dewetting region in a deep-coated P3HT film (FIG. 3A). This phenomenon occurred in a deep-coating process in which film thickness and coverage were determined according to the solvent evaporation equilibrium and drawing speed. The high boiling point of DCB (180°C) provides extended time for solvent evaporation and P3HT coagulation to reach a solute that is thermodynamically stable. This mobility induced film dewetting of polymeric semiconductor materials.

To overcome the dewetting problem, solvent additive CB or DCB was used in the P3HT-CF solution. The present inventor was able to obtain various film forms according to a method of adding a solvent. The solvent additive floating method prevented dewetting regardless of the solvent additive (CB or DCB), but produced a non-uniform film. The wave pattern of the P3HT film was generated by unstable solvent evaporation during the dip-coating process, probably because the solvent additives were non-uniformly mixed and distributed in the polymer solution (Fig. 3b). In contrast, the solvent additive mixing method introduced additives into the polymer solution prior to floating and successfully made a uniform and homogeneous film on the OTS-treated silicon substrate (FIG. 3C). The CB and DCB additives produced a uniform P3HT film without irregular wave patterns in a volume ratio ranging from 5 to 10%.

Dip-coated films prepared from two-phase solutions containing solvent additives were investigated using an optical microscope (OM). CF:CB and CF:DCB films processed using the solvent additive floating method contained P3HT aggregates and achieved little uniform film morphology (FIG. 3D). These aggregates abundantly existed near the edge of the film, making them non-uniform and disadvantageous for TFT device applications. The dip-coated film from the solvent additive mixing method using CF:CB as a solvent additive showed a clean and uniform film with a smooth surface topology desirable for large-area device applications (Fig. 3e). . On the other hand, the film processed in CF:DCB could not be identified in the picture, but included a wave pattern that can be observed in the enlarged OM image (FIG. 3C ).

Atomic force microscopy (AFM) was used to determine the nanoscale morphology of deep-coated P3HT films (Figure 4). AFM images clearly showed that the deep-coated P3HT film prepared from a high boiling point solvent contained thick nanowires well arranged, while the film treated with a low boiling point solvent (CF) contained a smaller crystalline phase. Larger nanowire sizes obtained from neat CB- or pure DCB-treated films showed highly crystallized films due to low solvent evaporation rates. These results are in good agreement with the UV-vis results, which showed that P2HT crystallization during the two-phase deep-coating process was greatly affected by the solvent boiling point.

In the same vein, solvent additives having a boiling point higher than that of the main solvent changed the surface roughness and surface morphology of the cast P3HT film. As the high boiling point solvent additive was mixed with the polymer solution in a large amount, the density and size of the P3HT nanowires increased compared to the film treated in a pure CF solvent. The volume ratio of the high boiling point solvent did not significantly affect the surface roughness of the cast film. When a small amount of high boiling point solvent was added to the polymer solution, strong P3HT crystallization occurred and it was more effective than using a high boiling point homogeneous solvent. The present inventor assumed that the main solvent CF is first evaporated to uniformly wet the substrate, and the remaining CB or DCB can be cast to the substrate so that the P3HT solution is fully self-assembled during solidification. These results indicate that the addition of a high boiling point solvent to the P3HT solution effectively helped the formation of a uniform film having a high crystalline structure due to the low evaporation rate of the high boiling point solvent.

4. Device characteristics

The electrical properties of the deep-coated P3HT film from a homogeneous or mixed solvent were investigated by measuring the field effect mobility of the P3HT film in a TFT with a top-contact transistor structure. A typical drain current (I _D ) versus gate voltage (V _G ) plot collected in the accumulation mode is shown in FIG. 5. When a high boiling point solvent was added to the polymer solution, the on-current and field effect mobility gradually increased as the amount of the additive increased. The highest field effect mobility obtained here, 3.91 x 10 ^-2 cm ² V ^-1 s ^-1, is P3HT processed using a solvent mixture containing 10 vol% CB in CF (prepared using a mixing method). Was obtained from the device. This value is 380 times higher than the value obtained in a device processed with a uniform CF solvent 0.0103 Х 10 ^-2 cm ² V ^-1 s ^-1 . On the other hand, devices processed using DCB solvent additives (prepared using a mixing method) showed less improved charge transport properties compared to CF:CB; The field effect mobility was 0.618 x 10 ^-2 cm ² V ^-1 s ^-1 and 0.950 x 10 ^-2 cm ² V ^-1 s ^-1 for the addition of 5 vol% and 10 vol%, respectively. The solvent mixture prepared by the mixing method was more effective in improving the hole field-effect mobillity than the floating method, which was in good agreement with the crystallized trend using UV-vis spectroscopy. These field effect mobility values correlate with P3HT crystallinity, as confirmed by UV-vis spectroscopy, indicating that polymer crystallinity improves the charge transport properties of the film.

5. Development of 2-phase system using solvent additives

The mechanism of film formation from the solvent mixture in a two-phase dip-coating system was explored. A two-phase system prepared using a solvent addition process such as a floating method and a mixing method is schematically illustrated (FIG. 6 ). An important solvent mixing factor to consider is the Hansen solubility parameter (HSP) and can be used to predict compatibility between solvents. Liquids with similar HSPs are expected to be miscible, and polymers are soluble in solvents with HSPs not significantly different from their own HSPs. HSP is a measure of solubility and dispersion. It has been widely used to characterize solvent mixtures and polymer solutions. The difference in HSP between the solvent additive and the main solvent is important in determining how these components mix in solution and affect polymer crystallization.

Table 1 lists the differences between HSP values of solvents in a two-phase system; The difference in HSP between CB and CF is the smallest with 0.8 MPa ^1/2 , while the difference in HSP between CF and DCB is 1.6 MPa ^1/2 . Therefore, CB and CF have better compatibility for intermixing than DCB and CF. This calculation provides insight into the two-phase separation behavior of the solvent mixtures CF:CB and CF:DCB.

P3HT CF CB DCB DI DMF THF γ at 20℃(mN/m) - 27.5 33.6 37.0 72.8 35.2 26.4 ρ(g/cm ³ ) - 1.48 1.11 1.30 One 0.944 0.889 δ(MPa ^½ ) 20.0 18.8 19.6 20.4 47.9 24.8 19.5 B.P.(℃) - 61.2 131 180.5 100 153 66

The system comprising the floating solvent additive CB on the main solvent CF has a small HSP difference, which allows the floating solvent additive to be gradually mixed into the lower P3HT solution to induce P3HT crystallization during the dip-coating process. Floating solvent additive DCB shows a large HSP difference from CF, which prevents DCB from diffusing into P3HT solution and interferes with P3HT crystallization, resulting in non-uniform film formation.

The two-phase system produced by the mixing method in which the solvent additive CB was mixed with CF showed a small HSP difference between CB and CF, and due to the high miscibility with CF, it resulted in good intermediate mixing between the solvent additive CB and the P3HT molecule. do. Strong P3HT crystallization and uniform film formation were induced during the dip-coating process. The mixture of solvent additives DCB and CF with a relatively high HSP difference diffused the aggregated DCB into solution. As observed in the UV-vis absorption spectrum and the device properties obtained from the solvent mixture CF:DCB, forced mixing induced strong P3HT crystallization compared to the floating method.

conclusion

The inventor has developed a two-phase deep-coating method that uses water as a reusable lower phase solvent to produce a highly crystalline P3HT thin film transistor. The inventors investigated the effect of solvent additives on polymer crystallinity and film formation, which is highly dependent on the particular solvent addition method (floating or mixing). The UV-vis absorption properties of the processed film influenced the solvent additive evaporation rate and the miscibility between the additive and the main solvent in film formation and polymer crystallization during the dip-coating process. The increase in the degree of polymer crystallinity in the dip-coated film obtained from the solvent mixture is due to the extended solvent drying time providing sufficient time for the P3HT molecule to self-assemble. These characteristics are consistent with the device performance. The apparatus treated from the CB:CF solvent mixture showed the highest average field effect mobility of 0.0391 cm ² V ⁻¹ s ⁻¹ . The present invention can be used to produce a uniform film on a large substrate and to promote long-range ordering of P3HT crystals without producing environmentally hazardous waste. The present invention provides a promising innovation in the development of low cost large area flexible electronic products.

Claims (16)

Water in the bottom phase; and
A composition for two-phase deep coating, comprising a conductive polymer solution as a top phase.
According to claim 1,
The solvent of the conductive polymer solution has a boiling point of 50 to 200°C, and the composition for two-phase deep coating is characterized in that crystals of the polymer film increase as the boiling point increases.
According to claim 1,
A composition for two-phase deep coating in which a solvent additive is floated on the conductive polymer solution.
According to claim 1,
A composition for two-phase deep coating in which a mixed solution in which a solvent additive is mixed with the conductive polymer solution is located.
The method of claim 3 or 4,
The solvent additive is a two-phase dip coating composition, characterized in that to reduce the evaporation rate of the conductive polymer solvent.
The method of claim 3 or 4,
The difference between Hansen solubility parameter (HSP) of the solvent and the solvent additive of the conductive polymer solution is 2.0 MPa ^1/2 or less.
The method of claim 6,
The solvent for the conductive polymer solution is a composition for two-phase deep coating, characterized in that chloroform (CF).
The method of claim 6,
The solvent additive is chlorobenzene (CB) or dichlorobenzene (DCB) either two-phase dip coating composition, characterized in that either.
According to claim 1,
The water is a two-phase dip coating composition, characterized in that the deionized water (DI water).
According to claim 1,
The conductive polymers are polyacetylene (PA), polythiophene (PT), poly(3-alkyl)thiophene (P3AT), polypyrrole (PPY), polyisocia Naphthalene (polyisothianapthelene: PITN), polyethylene dioxythiophene (PEDOT), polyparaphenylene vinylene (PPV), poly(2,5-dialkoxy)paraphenylene vinylene (poly(2, 5-dialkoxy)paraphenylene vinylene, polyparaphenylene (PPP), perylene tetracarboxylic diimide (PTCDI), polyparaphenylene sulphide (PPS), polyheptadiyne: PHT), poly(3-hexyl)thiophene (poly(3-hexyl)thiophene: P3HT), polyaniline (polyaniline: PANI), and two or more selected from the group consisting of derivatives thereof Deep coating composition.
According to claim 1,
The conductive polymer is a poly(3-hexyl)thiophene (poly(3-hexyl)thiophene: P3HT) composition for two-phase deep coating, characterized in that.
1) placing water in the bottom phase;
2) preparing a two-phase dip coating solution by dropping a conductive polymer solution onto water as a top phase;
3) immersing the substrate in the two-phase dip coating solution; and
4) A method of forming a semiconductor polymer thin film, comprising recovering the substrate.
The method of claim 12,
2) After the step, characterized in that it further comprises the step of floating by dropping a solvent additive on the conductive polymer solution (floating), the method of forming a semiconductor polymer thin film.
The method of claim 12,
In the 2) step, characterized in that it further comprises the step of mixing the conductive polymer solution with a solvent additive before dropping, a method for forming a semiconductor polymer thin film.
A semiconductor polymer thin film formed by any one of claims 12 to 14.
Field-effect transistors (FETs) comprising the semiconductor polymer thin film according to claim 15.

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