KR102220438B1 - Method and apparatus for single crystal growth of organic materials using ionic liquid - Google Patents

Abstract

The present invention relates to a method and apparatus for growing a single crystal of a high-purity organic material using an ionic liquid, comprising: a mixing step of mixing an organic material with an ionic liquid; an organic material mixed with the ionic liquid by heat treatment under a first condition A solution step of solutionizing, a nucleation step of injecting a seed into an ionic liquid containing the solutionized organic material under a second condition, a single crystal growth step of growing a single crystal under a third condition, and a grown organic material single crystal It is characterized in that it comprises a separation step of separating from the ionic liquid, and obtains a single crystal of an organic material purified to a higher purity than before being mixed with the ionic liquid. According to the present invention, there is an effect of growing a single crystal of a high purity organic material at low cost by a simple process.

Description

Method and apparatus for growing organic material single crystal using ionic liquid {METHOD AND APPARATUS FOR SINGLE CRYSTAL GROWTH OF ORGANIC MATERIALS USING IONIC LIQUID}

The present invention relates to a method and apparatus for growing a single crystal of an organic material, and more particularly, to a method and apparatus for growing a single crystal after mixing an organic material in an ionic liquid.

As examples of using organic materials in electronic devices such as organic electroluminescence (EL) devices, organic semiconductor devices, organic photoelectric conversion devices, and organic sensor devices are increasing, interest in single crystal organic materials is increasing. However, due to the lack of efficient organic material single crystal growth technology, organic electronic devices mostly use organic materials in an amorphous state.

As a conventional method for growing single crystals of organic materials, there is a method of growing a single crystal by dissolving an organic material in a solvent and then gradually evaporating the solvent at a certain temperature. However, this method not only takes too long a single crystal growth time, but also has a problem in that it is difficult to control a process required to grow a high-quality single crystal. These problems eventually lead to an increase in the cost of single crystal growth, and thus, are an obstacle to industrial use of the organic material single crystal.

In addition, the conventional organic material single crystal growth method has a problem that impurities are not easily removed. Therefore, in order to obtain a high-purity single crystal, the organic material must first be purified to high purity by a method such as sublimation purification disclosed in the paper [HJ Wagner, el al., Journal of Materials Science, 17, 2781 (1982)], and then single crystal growth must be performed. There was a hassle.

Accordingly, there is a need for a new method capable of solving various problems of the prior art, purifying organic materials with a simple process at low cost, and simultaneously growing single crystals.

H.J. Wagner, el al., Journal of Materials Science, 17, 2781 (1982)

An object of the present invention is to provide a novel organic material single crystal growth method and apparatus capable of solving the problems of the conventional purification method as described above.

Specifically, an object of the present invention is to provide a single crystal growing method and apparatus capable of growing a single crystal of a high purity organic material of 99% or more, preferably 99.5% or more, and more preferably 99.9% or more with only one step.

Another object of the present invention is to provide a single crystal growing method and apparatus capable of efficiently growing a single crystal of a high purity organic material at low cost.

Another object of the present invention is to provide a method and apparatus for growing a single crystal that is easy to design and control a process and that can respond to various organic materials.

An organic material single crystal growing method according to an aspect of the present invention for achieving the above object comprises: a mixing step of mixing an organic material with an ionic liquid; A solution step of heat-treating under a first condition to solution the organic material mixed in the ionic liquid; A nucleation step of injecting a seed into an ionic liquid containing the organic material that has been solutionized under a second condition and generating nuclei on the seed surface; A single crystal growing step of growing a single crystal under a third condition; And a separation step (S50) of separating the grown single crystal of the organic material from the ionic liquid, and obtaining a single crystal of the organic material purified to higher purity than before being mixed with the ionic liquid. In this case, the first condition, the second condition, or the third condition may be a condition that changes with time.

In the present invention, the seed introduced into the ionic liquid may be a single crystal of the same material as the organic material to be crystallized, or a hollow microtube, and the solution may be at least one of melting or melting.

In addition, by performing the mixing step, solution step, nucleation step, single crystal growth step, and separation step once, a high purity single crystal organic material of 99% or more can be obtained, and the organic material single crystal separated from the ionic liquid It may further include washing and drying.

After the separating step, a sweating process for removing surface impurities of the separated organic material single crystal may be further performed, and a filtering step for filtering out unsolutionized organic material between the solution step and the nucleation step You can proceed further.

An organic material single crystal growth apparatus according to another aspect of the present invention includes: a stage; A container body supported by the stage and accommodating a mixture of an organic material and an ionic liquid; A temperature controller for heating a mixture of an organic material and an ionic liquid accommodated in the container body; And a seed holder in which a seed is inserted into a mixture of an organic material and an ionic liquid contained in the container body and fixed to an end thereof, wherein the container body and the seed holder are relatively movable.

Here, the seed may be a single crystal or a hollow microtube made of the same material as the organic material, and the relative movement may be at least one of vertical movement and rotational movement.

In addition, a gas inlet portion for introducing gas into the container body; And a gas discharge part for discharging gas from the inside of the container body.

The organic material single crystal according to another aspect of the present invention may be grown by any one of the above methods, and the half width of the X-ray ^{may be 0.1 o} or less.

According to the present invention, by using a method of growing a single crystal after mixing an organic material with an ionic liquid to form a solution, there is an effect of solving various problems of the conventional purification method.

Specifically, there is an effect of being able to grow a single crystal of an organic material with a high purity of 99% or more, preferably 99.5% or more, and more preferably 99.9% or more with only one step.

Further, according to the present invention, there is an effect of efficiently growing a single crystal of a high-purity organic material at low cost.

Further, according to the present invention, process design and control are easy, and there is an effect that can cope with various organic materials.

1 is a main flowchart of a method of growing a single crystal of an organic material using an ionic liquid according to the present invention.
2 is an example of a temperature change curve for proceeding the organic material single crystal growth method according to the present invention.
3 is a schematic cross-sectional view of an organic material single crystal growing apparatus according to the present invention.
4 is an exemplary diagram using microtubes for self-seed formation.
FIG. 5(a) is an XRD analysis result of an NPB single crystal grown according to the present invention, and FIG. 5(b) is an XRD analysis result of an NPB polycrystal.
6(a) is an XRD analysis result of an Alq3 single crystal grown according to the present invention, and FIG. 6(b) is an XRD analysis result of an Alq3 polycrystal.
7(a) is an Alq3 single crystal grown according to the present invention, and FIG. 7(b) is a scanning electron micrograph of an Alq3 polycrystal.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings. The following description includes specific embodiments, but the present invention is not limited or limited by the described embodiments. In describing the present invention, when it is determined that a detailed description of a related known technology may obscure the subject matter of the present invention, a detailed description thereof will be omitted.

In the organic material single crystal growth method according to the present invention, an organic material to be grown single crystal is mixed in an ionic liquid, and then heat-treated under the first condition to solution the organic material, and then the single crystal is grown under the second condition. It is characterized in that a single crystal of a high purity organic material is grown through a process of generating a single crystal nucleus by introducing a seed for and then growing the single crystal under the third condition. Here, the first, second, and third conditions mean process conditions such as temperature, pressure, and process atmosphere.

Ionic liquid refers to a liquid composed of only ions, and is generally a molten salt in a broad sense consisting of a large cation and a smaller anion. Although not particularly limited, the cation constituting the ionic liquid is the following [Chemical Formula 1] can be used. In [Chemical Formula 1], R1, R2, R3 and R4 may be a linear or branched alkyl group having n carbon atoms.

[Formula 1]

Further, the anion constituting the ionic liquid with the cation is _{^{Cl -, Br -, NO 3}} -, BF 4 -, PF 6 -, AlCl 4 -, Al 2 Cl 7 -, AcO -, CH 3 COO -, CF ^{_{3 COO -, CH 3 SO 3}} -, CF 3 SO 3 -, (CF 3 SO 2) 2 N -, (CF 3 SO 2) 3 C -, (CF 3 CF 2 SO 2) 2 N -, C 4 ^{_{F 9 SO 3 -, C 3}} F 7 COO -, (CF 3 SO 2) (CF 3 CO) N -, C 4 F 10 N -, C 2 F 6 NO 4 S 2 -, C 2 F 6 NO 6 ^{_{S 2 -, C 4 F 10}} NO 4 S 2 -, CF 3 SO 2 -, C 4 F 9 SO 2 -, C 2 H 6 NO 4 S 2 -, C 3 F 6 NO 3 S -, CH 3 CH It may be one of anions such as (OH)CO ₂ ^-.

The ionic liquid has a low melting point due to its structural characteristics and a very low vapor pressure, so that it exists as a stable liquid over a wide temperature range. In addition, it has excellent thermal stability and ionic conductivity, can dissolve various organic, inorganic, and polymeric materials of hydrophilic and hydrophobic properties, and is an eco-friendly material with low volatility, flame retardancy and low explosive properties compared to general organic solvents.

1 is a main flowchart of a method of growing a single crystal of an organic material using an ionic liquid according to the present invention.

Referring to FIG. 1, the organic material single crystal growing method according to the present invention will be described, a mixing step (S10) of mixing an organic material to be grown single crystal with an ionic liquid, and heat treatment under the first condition to organically form the organic material in the ionic liquid. Solutionization step (S20) of solutionizing the material, nucleation step (S30) of injecting a seed into an ionic liquid containing an organic material solutionized under the second condition and generating nuclei on the seed surface (S30), single crystal under the third condition And a single crystal growing step (S40) of growing a single crystal and a separation step (S50) of separating the grown organic material single crystal from the ionic liquid.

More specifically, the mixing step (S10) of mixing an organic material with an ionic liquid is a step of putting an organic material to be grown single crystal into the ionic liquid and mixing it. At this time, the agitation may be performed by a method such as mechanical stirring or magnetic stirring so that the solid organic material can be more evenly mixed with the ionic liquid. The organic material is an organic material for growing high-purity single crystals using the method according to the present invention, and the material is not specifically limited, but the electron injection layer, electron transport layer, hole injection layer, and hole transport of the organic electroluminescent device It is preferably a conductive organic material used for a layer, a light emitting layer, a light absorbing layer of an organic photoelectric conversion element, an organic semiconductor layer of an organic semiconductor element, and the like. In addition, the organic material mixed with the ionic liquid may be a low-purity organic material containing impurities.

In addition, the ionic liquid may be appropriately selected depending on the organic material to be mixed, and in particular, an imidazolium-based ionic liquid having a long alkyl substituent is suitable as the ionic liquid of the present invention. For example, 1-octyl-3-methylimidazolium trifluoromethylsulfonylimide [l-octyl-3-methylimidazolium bis (trifluoromethylsulfonyl)imide] (hereinafter abbreviated as'[Omim][TFSI]'), 1-butyl-3-methylimidazolium trifluoromethylsulfonylimide [l-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl) imide], 1-ethyl-3-methylimidazolium trifluoromethylsulfonylamide [(l-Ethyl-3-methylimidazolium bis (trifluoromethylsulfonyl) amide], 1-decyl-3-methylimidazolium trifluoromethylsulfonylamide [1-Decyl-3-methylimidazolium bis (trifluoromethylsulfonyl) amide], 1- Dodecyl-3-methylimidazolium trifluoromethylsulfonylamide [1-Dodecyl-3-methylimidazolium bis (trifluoromethylsulfonyl) amide] and the like may be used.

^{The ionic liquid is theoretically capable of numerous combinations ranging from 10 to 18} by the combination of cations and anions, so it can cope with various organic materials. That is, it is possible to select and use an ionic liquid having properties suitable for the organic material to be grown for high purity single crystal. In particular, commercially used conductive organic materials, such as conductive organic materials for organic electroluminescent devices, have similar basic structures and polarities, and based on these basic structures, some of the reactive groups are substituted, so that similar crystallization behavior appears. Even if various ionic liquids are not designed, the single crystal growth method according to the present invention can be used for various conductive organic materials as a method of optimizing process conditions using some ionic liquids such as [Omim] [TFSI].

After mixing the organic material and the ionic liquid, heat treatment under the first condition is performed to perform a solution step (S20) of solutionizing the organic material in the ionic liquid. Here, solutionization may mean dissolution or melting, and may be a mixture of dissolution and melting. Whether dissolution or melting is the main mechanism for solutionization can be determined by the organic material and ionic liquid pair and the first condition. The first condition refers to a heat treatment process condition such as a first temperature, a first pressure, and a first atmospheric condition, and may be a condition that changes with time rather than any one fixed condition. For example, after mixing the organic material and the ionic liquid, while maintaining the first temperature for a predetermined period of time, the organic material may be solutionized, but the solution may be made while changing the temperature at a predetermined rate. Also, the first condition does not require uniformity depending on the location. For example, a container in which an organic material and an ionic liquid are mixed may be heat treated to generate a predetermined temperature gradient depending on the location.

For single crystal growth, the organic material must first be solution in the ionic liquid, so the first condition for high process yield is 80% or more, preferably 90% or more, and more preferably of the organic material mixed in the ionic material. May be set to a condition in which substantially the entire amount is solutionized, and this may be achieved by setting the first temperature condition to a high temperature sufficient for the organic material to be solutionized in total amount.

After the solutionization step (S20), a nucleation step (S30) of injecting a seed into an ionic liquid containing a solutionized organic material and generating nuclei on the seed surface is performed. Here, the introduction of the seed does not necessarily mean that the seed is completely immersed in the ionic liquid, and it should be understood that at least a portion of the seed is in contact with the ionic liquid.

The nucleation step is performed under the second condition, and the second condition may be a condition in which the organic material crystal is easily nucleated on the seed surface. For example, when the main mechanism of solutionization is dissolution, the second condition may be a condition at a lower temperature than the first condition. In the case of an organic material whose solubility decreases at a low temperature, a driving force for crystallization increases under the second condition, which is a temperature lower than the first condition, so that nucleation can be easily performed on the seed surface. In addition, when the main mechanism of solutionization is melting, the second condition may be a condition of a higher temperature than the first condition. Depending on the organic material-ionic liquid pair, the driving force for crystallization may increase at a higher temperature than the melting temperature, so that nucleation can be easily performed on the seed surface under the second condition at a temperature higher than the first condition.

Meanwhile, the second condition does not necessarily mean a fixed condition, but may be a condition that changes over time. That is, after the heat treatment under the first condition, nucleation may be induced while maintaining a constant lower or higher temperature than that, but the temperature may be gradually decreased or increased to allow nucleation to occur. Also, the second condition does not require uniformity depending on the location. For example, a predetermined temperature gradient may be generated according to the seed input direction.

The seed may be a high-purity single crystal of the same material as the molten organic material, and a hollow microtube may be used to form a self-seed. In the case of using the microtube, the molten organic material may be crystallized while rising to the hollow portion of the microtube due to capillary phenomenon to serve as a seed, and for this purpose, the diameter of the hollow region of the microtube may be 800 μm or less.

After the nucleation step (S30), a single crystal growth step of growing a single crystal under the third condition is performed (S40). Here, the third condition refers to a process condition for growing a single crystal of an organic material solution in an ionic liquid, such as a third temperature, a third pressure, and a third atmospheric condition. It may be a changing condition. Also, the third condition does not require uniformity depending on the location. For example, a predetermined temperature gradient may be generated according to the seed input direction.

The third condition may be a condition in which at least one of temperature, pressure, and atmosphere is different from the first condition and/or the second condition, and it is preferable that the pressure and atmosphere are the same and the temperature is different. When the main mechanism of solutionization is dissolution, the third temperature may be a temperature lower than the first temperature or the second temperature, and when the main mechanism of solutionization is melting, the third temperature is higher than the first temperature or the second temperature. Can be

Meanwhile, in the nucleation step (S20) and/or the single crystal growth step (S30), the seed may be moved relative to the container containing the organic material and the ionic liquid. Here, the relative movement may include rotation or vertical movement. For example, while rotating the seed at a speed of 9 rph or less, the seed can be moved upward at a speed of 2 mm or less per hour, and in this process, a single crystal can be induced to grow from the seed.

On the other hand, in the above description, an example in which an organic material is dissolved and a single crystal is grown by changing the temperature has been described, but by changing the pressure instead of the temperature or changing both the temperature and pressure, the solution and single crystallization of the organic material are induced. You may.

In the single crystal growth step (S30), the organic material dissolved or melted in the ionic liquid is precipitated as a high-purity single crystal in a state where impurities are excluded. Therefore, when the organic material single crystal is separated from the ionic liquid containing impurities, the organic material purified with high purity. A single crystal can be obtained (S50).

Although only the step S50 is shown in FIG. 1, a process of washing the single crystal of the organic material separated from the ionic liquid and then drying may be further performed.In order to remove the impurities contained in the surface of the single crystal of the organic material, the surface is heated to an appropriate temperature or You can further proceed with the sweating process such as slightly melting only the part. In addition, when a single crystal is grown in a state in which the organic material mixed with the ionic liquid is not fully solutionized in the solution step (S20) and part of it is not dissolved or melted, the low-purity organic material is highly purified in the separation step (S50). Since it may be mixed with the single crystal, a filtering step for filtering out the organic material that has not been solution may be further performed between the solutionization step S20 and the nucleation step S30.

At a high temperature such that a large amount of organic materials are dissolved or melted, general organic solvents are highly volatile and do not exist as a stable liquid in many cases. Even if they exist as liquids, the ratio with organic materials is not kept constant, and organic materials Incorporation of impurities due to reaction with and the like becomes a problem. On the other hand, since ionic liquids have a wide range of temperatures that stably exist as liquids, they can be heat-treated to a relatively high temperature, so that a large amount of organic materials can be dissolved or melted, and characteristic changes are small even at such high temperatures. Since the amount of the organic material dissolved or melted eventually affects the single crystal process yield, it is possible to grow the organic material single crystal at low cost according to the present invention in which the single crystal is grown using an ionic liquid.

In particular, according to the present invention, by growing a single crystal using an ionic liquid, high-purity single crystal growth is possible without prior purification. According to an example to be described later, it was possible to grow a single crystal of an organic material with a high purity of 99.9% or more with only one step of growing a single crystal after a solution of a low-purity organic material in an ionic liquid.

In addition, the vapor pressure of ionic liquids is very low, so the ratio with organic materials is kept constant even when heat-treated at high temperatures, so process design and control are easy, and because they are chemically stable, the amount of impurities incorporated into organic material crystals is negligible. . These effects are characteristics that cannot be expected in the conventional single crystal growth method using a general organic solvent.

2 is an example of a temperature change curve for proceeding the organic material single crystal growth method according to the present invention. Referring to FIG. 2, after mixing an organic material with an ionic liquid, the temperature is raised to a first temperature T1 at a predetermined rate and maintained for a predetermined period of time (t2-t1) to form a solution of the organic material. The first temperature can be set to a temperature such that the organic material can be solutionized as much as possible according to the combination of the organic material and the ionic liquid, and the solution temperature of the organic material can be significantly reduced by using the ionic liquid. I can. In addition, since the mixed organic material may contain low-quality initial crystals, it is preferable to set the time to be maintained at the first temperature T1 to a sufficient time so that the entire amount of the organic material including the initial crystal can be solution.

After the holding time at the first temperature (T1) is over, the temperature is lowered at a predetermined rate to the second temperature (T2), which is the single crystal growth temperature after seeding, and maintained at the second temperature (T2) for a certain time (t4-t3). Let it. Depending on the second temperature T2, the growth rate of the single crystal and the quality of the grown single crystal may be different, and the purity of the crystal may be different. In order to form a high-purity single crystal, it is preferable that the second temperature T2 is as high as possible. Meanwhile, since nucleation and single crystal growth proceed while the temperature is lowered from the first temperature T1 to the second temperature T2 or the second temperature T2 is maintained, the time to be maintained at the second temperature T2 is It is preferable to set it to a time sufficient to allow most of the solution organic material to crystallize.

After growing the single crystal at the second temperature T2, the temperature may be lowered at a predetermined rate to perform the separation step S50.

The temperature change curve of FIG. 2 is only an example, and the present invention is not limited thereto. For example, instead of maintaining the organic material at a first temperature for a certain period of time, it may be made to be solution in the process of raising the temperature to the first temperature at a predetermined rate. In this case, the rate of temperature increase is relatively small. good. In addition, although FIG. 2 shows that the second temperature is lower than the first temperature, the second temperature may be higher than the first temperature. In the process of changing the temperature at a predetermined rate instead of maintaining the second temperature for a certain period of time, It is also possible to allow single crystal growth to occur. The temperature at which the mixing step S10 and the separation step S50 are performed is not limited to room temperature, and for example, an organic material may be mixed with the ionic liquid at the first temperature T1.

According to the organic material single crystal growth method according to the present invention described above, it is only necessary to proceed with the single crystal growth by mixing the organic material in the ionic liquid and adding a seed to the solution. Can grow. In particular, as described through the examples, according to the method according to the present invention, it is possible to grow a single crystal with high purity of 99.9% or more with only one process.

In addition, since such a process using an ionic liquid can be performed in a short time at atmospheric pressure or low vacuum, and there is little loss of raw materials, the process yield is high, and thus there is an advantage in terms of cost compared to the conventional single crystal growth or purification method.

The present invention also has an advantageous effect in terms of ease of design and control of process conditions. In other words, since general organic solvents are highly volatile, they are difficult to apply to organic materials that require high temperatures for solutionization, and the organic solvent is volatilized during the heat treatment and the process is not performed as designed, such as uniform nucleation. The soluble liquid can cope with most organic materials and exists in a liquid phase over a wide temperature range, and is chemically stable, so that the mixing ratio of the ionic liquid and the organic material is substantially the same during the heat treatment process.

3 is a schematic cross-sectional view of an organic material single crystal growing apparatus according to another aspect of the present invention. Referring to FIG. 3, the organic material single crystal growing apparatus 100 according to the present invention includes a stage 110, a container body 120 supported by the stage and accommodating a mixture 200 of an organic material and an ionic liquid. ), a temperature control unit 130 provided around the container body 120 to heat a mixture 200 of an organic material and an ionic liquid, and a gas inlet unit for introducing gas into the container body 120 ( 140), a gas discharge unit 150 for discharging gas from the inside of the container body 120, a container cover 160 for covering and sealing the container body 120, and a seed holder for fixing the seed 310 It consists of 300, including.

In more detail, the stage 110 is configured to support the container body 120 and may be configured to vertically move and/or rotate. The container body 120 accommodates an ionic liquid in which an organic material for growing a single crystal is mixed. The container body 120 may be formed of a material having excellent heat resistance, such as ceramic, and is preferably formed of a material that does not react with ionic liquids and organic materials when heated at high temperatures. The temperature control unit 130 is a component for heating the organic material to be a solution in the ionic liquid, and may be a resistance heating type heater. In FIG. 3, the temperature controller 130 is illustrated as a coil heater surrounding the container body 120, but the shape, type, and installation position of the temperature controller 130 are not limited thereto. The temperature control unit 130 may be a heater capable of raising a temperature of 400° C. or more, and may be designed to have a constant temperature gradient in all directions of the container body 120.

The gas inlet 140 and the gas discharge unit 150 are configured to adjust the gas atmosphere inside the container body 140. For example, by connecting the gas inlet 140 to an inert gas supply source such as nitrogen or argon, the process may be performed while the inside of the container body 140 is maintained in an inert gas atmosphere. A vacuum pump may be connected to the gas discharge unit 150 to perform the process while maintaining the inside of the container body 140 in a vacuum atmosphere. In order to maintain the atmosphere or pressure inside the container body 140, a closed space needs to be formed, and the container cover 160 covers the upper portion of the container body 140 to form a closed space.

The seed holder 300 is a configuration for inserting the seed into the ionic liquid by fixing the seed 310 at an end thereof, and may be configured to be vertically moved and/or rotated. The seed 310 may be a high-purity single crystal of the same material as the organic material to be grown for the single crystal.

Meanwhile, instead of fixing the seed 310 at the end of the seed holder 300, a microtube for self-seed formation may be fixed and introduced into the ionic liquid, which is illustrated in FIG. 4. As shown in FIG. 4, a hollow microtube 320 is fixed to an end of the seed holder 300 instead of the seed 310, and the diameter of the hollow region may be 800 μm or less. When such microtubes are introduced into an ionic liquid in which an organic material is solution, the organic material solution rises to the hollow region of the microtube due to a capillary phenomenon, and crystallization due to a slight temperature difference may form the seed 330. In this way, when a micro tube is used, a single crystal of an organic material can be grown without a separate single crystal seed 310.

In the single crystal growth step, the container body 12 and the seed holder 300 may be moved vertically or in a rotational direction, and the vertical movement speed may be 2mm or less per hour, and the rotation speed may be 9 rph or less. In FIG. 3, both the stage 110 and the seed holder 300 are shown to be capable of vertical movement and rotational movement, but only one of them may be configured to vertically move or rotate if necessary.

The apparatus of FIG. 3 is exemplary, and it should be understood that the apparatus for growing an organic material single crystal according to the present invention is not limited to the configuration of FIG. 3. Some configurations of FIG. 3 may be omitted or changed, or configurations not shown in FIG. 3 may be added. For example, a measurement unit capable of measuring process conditions such as temperature and pressure may be installed in the container body 120 or the container cover 160, and control the temperature controller 130 by receiving the measurement result of the measurement unit. A control device may be provided.

Hereinafter, a result of growing a single crystal of a high-purity organic material using an ionic liquid according to the present invention will be described through examples.

< Example 1>

Example 1 is a conductive organic material used as a material of an organic electroluminescent device, N,N'-bis-(1-naphyl)-N,N'-diphenyl-1,1'-biphenyl-4,4'-diamine (Hereinafter abbreviated as'NPB') is an example of growing a single crystal using [Omim][TFSI] ionic liquid. The formula of NPB is shown in [Chemical Formula 2] below.

[Formula 2]

As a result of scanning electron microscope (SEM) observation, the NPB particles before mixing with the ionic liquid had an amorphous shape of about 1 to 2 μm, and as a result of HPLC (High Performance Liquid Chromatography) purity analysis, the purity was 82.4%.

The low-purity NBP before purification is pulverized and mixed with [Omim][TFSI] ionic liquid at a mixing ratio of 10 wt%, and then 5℃/min from room temperature to 260℃ in a heat treatment furnace maintained in an argon (Ar) gas atmosphere. While increasing the temperature at a rate, NPB was solution. Then, after the microtube was added, the nucleation was induced by slow cooling to 230°C at a rate of 10°C/h, and isothermal heat treatment at 230°C for 12 hours to grow a single crystal. The formed NPB single crystal was separated from the ionic liquid, washed with isopropyl alcohol (IPA), and dried in an oven at 60° C. for 24 hours to obtain a final NPB crystal. The crystallinity of the crystal thus obtained was analyzed by X-ray diffractometry (XRD), and the purity was confirmed by HPLC.

5(a) is an XRD analysis result of an NPB single crystal grown according to Example 1, and for comparison, the XRD analysis result of an NPB polycrystal is shown in FIG. 5(b). As can be seen in FIG. 5, an excellent NPB single crystal having an ^{X-ray half width of 0.1 o or less was grown by the method of the present invention.} In addition, as a result of HPLC purity analysis, it was confirmed that the grown NPB single crystal has a high purity of 99.92%. That is, in the case of the method of the present invention, it can be seen that a high purity NPB single crystal of 99.9% or more can be obtained through only one simple heat treatment process.

< Example 2>

Example 2 is an example in which tris-(8-hydroxyquinoline) aluminum (hereinafter abbreviated as'Alq3'), a conductive organic material used as a material for an organic electroluminescent device, was purified using [Omim][TFSI] ionic liquid to be. Compared with Example 1, only the organic material was changed from NPB to Alq3, and the remaining process conditions were the same. The formula of Alq3 is shown in [Chemical Formula 3] below.

[Formula 3]

FIG. 6(a) is an XRD analysis result of an Alq3 single crystal grown in Example 2, and for comparison, the XRD analysis result of an Alq3 polycrystal is shown in FIG. 6(b). As can be seen in Figure 6, by the method of the present invention, an excellent Alq3 single crystal having an ^{X-ray half width of 0.1 o or less was grown.} In addition, as a result of HPLC purity analysis, it was confirmed that the purity of the grown Alq3 single crystal was similar to that of the NPB single crystal.

7(a) and 7(b) are scanning electron micrographs of Alq3 single crystal and Alq3 polycrystal grown in Example 2, respectively. From FIG. 7, it was confirmed that the Alq3 polycrystal was a needle shape having a size of several µm or less, while crystal growth having a size of several hundred µm or more was achieved after the single crystal growth process according to the present invention.

From the above results, it can be seen that by using the single crystal growth method using an ionic liquid disclosed in the present invention, it is possible to grow an organic material into a high purity single crystal of about 99.9% through a simple and low-cost process. However, this has a very important meaning in that it overcomes the fundamental limitations of the conventional method. In the examples, only the results of purification of NPB and Alq3 are disclosed, but this is exemplary, and the single crystal growth method according to the present invention can be effectively applied to most of organic materials used in organic electroluminescent devices, organic photoelectric conversion devices, and organic semiconductor devices. . The reason why such an excellent effect is exhibited by the single crystal growth method using an ionic liquid is not fully elucidated, but in the case of conductive organic materials used in organic electroluminescent devices, etc., the composition and molecular weight are similar to that of the ionic liquid, so mixing is easy. , It can be inferred because it is very advantageous in terms of kinetics in a solution, and exhibits excellent behavior in crystallization.

Although described with reference to the above limited embodiments and drawings, these are only examples, and it will be apparent to those skilled in the art that various modifications can be implemented within the scope of the technical idea of the present invention. For example, it should be understood that the present invention does not exclude the use of a mixture of plural types of ionic liquids as ionic liquids or use of mixtures with other solvents. Therefore, the scope of protection of the present invention should be determined by the description of the claims and their equivalent range.

100: organic material single crystal growth device
120: container body
130: temperature control unit
140: gas inlet
150: gas exhaust
160: container cover
200: organic material and ionic liquid mixture
300: seed holder
310, 330: seed
320: micro tube

Claims (14)

A mixing step of mixing an organic material with an ionic liquid;
A solutionization step of heat-treating under a first condition to make an organic material mixed with the ionic liquid solution;
A nucleation step of injecting a seed into an ionic liquid containing the organic material that has been solutionized under a second condition and generating nuclei on the seed surface;
A single crystal growing step of growing a single crystal while moving the seed upward under a third condition; And
A separation step (S50) of separating the grown single crystal of the organic material from the ionic liquid;
Including,
An organic material single crystal growth method using an ionic liquid, characterized in that to obtain a single crystal of an organic material purified with higher purity than before being mixed with the ionic liquid. The method of claim 1,
The seed is an organic material single crystal growth method using an ionic liquid, characterized in that the single crystal of the same material as the organic material or a hollow microtube. The method of claim 1,
The solutionization is at least one of melting or melting. A method of growing a single crystal of an organic material using an ionic liquid. The method of claim 1,
An organic material single crystal growth method using an ionic liquid, characterized in that 99% or more of a high purity single crystal organic material is obtained by performing the mixing step, solutionization step, nucleation step, single crystal growth step, and separation step once. The method of claim 1,
The organic material single crystal growth method using an ionic liquid, characterized in that it further comprises the step of washing and drying the organic material single crystal separated from the ionic liquid. The method of claim 1,
The first condition, the second condition, or the third condition is a condition that changes with time. The method of claim 1,
After the separation step, the organic material single crystal growth method using an ionic liquid, characterized in that further proceeding with a sweating process for removing surface impurities of the separated organic material single crystal. The method of claim 1,
Between the solution step and the nucleation step,
Organic material single crystal growth method using an ionic liquid, characterized in that further performing a filtering step to filter out the organic material that has not been solution. As an organic material single crystal growth device using an ionic liquid to obtain a single crystal of an organic material purified with higher purity than before being mixed with an ionic liquid,
stage;
A container body supported by the stage and accommodating a mixture of an organic material and an ionic liquid;
A temperature controller for heating a mixture of an organic material and an ionic liquid accommodated in the container body;
A seed holder in which a seed is inserted into a mixture of an organic material and an ionic liquid accommodated in the container body;
Including,
The container body and the seed holder are relatively movable,
The organic material single crystal growth apparatus, characterized in that the relative movement includes vertical movement. The method of claim 9,
The organic material single crystal growing apparatus, wherein the seed is a single crystal of the same material as the organic material. The method of claim 9,
The organic material single crystal growth apparatus, characterized in that the relative movement further includes a rotational movement. The method of claim 9,
A gas inlet portion for introducing gas into the container body; And
Organic material single crystal growth apparatus, characterized in that it further comprises a gas discharge unit for discharging the gas from the inside of the container body. An organic material single crystal grown by the method of any one of claims 1 to 8. The method of claim 13,
Organic material single crystal, characterized in that the X-ray half width is 0.1 ^{o or less.}

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