Manufacturing method of doped organic semiconductor film

Abstract

The invention relates to a doped organic semiconductor thin film and a manufacturing method thereof. According to the manufacturing method of the doped organic semiconductor thin film, the dopant material is dissolved in the organic solvent with strong polarity, so that even if the dopant material is mixed with the organic semiconductor material, doping does not occur in the solution, and the composite dopant material can be prevented from precipitating in the doping process performed in the solution phase. In addition, since a high level of doping is induced in the organic semiconductor thin film manufactured using the method, conductivity is improved.

Description

Technical Field

[0001] The present invention relates to an organic semiconductor, and more particularly, to a doped organic semiconductor. Background Art

[0002] In the semiconductor industry of rice, which is called the advanced industry, doping, in which impurities are intentionally added to control electrical, optical, and structural properties, is an indispensable necessary technique. Molecular doping is similar to doping, but a dopant composed of molecules rather than atoms undergoes a charge transfer reaction with a semiconductor to form carriers, and is being widely studied as a technique for improving the conductivity of various organic and inorganic semiconductors, controlling energy levels, and changing absorption characteristics.

[0003] Since molecular doping transfers charge through the relative energy level difference between the host semiconductor and the guest dopant, controlling this is a key element of this technique. For example, p-doping requires the highest occupied molecular orbital (HOMO) energy level of the semiconductor to be higher than the lowest unoccupied molecular orbital (LUMO) energy level of the dopant. Meeting this condition can improve the performance of various electronic devices, but the heat inevitably generated during the operation of the device can cause the dopant to diffuse and hinder the operating stability of the device. Among various dopant materials, organic dopants are materials composed of organic compounds and have the characteristic of being easy to control the molecular weight, so they are advantageous materials for suppressing thermal diffusion and improving operating stability.

[0004] In particular, organic p-dopants are used as key materials for reducing the operating voltage and power consumption of photovoltaic devices due to their excellent operating stability, and their demand is expected to further increase in the future.

[0005] Generally, when an organic semiconductor is doped in a solution, it is known that its solubility drops sharply and precipitation occurs. Here, the formed doped organic semiconductor precipitate significantly reduces the uniformity of the film during the film coating process and interferes with the operation of electronic and photovoltaic devices as defects or suppresses their performance. In particular, since organic solvents with low polarity generally have low dopant solubility, there is a problem of dilution during the mixing of the organic semiconductor solution and the dopant solution in the manufacturing process of an organic semiconductor film, which brings difficulties to the manufacturing process of photovoltaic devices where thickness control is important. Summary of the Invention

[0006] Technical Problem

[0007] The technical problem to be solved by the present invention is to provide a doped organic semiconductor film and a manufacturing method thereof.

[0008] The technical problem of the present invention is not limited to the above technical problem, and those skilled in the art will clearly understand other technical problems not mentioned from the following description.

[0009] Technical solution

[0010] To solve the above problems, one aspect of the present invention provides a method for manufacturing a doped organic semiconductor thin film. The method may include preparing a composite doping solution, the composite doping solution containing an organic compound having a resonance structure with at least one cyano group (C≡N), a Lewis acid, and a first organic solvent; preparing an organic semiconductor solution containing an organic semiconductor material and a second organic solvent; mixing the composite doping solution and the organic semiconductor solution to produce a mixed solution; and coating the mixed solution on a substrate to form a thin film and evaporating the organic solvent in the thin film.

[0011] The first organic solvent may have a dielectric constant value larger than that of the second organic solvent.

[0012] The first organic solvent may be an organic solvent with strong polarity compared to the second organic solvent, and may have a dielectric constant value of 16 to 50 at room temperature. For example, the first organic solvent may include at least one selected from acetone, acetonitrile (ACN), dimethylformamide (DMF), and combinations thereof, but is not limited thereto.

[0013] The second organic solvent may be an organic solvent with weak polarity compared to the first organic solvent, and may have a dielectric constant value of 1 to 15 at room temperature. For example, the second organic solvent may include at least one selected from dichlorobenzene (DCB), ethyl acetate (EtOAc), and combinations thereof, but is not limited thereto.

[0014] In the mixed solution, the binding of the organic compound and the Lewis acid can be inhibited. In the thin film where the organic solvent has been evaporated, the composite dopant compound formed by binding the organic compound and the Lewis acid can dope the organic semiconductor material.

[0015] This binding can form a Lewis pair formed by the cyano group (C≡N) of the organic compound and the Lewis acid.

[0016] The organic semiconductor material may include an alkyl side chain in its molecular structure.

[0017] To solve the above problems, another aspect of the present invention provides a doped organic semiconductor thin film. The doped organic semiconductor thin film contains a composite dopant compound and an organic semiconductor material doped with the composite dopant compound, in which an organic compound having a resonance structure and a Lewis acid are combined, and the resonance structure has at least one cyano group (C≡N).

[0018] The binding of the organic compound and the Lewis acid forms a Lewis pair between the cyano group (C≡N) of the organic compound and the Lewis acid.

[0019] Although the thin film is formed using a composite doping solution containing an organic compound, a Lewis acid, and an organic solvent, the bonding can be formed after evaporation of the organic solvent.

[0020] The organic solvent can have a dielectric constant value of 16 to 50 at room temperature.

[0021] The organic solvent can be at least one selected from, but not limited to, acetone, acetonitrile (ACN), dimethylformamide (DMF), and combinations thereof.

[0022] The organic semiconductor material can include an alkyl side chain in its molecular structure.

[0023] Beneficial Effects

[0024] The method for manufacturing a doped organic semiconductor thin film of the present invention includes dissolving a dopant material in a strongly polar organic solvent so that even when mixed with an organic semiconductor material, no doping occurs in the solution, thereby eliminating the precipitation phenomenon of the composite dopant material during the doping process in the solution phase. In addition, the organic semiconductor thin film manufactured by this method has improved conductivity by having a high level of doping. Description of the Drawings

[0025] Figure 1 is a flowchart of a method for manufacturing a doped organic semiconductor thin film according to an embodiment of the present invention.

[0026] Figure 2 shows a schematic diagram of a bond formed between an organic semiconductor compound having a resonance structure and a Lewis acid according to the polarity of the solvent, and (b) a graph showing the LUMO levels of the organic material before / after binding of the Lewis acid according to an embodiment of the present invention.

[0027] Figure 3 shows a photograph for confirming whether an organic semiconductor material is doped according to the type of organic solvent used in an embodiment of the present invention.

[0028] Figure 4 shows the UV-vis-NIR absorbance graph of an organic semiconductor compound solution doped with a dopant compound in an embodiment of the present invention (left) and the UV-vis-NIR absorbance graph after 7 days (right).

[0029] Figure 5 shows a digital camera photograph of an organic semiconductor compound thin film with a dopant ratio of 20 mol% in an embodiment of the present invention (left) and a graph showing UV-vis-NIR absorbance (right).

[0030] Figure 6Digital camera photos (left) of an organic semiconductor compound thin film with a dopant ratio of 50 mol% in an embodiment of the present invention and a graph showing UV-vis-NIR absorbance (right).

[0031] Figure 7 Digital camera photos of the surface of a thin film taken immediately after thin film formation (left) and 30 seconds after thin film formation (right) in an embodiment of the present invention when acetonitrile (ACN) is used as a dopant solvent.

[0032] Figure 8 Digital camera photos (left) of a thin film when a PCDTFBT organic semiconductor material is doped at a 50% molar ratio in an embodiment of the present invention, its UV-vis-NIR absorbance graph (middle), and the UV-vis-NIR absorbance graph of a PDPP3T organic semiconductor film doped in the same manner (right).

[0033] Figure 9 UV-vis-NIR absorbance graph (left) of an organic semiconductor thin film using a doping solution (wherein a doping material is dissolved in ACN) in an embodiment of the present invention and a conductivity graph (right) showing a doped organic semiconductor thin film prepared by dissolving a doping material in ACN and DMF solvents.

[0034] Figure 10 Digital camera photos of an organic semiconductor solution using various organic solvents and thin films manufactured using the organic semiconductor solution in an embodiment of the present invention. Detailed Description

[0035] The present invention can be modified in various ways and can take many forms. The detailed embodiments are shown in the drawings and described in detail herein. However, this is not intended to limit the present invention to the specific forms disclosed, and it should be understood that the present invention includes all modifications, equivalents, or alternatives within the spirit and technical scope of the present invention. When describing each drawing, like reference numerals are used for like components.

[0036] Unless otherwise defined, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by those of ordinary skill in the art to which the present invention pertains. Terms defined in a commonly used dictionary should be interpreted as having a meaning consistent with their meaning in the context of the relevant art, and should not be interpreted in an ideal or overly formal sense, unless explicitly defined in this application.

[0037] Throughout the specification, when a part is referred to as "including" a component, this does not mean excluding other components, but means that other components can be included, unless otherwise specifically stated.

[0038] The terms "about", "substantially", etc. used throughout this specification refer to when material tolerances are presented in the given sense, they are at or near the numerical value, and are used to prevent unethical infringers from unfairly taking advantage of the disclosed content, in which precise or absolute numerical values are stated for the purpose of aiding in the understanding of this specification.

[0039] Method for manufacturing doped organic semiconductor thin film

[0040] Figure 1 is a flowchart of a method for manufacturing a doped organic semiconductor thin film according to an embodiment of the present invention.

[0041] Reference Figure 1 , a method for manufacturing a doped organic semiconductor thin film of the present invention is provided. First, an organic compound including a resonance structure having at least one cyano group (C≡N) and a first organic solvent can be mixed to obtain a first mixed solution. Separately, a Lewis acid combined with the cyano group (C≡N) can be mixed with the first organic solvent to obtain a second mixed solution. The first mixed solution and the second mixed solution are mixed in a certain proportion to prepare a composite doping solution.

[0042] The organic compound can include an organic resonance structure having at least one, for example, two or more cyano groups (C≡N) in the molecule. The above-mentioned cyano group (C≡N) is an electron-withdrawing group (EWG) that draws electrons from the resonance structure, and can point to a Lewis base that provides electrons to the Lewis acid. The organic compound can form a Lewis pair by combining with the Lewis acid material detailed below, and can form a composite dopant compound having strong doping characteristics in the organic semiconductor thin film, or can itself be used as an organic dopant material.

[0043] The above-mentioned organic compound can be represented by the following Chemical Formula 1.

[0044] [Chemical Formula 1]

[0045] R-C≡N

[0046] The above R is an organic resonance structure and can include at least one selected from, for example, an aromatic ring, a quinone-type ring, a double bond, a triple bond, allene, butadiene, polyene, oxocarbon, pseudooxocarbon, radialene, their analogs, and their derivatives.

[0047] Specifically, the above R can include at least one selected from the compounds represented by the following Chemical Formulas 2 to 24, but is not limited thereto.

[0048] [Chemical Formula 2]

[0049]

[0050] [Chemical Formula 3]

[0051]

[0052] [Chemical Formula 4]

[0053]

[0054] [Chemical Formula 5]

[0055]

[0056] [Chemical Formula 6]

[0057]

[0058] [Chemical Formula 7]

[0059]

[0060] [Chemical Formula 8]

[0061]

[0062] [Chemical Formula 9]

[0063]

[0064] [Chemical Formula 10]

[0065]

[0066] [Chemical Formula 11]

[0067]

[0068] [Chemical Formula 12]

[0069]

[0070] [Chemical Formula 13]

[0071]

[0072] [Chemical Formula 14]

[0073]

[0074] [Chemical Formula 15]

[0075]

[0076] [Chemical Formula 16]

[0077]

[0078] [Chemical Formula 17]

[0079]

[0080] [Chemical Formula 18]

[0081]

[0082] [Chemical Formula 19]

[0083]

[0084] [Chemical Formula 20]

[0085]

[0086] [Chemical Formula 21]

[0087]

[0088] [Chemical Formula 22]

[0089]

[0090] [Chemical Formula 23]

[0091]

[0092] [Chemical Formula 24]

[0093]

[0094] The above-mentioned organic compound can be a p-type or n-type organic dopant, such as a p-type organic dopant, and can include at least one selected from, for example, tetracyanoethylene (TCNE), 7,7,8,8-tetracyanoquinodimethane (TCNQ), 2,3,5,6-tetrafluoro-tetracyanoquinodimethane (FTCNQ), 2,5-difluoro-7,7,8,8-tetracyanoquinodimethane (F2TCNQ), 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ), 2,3,5,6-tetrafluoro-tetracyanoquinodimethane (F4TCNQ), its analogs and its derivatives. In a specific example, the organic compound can be 2,3,5,6-tetrafluoro-tetracyanoquinodimethane (F4TCNQ), but is not limited thereto.

[0095] The organic compound can be dissolved in the first organic solvent detailed below to prepare the first doping solution. The concentration of the first doping solution can be from 0.5 mg / mL to 30 mg / mL, specifically from 1 mg / mL to 20 mg / mL, for example from 2 mg / mL to 10 mg / mL, but is not limited thereto.

[0096] The Lewis acid (LA) can combine with the cyano group in the molecule of the organic compound present in the organic semiconductor thin film detailed below to form a composite dopant compound that dopes the organic semiconductor material. The above bond is a bond in which the cyano group (C≡N) as a Lewis base in the organic compound forms a Lewis pair with the Lewis acid, and can include, for example, a covalent bond, a coordination bond, or a secondary bond containing these, such as a van der Waals bond, a dipole-dipole bond, etc. In a specific example, the Lewis acid can include, but is not limited to, at least one selected from tris(pentafluorophenyl)borane (BCF), bis(pentafluorophenyl)zinc (Zn(C6F2)2), boron tribromide (BBr3), molybdenum chloride (MoCl5), and combinations thereof.

[0097] The second doping solution can be prepared by dissolving a Lewis acid material in a first organic solvent detailed below. The concentration of the second doping solution can be from 20 mg / mL to 200 mg / mL, specifically from 50 mg / mL to 150 mg / mL, for example from 80 mg / mL to 120 mg / mL, but not limited thereto.

[0098] The first organic solvent can be a solvent with Lewis basicity or a polar organic solvent with a high dielectric constant value. Specifically, the first organic solvent can have a larger dielectric constant value than the second organic solvent described below. Specifically, the dielectric constant value of the first organic solvent at room temperature can be 16 to 50, more specifically 18 to 45, and in one specific example 20 to 40. In the mixed doping solution, the first organic solvent with strong polarity can have the effect of inhibiting the formation of a composite dopant material formed by the formation of a Lewis pair bond between the Lewis acid material and the organic compound. For example, the first organic solvent can be at least one selected from acetone, acetonitrile (ACN), dimethylformamide (DMF), and combinations thereof.

[0099] The above mixed solution can be a mixture formed by mixing the organic compound material contained in the first mixed solution and the Lewis acid material contained in the second mixed solution in a molar ratio of 1:1 to 1:10, specifically 1:1 to 1:7, more specifically 1:1 to 1:5, and in one specific example 1:1 to 1:4, but not limited thereto.

[0100] Individually, an organic semiconductor solution in which an organic semiconductor material is dissolved in a second organic solvent can be prepared.

[0101] The second organic solvent can be a polar organic solvent that can dissolve the organic semiconductor material and has a low dielectric constant value, specifically 1 to 15 at room temperature, more specifically 3 to 12, and in one specific embodiment 5 to 10.

[0102] The organic semiconductor material can be an organic material capable of being doped with the above-mentioned composite dopant compound. Specifically, it can be an organic semiconductor material having an alkyl side chain in its molecular structure. The organic semiconductor material having an alkyl side chain in its molecular structure can be a material that is highly likely to aggregate and form a precipitate in solution during the doping process. The above-mentioned organic semiconductor material is, for example, PDPP3T (Poly{2,2'-[(2,5-bis(2-hexyldecyl)-3,6-dioxo-2,3,5,6-tetrahydropyrrolo[3,4-c]pyrrole-1,4-diyl)dithiophene]-5,5'-diyl-alt-thiophen-2,5-diyl}), PCDTFBT (Poly[(5-fluoro-2,1,3-benzothiadiazole-4,7-diyl)(4,4-dihexadecyl-4H-cyclopenta[2,1-b;3,4-b']dithiophene-2,6-diyl)(6-fluoro-2,1,3-benzothiadiazole-4,7-diyl)(4,4-dihexadecyl-4H-cyclopenta[2,1-b;3,4-b']dithiophene-2,6-diyl)]), P3HT (Poly(3-hexylthiophene-2,5-diyl)), and combinations thereof, but is not limited thereto.

[0103] The concentration of the above-mentioned organic semiconductor solution can be, but is not limited to, 1-50 mg / mL, specifically 3-40 mg / mL, more specifically 5-30 mg / mL, for example 7-20 mg / mL.

[0104] Next, the step of preparing a mixed solution by mixing the composite doping solution and the organic semiconductor solution can be performed.

[0105] The mixed solution is a mixture of a composite doping solution and an organic semiconductor solution, and with respect to the total number of moles of the organic semiconductor material and the composite dopant material, the dopant ratio of the composite doping solution can be 5 mol% to 70 mol%, specifically 10 mol% to 60 mol%, and in one embodiment 20 mol% to 50 mol%.

[0106] The mixed solution contains an organic compound material, a Lewis acid material, and an organic semiconductor material in an organic solvent. In the mixed solution, the first organic solvent with strong polarity may have formed a bond by reacting with the Lewis acid, thereby inhibiting the reaction between the cyano group of the organic compound and the Lewis acid, that is, inhibiting the formation of a Lewis pair, and thus inhibiting the formation of the composite dopant compound. In the mixed solution where the formation of the composite dopant compound is inhibited, in the film manufacturing process detailed below, only after the solvent evaporates can the Lewis acid and the cyano group combine to form a p-type composite dopant compound with strong oxidizing properties, thereby enabling a very high doping level. Therefore, the mixed solution can be referred to as a doping solution with potential doping ability, which induces doping after film formation and does not react in the solution. If an organic solvent with low polarity (such as the second organic solvent) is used as the first organic solvent, in the step of preparing the mixed solution, the cyano group of the organic compound and the Lewis acid may react to form a composite dopant compound, such as F4TCNQ:BCF, P3HT, and then precipitate, which may lead to the formation of precipitation in the solution. As a result, when performing the following film preparation process, an uneven organic semiconductor film that may not be desired may be formed.

[0107] Then, the step of coating the above mixed solution on a substrate to form a film and evaporating the organic solvent in the film can be carried out.

[0108] The method of forming the film can be based on the methods of forming a film from a solution well-known in the art, and non-limiting examples thereof include dip coating, bar coating, spray coating, brush coating, spin coating, slot-die coating, solution casting, gravure coating, roll coating, drop coating, printing, etc.

[0109] The organic solvent can include at least one selected from the above first organic solvent and the second organic solvent, and evaporates during the film formation process, specifically most of the organic solvent, such as all of the organic solvent, so that no organic solvent remains in the film. When the organic solvent evaporates, the cyano group of the organic compound in the organic semiconductor film can react and combine with the Lewis acid to form a p-type composite dopant compound with strong oxidizing properties. The composite dopant compound can be a doping material with strong oxidizing properties and can perform a high-level doping on the organic semiconductor material.

[0110] The composite dopant compound is formed by a bond between the above-mentioned organic compound and a Lewis acid, and may include at least one Lewis pair within the molecular structure, particularly a bond between a cyano group and a Lewis acid.

[0111] The fabricated thin film can have a nano-thickness, for example, a thickness of dozens to hundreds of nanometers.

[0112] Hereinafter, to more specifically illustrate the present invention, preferred experimental examples of the present invention will be described in more detail with reference to the accompanying drawings. However, the present invention is not limited to the embodiments described herein and can be implemented in other forms.

[0113] Test example: Synthesis of mixed doping solution F4TCNQ:BCF

[0114] The first doping solution is prepared by dissolving the organic compound F4TCNQ having a cyano group at 2 - 10 mg / mL in a first organic solvent. The materials used as the first organic solvent are acetone, acetonitrile (ACN), or dimethylformamide (DMF). Separately, the Lewis acid material tris(pentafluorophenyl)borane (BCF) is dissolved at 100 mg / mL in each first organic solvent to prepare a second doping solution. Each doping solution is heated to 90 °C to prevent precipitation and completely dissolve.

[0115] The first mixed solution and the second mixed solution are mixed so that the molar ratio of the organic compound having a cyano group to the Lewis acid material is 1:2 to 1:4 to prepare a composite doping solution. If the color of the composite doping solution changes compared to before mixing, it is confirmed that a reaction has occurred between the two materials. All of the above processes are carried out under a nitrogen atmosphere.

[0116] Example: Formation of organic semiconductor thin film doped with mixed doping solution

[0117] An organic semiconductor solution was prepared by dissolving an organic semiconductor material in a second organic solvent, dichlorobenzene (DCB), at a concentration of 10 mg / mL. The organic semiconductor materials include PDPP3T (poly{2,2'-[(2,5-bis(2-hexyldecyl)-3,6-dioxo-2,3,5,6-tetrahydropyrrolo[3,4-c]pyrrole-1,4-diyl)dithiophene]-5,5'-diyl-alt-thiophene-2,5-diyl}), PCDTFBT (poly[(5-fluoro-2,1,3-benzothiadiazole-4,7-diyl)(4,4'-hexacosan-4H-cyclopenta[2,1-b;3,4-b']dithiophene-2,6-diyl)(6-fluoro-2,1,3-benzothiadiazole-4,7-diyl)(4,4'-hexacosan-4H-cyclopenta[2,1-b;3,4-b']dithiophene-2,6-diyl)]), or P3HT (poly(3-hexylthiophene-2,5-diyl)). The organic semiconductor solution was mixed with the mixed doping solution generated in the test example such that F4TCNQ was 20 - 50 mol% based on the total number of moles of the organic semiconductor material and the composite doping material to prepare a mixed solution. The mixed solution was coated on a washed glass substrate and spin-coated at 1000 rpm for 60 seconds to form a doped organic semiconductor thin film with a thickness of several tens of nanometers. The presence of doping was confirmed based on whether the mixed doping solution precipitated.

[0118] Figure 2 Fig. (a) shows a schematic diagram illustrating the bond formed between an organic semiconductor compound having a resonance structure and a Lewis acid according to the polarity of the solvent, and Fig. (b) shows a graph illustrating the LUMO levels of the organic material before / after binding of the Lewis acid according to an embodiment of the present invention.

[0119] Reference Figure 2 , the organic compound (F4TCNQ) having a resonance structure of the present invention can form a composite dopant compound (F4TCNQ - BCF4) by forming a bond between the organic semiconductor compound and the Lewis acid (BCF) in a non-polar organic solvent. On the other hand, in a polar organic solvent, the organic compound (F4TCNQ) does not form a bond with the Lewis acid (BCF). Instead, the material serving as the polar organic solvent can react with the Lewis acid (BCF) to form a bond, thus inhibiting the formation of the composite compound. Although the organic compound (F4TCNQ) itself has a relatively high LUMO level, when the composite dopant compound (F4TCNQ - BCF4) is formed, the LUMO level is sufficiently reduced such that holes can move toward the organic semiconductor material.

[0120] Table 1

[0121]

[0122] Table 1 shows the dielectric constants of organic solvents according to embodiments of the present invention. Figure 3 Shown is a photograph for confirming whether an organic semiconductor material is doped using the type of organic solvent according to an embodiment of the present invention.

[0123] Referring to Table 1 and Figure 3 , when the organic semiconductor material PDPP3T is dissolved in dichlorobenzene (DCB), the organic compound F4TCNQ having a cyanide group is dissolved in dichlorobenzene (DCB) or ethyl acetate (EtOAc), and then the organic semiconductor (PDPP3T) solution and the organic compound solution are mixed at 50 mol%, it can be seen that the organic semiconductor (PDPP3T) is doped and precipitates in the solution. At this time, the dielectric constants of ethyl acetate (EtOAc) and dichlorobenzene (DCB) as organic solvents are 6.02 and 9.93, respectively, which are solvents with weak polarity. Therefore, it can be seen that when using organic solvents with low polarity such as ethyl acetate (EtOAc) or dichlorobenzene (DCB) to dissolve the organic semiconductor material and the organic compound, doping occurs in the solution. On the other hand, when the organic compound material having a cyanide group is dissolved in relatively polar acetonitrile (ACN) or dimethylformamide (DMF) and mixed with an organic semiconductor solution with a relatively non-polar solvent dichlorobenzene (DCB), it can be confirmed that the organic semiconductor material PDPP3T is not doped and no precipitate is formed. Here, the dielectric constants of acetonitrile (ACN) and dimethylformamide (DMF) as organic solvents are 37.5 and 36.7, respectively, which are solvents with strong polarity. Therefore, when the organic compound having a cyanide group is dissolved in a strongly polar organic solvent, the organic semiconductor material is dissolved in a weakly polar organic solvent, and they are mixed to form a mixed solution, it can be determined that the Lewis acid reacts with the strongly polar solvent rather than with the cyanide group (C≡N), thereby inhibiting the doping of the organic semiconductor material, and thus no organic semiconductor precipitate is formed.

[0124] Figure 4 Shown is a graph (left) showing the UV-vis-NIR absorbance of an organic semiconductor compound solution doped with a dopant compound according to an embodiment of the present invention and a graph (right) showing the UV-vis-NIR absorbance after 7 days.

[0125] Referring to Figure 4 , when doping an organic semiconductor with a dopant compound using various organic solvents, it can be seen that even after one week, no significant change is observed in the absorbance characteristics of the solution, so it exhibits excellent stability.

[0126] Figure 5The digital camera photo (left) of the organic semiconductor compound thin film with a doping ratio of 20 mol% in the embodiment of the present invention and the graph showing the UV-vis-NIR absorbance (right) are shown.

[0127] Reference Figure 5 , dichlorobenzene (DCB), ethyl acetate (EtOAc), acetonitrile (ACN), or dimethylformamide (DMF) as a dopant solvent is mixed with F4TCNQ and BCF to be used as a dopant solution, PDPP3T dissolved in dichlorobenzene (DCB) is used as an organic semiconductor solution, the above solutions are mixed at a doping ratio of 20 mol% to prepare a mixed solution, and the mixed solution is spin-coated to form an organic semiconductor thin film. The results show that when using low-polarity organic solvents DCB and EtOAc as dopant solvents, the organic semiconductor thin film is uneven and there are precipitates remaining on its surface, but when using high-polarity organic solvents ACN and DMF as dopant solvents, it is confirmed that no precipitates are found on the film surface and the film is formed uniformly.

[0128] Figure 6 The digital camera photo (left) of the organic semiconductor compound thin film with a dopant ratio of 50 mol% in the embodiment of the present invention and the graph showing the UV-vis-NIR absorbance (right) are shown.

[0129] Reference Figure 6 , acetone, acetonitrile (ACN), or dimethylformamide (DMF) is mixed with F4TCNQ and BCF as a dopant solvent to form an organic compound solution, and PDPP3T dissolved in dichlorobenzene (DCB) is used as an organic semiconductor solution. The above solutions are mixed at a doping ratio of 50 mol% to prepare a mixed solution, and the mixed solution is spin-coated to form an organic semiconductor thin film. The results show that when using relatively high-polarity organic solvents as dopant solvents, the doping is good and no precipitate is formed, thus forming a smooth thin film. In addition, the UV-vis-NIR absorbance measurement results show that the neutral PDPP3T peak appearing near 800 nm decreases rapidly, while the polaron peak increases rapidly, confirming good doping.

[0130] Figure 7 The digital camera photo of the thin film surface (left) where the mixed doping solution is dropped on the substrate and the organic semiconductor thin film is immediately coated and the digital camera photo of the thin film surface (right) where the mixed doping solution is dropped on the substrate and the organic semiconductor thin film is coated after 30 seconds in the embodiment of the present invention are shown.

[0131] Refer to Figure 7, to confirm the role of the dopant solvent, a mixed dopant solution using ACN as the dopant solvent was dropped onto the substrate, held for 30 seconds, and then the organic semiconductor film was spin-coated. The results showed that it was confirmed that an uneven film was formed. This is because ACN inhibited the reaction between F4TCNQ and BCF, but its boiling point was low and it evaporated rapidly, causing doping and resulting in the formation of an uneven film. This result may mean that the Lewis acid combines with the dopant solvent for potential doping rather than with the CN group, inhibiting the formation of the dopant with strong oxidation properties. However, the solvent evaporates to form a bond between the Lewis acid and the CN group, and this bond exhibits strong oxidation properties and then reacts with the organic semiconductor.

[0132] Figure 8 Shown are a digital camera photograph (left) of a film when the PCDTFBT organic semiconductor material is doped at a 50% molar ratio according to an embodiment of the present invention, its UV-vis-NIR absorbance graph (middle), and a UV-vis-NIR absorbance graph of a PDPP3T organic semiconductor film doped in the same manner (right).

[0133] Reference Figure 8 , when the dopant solution of the present invention (F4TCNQ:BCF solution dissolved in ACN) is applied to the conjugated polymer PCDTFBT for doping, it can be confirmed that the strongly polar solvent ACN forms a uniform film in the solution state without forming precipitation, and a very high level of doping occurs. Therefore, it can be seen that when a solvent with strong polarity and Lewis basicity is used, the formation of the dopant is inhibited in the solution, but after the film is formed, the solvent evaporates to form a composite dopant with strong oxidation properties, and then the organic semiconductor is doped.

[0134] Figure 9 Shown is a UV-vis-NIR absorbance graph (left) of an organic semiconductor film using a dopant solution in which the dopant material is dissolved in ACN according to an embodiment of the present invention, and a conductivity graph (right) showing a doped organic semiconductor film prepared by dissolving the dopant material in ACN and DMF solvents.

[0135] Reference Figure 9, F4TCNQ:BCF, F4TCNQ, and BCF, which are used as doping materials, are respectively dissolved in a strongly polar organic solvent ACN to prepare doping solutions, and the conductivity of organic semiconductor thin films doped with these doping solutions is measured. The conductivity of the organic semiconductor thin films is measured to be 16.51 S / cm (F4TCNQ:BCF) and 0.036 S / cm (F4TCNQ). In the case of BCF, since doping does not occur, the conductivity cannot be measured. Additionally, F4TCNQ:BCF, F4TCNQ, and BCF, which are used as doping materials, are respectively dissolved in a weakly polar organic solvent DMF to prepare doping solutions, and the conductivity of the organic semiconductor thin films doped with these is measured. The conductivity of the organic semiconductor thin films is measured to be 2.77 S / cm (F4TCNQ:BCF), 0.010 S / cm (F4TCNQ), and 0.0018 S / cm (BCF). As described above, when using F4TCNQ:BCF as the doping material, the doping ability can be improved by using ACN or DMF as the dopant solvent. In particular, when using the polar organic solvent ACN, the conductivity of the organic semiconductor thin film can be improved by better doping.

[0136] Figure 10 Digital photos of an organic semiconductor solution using various organic solvents and a thin film manufactured using the organic semiconductor solution according to an embodiment of the present invention are shown.

[0137] Reference Figure 10 , a solution is used to manufacture an organic semiconductor thin film. In this solution, a doping solution of F4TCNQ dissolved in DCB, ACN, or DMF is mixed with an organic semiconductor solution of an organic semiconductor P3HT dissolved in DCB at a molar ratio of 20%. The results show that it can be confirmed that when the organic compound F4TCNQ having a cyanide group is dissolved in strongly polar ACN or DMF and mixed with the organic semiconductor P3HT solution, precipitation occurs due to the strong reaction between F4TCNQ and P3HT. The above results are different from those in the case of the organic semiconductor material doping composite dopant compound of the present invention. It can be seen that when an organic compound having a cyano group sufficiently acts as a p-type dopant, a reaction occurs between the p-type dopant and P3HT when using a polar organic solvent, resulting in doping.

[0138] As described above, the method for manufacturing a doped organic semiconductor thin film according to the present invention can achieve a solution-phase doping process for an organic semiconductor material having an alkyl side chain (the alkyl side chain is difficult to dope because it is very likely to aggregate and form precipitation in the solution during the doping process), and thus can be applied to a wide range of fields, including light-emitting devices such as organic light-emitting diodes and quantum dot light-emitting diodes, photovoltaic devices such as perovskite solar cells and organic solar cells, transistors, thermoelectric devices, electrochemical devices, spin devices, sensors, catalysts, and electrodes, etc.

[0139] Although the exemplary embodiments of the present invention have been described above, those of ordinary skill in the art should understand that various changes, substitutions, and alterations can be made herein without departing from the spirit and scope of the present invention as defined by the appended claims.

Claims

1. A method for preparing a doped organic semiconductor thin film, comprising: Preparing a composite doping solution, the composite doping solution comprising an organic compound having a resonance structure, a Lewis acid, and a first organic solvent, the resonance structure having at least one cyano group (C≡N); Preparing an organic semiconductor solution comprising an organic semiconductor material and a second organic solvent; Mixing the composite doping solution and the organic semiconductor solution to produce a mixed solution; And Coating the mixed solution on a substrate to form a thin film, and evaporating the organic solvent in the thin film.

2. The method according to claim 1, wherein the first organic solvent has a larger dielectric constant value than the second organic solvent.

3. The method according to claim 2, wherein the first organic solvent has a dielectric constant value of 16 to 50 at room temperature.

4. The method according to claim 2, wherein the second organic solvent has a dielectric constant value of 1 to 15 at room temperature.

5. The method according to claim 3, wherein the first organic solvent comprises at least one selected from acetone, acetonitrile (ACN), dimethylformamide (DMF), and combinations thereof.

6. The method according to claim 4, wherein the second organic solvent comprises at least one selected from dichlorobenzene (DCB), ethyl acetate (EtOAc), and combinations thereof.

7. The method according to claim 1, wherein the combination of the organic compound and the Lewis acid is inhibited in the mixed solution, and in the thin film from which the organic solvent has been evaporated, the organic semiconductor material is doped with a composite doping compound formed by the combination of the organic compound and the Lewis acid.

8. The method according to claim 7, wherein the combination forms a Lewis pair formed by the cyano group (C≡N) of the organic compound and the Lewis acid.

9. The method according to claim 1, wherein the organic semiconductor material comprises an alkyl side chain in its molecular structure.

10. A doped organic semiconductor thin film, comprising: A composite dopant compound in which an organic compound having a resonance structure and a Lewis acid are combined, the resonance structure having at least one cyano group (C≡N); and An organic semiconductor material doped with the composite dopant compound.

11. The doped organic semiconductor thin film according to claim 10, wherein the combination of the organic compound and the Lewis acid forms a Lewis pair between the cyano group (C≡N) of the organic compound and the Lewis acid.

12. The doped organic semiconductor thin film according to claim 11, wherein the thin film is formed using a composite doping solution comprising the organic compound, the Lewis acid, and an organic solvent, and the combination of the organic compound and the Lewis acid is formed after evaporation of the organic solvent while forming the thin film.

13. The doped organic semiconductor thin film according to claim 12, wherein the organic solvent has a dielectric constant value of 16 to 50 at room temperature.

14. The doped organic semiconductor thin film according to claim 13, wherein the organic solvent comprises at least one selected from acetone, acetonitrile (ACN), dimethylformamide (DMF), and combinations thereof.

15. The doped organic semiconductor thin film according to claim 10, wherein the organic semiconductor material contains an alkyl side chain in its molecular structure.

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