Bismuth compound, composition for forming thin film comprising same, and method for synthesizing bismuth selenide by using same

Abstract

The present invention provides: a bismuth compound represented by chemical formula 1, which can be effectively usable as a thin film precursor; and a composition for forming a thin film, comprising same. In addition, the present invention provides a method for synthesizing bismuth selenide (Bi2Se3) with excellent uniformity and high purity by using the composition for forming a thin film. [Chemical formula 1] (In chemical formula 1, R1) to R12 are each independently linear or branched C1-C10 alkyl.)

Description

Bismuth compound, composition for forming a thin film containing the same, and method for synthesizing bismuth selenide using the same

[0001] The present invention relates to a bismuth compound, a composition for forming a thin film containing the same, and a method for synthesizing bismuth selenide (Bi2Se3) using the same.

[0002] Bismuth selenide (Bi2Se3) is a representative topological insulator. It is capable of absorbing light from a wide range of wavelengths due to the unique band structure generated on the surface caused by strong spin-orbit coupling, and is thus attracting attention as a material for broadband optical sensors with excellent response performance and stability.

[0003] Bismuth selenide has defects within the crystal that significantly affect its electrical properties. In particular, selenium deficiency can cause n-type conductivity, which can negatively affect the sensitivity and response speed of the optical sensor. Therefore, research is ongoing on precise processes to prevent the inclusion of impurities during the synthesis process.

[0004] In addition, in the case of the solution synthesis method that synthesizes by simultaneously dissolving bismuth and selenium precursors in a solvent, which was mainly used in the past, there is a limitation that it is difficult to apply to a large-area process due to low uniformity of crystals. Therefore, there is a need to develop a bismuth precursor that can be applied to a large-area process with excellent uniformity and a new method for synthesizing bismuth selenide using the same.

[0005] The present invention provides a novel bismuth compound and a method for producing the same.

[0006] In addition, the present invention provides a composition for forming a thin film comprising the bismuth compound.

[0007] In addition, the present invention provides a method for synthesizing bismuth selenide (Bi2Se3) using the composition for forming a thin film.

[0008] In addition, the present invention provides an optical sensor including the bismuth selenide (Bi2Se3).

[0009] The present invention provides a bismuth compound represented by the following chemical formula 1.

[0010] [Chemical Formula 1]

[0011]

[0012] (In the above chemical formula 1,

[0013] R 1 Inland R 12 are each independently a straight-chain or branched-chain C1-C10 alkyl.)

[0014] For example, the above R 1 Inland R 12 Each may independently be a straight-chain or branched-chain C1-C5 alkyl.

[0015] For example, the above R 1 Inland R 6 are C1-C5 alkyl of the same straight or branched chain; R 7 Inland R 12 may be C1-C5 alkyl of the same straight or branched chain.

[0016] For example, the above R 1 Inland R 6 are each independently a branched C3-C5 alkyl; R 7 Inland R 12 Each can independently be a straight-chain C1-C5 alkyl.

[0017] For example, the above R 1 Inland R 6 are C3-C5 alkyl of the same branched chain; R 7 Inland R 12 may be identical to each other and be straight-chain C1-C5 alkyl.

[0018] In addition, the present invention provides a composition for forming a thin film comprising the bismuth compound described above.

[0019] In addition, the present invention provides a method for manufacturing a bismuth-containing thin film using the above-described thin film forming composition.

[0020] In addition, the present invention provides a method for synthesizing bismuth selenide (Bi2Se3) using the composition for forming a thin film described above.

[0021] For example, the composition for forming the thin film may include an organic solvent.

[0022] For example, the method for synthesizing bismuth selenide (Bi2Se3) described above may include a) a step of coating a substrate by injecting the composition for forming a thin film; and b) a step of injecting selenium (Se) powder into the substrate and performing a heat treatment.

[0023] In addition, the present invention provides an organic photoelectric device comprising bismuth selenide (Bi2Se3) synthesized by the above-described synthesis method.

[0024] The bismuth compound according to the present invention has a novel structure including an alkoxyalkylamide ligand, has good thermal stability, excellent cohesion, and a high crystalline structure, and is therefore useful as a precursor for a bismuth-containing thin film, and further enables the production of a bismuth-containing thin film of higher quality.

[0025] In addition, the bismuth compound according to the present invention exists as a solid at room temperature and thus has good handleability.

[0026] In addition, when synthesizing bismuth selenide (Bi2Se3) using a composition for forming a thin film including a bismuth compound according to the present invention, bismuth selenide (Bi2Se3) can be synthesized with excellent uniformity and high purity even in a large-area process.

[0027] In addition, an optical sensor including bismuth selenide (Bi2Se3) synthesized by the method of synthesizing bismuth selenide (Bi2Se3) according to the present invention can implement excellent response performance and stability.

[0028] Figure 1 is a diagram showing the crystal structure of the bismuth compound [Bi(edpa)3]2 manufactured in Example 1.

[0029] Figure 2 is a thermogravimetric analysis (TGA) spectrum of the bismuth compound [Bi(edpa)3]2 manufactured in Example 1.

[0030] Figure 3 is a schematic diagram showing a method for synthesizing bismuth selenide.

[0031] Figure 4 shows the results of observing bismuth selenide synthesized in Example 6 using an optical microscope.

[0032] Figure 5 shows the Raman spectrum results of bismuth selenide synthesized in Example 6.

[0033] Figure 6 is an X-ray photoelectron spectroscopy (XPS) result spectrum of bismuth selenide synthesized in Example 6.

[0034] Figure 7 shows the optical absorption spectrum and optical band gap result spectrum of bismuth selenide synthesized in Example 6.

[0035] Figure 8 shows the results of analyzing the photocurrent change according to voltage of the photosensor manufactured in Example 7.

[0036] Figure 9 shows the results of analyzing the photocurrent change according to the power of the optical sensor manufactured in Example 7.

[0037] Hereinafter, the present invention will be described in more detail. Unless otherwise defined, the technical and scientific terms used herein have the meanings commonly understood by those of ordinary skill in the art to which this invention pertains. In the following description, descriptions of well-known functions and configurations that may unnecessarily obscure the gist of the present invention will be omitted.

[0038] As used herein, the singular forms may be intended to include the plural forms as well, unless the context clearly indicates otherwise.

[0039] Additionally, the term “includes” in this specification is an open-ended description equivalent to expressions such as “comprises,” “contains,” “has,” or “characterizes,” and does not exclude additional elements, materials, or processes not listed.

[0040] The numerical ranges used herein include the lower and upper limits and all values ​​within that range, increments logically derived from the shape and width of the defined range, all doubly defined values, and all possible combinations of the upper and lower limits of numerical ranges defined in different shapes. Unless otherwise specified herein, values ​​outside the defined range that may arise due to experimental error or rounding of values ​​are also included in the defined numerical range.

[0041] Unless otherwise specified herein, “about” may be considered a value within 30%, 25%, 20%, 15%, 10% or 5% of the stated value.

[0042] The term "alkyl" as used herein refers to an organic radical derived from an aliphatic hydrocarbon by the removal of a single hydrogen, and may include both linear and branched alkyls. The alkyl may have 1 to 10 carbon atoms, specifically 1 to 7 carbon atoms, specifically 1 to 5 carbon atoms. The linear alkyl includes, for example, methyl, ethyl, n-propyl, n-butyl, n-pentyl, n-hexyl, n-heptyl, and the branched alkyl includes, but is not limited to, isopropyl, sec-butyl, isobutyl, tert-butyl, isopentyl, 2-methylhexyl, 3-methylbutyl, 2-methylpentyl, 3-methylpentyl, 4-methylpentyl, 2-methylhexyl, 3-methylhexyl, 2-methylpentyl, 3-methylpentyl, 4-methylpentyl, 2-methylhexyl, 3-methylhexyl, 4-methylhexyl, 5-methylhexyl, 2,3-dimethylbutyl, 2,3-dimethylpentyl, 2,4-dimethylpentyl, and the like.

[0043] Additionally, the term “bismuth compound” in this specification can be represented by chemical formula 1 and has a meaning equivalent to the expression “bismuth precursor”.

[0044] Hereinafter, the present disclosure will be described in detail. However, this is merely exemplary and the present disclosure is not limited to the specific embodiments described as examples.

[0045] One aspect of the present invention provides a novel bismuth precursor capable of producing a bismuth-containing thin film, which is a bismuth compound represented by the following chemical formula 1.

[0046] [Chemical Formula 1]

[0047]

[0048] (In the above chemical formula 1,

[0049] R 1 Inland R 12 are each independently a straight-chain or branched-chain C1-C10 alkyl.)

[0050] According to one aspect, a bismuth compound has a highly crystalline structure with good thermal stability and excellent cohesion due to the structural features of the above chemical formula 1, for example, three alkoxyalkylamide ligands bonded to a bismuth element. In addition, due to the form of a binuclear structure including a bismuth central metal coordinated with a bridging oxygen atom, it is chemically more stable, and thus, when used as a thin film precursor, the elemental composition of the thin film can be easily controlled.

[0051] The bismuth compound according to the present invention can be deposited using various deposition methods, and a high-density, high-purity bismuth-containing thin film can be manufactured at a high deposition rate.

[0052] For example, in the chemical formula 1 above, R 1 Inland R 12 Each may independently be a straight-chain or branched-chain C1-C5 alkyl.

[0053] For example, the bismuth compound may be selected from the following structures.

[0054]

[0055] As a specific example, the above R 1 Inland R 6 are C1-C5 alkyl of the same straight or branched chain; R 7 Inland R 12 may be C1-C5 alkyl of the same straight or branched chain.

[0056] For example, in the chemical formula 1 above, R 1 Inland R 6 are each independently a branched C3-C5 alkyl; R 7 Inland R 12 Each can independently be a straight-chain C1-C5 alkyl.

[0057] As a specific example, the above R 1 Inland R 6 are C3-C5 alkyl of the same branched chain; R 7 Inland R 12 may be identical to each other and be straight-chain C1-C5 alkyl.

[0058] For example, in the chemical formula 1 above, R 1 Inland R 6 are identical to each other i-propyl or t-butyl; R 7 Inland R 12 can be methyl, ethyl or n-propyl, each of which is identical to the other.

[0059] For example, the above R 1 Inland R 6 are identical to each other as t-butyl; R 7 Inland R 12 can be identically ethyl.

[0060] Specifically, the bismuth compound according to one aspect may be selected from the structures below, but is not limited thereto.

[0061]

[0062]

[0063] Hereinafter, a method for producing a bismuth compound represented by the chemical formula 1 according to one embodiment is specifically described, but it is of course possible to synthesize the bismuth compound by other methods that can be recognized by a person skilled in the art, and the organic solvent used therein is not limited, and the reaction time and temperature can also be changed within a range that does not deviate from the core of the invention.

[0064] According to one aspect, the bismuth compound represented by the above chemical formula 1 may be prepared by reacting a compound represented by the following chemical formula 2 and a compound represented by the following chemical formula 3.

[0065] [Chemical Formula 2]

[0066] BiX3

[0067] [Chemical Formula 3]

[0068]

[0069] (In the above chemical formulas 2 and 3,

[0070] X is a halogen;

[0071] R 21 and R 22 are each independently a straight-chain or branched-chain C1-C10 alkyl;

[0072] M is an alkali metal.)

[0073] For example, in the above chemical formulas 2 and 3, X is Cl; R 21 and R 22 are each independently a straight or branched C1-C5 alkyl; M may be Na.

[0074] The above reaction is carried out at 10 to 30°C for 1 to 15 hours, specifically at 20 to 30°C for 5 to 15 hours, but is not limited thereto and may vary depending on the type and amount of reactant and solvent used.

[0075] In the above reaction, for 1 mole of the compound of the chemical formula 2, the compound of the chemical formula 3 can be used in an amount of 3.0 to 4.0 moles, preferably 3.0 to 3.5 moles.

[0076] According to one embodiment, all of the above reactions can be carried out in an organic solvent, and the usable organic solvent is not limited, but an organic solvent having high solubility for the above reactants can be used, and specifically, one or more mixed organic solvents selected from hexane, diethyl ether, toluene, tetrahydrofuran, etc. can be used.

[0077] After the above reaction, if necessary, the purity can be maximized by purification using filtration, extraction, recrystallization, distillation, sublimation, chromatography, etc.

[0078] The bismuth compound manufactured above is a stable solid at room temperature, is easy to handle, and can be used to manufacture a high-quality bismuth-containing thin film.

[0079] Another aspect of the present invention provides a composition for forming a thin film, comprising the bismuth compound.

[0080] A composition for forming a thin film according to one aspect includes a bismuth compound represented by the above chemical formula 1 as a thin film precursor, and the content of the bismuth compound in the composition may be included within a range that can be recognized by a person skilled in the art in consideration of the thin film formation conditions, the thickness of the thin film, the characteristics of the thin film, the use of the thin film, etc.

[0081] In addition, the present invention provides a method for manufacturing a bismuth-containing thin film using the composition for forming the thin film.

[0082] According to one aspect, the method for manufacturing the bismuth-containing thin film can provide the bismuth-containing thin film on a substrate through a known deposition method. Specifically, the deposition method can be a solution process or vacuum deposition.

[0083] For example, the solution process may be spin coating, drop casting, dip coating, spray coating, flow casting, screen printing, inkjet printing, and micro-contact printing.

[0084] For example, the vacuum deposition may be specifically chemical vapor deposition (CVD), plasma-enhanced chemical vapor deposition (PECVD), atomic layer deposition (ALD), low-pressure vapor deposition, plasma-enhanced atomic layer deposition, etc.

[0085] In addition, the present invention provides a method for synthesizing bismuth selenide (Bi2Se3) using the composition for forming a thin film.

[0086] The thin film forming composition according to one embodiment may include an organic solvent. The organic solvent is not particularly limited as long as it has high solubility in the bismuth compound according to one embodiment of the present invention. Specifically, one or more mixed organic solvents selected from hexane, diethyl ether, toluene, tetrahydrofuran, etc. may be used. Tetrahydrofuran is preferably used.

[0087] As an example, the method for synthesizing the bismuth selenide (Bi2Se3) is as follows:

[0088] a) a step of coating by injecting the composition for forming a thin film onto a substrate; and

[0089] b) A step of adding selenium (Se) powder to the substrate and performing heat treatment may be included.

[0090] A method for synthesizing bismuth selenide (Bi2Se3) according to an embodiment of the present invention can synthesize bismuth selenide (Bi2Se3) with excellent uniformity, so that it can be usefully used in large-area processes, and has the advantage of being able to synthesize bismuth selenide (Bi2Se3) with excellent purity by minimizing the inclusion of impurities during the synthesis process.

[0091] In a method for synthesizing bismuth selenide (Bi2Se3) according to one aspect, all of the above reactions can be performed under an inert gas atmosphere such as nitrogen or argon.

[0092] For example, the step a) may be performed by various methods of forming a thin film using a solution process, and preferably may be performed by at least one method selected from spin coating, drop casting, dip coating, spray coating, flow casting, screen printing, inkjet printing, and micro-contact printing, and more preferably may be performed by a spin coating method.

[0093] For example, the substrate is not limited to a conventional substrate, and non-limiting examples thereof include a substrate including one or more semiconductor materials selected from the group consisting of Si, SiO2, Pt, TiN, Ge, SiGe, GaP, GaAs, SiC, SiGeC, InAs, and InP; a Silicon On Insulator (SOI) substrate; a quartz substrate; or a glass substrate for a display; a flexible plastic substrate such as polyimide, polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polymethyl methacrylate (PMMA), polycarbonate (PC), polyethersulfone (PES), and polyester; and the like, but is not limited thereto.

[0094] In a method for synthesizing bismuth selenide (Bi2Se3) according to an embodiment, a step of hydrophilic treatment of the surface of the substrate may be performed prior to step a) to improve coatability, and specifically, hydrophilic treatment may be performed through UV light treatment, plasma treatment, or discharge treatment, but is not necessarily limited thereto.

[0095] In a method for synthesizing bismuth selenide (Bi2Se3) according to one embodiment, the bismuth compound and selenium powder according to one embodiment can be used in a weight ratio of 1:0.5 to 3, or a weight ratio of 1:0.5 to 2, or a weight ratio of 1:0.5 to 1.5, but the present invention is not necessarily limited thereto, and is preferred because it can have a better purity in the said range.

[0096] In a method for synthesizing bismuth selenide (Bi2Se3) according to a preferred embodiment, the composition for forming a thin film may contain 0.1 to 10.0 wt%, or 1.0 to 8.0 wt%, or 3.0 to 6.0 wt% of the bismuth compound according to an embodiment of the present invention, but is not necessarily limited thereto.

[0097] For example, step b) may be performed at a pressure of 0.5 to 2.0 Torr and a temperature of 100 to 500°C under an inert transport gas. Specifically, the inert transport gas may be argon gas, and may be performed at a pressure of 1.0 to 2.0 Torr and a temperature of 200 to 400°C. Specifically, the heat treatment time may be performed for 1 minute to 3 hours, or 1 minute to 60 minutes, or 10 minutes to 40 minutes, but is not necessarily limited thereto.

[0098] In a method for synthesizing bismuth selenide (Bi2Se3) according to one embodiment, a step of removing an organic solvent by heating the coated substrate after step a) may be further included. Specifically, the heating may be performed at a temperature of 50 to 200°C, or a temperature of 70 to 130°C, but is not necessarily limited thereto and may vary depending on the type of organic solvent used.

[0099] According to a method for synthesizing bismuth selenide (Bi2Se3) according to one aspect of the present invention, even if bismuth selenide (Bi2Se3) is synthesized in the form of a thin film and manufactured through a large-area process, excellent uniformity and reproducibility can be achieved.

[0100] For example, according to a method for synthesizing bismuth selenide (Bi2Se3) according to one aspect of the present invention, the thickness of the bismuth selenide (Bi2Se3) layer formed on the substrate may be 5 to 50 nm.

[0101] In addition, the present invention provides an organic photoelectric device comprising bismuth selenide (Bi2Se3) synthesized by the above-described synthesis method. Any device in which bismuth selenide (Bi2Se3) according to one embodiment can be used is not limited, and non-limiting examples thereof include an organic light-emitting diode, an organic solar cell, or an organic photosensor, and preferably an organic photosensor.

[0102] Bismuth selenide (Bi2Se3) synthesized by a method for synthesizing bismuth selenide (Bi2Se3) according to an aspect has excellent purity due to minimal inclusion of impurities during the synthesis process, and thus an organic photoelectric device including a photoactive layer containing the bismuth selenide (Bi2Se3) can realize excellent response performance and stability.

[0103] Hereinafter, embodiments of the present invention will be described in detail so that those skilled in the art can easily implement them. However, the present invention may be implemented in various different forms and is not limited to the embodiments described herein.

[0104] The bismuth compound according to the present invention is 1 H NMR spectrum, 13 The structure of the obtained bismuth compound was analyzed through C NMR spectrum and elemental analysis.

[0105] Additionally, thermogravimetric analysis (TGA) was used to determine the thermal stability, volatility, and decomposition temperature of the manufactured bismuth compound. TGA analysis was performed by heating the obtained compound to 800°C at a rate of 10°C / min under an argon atmosphere, while injecting argon gas at a pressure of 1.5 bar / min.

[0106] [Example 1] Preparation of bismuth compound 1: [Bi(edpa)3]2

[0107]

[0108] Step 1: N-ethoxy-2,2-dimethylpropanamide (edpaH) (6 mmol, 0.787 g) and 25 mL of tetrahydrofuran were placed in a flask, 1.2 equivalents of NaH (7.2 mmol, 0.173 g) were added, and the mixture was stirred at room temperature for 12 h. (Caution: H2 gas will be generated.) After stirring, the remaining NaH was removed by filtration. The filtered solution was purified under reduced pressure to remove tetrahydrofuran, obtaining Na(edpa) (white solid, 0.971 g, yield 97%).

[0109] Step 2: In another flask, add BiCl3 (3.9 mmol, 1.224 g) and 25 mL of toluene, add 3.2 equivalents of Na(edpa) (12.4 mmol, 2.076 g), and stir at room temperature for 12 h. The produced NaCl was filtered and the pressure was reduced to obtain [Bi(edpa)3]2 (white solid, 1.372 g, yield 55%).

[0110] 1 H NMR (C6D6, 500 MHz): δ 4.02 (q, 2H), 1.44 (s, 9H), 1.10 (t, 3H).

[0111] 13 C NMR (C6D6, 125 MHz): δ 169.01, 69.49, 38.03, 28.33, 15.21.

[0112] Anal. Calcd for C 42 H 84 N6O6Bi2: C, 39.32; H, 6.60; N, 6.55. Found: C, 39.47; H, 6.59; N, 6.52.

[0113] The crystal structure of the bismuth compound 1 ([Bi(edpa)3]2) manufactured in FIG. 1 is illustrated, and FIG. 2 shows the spectrum resulting from TGA analysis. Referring to FIG. 2, a rapid mass decrease was observed around 190°C, and thereafter, a mass decrease of about 65% was observed at about 233°C. From the TGA analysis, it was confirmed that the bismuth compound of the present invention has excellent thermal stability.

[0114] [Example 2] Preparation of bismuth compound 2: [Bi(empa)3]2

[0115]

[0116] Step 1: N-ethoxy-2-methylpropanamide (empaH) (5 mmol, 0.656 g), 25 mL of hexane, and 3 mL of tetrahydrofuran were placed in a flask, 1.2 equivalents of NaH (6 mmol, 0.144 g) were added, and the mixture was stirred at room temperature for 4 hours. (Caution: H2 gas will be generated.) After stirring, the remaining NaH was removed by filtration. The filtered solution was purified under reduced pressure to remove hexane and tetrahydrofuran, obtaining Na(empa) (white solid, 0.756 g, yield 99%).

[0117] Step 2: In another flask, BiCl3 (1 mmol, 0.315 g) and 25 mL of toluene were added, 3.2 equivalents of Na(empa) (3.2 mmol, 0.490 g) were added, and the mixture was stirred at room temperature for 12 h. The resulting NaCl was filtered and the pressure was reduced to obtain [Bi(empa)3]2 (light brown solid, 0.358 g, yield 60%).

[0118] 1 H NMR (C6D6, 500 MHz): δ 4.02 (q, 2H), 2.81 (br, 1H), 1.29 (d, 6H), 1.13 (t, 3H).

[0119] [Example 3] Preparation of bismuth compound 3: [Bi(mdpa)3]2

[0120]

[0121] Step 1: N-methoxy-2,2-dimethylpropanamide (mdpaH) (5 mmol, 0.656 g), 25 mL of hexane, and 3 mL of tetrahydrofuran were placed in a flask, 1.2 equivalents of NaH (6 mmol, 0.144 g) were added, and the mixture was stirred at room temperature for 4 hours. (Caution: H2 gas will be generated.) After stirring, the remaining NaH was removed by filtration. The filtered solution was purified under reduced pressure to remove hexane and tetrahydrofuran, obtaining Na(mdpa) (white solid, 0.756 g, yield 99%).

[0122] Step 2: In another flask, add BiCl3 (1 mmol, 0.315 g) and 25 mL of toluene, add 3.2 equivalents of Na(mdpa) (3.2 mmol, 0.490 g), and stir at room temperature for 12 h. The produced NaCl was filtered and the pressure was reduced to obtain [Bi(mdpa)3]2 (white solid, 0.409 g, yield 68%).

[0123] 1 H NMR (C6D6, 500 MHz): δ 3.58 (s, 3H), 1.39 (s, 9H).

[0124] 13 C NMR (C6D6, 125 MHz): δ 169.12, 60.56, 37.68, 28.11.

[0125] [Example 4] Preparation of bismuth compound 4: [Bi(epa)3]2

[0126]

[0127] Step 1: N-ethoxypropionamide (epaH) (6 mmol, 0.703 g) and 25 mL of hexane were placed in a flask, 1.2 equivalents of NaH (7.2 mmol, 0.173 g) were added, and the mixture was stirred at room temperature for 3 hours. (Caution: H2 gas will be generated.) After stirring, the remaining NaH was removed by filtration. The filtered solution was purified under reduced pressure to remove hexane, obtaining Na(epa) (white solid, 0.825 g, yield 99%).

[0128] Step 2: In another flask, add BiCl3 (1 mmol, 0.315 g) and 25 mL of toluene, add 3.2 equivalents of Na(epa) (3.2 mmol, 0.445 g), and stir at room temperature for 12 h. The produced NaCl was filtered and the pressure was reduced to obtain [Bi(epa)3]2 (brown solid, 0.345 g, yield 62%).

[0129] 1 H NMR (C6D6, 400 MHz): δ 4.01 (br, 2H), 2.33 (br, 2H), 1.29 (d, 6H), 1.16 (s, 3H).

[0130] [Example 5] Preparation of bismuth compound 5: [Bi(mpa)3]2

[0131]

[0132] Step 1: N-methoxypropionamide (mpaH) (9 mmol, 0.928 g) and 25 mL of tetrahydrofuran were placed in a flask, 1.2 equivalents of NaH (10.8 mmol, 0.259 g) were added, and the mixture was stirred at room temperature for 4 hours. (Caution: H2 gas will be generated.) After stirring, the remaining NaH was removed by filtration. The filtered solution was purified under reduced pressure to remove tetrahydrofuran, obtaining Na(mpa) (white solid, 1.104 g, yield 98%).

[0133] Step 2: In another flask, add BiCl3 (1 mmol, 0.315 g) and 25 mL of toluene, add 3.2 equivalents of Na(mpa) (3.2 mmol, 0.4 g), and stir at room temperature for 12 h. The produced NaCl was filtered and the pressure was reduced to obtain [Bi(mpa)3]2 (white solid, 0.291 g, yield 56%).

[0134] 1 H NMR (C6D6, 500 MHz): δ 3.61 (s, 3H), 2.26 (br, 2H), 1.16 (br, 3H).

[0135] [Example 6] Synthesis of bismuth selenide (Bi2Se3)

[0136] A bismuth precursor solution was prepared by mixing 0.2 g of the bismuth compound 1 ([Bi(edpa)3]2) prepared in Example 1 with a tetrahydrofuran solvent at a concentration of 5 wt% and stirring at room temperature for 60 minutes.

[0137] The SiO2 (thickness 300 nm) / Si(001) substrate was exposed to UV for 60 s to convert the surface of the substrate to a hydrophilic state. The bismuth precursor solution was applied to the hydrophilic surface-treated substrate, and the first spin coating (1000 rpm, 10 s) was performed, followed by the second spin coating (2000 rpm, 30 s). Then, the coated substrate was placed on a hot plate and heat-treated at 100°C for 2 minutes to remove the solvent. The substrate on which the solvent-removed single precursor film was formed was placed inside a thermal reactor (furnace), and then, at 1.5 Torr pressure and 300°C, 1000 sccm of argon transport gas was injected, and 0.2 g of selenium powder was heated for 30 minutes to synthesize bismuth selenide (Bi2Se3). A schematic diagram of the synthesis process of Example 6 above is shown in Figure 3.

[0138] In addition, the results of observing the bismuth selenide synthesized on the substrate using an optical microscope are shown in Fig. 4, through which it can be confirmed that the bismuth selenide is formed in the form of a uniform thin film over the entire surface.

[0139] Figure 5 is the Raman spectrum result of the synthesized bismuth selenide, and the typical phonon mode (A) of the bismuth selenide layered material 1 1g , E 2 g , A 2 1g ) was observed, confirming the successful synthesis of bismuth selenide layered material.

[0140] Figure 6 is the X-ray photoelectron spectroscopy spectrum of the synthesized bismuth selenide, and the synthesized two-dimensional bismuth selenide is Bi 3+ Wow Se 2- It was confirmed that the bismuth and selenium elements were combined in high purity without any impurity peaks such as oxides.

[0141] Figure 7 shows the optical absorption spectrum and optical band gap result spectrum of the synthesized bismuth selenide, and the optical absorption result and optical band gap value according to the wavelength of the synthesized two-dimensional bismuth selenide were confirmed. The tauplot calculation method was used based on the optical absorption spectrum, and the direct band gap of 1.3 eV and the indirect band gap value of 0.2 eV of the bismuth selenide material were confirmed.

[0142] [Example 7] Fabrication of an optical sensor

[0143] In Example 6, a two-terminal structure optical sensor was fabricated by sequentially depositing 5 nm thick Cr and 100 nm thick Au in selective areas using thermal evaporation and a shadow mask on a bismuth selenide sample synthesized on a SiO2 / Si substrate.

[0144] The results of the analysis of the photocurrent change according to the voltage of the photosensor are shown in Fig. 8. It was confirmed that the switching pattern was reliable as it showed good on / off regardless of the voltage for visible light (532 nm) and near-infrared (1064 nm) light sources, and it was confirmed that the photocurrent generated increased as the applied voltage increased.

[0145] The results of the analysis of the photocurrent change according to the power of the optical sensor are shown in Fig. 9. It was confirmed that the switching pattern was reliable as it showed good on / off regardless of the voltage for visible light (532 nm) and near-infrared (1064 nm) light sources, and it was confirmed that the photocurrent generated increased as the light source intensity increased.

[0146] That is, it was confirmed that the method for synthesizing bismuth selenide (Bi2Se3) according to the present invention can synthesize bismuth selenide with excellent uniformity and high purity, and that an organic photoelectric device employing this as a photoactive layer material has excellent response performance and stability.

[0147] While the embodiments of the present invention have been described in detail above, those skilled in the art will appreciate that various modifications and variations can be made to the present invention without departing from the spirit and scope of the invention as defined in the appended claims. Therefore, modifications to future embodiments of the present invention will not depart from the scope of the invention.

Claims

1. A bismuth compound represented by the following chemical formula 1: [Chemical Formula 1] In the above chemical formula 1, R 1 Inland R 12 are each independently a straight or branched C1-C10 alkyl.

2. In paragraph 1, The above R 1 Inland R 12 Bismuth compounds, each independently a straight or branched C1-C5 alkyl.

3. In paragraph 1, The above R 1 Inland R 6 are C1-C5 alkyl of the same straight or branched chain; R 7 Inland R 12 Bismuth compounds, which are C1-C5 alkyl of the same straight or branched chain.

4. In paragraph 1, The above R 1 Inland R 6 are each independently a branched-chain C3-C5 alkyl; R 7 Inland R 12 Bismuth compounds, each independently a straight-chain C1-C5 alkyl.

5. In paragraph 1, The above R 1 Inland R 6 are C3-C5 alkyl of the same branched chain; R 7 Inland R 12 Bismuth compounds, which are identical to each other and are straight-chain C1-C5 alkyl.

6. In paragraph 1, A bismuth compound, wherein the bismuth compound is selected from the following compounds.

7. A composition for forming a thin film, comprising a bismuth compound according to any one of claims 1 to 6.

8. A method for producing a bismuth-containing thin film using a thin film forming composition according to Article 7.

9. A method for synthesizing bismuth selenide (Bi2Se3) using a composition for forming a thin film according to Article 7.

10. In paragraph 9, A method for synthesizing bismuth selenide (Bi2Se3), wherein the composition for forming the above thin film comprises an organic solvent.

11. In paragraph 9, a) a step of coating by injecting the composition for forming a thin film onto a substrate; and b) a step of adding selenium (Se) powder to the substrate and performing heat treatment; including; A method for synthesizing bismuth selenide (Bi2Se3).

12. In paragraph 11, A method for synthesizing bismuth selenide (Bi2Se3), further comprising, after step a), a step of removing an organic solvent by heating the coated substrate.

13. In paragraph 11, A method for synthesizing bismuth selenide (Bi2Se3), wherein step b) is performed at a pressure of 0.5 to 2.0 Torr and a temperature of 100 to 500°C under an inert transport gas.

14. An organic photoelectric device comprising bismuth selenide (Bi2Se3) synthesized by a synthesis method according to any one of claims 9 to 13.

15. In paragraph 14, The above organic photoelectric device is an organic photoelectric device that is an organic light-emitting diode, an organic solar cell, or an organic photosensor.

Images