jaehyun lee - Academia.edu (original) (raw)

Papers by jaehyun lee

SID Symposium Digest of Technical Papers, 2013

ABSTRACT We describe two novel blue emission materials based on a new type of dual core concept. ... more ABSTRACT We describe two novel blue emission materials based on a new type of dual core concept. 1-Phenyl-6-(10-phenyl-anthracen-9-yl)-pyrene (Ph-AP-Ph) and 1-[1,1';3',1"]terphenyl-5'-yl-6-(10-[1,1';3',1"]terphenyl-5'-yl-anthracen-9-yl)-pyrene (TP-AP-TP) were synthesized through boronylation and Suzuki coupling reactions. The T-g values of Ph-AP-Ph and TP-AP-TP were 228 degrees C and 243 degrees C, respectively, compared to values of 135 degrees C and 139 degrees C for the single core materials 9-(3',5'-diphenylphenyl)-10-(3'",5'"-diphenylbiphenyl-4"-yl)anthracene (MAM) and 1,6-bis-[1,1';3',1"]terphenyl-5'-yl-pyrene (TP-P-TP). One of the dual core derivatives, TP-AP-TP, exhibited an ELmax value of 456 nm and a high luminance EQE of 7.51% when used in an EL device. The dual core chromophore materials had narrower PL and EL spectra and better thermal properties than the single core chromophore materials. A device based on TP-AP-TP showed twice the lifetime of a device based on the commercialized material, 2-methyl-9,10-bis(naphthalen-2-yl)anthracene (MADN).

Journal of Vacuum Science & Technology A: Vacuum, Surfaces, and Films, 2010

A technique involving a combination of using self-assembled nanomask and anisotropic plasma etchi... more A technique involving a combination of using self-assembled nanomask and anisotropic plasma etching is developed for fabricating vertically aligned single-crystalline Si nanowires (SiNWs). The SiNWs are shown to have excellent field emission performance with the turn-on field as low as 0.8 MV∕m and the threshold field being 5.0 MV∕m. In addition, an emission current density of 442 mA∕cm2 can be obtained at an applied field of ∼14 MV∕m. The technique is easily employed to fabricate arrays of SiNW-based field emission microtriodes. Mechanisms are proposed to explain the formation of the SiNWs and the observed field emission properties.

Journal of Nanoscience and Nanotechnology, 2014

New three indenofluorenedione derivatives were synthesized and proposed for electron transporting... more New three indenofluorenedione derivatives were synthesized and proposed for electron transporting layer (ETL). Three compounds are indeno[1,2-b]fluorene-6,12-dione (IF-dione), 2,8-Difluoro-indeno[1,2-b]fluorene-6,12-dione (Mono-F-lF-dione), and 1,2,3,7,8,9-Hexafluoro-indeno[1,2- b]fluorene-6,12-dione (Tri-F-IF-dione). UV-visible (UV-Vis) absorption of three compounds in THF solution state showed different absorption maximum values as follows: 292, 318 and 334 nm (IF-dione), 289, 314 and 329 nm (Mono-F-IF-dione), 285, 319 and 334 nm (Tri-F-IF-dione). Three compounds were inserted between emitting layer (EML) and cathode electrode as an ETL in OLED device: ITO/2-TNATA (60 nm)/NPB (15 nm)/Alq3 (30 nm)/synthesized compounds (30 nm)/LiF (1 nm)/Al (200 nm). I-V characteristics of three devices were investigated at 20 mA/cm2. Operating voltages of three compounds were 7.06 V (IF-dione), 6.42 V (MonoF-IF-dione), 5.36 V (TriF-IF-dione), respectively.

Journal of Nanoscience and Nanotechnology, 2014

New hole injection layer (HIL) materials for organic light-emitting diodes (OLEDs) based on pheno... more New hole injection layer (HIL) materials for organic light-emitting diodes (OLEDs) based on phenothiazine and phenoxazine were synthesized, and the electro-optical properties of the synthesized materials were examined by UV-vis and photoluminescence spectroscopy, and by cyclic voltammetry. 10,10 0 -bis(4-tert-butylphenyl)-N7,N7 0 -di(naphthalen-1-yl)-N7,N7 0 -diphenyl-10H,10 0 H-3,3 0 -biphenoxazine-7,7 0 -diamine (1-PNA-BPBPOX) showed glass transition temperatures (T g ) of 161°C, which was higher than that (110°C) of Tris(N-(naphthalen-2-yl)-N-phenyl-amino) triphenylamine (2-TNATA), a commercial HIL material. The HOMO levels of the synthesized materials were 4.9-4.8 eV, indicating a good match between the HOMO of indium tin oxide (ITO) (4.8 eV) and the HOMO of N,N 0 -bis(naphthalen-1-yl)-N,N 0 -bis(phenyl)benzidine (NPB) (5.4 eV), a common hole transfer layer (HTL) material. Because the synthesized materials showed minimal absorption at wavelengths shorter than 450 nm, they have good potential for use as effective HIL materials. The synthesized materials were used as the HIL in OLED devices, yielding power efficiencies of 2.8 lm/W (1-PNA-BPBPOX) and 2.1 lm/W (2-TNATA). These results indicate that 1-PNA-BPBPOX yields a higher power efficiency, by a factor of 33%, than the 2-TNATA commercial HIL material. Also, 1-PNA-BPBPOX exhibited a longer device lifetime than 2-TNATA.

Journal of Nanoscience and Nanotechnology, 2013

New blue emitting materials, 7-diphenylamino-4-methyl-coumarin (DPA-MC) and amino-tri(4-methylcou... more New blue emitting materials, 7-diphenylamino-4-methyl-coumarin (DPA-MC) and amino-tri(4-methylcoumarin) (T-MC) including coumarin moiety were synthesized by Ullman reaction. Optical and electronic properties were examined by UV-Vis. Absorption spectrum, PL spectrum, and cyclic voltammetry. UV-Vis. spectra of DPA-MC and T-MC in a film state showed maximum absorption wavelengths of 382 nm and 399 nm, respectively. PL spectra of DPA-MC and T-MC show maximum emission wavelengths of 463 nm and 481 nm respectively. Non-doped OLED devices were fabricated by using the synthesized materials as an emitting material layer. DPA-MC compound showed highly efficient luminescence properties. EL spectrum of DPA-MC exhibited a maximum value of 463 nm and DPA-MC device provided luminescence efficiency of 3.83 cd/A, power efficiency of 2.46 Im/W, external quantum efficiency of 3.71% and CIE coordinates of (0.154, 0.190) at a current density of 10 mA/cm2. In particular, Power efficiency increased by more than 1.6 times in DPA-MC (2.46 ImNW), which is higher than commercialized material, DPVBi (1.46 Im/W). High EL performance might come from ambipolar effects of a molecular structure.

Journal of Banking & Finance, 2010

This paper provides an empirical basis for identifying insider transactions by deriving a theoret... more This paper provides an empirical basis for identifying insider transactions by deriving a theoretical model, which incorporates the relationship between insider transactions and time series of stock returns. Thus, this model enables us detecting insider transactions by applying stock return time series. We show that when there is an insider transaction in the market, time series can be derived as an ARMA(1,1) process having closed solution coefficients. For validation of the model, we test publicly released insider transactions and reverse takeover events using the minute-by-minute stock price data. The selected events show higher pass rate of the detection criteria than the current detection system which shows that our model produces smaller Type II error than the existing post transaction-based cumulative abnormal return model.

IEICE Transactions on Electronics, 2011

Deoxyribonucleic Acid Sensitive Graphene Field-Effect Transistors

IEEE Electron Device Letters, 2000

ABSTRACT

Chemistry of Materials, 2011

ABSTRACT We developed high-performance stable n-type organic field-effect transistors (OFETs) usi... more ABSTRACT We developed high-performance stable n-type organic field-effect transistors (OFETs) using indenofluorenediones with different numbers of fluorine substituents (MonoFIF- dione, DiF-IF-dione, and TriF-IF-dione). Top-contact OFETs were fabricated via the vacuum deposition of indenofluorenediones as the semiconducting channel material on polystyrenetreated SiO2/Si substrates. TriF-IF-dione FETs with Au source/ drain contacts exhibited good device performances, with a fieldeffect mobility of 0.16 cm2/(V s), an on/off current ratio of 106, and a threshold voltage of 9.2 V. We found that the electrical stability for OFETs based on indenofluorenedione improved with the number of fluorine substituents, which was attributed to higher activation energies for charge trap creation. Moreover, the TriF-IF-dione FETs yielded excellent environmental stability properties, because the LUMO energy levels were relatively low, compared with those of the MonoF-IF-dione FETs.

Asia-Pacific Journal of Financial Studies, 2009

In this paper we perform theoretical and empirical analyses on the insiders' optimal "stealth" st... more In this paper we perform theoretical and empirical analyses on the insiders' optimal "stealth" strategy and expected profits from mimicking trading when the insiders' trading information is publicly available. When insiders select a mixed strategy of AR (1) process as the information exposure strategy in a multi-period model, we find the optimal AR (1) coefficient that maximizes the insiders' profit is negative. Also, (1) the greater the transaction volume of mimicking traders in the market and the longer the information exposure period, the closer the optimum AR (1) coefficient becomes to -1; (2) The larger the mimicking transaction volume, the smaller the insider's profit gets; and (3) When the volume of mimicking transaction is large and the private information is not much valuable, the likelihood of loss is high. We also validate certain theoretical results of our model using publicized ownership change data of major shareholders. As a result, we find the strategic evidences in the sample of insider transactions closing within 15 trading days. Also, although mimicking traders' losses have not been reported, they can suffer losses when the private information is not much valuable and the insiders take a significant strategic action.

Applied Physics Letters, 2012

ABSTRACT

SID Symposium Digest of Technical Papers, 2013

ABSTRACT We describe two novel blue emission materials based on a new type of dual core concept. ... more ABSTRACT We describe two novel blue emission materials based on a new type of dual core concept. 1-Phenyl-6-(10-phenyl-anthracen-9-yl)-pyrene (Ph-AP-Ph) and 1-[1,1';3',1"]terphenyl-5'-yl-6-(10-[1,1';3',1"]terphenyl-5'-yl-anthracen-9-yl)-pyrene (TP-AP-TP) were synthesized through boronylation and Suzuki coupling reactions. The T-g values of Ph-AP-Ph and TP-AP-TP were 228 degrees C and 243 degrees C, respectively, compared to values of 135 degrees C and 139 degrees C for the single core materials 9-(3',5'-diphenylphenyl)-10-(3'",5'"-diphenylbiphenyl-4"-yl)anthracene (MAM) and 1,6-bis-[1,1';3',1"]terphenyl-5'-yl-pyrene (TP-P-TP). One of the dual core derivatives, TP-AP-TP, exhibited an ELmax value of 456 nm and a high luminance EQE of 7.51% when used in an EL device. The dual core chromophore materials had narrower PL and EL spectra and better thermal properties than the single core chromophore materials. A device based on TP-AP-TP showed twice the lifetime of a device based on the commercialized material, 2-methyl-9,10-bis(naphthalen-2-yl)anthracene (MADN).

Journal of Vacuum Science & Technology A: Vacuum, Surfaces, and Films, 2010

A technique involving a combination of using self-assembled nanomask and anisotropic plasma etchi... more A technique involving a combination of using self-assembled nanomask and anisotropic plasma etching is developed for fabricating vertically aligned single-crystalline Si nanowires (SiNWs). The SiNWs are shown to have excellent field emission performance with the turn-on field as low as 0.8 MV∕m and the threshold field being 5.0 MV∕m. In addition, an emission current density of 442 mA∕cm2 can be obtained at an applied field of ∼14 MV∕m. The technique is easily employed to fabricate arrays of SiNW-based field emission microtriodes. Mechanisms are proposed to explain the formation of the SiNWs and the observed field emission properties.

Journal of Nanoscience and Nanotechnology, 2014

New three indenofluorenedione derivatives were synthesized and proposed for electron transporting... more New three indenofluorenedione derivatives were synthesized and proposed for electron transporting layer (ETL). Three compounds are indeno[1,2-b]fluorene-6,12-dione (IF-dione), 2,8-Difluoro-indeno[1,2-b]fluorene-6,12-dione (Mono-F-lF-dione), and 1,2,3,7,8,9-Hexafluoro-indeno[1,2- b]fluorene-6,12-dione (Tri-F-IF-dione). UV-visible (UV-Vis) absorption of three compounds in THF solution state showed different absorption maximum values as follows: 292, 318 and 334 nm (IF-dione), 289, 314 and 329 nm (Mono-F-IF-dione), 285, 319 and 334 nm (Tri-F-IF-dione). Three compounds were inserted between emitting layer (EML) and cathode electrode as an ETL in OLED device: ITO/2-TNATA (60 nm)/NPB (15 nm)/Alq3 (30 nm)/synthesized compounds (30 nm)/LiF (1 nm)/Al (200 nm). I-V characteristics of three devices were investigated at 20 mA/cm2. Operating voltages of three compounds were 7.06 V (IF-dione), 6.42 V (MonoF-IF-dione), 5.36 V (TriF-IF-dione), respectively.

Journal of Nanoscience and Nanotechnology, 2014

New hole injection layer (HIL) materials for organic light-emitting diodes (OLEDs) based on pheno... more New hole injection layer (HIL) materials for organic light-emitting diodes (OLEDs) based on phenothiazine and phenoxazine were synthesized, and the electro-optical properties of the synthesized materials were examined by UV-vis and photoluminescence spectroscopy, and by cyclic voltammetry. 10,10 0 -bis(4-tert-butylphenyl)-N7,N7 0 -di(naphthalen-1-yl)-N7,N7 0 -diphenyl-10H,10 0 H-3,3 0 -biphenoxazine-7,7 0 -diamine (1-PNA-BPBPOX) showed glass transition temperatures (T g ) of 161°C, which was higher than that (110°C) of Tris(N-(naphthalen-2-yl)-N-phenyl-amino) triphenylamine (2-TNATA), a commercial HIL material. The HOMO levels of the synthesized materials were 4.9-4.8 eV, indicating a good match between the HOMO of indium tin oxide (ITO) (4.8 eV) and the HOMO of N,N 0 -bis(naphthalen-1-yl)-N,N 0 -bis(phenyl)benzidine (NPB) (5.4 eV), a common hole transfer layer (HTL) material. Because the synthesized materials showed minimal absorption at wavelengths shorter than 450 nm, they have good potential for use as effective HIL materials. The synthesized materials were used as the HIL in OLED devices, yielding power efficiencies of 2.8 lm/W (1-PNA-BPBPOX) and 2.1 lm/W (2-TNATA). These results indicate that 1-PNA-BPBPOX yields a higher power efficiency, by a factor of 33%, than the 2-TNATA commercial HIL material. Also, 1-PNA-BPBPOX exhibited a longer device lifetime than 2-TNATA.

Journal of Nanoscience and Nanotechnology, 2013

New blue emitting materials, 7-diphenylamino-4-methyl-coumarin (DPA-MC) and amino-tri(4-methylcou... more New blue emitting materials, 7-diphenylamino-4-methyl-coumarin (DPA-MC) and amino-tri(4-methylcoumarin) (T-MC) including coumarin moiety were synthesized by Ullman reaction. Optical and electronic properties were examined by UV-Vis. Absorption spectrum, PL spectrum, and cyclic voltammetry. UV-Vis. spectra of DPA-MC and T-MC in a film state showed maximum absorption wavelengths of 382 nm and 399 nm, respectively. PL spectra of DPA-MC and T-MC show maximum emission wavelengths of 463 nm and 481 nm respectively. Non-doped OLED devices were fabricated by using the synthesized materials as an emitting material layer. DPA-MC compound showed highly efficient luminescence properties. EL spectrum of DPA-MC exhibited a maximum value of 463 nm and DPA-MC device provided luminescence efficiency of 3.83 cd/A, power efficiency of 2.46 Im/W, external quantum efficiency of 3.71% and CIE coordinates of (0.154, 0.190) at a current density of 10 mA/cm2. In particular, Power efficiency increased by more than 1.6 times in DPA-MC (2.46 ImNW), which is higher than commercialized material, DPVBi (1.46 Im/W). High EL performance might come from ambipolar effects of a molecular structure.

Journal of Banking & Finance, 2010

This paper provides an empirical basis for identifying insider transactions by deriving a theoret... more This paper provides an empirical basis for identifying insider transactions by deriving a theoretical model, which incorporates the relationship between insider transactions and time series of stock returns. Thus, this model enables us detecting insider transactions by applying stock return time series. We show that when there is an insider transaction in the market, time series can be derived as an ARMA(1,1) process having closed solution coefficients. For validation of the model, we test publicly released insider transactions and reverse takeover events using the minute-by-minute stock price data. The selected events show higher pass rate of the detection criteria than the current detection system which shows that our model produces smaller Type II error than the existing post transaction-based cumulative abnormal return model.

IEICE Transactions on Electronics, 2011

Deoxyribonucleic Acid Sensitive Graphene Field-Effect Transistors

IEEE Electron Device Letters, 2000

ABSTRACT

Chemistry of Materials, 2011

ABSTRACT We developed high-performance stable n-type organic field-effect transistors (OFETs) usi... more ABSTRACT We developed high-performance stable n-type organic field-effect transistors (OFETs) using indenofluorenediones with different numbers of fluorine substituents (MonoFIF- dione, DiF-IF-dione, and TriF-IF-dione). Top-contact OFETs were fabricated via the vacuum deposition of indenofluorenediones as the semiconducting channel material on polystyrenetreated SiO2/Si substrates. TriF-IF-dione FETs with Au source/ drain contacts exhibited good device performances, with a fieldeffect mobility of 0.16 cm2/(V s), an on/off current ratio of 106, and a threshold voltage of 9.2 V. We found that the electrical stability for OFETs based on indenofluorenedione improved with the number of fluorine substituents, which was attributed to higher activation energies for charge trap creation. Moreover, the TriF-IF-dione FETs yielded excellent environmental stability properties, because the LUMO energy levels were relatively low, compared with those of the MonoF-IF-dione FETs.

Asia-Pacific Journal of Financial Studies, 2009

In this paper we perform theoretical and empirical analyses on the insiders' optimal "stealth" st... more In this paper we perform theoretical and empirical analyses on the insiders' optimal "stealth" strategy and expected profits from mimicking trading when the insiders' trading information is publicly available. When insiders select a mixed strategy of AR (1) process as the information exposure strategy in a multi-period model, we find the optimal AR (1) coefficient that maximizes the insiders' profit is negative. Also, (1) the greater the transaction volume of mimicking traders in the market and the longer the information exposure period, the closer the optimum AR (1) coefficient becomes to -1; (2) The larger the mimicking transaction volume, the smaller the insider's profit gets; and (3) When the volume of mimicking transaction is large and the private information is not much valuable, the likelihood of loss is high. We also validate certain theoretical results of our model using publicized ownership change data of major shareholders. As a result, we find the strategic evidences in the sample of insider transactions closing within 15 trading days. Also, although mimicking traders' losses have not been reported, they can suffer losses when the private information is not much valuable and the insiders take a significant strategic action.

Applied Physics Letters, 2012

ABSTRACT