• Bulletin of the Korean Chemical Society
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• v.33 no.9
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• pp.2897-2902
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• 2012

New photovoltaic donor materials, 4,4'-(2,2'-bithiazole-5,5'-diyl)bis(N,N-diphenylbenzenamine) (BDT) and 4-(2,2'-bithiazol-5-yl)-N,N-diphenylbenzenamine (BT), were synthesized. A solution processable triphenylamine-containing bithiazole (BDT and BT) was blended with a [6,6]-phenyl $C_{61}$ butyric acid methyl ester (PCBM) acceptor to study the performance of small-molecule-based bulk heterojunction (BHJ) photovoltaic devices. Optimum device performance was achieved after annealing, for device with a BDT/PCBM ratio of 1:4. The open-circuit voltage, short-circuit current, and power conversion efficiency of the device with the aforementioned BDT/PCBM ratio were 0.51 V, 4.10 $mA\;cm^{-2}$, and 0.68%, respectively, under simulated AM 1.5 solar irradiation (100 $mW\;cm^{-2}$).

• Bulletin of the Korean Chemical Society
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• v.31 no.7
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• pp.1941-1944
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• 2010

The heterojunction structures of BiOCl/$Bi_3O_4Cl$, exhibiting considerable visible-light photocatalytic efficiency, were prepared by a simple wet-chemical process at ambient condition. The prepared nanocomposites were characterized by XRD, TEM, and UV-visible diffuse reflectance spectra. Under visible light (${\lambda}\geq$420 nm) irradiation, BiOCl/$Bi_3O_4Cl$ exhibited an enhanced photocatalytic activity in decomposing 2-propanol (IP) in gas phase and salicylic acid (SA) in aqueous solution, whereas the bare BiOCl and $Bi_3O_4Cl$ showed negligible activities. It is deduced that the remarkable visible-light photocatalytic activity of the BiOCl/$Bi_3O_4Cl$ originates from the hole $(h^+)$ transfer between VB of the $Bi_3O_4Cl$ and BiOCl semiconductors.

• Bulletin of the Korean Chemical Society
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• v.34 no.7
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• pp.2148-2154
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• 2013

Three push-pull organic semiconductors, TPA-$Th_3$-MMN (1), TPA-ThTT-MMN (2), and TPA-ThDTT-MMN (3), comprising a triphenylamine donor and a methylene malononitrile acceptor linked by various ${\pi}$-conjugated thiophene units were synthesized, and the effects of the ${\pi}$-conjugated bridging unit on the photovoltaic characteristics of solution-processed small-molecule organic solar cells based on these semiconductors were investigated. Planar bridging units with extended ${\pi}$-conjugation effectively facilitated intermolecular ${\pi}-{\pi}$ packing interactions in the solid state, resulting in enhanced $J_{sc}$ values of the SMOSCs fabricated with bulk heterojunction films.

• Proceedings of the IEEK Conference
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• 2000.06b
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• pp.286-289
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• 2000

PHEMT's with three different doping structures, -SH(single-heterojunction), DH (double-heterojunction), and DC(doped-channel)-,were designed, fabricated and characterized to study the effect of doping layer structures on the performance of millimeter-wave PHEMT's. 0.25${\mu}{\textrm}{m}$ DH-PHEMT with below-channel doping of 1$\times$10$^{12}$ c $m^{-2}$ was superior to SH-PHEMT by 40％ in $I_{dss}$, 20％ in f/sib T/ and showed broador gm- $I_{D}$ characteristics which is advantageous to power applications DH-PHEMT showed similar DC and small-signal performance compared with DC-PHEMT. Taking the much higher carrier mobility into considerations, DH-PHEMT is believed to be the best candidate for millimeter-wave, low-noise and/or power applications.s.s.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.39 no.10
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• pp.16-24
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• 2002

In this paper, we fabricated heterojunction phototransistors(HPT's) with optically transparent ITO emitter contacts. Heterojunction transistors(HBT's) having the same device layout were fabricated to compare with HPT's. The model parameters of the devices were extracted and compared. Emitter contact resistance(RE) of the HPT was about 6.4$\Omega$, which was very similar to that of HBT and the other DC model parameters of the Inp/InGaAs HPT showed the similarities to those of the HIBT.

• JSTS:Journal of Semiconductor Technology and Science
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• v.16 no.2
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• pp.215-220
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• 2016

Monolithically integrated devices are strongly desired in next generation power ICs to reduce the chip size and improve the efficiency and frequency response. Three examples of the embedment of different functional diode(s) into AlGaN/GaN heterojunction field-effect transistors are presented, which can minimize the parasitic effects caused by interconnection between devices.

• Proceedings of the Korean Vacuum Society Conference
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• 2015.08a
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• pp.243.2-243.2
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• 2015

We report a high-performing nanoscale NiO thin film grown by thermal oxidation of sputtered Ni film. The structural, physical, optical and electrical properties of nanoscale NiO were comprehensively investigated. A quality transparent heterojunction (NiO/ZnO) was formed by large-area applicable sputtering deposition method that has an extremely low saturation current of 0.1 nA. Considerable large rectification ratio of more than 1000 was obtained for transparent heterojunction device. Mott-Schottky analyses were applied to develop the interface of NiO and ZnO by establishing energy diagrams. Nanoscale NiO has the accepter carrier concentration of the order of 1018 cm-3. Nanoscale NiO Schottky junction device properties were comprehensively studied using room temperature impedance spectroscopy.

• Proceedings of the Korean Vacuum Society Conference
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• 2015.08a
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• pp.249.1-249.1
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• 2015

Quantum dots (QDs) are attracting growing attention for photovoltaic device applications because of their unique electronic, optical and physical properties. Lead sulfide (PbS) QDs are one of the most widely studied materials for the devices and known to have size-tunable properties. In this context, we investigated the relationship between the size of PbS QDs and two synthesizing conditions, a concentration of ligand, oleic acid in this work, and injection temperature. The inverted colloidal quantum dot solar cells based on the heterojunction of n-type zinc oxide layer and p-type PbS QDs were also fabricated. The size of the QDs and cell properties were observed to depend on both the QD synthesizing conditions, and hence the overall efficiency of the cell could vary even though the size of QDs used was same. The QD synthesizing conditions were finally optimized for the maximum cell efficiency.

• 한국신재생에너지학회:학술대회논문집
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• 2009.06a
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• pp.77-79
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• 2009

Amorphous/crystalline silicon heterojunction solar cells, TCO/a-Si:H (p)/c-Si(n)/a-Si:H(n)/Al, are investigated. The influence of various parameters for the front structures was studied. We used thin (10 nm) a-Si:H(p) layers of amorphous hydrogenated silicon are deposited on top of a thick ($500{\mu}m$) crystalline c-Si wafer. This work deals with the influence of the a-Si:H(p) doping concentration on the solar cell performance is studied.

• 한국신재생에너지학회:학술대회논문집
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• 2011.05a
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• pp.128.1-128.1
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• 2011

In amorphous silicon and crystalline silicon(a-Si:H/c-Si) heterojuction solar cells, intrinsic hydrogenated amorphous silicon(a-Si:H) films play an important role to passivate the crystalline silicon wafer surfaces. We have studied the correlation between the surface passivation quality and nature of the Si-H bonding at the a-Si:H/c-Si interface. The samples were obtained by VHF-CVD under different deposition conditions. The passivation quality and analysis of all structures studied was performed by means of quasi steady state photoconductance(QSSPC) methods and fourier transform infrared spectrometer(FTIR) measurements respectively.