• Macromolecular Research
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• v.14 no.6
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• pp.630-633
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• 2006

In heterojunction photovoltaic devices of $ITO/TiO_2/poly$(3-alkylthiophene)/Au, the photo current was characterized at different temperatures for different alkyl chain lengths and regioregularities: regiorandom, regioregular poly(3-hexylthiophene), and regioregular poly(3-dodecylthiophene). The regioregularity and alkyl chain length affected the photovoltaic characteristics due to differences in hole-carrier transportation. The drift charge mobilities of these devices were analyzed by the space-charge-limited current theory using the relation between the dark current and the bias voltage. The photocurrent in the devices based on poly(3-alkylthiophene)s decreased rapidly below the temperature at which the drift charge mobility was $10^{-5}\;cm^2/V{\cdot}s$.

• Korean Journal of Optics and Photonics
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• v.2 no.2
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• pp.108-113
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• 1991

This paper describes the necessity and utility of Langmuir-Blodgett (L-B) methods in developing molecular electronic devices. It also covers the application area and limitations of the methods. With L-B methods, the membrane thickness can be controlled in a range of 50 nm and 1000 nm depending on nature of the materials and layering methods. The molecular arrangement within the membrane can be altered by altering the surface pressure and nature of the layering materials. Such a variation can be altered by altering the surface pressure and nature of the layering materials. Such a variation can offer a new application of the methods to the future electronic devices. More over 2nd and 3rd nonlinearity generated in the nonsymmetric thin membrane will be used in the development of the optoelectronic devices.

• Electronics and Telecommunications Trends
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• v.33 no.6
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• pp.81-93
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• 2018

Metamaterials are artificial media that can control the properties of waves at will. Active photonic metadevice technologies cover the device and material technologies that control the visible and IR light through an external signal (mainly an electrical signal). The application areas of active photonic metadevices are tremendous for example holography, active HOE, bio imaging, IR imaging, telecommunication, and optoelectronic devices. In this paper, the technical trends and prospects of active metamaterials, active meta holography, active meta devices, nano-optical telecommunication devices, and IR imaging meta devices are reviewed.

• Bulletin of the Korean Chemical Society
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• v.35 no.2
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• pp.505-512
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• 2014

A new donor-accepter-donor-accepter-donor (D-A-D-A-D) type 2,1,3-benzothiadiazole-thiophene-based acceptor unit 2,5-di(4-(5-bromo-4-octylthiophen-2-yl)-2,1,3-benzothiadiazol-7-yl)thiophene ($DTBTTBr_2$) was synthesized. Copolymerized with fluorene and indeno[1,2-b]fluorene electron-rich moieties, two alternating narrow band gap (NBG) copolymers PF-DTBTT and PIF-DTBTT were prepared. And two copolymers exhibit broad and strong absorption in the range of 300-700 nm with optical band gap of about 1.75 eV. The highest occupied molecular orbital (HOMO) energy levels vary between -5.43 and -5.52 eV and the lowest unoccupied molecular orbital (LUMO) energy levels range from -3.64 to -3.77 eV. Potential applications of the copolymers as electron donor material and $PC_{71}BM$ ([6,6]-phenyl-$C_{71}$ butyric acid methyl ester) as electron acceptors were investigated for photovoltaic solar cells (PSCs). Photovoltaic performances based on the blend of PF-DTBTT/$PC_{71}BM$ (w:w; 1:2) and PIF-DTBTT/$PC_{71}BM$ (w:w; 1:2) with devices configuration as ITO/PEDOT: PSS/blend/Ca/Al, show an incident photon-to-current conversion efficiency (IPCE) of 2.34% and 2.56% with the open circuit voltage ($V_{oc}$) of 0.87 V and 0.90 V, short circuit current density ($J_{sc}$) of $6.02mA/cm^2$ and $6.12mA/cm^2$ under an AM1.5 simulator ($100mA/cm^2$). The photocurrent responses exhibit the onset wavelength extending up to 720 nm. These results indicate that the resulted narrow band gap copolymers are viable electron donor materials for polymer solar cells.

• Nuclear Engineering and Technology
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• v.52 no.12
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• pp.2860-2866
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• 2020

Oxide dispersion-strengthened materials W-1wt%Pr₂O₃ and W-1wt%La₂O₃ were synthesized by wet chemical method and spark plasma sintering. The field emission scanning electron microscopy (FE-SEM) analysis, XRD and Vickers microhardness measurements were conducted to characterize the samples. The irradiations were carried out with a 5 keV helium ion beam to fluences up to 5.0 × 10²¹ ions/m² under 600 ℃ using the low-energy ion irradiation system. Transmission electron microscopy (TEM) study was performed to investigate the microstructural evolution in W-1wt%Pr₂O₃ and W-1wt%La₂O₃. At 1.0 × 10²⁰ He⁺/m², the average loops size of the W-1wt%Pr₂O₃ was 4.3 nm, much lower than W-1wt% La₂O₃ of 8.5 nm. However, helium bubbles were not observed throughout in both doped W materials. The effects of pre-irradiation with 1.0 × 10²¹ He⁺/m² on trapping of injected deuterium in doped W was studied by thermal desorption spectrometry (TDS) technique using quadrupole mass spectrometer. Compared with the samples without He⁺ pre-irradiation, deuterium (D) retention of doped W materials increased after He⁺ irradiation, whose retention was unsaturated at the damage level of 1.0 × 10²²D₂⁺/m². The present results implied that irradiation effect of He⁺ ions must be taken into account to evaluate the deuterium retention in fusion material applications.

• Korean Journal of Materials Research
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• v.20 no.5
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• pp.241-245
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• 2010

One of the weak points of the Cr-doped SZO is that until now, it has only been fabricated on perovskite substrates, whereas NiO-ReRAM devices have already been deposited on Si substrates. The fabrication of RAM devices on Si substrates is important for commercialization because conventional electronics are based mainly on silicon materials. Cr-doped ReRAM will find a wide range of applications in embedded systems or conventional memory device manufacturing processes if it can be fabricated on Si substrates. For application of the commercial memory device, Cr-doped $SrZrO_3$ perovskite thin films were deposited on a $SrRuO_3$ bottom electrode/Si(100)substrate using pulsed laser deposition. XRD peaks corresponding to the (112), (004) and (132) planes of both the SZO and SRO were observed with the highest intensity along the (112) direction. The positions of the SZO grains matched those of the SRO grains. A well-controlled interface between the $SrZrO_3$:Cr perovskite and the $SrRuO_3$ bottom electrode were fabricated, so that good resistive switching behavior was observed with an on/off ratio higher than $10^2$. A pulse test showed the switching behavior of the Pt/$SrZrO_3:Cr/SrRuO^3$ device under a pulse of 10 kHz for $10^4$ cycles. The resistive switching memory devices made of the Cr-doped $SrZrO_3$ thin films deposited on Si substrates are expected to be more compatible with conventional Si-based electronics.

• Proceedings of the Polymer Society of Korea Conference
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• 2006.10a
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• pp.74-75
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• 2006

In organic opto-electronic applications, such as light emitting diodes (LEDs) and photovoltaic devices (PVDs), the morphology of the active layer is of crucial importance. To control the morphology of the active layer the self-assembling properties of block copolymers was used. Several rod-coil semiconducting diblock copolymers consisting of a conjugated block and a second coil block functionalized with electron transporting and/or accepting materials (such as $C_{60}$) were synthesized. The conjugated block acting as light absorbing, electron donating and hole transporting material. The donor/acceptor photovoltaic devices performance with active layer the above mentioned semiconducting block copolymers will be presented.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.99-99
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• 2014

Transparent oxide semiconductors (TOSs) are. currently attracting attention for application to transparent electrodes in optoelectronic devices and active channel layers in thin-film transistors. One of the key issues for the realization of next generation transparent electronic devices such as transparent complementary metal-oxide-semiconductor thin-film transistors (CMOS TFTs), transparent wall light, sensors, and transparent solar cell is to develop p-type TOSs. In this talks, I will introduce issues and status related to p-type TOSs such as LnCuOQ (Ln=lanthanide, Q=S, Se), $SrCu_2O_2$, $CuMO_2$ (M=Al, Ga, Cr, In), ZnO, $Cu_2O$ and SnO. The growth and properties of SnO and Cu-based oxides and their application to electronic devices will be discussed.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.11a
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• pp.175-177
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• 2002

Electrical characteristics of the Si-O superlattice diode as a function of annealing conditions have been studied. The nanocrystalline silicon/adsorbed oxygen superlattice formed by molecular beam epitaxy (MBE) system. Consequently, the experimental results of superlattice diode with multilayer Si-O structure showed the stable and good insulating behavior with high breakdown voltage. This is very useful promise for Si-based optoelectronic and quantum device as well as for the replacement of silicon-on-insulator (SOI) in ultra high speed and lower power CMOS devices in the future, and it can be readily integrated with silicon ULSI processing.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.11a
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• pp.202-205
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• 2002

The photoluminescence (PL) characteristics of the silicon-oxygen(Si-O) superlattice formed by molecular beam epitaxy (MBE) were studied. To confirm the presence of the nanocrystalline Si structure, Raman scattering measurement was performed. The blue shift was observed in the PL peak of the oxygen-annealed sample, compared to the hydrogen-annealed sample, which is due to a contribution of smaller crystallites. Our results determine the right direction for the fabrication of silicon-based optoelectronic and quantum devices as well as for the replacement of silicon-on-insulator (SOI) in high-speed and low-power silicon MOSFET devices in the future.