Ho-nyeon Lee

p-Channel Tin Monoxide Thin Film Transistor Fabricated by Vacuum Thermal Evaporation

By using tin monoxide films, p-channel oxide semiconductor thin film transistors were fabricated with a bottom-gate and bottom-contact structure. A p-type tin monoxide semiconductor thin film was obtained from tin monoxide powder by vacuum thermal evaporation. The as-deposited film showed an amorphous phase, and a polycrystalline tin monoxide was obtained by thermal annealing after the deposition. The hole concentration was on the order of 1017 cm-3, and the Hall mobility was 2.83 cm2 V-1 s-1. The resulting on-current/off-current ratio was more than 102, and the field-effect mobility was approximately 4×10-5 cm2 V-1 s-1.

Fabrication of highly efficient and stable doped red organic light-emitting device using 2-methyl-9,10-di(2-napthyl)anthracene and tris(8-hydroxyquinolinato)aluminum as cohost materials

The authors fabricated red organic light-emitting devices using DCJTB as red dopant, and blue-emitting MADN and green-emitting Alq3 as cohost materials for emission layers. The luminance efficiency of 2% DCJTB-doped Alq3(20%)∕MADN(80%) device was 5.42cd∕A at 20mA∕cm2, while that of equivalently doped Alq3 single-host device was 1.79cd∕A, and remained over 5.2cd∕A up to 200mA∕cm2. At the benchmark luminance of 7680cd∕m2, the power efficiency of DCJTB-doped Alq3∕MADN device was 4.1 times better than that of Alq3 single-host device. Moreover, the half-decay lifetime of DCJTB-doped Alq3∕MADN device measured at an initial luminance of 1000cd∕m2 was 14000h.

Characteristics of charged and metastable species in micro-discharges of AC- plasma display panel

The temporal effects of charged and metastable particles in the micro-discharges of an AC plasma display panel (AC-PDP) were investigated under actual driving conditions. The discharge gas used in the 4-in PDP was Neon + 4% Xenon. The discharge characteristics in terms of the time scale related to the space-charge decay, wall charge decay, metastable decay, and charge accumulation were investigated using a pulse technique. For Neon + 4% Xenon gas-mixture discharges of 500 torr, 4 /spl mu/s was related to the time scale of the space-charge decay and wall-charge accumulation time. The minimum sustain voltage started to dramatically increase at 20 /spl mu/s, which was related to the time scale of the metastable particles. Whereas, after 40 /spl mu/s, the minimum sustain voltage slowly increased with a slope of 0.01581, which was related to the inverse of the time scale of the wall charge decay.

Effect of helium addition on discharge characteristics in a flat fluorescent lamp

The discharge characteristics of a multielectrode dual coplanar in a mercury-free flat fluorescent lamp were investigated using brightness-efficiency measurement and the infrared (IR) spectrum and intensified charge coupled device (ICCD) characteristics. The level of brightness was above 14900cd∕m2 under the conditions of neon-–50% xenon–8% He gas composition, 150Torr pressure, and 20kHz alternating current pulse. The ICCD results revealed a faster and wider discharge with a Ne–50% Xe–8% He gas composition. The effect of adding helium (He) to Ne–50% Xe revealed a faster peak emission, as confirmed by ICCD images. From the gated IR emission spectrum, the intensity ratio of I823nm∕I828nm was ∼8% higher with Ne–50% Xe–8% He than with Ne–50% Xe under the same pressure and applied voltage conditions.

P-16: Integration of the 4.5″ Active Matrix Organic Light-emitting Display with Organic Transistors

We developed an active matrix organic light-emitting display(OLED) on a glass using two organic thin-film transistors(OTFTs) and a capacitor in a pixel. The OTFTs has bottom contact structure with a unique gate insulator and pentacene for the active layer. The width and length of the switching OTFT is 500 μm and 10 μm respectively and the driving OTFT has 900 μm channel width with the same channel length. The characteristics of the OTFTs were examined by test cells around display area and generated images on the panel. The mobility was 0.3 cm2V−1S−1 and the current on/off ratio was 106. The uniformity and stability were confirmed through still and moving images on the panel. The organic light-emitting layers were fabricated by shadow mask process and color fluorescence materials were used for the emitting layers. The resolution of the panel is 64×RGB×64 in 4.5 inch diagonal and the aperture ratio was 25%.

A Study on Characteristics of Microcrystalline-silicon Films Fabricated by PECVD Method

Characteristics of microcrystalline-silicon thin-films deposited by plasma-enhanced chemical-vapor deposition (PECVD) method were studied. There were optimum values of RF power density and dilution ratio ; maximum grain size of about 35 nm was obtained at substrate temperature of 250 with RF power density of 1.1 W/ and dilution ratio of 0.91. Larger grain was obtained with higher substrate temperature up to 350 . Grain size dependence on RF power density and dilution ratio could be explained by etching effects of hydrogen ions and changes of species of reactive precursors on growing surface. Surface-mobility activation of reactive precursors by temperature could be a reason of grain-size dependence on the substrate temperature. Microcrystalline-silicon thin-films that could be used for flat-panel electronics such as active-matrix organic-light-emitting-diodes are expected to be fabricated successfully using these results.

Passivation Layers for Organic Thin-film-transistors

Inorganic layers, such as SiOxNy and SiOx deposited using plasma sublimation method, were tested as passivation layer for organic thin-film-transistors (OTFTs). OTFTs with bottom-gate and bottom-contact structure were fabricated using pentacene as organic semiconductor and an organic gate insulator. SiOxNy layer gave little change in characteristics of OTFTs, but SiOx layer degraded the performance of OTFTs severely. Inferior barrier properties related to its lower film density, higher water vapor transmission rate (WVTR) and damage due to process environment of oxygen of SiOx film could explain these results. Polyurea and polyvinyl acetates (PVA) were tested as organic passivation layers also. PVA showed good properties as a buffer layer to reduce the damage come from the vacuum deposition process of upper passivation layers. From these results, a multilayer structure with upper SiOxNy film and lower PVA film is expected to be a superior passivation layer for OTFTs.

Efficient Organic Light-emitting Diodes with Aluminum-doped Zinc Oxide Anodes

Properties of organic light-emitting diodes (OLEDs) with aluminum-doped zinc oxide (ZnO:Al) anodes showed different behaviors from OLEDs with indium tin oxide (ITO) anodes according to driving conditions. OLEDs with ITO anodes gave higher current density and luminance in lower voltage region and better EL and power efficiency under lower current density conditions, However, OLEDs with ZnO:Al anodes gave higher current density and luminance in higher voltage region over about 8V and better EL and power efficiency under higher current density over . These seemed to be due to the differences in conduction properties of semiconducting ZnO:Al and metallic ITO. OLEDs with ZnO:Al anodes showed nearly saturated efficiency under high current driving conditions compared with those of OLEDs with ITO anodes. This meant better charge balance in OLEDs with ZnO:Al anodes. These properties of OLEDs with ZnO:Al anodes are useful in making bright display devices with efficiency.

Integration of 4.5” active matrix organic light‐emitting display with organic transistors

Abstract We developed a 4.5” 192x64 active matrix organic light‐emitting diode display on a glass using organic thin‐film transistor (OTFT) switching‐arrays with two transistors and a capacitor in each sub‐pixel. The OTFTs has bottom contact structure with a unique gate insulator and pentacene for the active layer. The width and length of the switching OTFT is 800 ? and 10? respectively and the driving OTFT has 1200? channel width with the same channel length. On/off ratio, mobility, on‐current of switching OTFT and on‐current of driving OTFT were 106,0.3∼0.5 cm2/V•sec, order of 10 μA and over 100 μA, respectively. AMOLEDs composed of the OTFT switching arrays and OLEDs made using vacuum deposition method were fabricated and driven to make moving images, successfully.