Electron transfer through an Langmuir-Blodgett(LB) monolayer film sandwiched between metal electrodes. We used an eicosanoic acid material and the material was very famous as a thin film insulating material. Eicosanoic acid monolayer was deposited by Langmuir-Blodgett(LB) technique and a subphase was a CdCl2 solution as a 2×10-4 mol/L. Also we used a bottom electrode as an Al/Al2O3 and a top electrode as a Al and Ti/Al. Here, the Al2O3 on the bottom electrode was deposited by thermal evaporation method. The Al2O3 layer was acted on a tunneling barrier and insulating layer in tunnel diode. It was found that the proper transfer surface pressure for film deposition was 25 mN/m and the limiting area per molecule was about 24 a2/molecule. When the positive and negative bias applied to the molecular device, the behavior shows that a tunnel switching characteristics. This result were analyzed regarding various mechanisms.

We investigated the effect of electron injection layer on the performance of organic light emitting devices (OLEDs). As an electron injection layer, the quinolate metal complexes were used. We optimized the device efficiency by varying the thickness of the quinolate metal complexes layer. The device with 1 nm of the quinolate metal complexes layer showed significant enhancement of the device performance and device lifetime. We also compared the effect of 8-hydroxyquinolinolatolithium (Liq) with that of bis(8-quinolinolato)-zinc (Znq2) and 8-hydroxyquinolinolatosodium (Naq) as an electron injection layer. As a result, Liq is considered as a better materials for the electron injection layer than Znq2 and Naq.

Diphosphine dinuclear gold(I) complexes were synthesized from the reaction of bridged diphosphines and gold ions. As a bridged diphosphine, 1,2-bis(diphenylphosphino)metbane (dppm) or 1,1'-Bis(diphenylphosphino) ferrocene (dppf) was introduced. As anionic ligands, CI was first coordinated to Au, resulting in (diphosphine)(AuCl)2. Then, the ligand, SPh, was substituted for Cl in the chloride complex to give (diphosphine)(AuSPh)2. As a result, three digold complexes, (dppm)(AuCl)2. (I), (dppf)(AuCl)2. (II), and (dppf)(AuSPh2. (III) were prepared in this study. The thermal properties were investigated at first hand to confirm that the gold complexes were in fact formed. The digold complexes were decomposed above 200℃ while the ligand, dppm or dppf, melts under 180℃ The photoluminescence (PL) spectra of the spin-coated thin films showed the maximum peak at 590, 595, and 540nm for the complex, I, II, and III, respectively. These complexes were found to give the orange color phosphorescence. Therefore, these digold complexes can be candidates for orange-red phosphorescent materials in organic electroluminescent devices (OELD). Further studies on application of the complexes as a dopant in an emitting layer are in progress in our laboratory.

Recently, the phosphorescent organic light-emitting devices (OLEDs) have been extensively studied for their high internal quantum efficiency. In this study, we synthesised several phosphorescent metal complexes, and certified their composition using NMR. We also investigated the characteristics of the phosphorescent OLEDs with the green emitting phosphor, Ir(ppy)3. The devices with a structure of indium-tin-oxide(ITO)/N,N'-diphenyl-N,N'-(3-methylphenyI-1,1'-biphenyl-4,4'-diamine (TPD)/metal complex doped in host materials/2,9-dimethyl-4,7-diphenyl-l,10-phenanthroline(BCP)/tris (8-hydroxyquinolinato) Aluminum(Alq3)/Li:Al/Al was fabricated, and its electrical and optical characteristics were studied. By changing the doping concentration of tris(2-phenylpyridine)iridium (Ir(ppy)3), we fabricated several devices and investigated their characteristics.

Organic semiconductors based on vacuum-deposited films of fused-ring polycyclic aromatic hydrocarbon have great potential to be utilized as an active layer for electronic and optoelectronic devices. In this study, pentacene thin films and electrode materials were deposited by Organic Molecular Beam Deposition (OMBD) and vacuum evaporation respectively. For the gate dielectric layer, photoacryl (OPTMER PC403 from JSR Co.) was spin-coated and cured at 220℃. Electrical characteristics of the device were investigated, where the channel length and width was 50 μm and 5 mm. It was found that field effect mobility was 0.039 cm2V-1s-1, threshold voltage was -8 V, and on/off current ratio was 106. Further details will be discussed.

By fabricating the organic light-emitting devices (OLEDs) based on phosphorescent material, the internal quantum efficiency can reach 100%, compared to 25% in the case of the fluorescent material. Thus, the phosphorescent OLEDs have recently been extensively studied and showed higher internal quantum efficiencies then the conventional OLEDs. In this study, we investigated the characteristics of the phosphorescent OLEDs, with the green emitting phosphor, Ir(ppy)3, (tris(2-phenylpyridine)iridium). The devices with a structure of ITO/TPD/Ir(ppy)3 doped in the host material /BCP/Alq3/Li:Al/Al were fabricated, and its electrical and optical characteristics were studied. By changing the doping concentration of Ir(ppy)3, we fabricated several devices and investigated the device characteristics. OLEDs doped into BCP by 10% showed the best characteristics. For 10% doped OLEDs, the maximum luminance of was over 10000 cd/m2, and the maximum power efficiency was 7.14 lm/W.

The effect of a-sexithiophene(α-6T) layers on the light emitting diode (LED) were studied. The α-6T was used for a buffer layer in electroluminescent (EL) devices. Enhanced carrier (hole) injection and improved emission efficiency were observed. Carrier injection characteristics were investigated as a function of α-6T later thickness. The efficiency of the electroluminescence was proportional to the thickness of α-6T layer. The highest efficiency was observed 600A of α-6T later, which was about 1.5 times higher than that of device without α-6T later. The device with a-6T showed an operation voltage lowered by 2V. The α-6T layer can substitute hole blocking layer, and control charge injection properties.

The tfTZ(4,4',4"-trifluoro-triazine) was used as a hole blocking material for the electroluminescent devices(ELDs) in this study. In general, the holes are outnumbered the electrons in hole transport and emitting layers because the hole transport is more efficient in most organic ELDs. The hole blocking layer are expected to control the excess holes to increase the recombination of holes and electrons and to decrease current density. The former study using the 2,4,6-triphenyl-1,3,5-triazine(TTA) as hole blocking layer showed that the TTA did not form stable films with vapor deposition technique. The tfTZ can generate stable evaporated films, moreover the fluorine group can lower the highest occupied molecular orbital(HOMO) level, which produces the energy barrier for the holes. The tfTZ has high electron affinities according to the data by the Cyclic-Voltammety(CV) method, which is developed for the measurement of HOMO and lowest occupied molecular orbital(LUMO) level of organic thin films. The lowered HOMO level is made the tfTZ to be applied for a hole blocking layer in ELDs. We fabricated multilayer ELDs with a structure of ITO/hole blocking layer(HBL)/hole transporting layer(HTL)/emitting layer/electrode. The hole blocking properties of this devices is confirmed from the lowered current density values compared with that without hole blocking layer.

Organic Electroluminescent devices(OELD) consisted of multilayer structures have been studied for the application the application to flat-panel display. Metal-chelate complexes, zinc bis(2-(2-hydroxyphenyl)benzoxazolate) (Zn(BOX)2) and zinc bis(2-(2-hydroxyphenyl)benzothiazolate) (Zn(BOX)2), have been intensively investigated as an white-light emitting layer and recognized to have good electroluminescent(EL) properties. In this study, (Zn(BOX)2) and (Zn(BTZ)2) were synthesized and characterized by FT-IR, 1H-NMR, UV-VIS and PL. Their EL properties were also studied and their ionization potential(IP) and electron affinity(EA) were also measured by cyclic voltammetry(CV).

A water-soluble conducting polymer (CPP400 Paste) containing a derivative of polythiophene with several dopant was investigated as an anode material for organic electroluminescent devices. The device of ITO/CPP 400 Paste/TPD/Alq3/Li:Al was fabricated, where CPP 400 Paste films were prepared by spin coating and TPD and Alq3, films were prepared by vacuum evaporation. It was found that the turn-on voltage, current density, and luminance of the devices were dependent upon the thickness of CPP 400 Paste film in the Electroluminescent and current-voltage characteristics of the devices. This phenomena were explained by the energy level diagram of the device with the energy levels of the CPP400 Paste obtained by cyclic voltammetric method.

Organic semiconductors based on conjugated thiophene oligomer have great potential to be utilized as an active layer for electronic and optoelectronic devices. In this study, a conjugated oligomer such as α-sexithiophene (α-6T) thin films was prepared by the Organic Molecular Beam Deposition (OMBD), and various electrode materials were also deposited by a simple vacuum evaporation, respectively. Those films were photolithographically patterned for the electrical measurements. Electrical charact-erization of the thin film transistor with various channel length were executed and the field effect mobility of these thin film transistors were also calculated by the formula using the experimental data.

Interfacial properties of electrode and organic thin layer is one of the most important factor in performing a Light Emitting Diodes(LED). Phthalocyanine copper was used as a buffer layer to improve interface characteristic, so that device efficiency was improved. In this study, LEDs were fabricated as like structures of Indium-Tin-Oxide (ITO) / N,N' -Diphenyl-N,N'-di(m-tolyl)-benzidine (TPD) / 8-Hydroxyquinoline aluminum(Alq) / Aluminum(Al) and Indium-Tin-Oxide(ITO) / N,N'-Diphenyl-N,N' -di(m-tolyl)-benzidine(TPD) / 2-(4-Biphenylyl)-5(4-tert-butyl-phenyl)-1,3,4-oxadiazole(PBD) / Aluminum(Al). In these devices, CuPC was layered at electrode/organic layer interface. As position is changing and thickness is changing, devices showed characteristic luminescence efficiency and luminescence inensity respectively. We showed in this study that luminescence efficiency was improved with CuPC layer in LEDs. The efficiency of device with layer CuPC is higher than that of 2 layer CuPC. However, the luminescence of 2 layer CuPC device got higher value.

The N-docosyl N'-methyl viologen-(TCNQ)2, (DMVT) was synthesized. We investigated the π-A isotherm of DMVT to find the optimal deposition condition. Temperature-dependent current-voltage characteristics of the DMVT LB films shows that there is an increase in conductivity at 330K or so. The in-plane electrical conductivity at room temperature is in the range of 10-7~10-6S/cm. From the plot of logarithmic conductivity as a function of reciprocal temperature, two types of activation energies, 0.04eV and 0.73eV, were obtained depending on the temperature range. The Ohmic behaviour was observed below 0.6V and the Schottky effect was confirmed at 2.5~6V, when the I-V characteristics was measured with Al/LB film/Al structure. I-V measurement for Al/LB film/ITO structure showed the asymmetrical I-V relationship, which resulted from the rectification property.

Recently, high luminance and efficiency were realize in organic thin film electroluminescence (EL) cells with multilayer structures including an emitting layer (EML), hole transporting layer (HTL), and an electron transporting layer (ETL). In this study, Bis(10-hydroxybenzo[h]quinolinato)beryllium (Bebq2) was synthesized. PL and EL characteristics of their thin film were investigated by fabricating the devices having a structure of ITO/PVK/Bebq2/Al, ITO/PVK dispersed with TPD/Bebq2/Al. The EL color of these device was greenish and the wavelength of their EL peaks was located, respectly, at 495nm, and 492.5nm.

Photo-crosslinkable polyimide(PI) which contains CF3 moiety was synthesized. Polarized UV light transformed ketone group of PI to hydroxyl group, which was confirmed by IR and UV-visible spectroscopy. We investigated the dichroic UV-absorption before and after photo-reaction with linearly polarized light. In particular we have attempted to clarify the relationship between the anisotropy of surface region and surface azimuthal anchoring energy and knew that the anchoring energy of photo-alignment PI is comparable with that of mechanical rubbing.

In this study, a new conducting materials, namely, a Schiff base (polymeric azomethine) was synthesized from 2,6-diamino-N-docosyl pyridinium bromide and terephthalaldehyde to obtain a soluble and fusible conducting polymer. The synthesized Schiff base structure was analyzed by using UV/vis absorption spectrophotometer, FT-IR spectrometer and 1H-NMR spectrometer. It was found that the Schiff base was successfully synthesized and soluble in carbon tetrachloride(CC14), its Langmuir-Blodgett film was easily fabricated, and its surface pressure was determined to be 30mN/m for solid state by measuring π-A isotherm.

Organic-based electroluminescent devices have attracted lots of interests because of their possible application as a large-area flat panel display. Polyimides have been used for photo-alignment in LCD(Liquid Crystal Display). However, the devices used in this study were fabricated with polyimide doped with N,N'-Diphenyl-N,N'-di(m-tolyl)-benzidine(TPD) (3, 10, 30wt%) for electroluminescent hole tranforting layer(EHTL). The photochemical and physical properties of EHTL was studied. The film thicknesses were reduced under illumination with UV light. Polyimide films doped with TPD(3wt%) was irradiated and the electrical properties of the films were studied.

In this study, organic electroluminescent devices(OELD) with a structure of a glass substrate/ITO/TPD/Tb(ACAC)3(Phen-Cl)/Alq3/Al was fabricated by vacuum evaporation method, where Tb complex was known to have green light emitting property. Electroluminescent(EL) and I-V characteristics of this structure were investigated. This triple-layer structure shows the green EL spectrum at the wavelwngth of 546nm, which is almost the same as the PL spectrum of Pb(ACAC)3(PhenCl). It was found in current-voltage(I-V) characteristics of the devices that the operating voltage was about 12V.

The polyimide film surface was modified with KOH aqueous solutions or sulfuric acid. The film thickness was increased by about 10% through the modification of film surface. Hydrolysis of amide bonds and hydration of water induced the increase. The polarity of the film surface increased and identified by contact angle measurement. The depth and roughness of modified was increased. After treatment of surface with water, alkyl and 4-pentyloxyaniline were introduced on the film surface by complex formation between anionic species formed on the imide surface and ammonium ion. The newly introduced alkyl group was identified by FT-IR spectroscopy. Surface polarity reduced dramatically and the roughness was increased after introduction of ammonium salt.

Thin films of Eu(TTA)3(phen), which was known to show red-light emitting properties, were deposited under various deposition condition. The thickness, surface morphology, and photoluminescence(PL) were measured with α-step profiler, Atomic Force Microscopy(AFM), and PL measurement apparatus. It was found that the thickness of Eu(TTA)3(phen) film can be controlled precisely by adjusting the amounts of Eu(TTA)3(phen) in the boat. As the thickness of these films increases, the surface roughness also increases. A structure of Al/Eu(TTA)3(phen)(850a)/TPD(600a)/ITO was fabricated, Electroluminescence(EL) spectrum of which shows the peak at the wavelength of 618nm.