As one of organic electroluminescent (EL) materials, we developed a method of fabricating an ink using low molecular- weight materials with a long emission lifetime for application to the inkjet method. Although the emission lifetime is usually long for low molecular-weight materials, their high manufacturing cost due to the necessity of vapor deposition is a disadvantage. We utilized the low molecular-weight material, tris-(8-hydroxyquinoline) aluminum (Alq3), and investigated its dispersibility in a solvent in which it has low solubility. In addition, we ascertained whether the material could maintain its photoluminescence characteristic under the irradiation of ultraviolet rays by investigating the emission of photoluminescence. Alq3 was crystallized into nanosize crystals, whose surface was then coated with a primary amine by the gas evaporation method. The fabricated ink contained crystals with an average size of 250nm and high dispersibility in tetradecane, in which Alq3 is insoluble. Thus, we made it possible to carry out an inkjet method with low molecular weight EL materials.

We carried out degradation analysis of a blue phosphorescent organic light emitting diode by both impedance spectroscopy and transient electroluminescence (EL) spectroscopy. The number of semicircles observed in the Cole-Cole plot of the modulus became three to two after the device was operated for 567 hours. Considering the effective layer thickness of the initial and degraded devices did not change by degradation and combining the analysis of the Bode-plot of the imaginary part of the modulus, the relaxation times of emission layer and hole-blocking with electron transport layers changed to nearly the same value by the increase of the resistance of emission layer. Decay time of transient EL of the initial device was coincident with that of the degraded one. These phenomena suggest that no phosphorescence quenching sites are generated in the degraded device, but the number of the emission sites decrease by degradation.

The historical review of Taiwan's researching activities on the features of PECVD grown SiOx are also included to realize the performance of Si nanocrystal based MOSLED made by such a Si-rich SiOx film with embedded Si nanocrystals on conventional Si substrate. A surface nano-roughened Si substrate with interfacial Si nano-pyramids at SiOx/Si interface are also reviewed, which provide the capabilities of enhancing the surface roughness induced total-internal-reflection relaxation and the Fowler-Nordheim tunneling based carrier injection. These structures enable the light emission and extraction from a metal-SiOx-Si MOSLED.

A new technique incorporating combinatorial deposition to develop thin-film phosphors by r.f. magnetron sputtering is demonstrated using subdivided powder targets. In comparison with development using conventional r.f. magnetron sputtering, the atomic ratios of Si and Ge as well as the Mn content in Zn2Si1-XGeXO4:Mn thin film phosphors could be more efficiently optimized in order to obtain the highest intensity in electroluminescent and photoluminescent emissions. High luminances of 11800 and 1536 cd/m2 were obtained in Zn2Si0.6Ge0.4O4:Mn thin-film electroluminescent devices fabricated under optimized conditions and driven at 1 kHz and 60 Hz, respectively.

The driving frequency dependence of EL characteristics were investigated in thick ceramic insulating type thin-film electroluminescent (TFEL) devices with various Mn-activated Y2O3-based phosphor thin-film emitting layers driven by a sinusoidal wave voltage. High luminous efficiencies of approximately 10 and 1 lm/W were obtained in the TFEL devices driven at 60 Hz and 1 kHz, respectively. The difference in luminous efficiency was mainly caused by the increase of input power in 1 kHz-driven-devices resulting from a dielectric loss of a thick BaTiO3 ceramic sheet used as the insulating layer. The correlation between the sound emission from the devices and the effective power consumed in the devices was found with variations in both the applied voltage and the frequency. The higher input power of the 1 kHz-driven-device may be attributable to sound emissions resulting from the piezo-electricity of BaTiO3 ceramics.

Electroluminescence (EL) under alternating-current (ac) operation is first reported for n+-polysilicon/SiO2/p-Si MOS capacitors with 50 nm Si-implanted SiO2. Visible EL can be observed with the naked eye in the dark. The ac operation by pulse-wave distinctly enhances the EL intensity and its lifetime. The pulse frequency affects the EL spectrum and thus the EL color. A model of EL mechanism is proposed for the Si-implanted MOS EL device, which has a possibility of visible light emitting device.

Thin-film electroluminescent (TFEL) devices have been newly developed using Y2GeO5 oxide phosphor thin films prepared by r.f. magnetron sputtering. Multicolor emissions were observed in TFEL devices fabricated using various impurity-activated Y2GeO5 phosphor thin films. A high-luminance TFEL device was fabricated using a Y2GeO5:Mn thin film prepared with a Mn content of 2 at.% and postannealed at 1020: luminances of 414 and 3020 cd/m2 and luminous efficiencies of 6.7 and 0.93 lm/W for yellow emission when driven at 60 Hz and 1 kHz, respectively. Newly developed oxide Y2GeO5:Mn phosphors are very promising for use as the thin-film emitting layer of TFEL devices.

BaAl2S4:Eu thin-film EL device using a new blue emitting EL phosphor was prepared by the two targets pulse-electron-beam evaporation. The maximum luminance level was 65 cd/m2 under the 50 Hz pulse voltage. The EL spectrum had blue emission with a peak around 470 nm due to the transition for Eu2+ ion. The CIE color coordinates of BaAl2S4:Eu EL device were x = 0.12 and y = 0.10. The performance of blue-emitting BaAl2S4:Eu EL devices is shown to be sufficient for commercial color EL display in color purity and luminance level.

Gd2O2S:Tb phosphor thin films have been prepared using the simple technique of electron beam evaporation for large area display applications. The photoluminescence and excitation spectra measurement of Gd2O2S:Tb phosphor thin films suggest that Tb3+ is incorporated into the Gd2O2S lattice at gadolinium sites. Relatively efficient electroluminescence is observed from a ZnS/Gd2O2S:Tb/ZnS sandwich cell.

A 14. 4-in. diagonal EL display with 640128 pixels has been developed in red/green multicolor structures by using a new phosphor layer consisting of Zn1-xMgxS:Mn and ZnS:Mn. The display is designed for 240 Hz-frame rate, enabling the luminance to be improved by a factor of two. In addition, the contrast ratio is strongly enhanced by optimizing the black background structure and color filters. Improved characteristics make it possible for the EL panel to meet the requirements for the public information display taking advantages of high-reliability, crisp image and wide-viewing angle. Furthermore, the possibility of full-color EL displays will be described on the basis of "color by white" approach.

Electroluminescent (EL) devices with mixed single layer that consist of fluorescent dyes, distylylbiphenyl derivative (DPVBi) and triphenylamine derivative (TPD), are studied. Blue light emission was observed from the device with DPVBi and TPD. White emission over 2,500 cd/m2 was observed from the devices with mixed single layer of DPVBi, TPD and dicyanomethylene derivative (DCM).

Optical recording has been performed successfully by the preirradiation of light upon the precursor of poly (arylene vinylene) conducting polymers such as poly (p-phenylene vinylene) (PPV) and poly (1,4-naphthalene vinylene) (PNV) and subsequent thermal treatment. The effect has been tentatively interpreted in terms of the deterioration of the irradiated area of the precursor polymer in which polymerization is suppressed. Furthermore, an orange electroluminescent (EL) diode utilizing PNV has been demonstrated for the first time and the EL properties of PNV are discussed in comparison with those of EL diode utilizing PPV. The EL emission of these two devices are discussed in terms of radiative recombination of the singlet polaron exciton formed by the injection of electrons and holes, the difference of effective conjugation length and the interchain transfer of polaron excitons.