GaN nanowire (NW)-based hybrid structures have attracted attention for optoelectronic applications due to their high surface area and efficient carrier transport. However, the optical transparency of GaN NWs is often limited by unintended residual species accumulated on the surface and in the inter-wire regions, as well as defect-related absorption, leading to reduced light transmission. In this work, we demonstrate that thermal annealing significantly improves the optical transparency of GaN NWs grown on indium tin oxide (ITO)/glass substrates. The transmittance increased from 47.9% to 78.5% at 550 nm after rapid thermal annealing at 800^oC for 3 min, while a comparable value (~75.5%) was achieved at 600^oC for 5 min. PbBr₃ was deposited onto the GaN NWs to form hybrid structures, and temperature-dependent photoluminescence (TDPL) measurements revealed enhanced emission stability with suppressed peak shift and reduced spectral broadening. Arrhenius analysis based on a two-channel model revealed that the activation energy of the dominant non-radiative recombination pathway increased from 62 meV in the as-grown sample to 85 meV after thermal annealing, while its relative contribution remained nearly unchanged. In contrast, the shallow trap-assisted pathway exhibited a similar activation energy of approximately 6 meV in both samples, but its contribution decreased from 0.35 to 0.17 after annealing. As a result, the internal quantum efficiency (IQE) improved from 75.9% to 87.4%. These results show that thermal annealing improves optical transparency by removing residuals and suppresses defect-related recombination, leading to enhanced carrier dynamics and improved optical performance of PbBr₃-based hybrid structures.

Cathodoluminescence (CL) spectroscopy provides valuable insights into the optical and electronic properties of materials by analyzing photon emission induced by electron beam excitation. In this study, we present a novel CL detection system integrated into a transmission electron microscope (TEM) specimen stage, enabling high-resolution optical analysis of internal microstructures. The system features a parabolic mirror, a focusing lens, and a UV-VIS range optical fiber to maximize light collection and transmission efficiency, with performance further enhanced by a liquid nitrogen cooling setup. Using this system, we successfully performed CL mapping of InGaN/GaN multiple quantum wells (MQWs) and GaN thin films. The results revealed that threading dislocations act as non-radiative centers in GaN and locally increase the bandgap energy in InGaN MQWs, causing a blue-shift in CL emission. These findings support a model in which dislocations induce carrier delocalization, preserving high radiative efficiency despite high dislocation densities. This work demonstrates the effectiveness of the TEM-integrated CL system for nanoscale optical characterization, offering a new pathway for studying defect-related phenomena in semiconductor materials.

Aggressive device scaling has severely degraded the switching characteristics of CMOS transistors. This issue has led to the development of tunneling FETs (TFETs) as an alternative. TFETs, with their asymmetric doping of the source and drain regions, offer improved subthreshold swing (SS) compared to conventional MOSFETs. However, despite this advantage, TFETs still suffer from ambipolar current, which increases off-state current (IOFF). This paper introduces an approach to applying hetero gate dielectrics (HGDs) in nanosheet (NS) TFETs to reduce ambipolar current characteristics. The magnitude of the drain electric field is reduced by selectively forming a high-k dielectric near the source region This configuration allows the TFETs to avoid unintended band-to-band tunneling (BTBT) and suppress ambipolar current during the off-state.

Eu³⁺-doped BaZrO₃ (BaZrO₃:Eu³⁺+) phosphor powders were prepared using a solid-state reaction by changing the molar concentration of Eu³⁺ within the range of 0.5 to 30 mol%. Irrespective of the molar concentration of Eu³⁺ ions, the crystal structures of all the phosphors were cubic. The excitation spectra of BaZrO₃:Eu³⁺+ phosphors consisted of an intense broad band centered at 277 nm in the range of 230~320 nm. The emission spectra were composed of a dominant orange band at 595 nm arising from the 5D0→7F1 magnetic dipole transition of Eu³⁺ and two weak emission bands centered at 574 and 615 nm, respectively. As the concentration of Eu³⁺ increased from 0.5 to 10 mol%, the intensities of all the emission bands gradually increased, approached maxima at 10 mol% of Eu³⁺ ions, and then showed a decreasing tendency with further increase in the Eu3+ ions due to the concentration quenching. The critical distance between neighboring Eu³⁺ ions for concentration quenching was calculated to be 11.21 Å, indicating that dipole-dipole interaction was the main mechanism of concentration quenching of BaZrO₃:Eu³⁺+ phosphors. The results suggest that the orange emission intensity can be modulated by doping the appropriate concentration of Eu³⁺ ions.

Mechanoluminescence (ML) is a phenomenon where the application of mechanical force to ML materials generates an electric field and produces light, holding significant promise as an eco-friendly technology. However, challenges in commercializing ML technology has arisen due to its low brightness and short luminous lifetime. To address this, in this work, we enhance ML efficiency by mixing carbon nanotubes (CNTs) into a ZnS: Cu embedded in a polydimethylsiloxane composite ML device. The inclusion of CNTs boosts ML intensity by 98% compared to devices without CNTs, as the increasing CNT fraction elevates conductivity, thereby amplifying ML intensity. However, this increase in CNT fraction also leads to enhanced light absorption within the device. Consequently, we observe a trend where ML intensity rises initially but declines beyond a CNT fraction of 0.0015 wt%. Based on these findings, we anticipate that our research will make valuable contributions to the advancement of electrical powerless mechanoluminescent technology.

The utilization of scanning transmission electron microscopy (STEM) in conjunction with cathodoluminescence (CL) has emerged as a valuable tool for the investigation of material optical properties. In recent years, this technique has facilitated significant advancements in the fields of plasmonics and quantum emitters by surpassing prior technical restrictions. The review commences by providing an outline of the diverse STEM-CL operating modes and technical aspects of the instrumentation. The review explains the fundamental physics of light production under electron beam irradiation and the physical basis for interpreting STEM-CL experiments for different types of excitations. Additionally, the review compares STEM-CL to other related techniques such as scanning electron microscope CL, photoluminescence, and electron energy-loss spectroscopy.

In this paper, laser-induced fluorescence properties of four plastics were characterized through spectrometer analysis for real-time microplastic counting. Recently, environmental problems related to microplastics have emerged. In order to detect microplastics, analysis methods such as FT-IR and Raman are used. However, they have the disadvantages of being timeconsuming and requiring a pretreatment process. In most plastic products on the market, 10% to 30% of plasticizers and reinforcing agents are added. Therefore, most microplastics present in seawater and freshwater emit fluorescence signals by 270 nm UV light source regardless of their type due to their molecular structure due to additives. Real-time microplastics counting is possible more easily by using the proposed laser-induced fluorescence detection method because of the fluorescence expression characteristic of 340 nm that appears due to the plasticizer of plastics.

Recently, as interest in appearance has increased, various studies on treatment method for short stature are being conducted. In this study, the effect of growth plate stimulation on the height growth of children and adolescents was studied. As a result of pre- and post-analysis of the experimental group, it was confirmed that the difference in average height according to growth plate stimulation was relatively large. In addition, in the results of analyzing the effects of demographic factors on the height growth of the experimental group and the control group, weight showed the greatest influence on height growth among the demographic factors affecting the height growth of the experimental group. The effect on the height growth of the control group was found to have an effect in the order of age, weight, and father’s height. The difference in height changed post-mortem between the experimental group and the control group was 1.10 cm for 3 months, and the difference was the result of growth plate stimulation. It was confirmed that growth plate stimulation had a significant effect on the height change of children and adolescents, except for weight, which is a common factor of height change in the experimental and control groups. Therefore, it is expected that it can be used as a treatment method for short stature.

A series of phosphors, SrWO₄:5 mol% Dy³⁺, SrWO₄:5 mol% Sm³⁺, and SrWO₄:5 mol% Dy³⁺:x Sm³⁺ (x＝1~15 mol%), were prepared using a facile co-precipitation. The crystal structure, morphology, photoluminescence properties, and application in anti-counterfeiting fields were investigated. The crystalline structures of the prepared phosphors were found to be tetragonal systems with the dominant peak occurring at the (112) plane. The excitation spectra of the Dy³⁺ singly-doped SrWO₄ phosphors were composed of an intense charge-transfer band centered at 246 nm in the range of 210~270 nm and two weak peaks at 351 nm and 387 nm due to the ⁶H_15/2→⁶P_7/2 and ⁶H_15/2→⁴I_13/2 transitions of Dy³⁺ ions, respectively. The wavelength of 246 nm was optimum for exciting the luminescence of Dy³⁺ and Sm³⁺ co-doped SrWO₄ phosphors. The emission spectra consisted of two intense blue and yellow emission bands at 480 nm and 573 nm corresponding to the ⁴F_9/2→⁶H_15/2 and ⁴F_9/2→⁶H_13/2 transitions of Dy³⁺, and two strong emission peaks at 599 nm and 643 nm originating from the ⁴G_5/2→⁶H_7/2 and ⁴G_5/2→⁶H_9/2 transitions of Sm³⁺, respectively. As the concentration of Sm³⁺ ions increased, the emission intensities of Dy³⁺ rapidly decreased, while the emission intensities of Sm³⁺ gradually increased. These results suggest that the color of the emission light can be tuned from yellow to white by changing the concentration of Sm³⁺ ions at a fixed 5 mol% Dy³⁺. Furthermore, the fluorescent security inks were synthesized for use in anti-counterfeiting applications.

Dy³⁺ and Eu³⁺-co-doped La₂MoO₆ phosphor thin films were deposited on sapphire substrates by radio-frequency magnetron sputtering at various growth temperatures. The phosphor thin films were characterized using X-ray diffraction (XRD), scanning electron microscopy, ultraviolet-visible spectroscopy, and fluorescence spectrometry. The optical transmittance, absorbance, bandgap, and photoluminescence intensity of the La₂MoO₆ phosphor thin films were found to depend on the growth temperature. The XRD patterns demonstrated that all the phosphor thin films, irrespective of growth temperatures, had a tetragonal structure. The phosphor thin film deposited at a growth temperature of 100℃ indicated an average transmittance of 85.3% in the 400~1,100 nm wavelength range and a bandgap energy of 4.31 eV. As the growth temperature increased, the bandgap energy gradually decreased. The emission spectra under ultraviolet excitation at 268 nm exhibited an intense red emission line at 616 nm and a weak emission line at 699 nm due to the ⁵D₀→⁷F₂ and ⁵D₀→⁷F₄ transitions of the Eu³⁺ ions, respectively, and also featured a yellow emission band at 573 nm, resulting from the ⁴F_9/2→⁶H_13/2 transition of the Dy³⁺ ions. The results suggest that La₂MoO₆ phosphor thin films can be used as light-emitting layers for inorganic thin film electroluminescent devices.

In this study, photoluminescence (PL) analysis was performed to evaluate the optical properties of commercial ZnO substrates. Particular attention was paid to the bound exciton (BX) luminescence, which is usually the strongest emission intensity of commercial substrates. At 15 K, PL analysis revealed that the BX peak due to donor-type impurities (donor-bound-exciton; DX) dominated, while two-electron satellite (TES) emission, donor-accepter pair (DAP) emission, and LO-phonon replica emission were also observed. The impurity concentration of the ZnO substrate was determined to be 10¹⁵ to 10¹⁶/cm³ by examination of the temperature variation of DAP, while the half width and intensity change of the luminescence revealed that the temperature change of BX can be interpreted almost the same as the analysis of free-exciton emission.

We investigated the temperature-dependent photoluminescence spectroscopy of colloidal InZnP/ZnSe/ZnS (core/ shell/shell) quantum dots with varying ZnSe and ZnS shell thickness in the 278~363 K temperature range. Temperature-dependent photoluminescence of the InZnP-based quantum dot samples reveal red-shifting of the photoluminescence peaks, thermal quenching of photoluminescence, and broadening of bandwidth with increasing temperature. The degree of bandgap shifting and line broadening as a function of temperature is affected little by shell composition and thickness. However, the thermal quenching of the photoluminescence is strongly dependent on the shell components. The irreversible photoluminescence quenching behavior is dominant for thin-shell-deposited InZnP quantum dots, whereas thick-shelled InZnP quantum dots exhibit superior thermal stability of the photoluminescence intensity.

The amount of electric power for photovoltaic power generation depends on the location of the power plant and the direction of solar cell. The solar cell controls the generation of solar power plants. Therefore, the structure of solar cell, manufacturing method, and optic technology were factors contributing to increased solar cell efficiency; however, the technical limit has been reached. Herein, we propose a new method to increase the solar cell efficiency using a wavelength conversion technology that converts ultraviolet and infrared rays, which are not effectively used in solar cells, into effective wavelength of solar cell. We used fluoride Na(Ca)YF₄ phosphor for wavelength conversion. Then, a wavelength-conversion fluorescent paste, prepared using an organic-silicon binder, was used to prepare a film that was applied to Si solar cells. It was confirmed that conversion efficiency improved by 5% or more.

New white-light-emitting SrSnO₃:Dy³⁺ phosphors were prepared using different concentrations of Dy³⁺ ions via a solid-state reaction. The phase structure, luminescence, and morphological properties of the synthesized phosphors were investigated using X-ray diffraction analysis, fluorescence spectrophotometry, and scanning electron microscopy, respectively. All the synthesized phosphors crystallized in an orthorhombic phase with a major (020) diffraction peak, irrespective of the concentration of Dy³⁺ ions. The excitation spectra were composed of a broad band centered at 298 nm, ascribed to the O^2--Dy³⁺ charge transfer band and five weak bands in the range of 350~500 nm. The emission spectra of SrSnO₃:Dy³⁺ phosphors consisted of three bands centered at 485, 577, and 665 nm, corresponding to the ⁴F_9/2→⁶H_15/2, ⁴F_9/2→⁶H_13/2, and ⁴F_9/2→⁶H_11/2 transitions of Dy³⁺, respectively. As the Dy³⁺ concentration increased from 1 to 15 mol%, the intensities of all the emission bands gradually increased, reached maxima at 15 mol% of Dy³⁺ ions, and then decreased rapidly at 20 mol% due to concentration quenching. The critical distance between neighboring Dy³⁺ ions for concentration quenching was calculated to be 9.4 Å. The optimal white light emission by the SrSnO₃:Dy³⁺ phosphors was obtained when the Dy³⁺ concentration was 15 mol%.

The white light of a hybrid LED is obtained by using red and green organic fluorescent layers made of polymethylmethacrylate (PMMA) films, which function as color down-conversion layers of blue light-emitting diodes. In this research, we studied the fluorescence properties of a red organic fluorophore, employing perylene bisimide derivatives applicable to hybrid LEDs. The solubility, thermal stability, and luminous efficiency are important characteristics of organic fluorophores for use in hybrid LEDs. The perylene fluorescent compounds (1A and 1B) were prepared by the reaction of 4-bromophenol and 4-iodophenol with N,N`-bis(4-bromo-2,6-diisopropylphenyl)-1, 6,7,12-tetrachloroperylene-3,4,9,10-tetracarboxyl diimide (1) in the presence of dimethyl formaldehyde (DMF) at 70℃. The synthesized derivatives were characterized by using 1H-NMR, FT-IR, UV/Vis absorption and PL spectra, and TGA analysis. Compounds 1A and 1B showed absorption and emission at 570 nm and 604 nm in the UV/Vis spectrum. We also documented favorable solubility and thermal stability characteristics of the perylene fluorophores in our work. Perylene fluorophore 1, with the 4-bromophenol substituent 1A, exhibited particularly good thermal stability and solubility in organic solvents.

ZnO nanorods were grown on SiO2 coated Si wafers and glass by the hydrothermal method. The structural and optical properties variation of ZnO nanorods as a function of growing time was studied. ～10 nm-thick ZnO thin films deposited on substrates by rf magnetron sputtering were employed as seed layers. Zinc nitrate hexahydrate (0.05 M) and hexamethylenetetramine (0.05 M) mixed in DI water were used as a reaction solution. ZnO nanorods were respectively grown for 30 min, 1 h, 2 h, 3 h, and 4 h by maintaining the reactor at 90℃. Crystallinity of ZnO nanorods was analyzed by X-ray diffraction, and the morphology of nanorods was observed by a field emission scanning electron microscope. Transmittance and absorbance were measured by a UV-Vis spectrophotometer, and energy band gap and urbach energy were obtained from the data. Photoluminescence measurements were carried out using Nd-Yag laser (266 nm).

Synthesis of the fluorescent Au nanoclusters is reported. The Au nanoclusters were synthesized via reduction of gold ions in reverse micelles with mild reducing agents. The Au nanoclusters show a bright red emission at 640 nm. The fluorescent Au nanoclusters attract great interest for sensor, electronic device and bio-imaging applications because of ultra-small size, high chemical stablity and bright emission. We believe that the fluorescent Au nanoclusters can have optoelectronic applications such as optical down conversion phosphors.

This study examined the malfunction mode of the HCMOS IC under narrow-band high-power electromagnetic wave. Magnetron is used to a narrow-band electromagnetic source. MFR (malfunction failure rate) was measured to investigate the HCMOS IC. In addition, we measured the resistance between specific pins of ICs, which are exposed and not exposed to the electromagnetic wave, respectively. As a test result of measurement, malfunction mode is shown in three steps. Flicker mode causing a flicker in LED connected to output pin of IC is dominant in more than 7.96 kV/m electric field. Self-reset mode causing a voltage drop to the input and output of IC during electromagnetic wave radiation is dominant in more than 9.1 kV/m electric field. Power-reset mode making a IC remained malfunction after electromagnetic radiation is dominant in more than 20.89 kV/m. As a measurement result of pin-to-pin resistance of IC, the differences between IC exposed to electromagnetic wave and normal IC were minor. However, the five in two hundred IC show a relatively low resistance. This is considered to be the result of the breakdown of pn junction when latch-up in CMOS occurred. Based on the results, the susceptibility of HCMOS IC can be applied to a basic database to IC protection and impact analysis of narrow-band high-power electromagnetic waves.

Single-layered transition metal dichalcogenides (TMDs) exhibit more interesting physical properties than those of bulk TMDs owing to the indirect to direct bandgap transition occurring due to quantum confinement. In this research, we demonstrate that layer-by-layer laser etching of molybdenum diselenide (MoSe₂) flakes could be controlled by varying the parameters employed in laser irradiation (time, intensity, interval, etc.). We observed a dramatic increase in the photoluminescence (PL) intensity (1.54 eV peak) after etching the samples, indicating that the removal of several layers of (MoSe₂) led to a change from indirect to direct bandgap. The laser-etched (MoSe₂) exhibited the single (MoSe₂) Raman vibration modes at ~239.4 cm^-1 and ~295 cm^-1, associated to out-of-plane A_1g and in-plane E¹ _2g Raman modes, respectively. These results indicate that controlling the number of MoSe2 layers by laser etching method could be employed for optimizing the performance of nano-electronic devices.

The effects of Eu3+ doping on the structural, morphological, and optical properties of MgMoO4:Dy3+,Eu3+ phosphors prepared by solid-state reaction technique were investigated. XRD patterns exhibited that all the synthesized phosphors showed a monoclinic system with a dominant (220) diffraction peak, irrespective of the content of Eu3+ ions. The surface morphology of MgMoO4:Dy3+,Eu3+ phosphors was studied using scanning electron microscopy and the grains showed a tendency to agglomerate as the content of Eu3+ ions increased. The excitation spectra of the phosphor powders were composed of a strong charge transfer band centered at 294 nm in the range of 230~340 nm and two intense peaks at 354 and 389 nm, respectively, arising from the 6H15/2→6P7/2 and 6H15/2→ 4M21/2 transitions of Dy3+ ions. The emission spectra of the Mg0.85MoO4:10 mol% Dy3+ phosphors without incorporating Eu3+ ions revealed a strong yellow band centered at 573 nm resulting from the 4F9/2→6H13/2 transitionof Dy3+. As the content of Eu3+ was increased, the intensity of the yellow emission was gradually decreased, while that of red emission band located at 614 nm began to appear, approached a maximum value at 10 mol%, and then decreased at 15 mol% of Eu3+. These results indicated that white light emission could be achieved by controlling the contents of the Dy3+ and Eu3+ ions incorporated into the MgMoO4 host crystal.

We studied white organic light-emitting diodes using blue fluorescent and red phosphorescent materials.White single OLEDs were fabricated using SH-1 : BD-2 (3 vol.%) and CBP : Ir(mphmq)2(acac) (2 vol.%) as emitting layer (EML). The white single OLED using SH-1 : BD-2 (3 vol.% 8 nm) / CBP : Ir(mphmq)2(acac) (2vol.% 22 nm) as emitting layer showed maximum current efficiency of 8.8 cd/A, Commission Internationale del``Eclairage (CIE) coordinates of (0.403, 0.351) at 1,000 cd/㎡, and variation of CIE coordinates with (0.402 ±0.012, 0.35 ± 0.002) from 500 to 3,000 cd/㎡. The white tandem OLED using SH-1 : BD-2 (3 vol.% 12 nm) /CBP : Ir(mphmq)2(acac) (2 vol.% 18 nm) showed maximum efficiency of 19.6 cd/A, CIE coordinates of (0.354,0.365) at 1,000 cd/㎡, and variation of CIE coordinates with (0.356 ± 0.016, 0.364 ± 0.002) from 500 to 3,000 cd/㎡. Maximum current efficiency of the white tandem OLED was more twice as high as the single OLED. Our findings suggest that tandem OLED was possible to produce improved efficiency and excellent color stability.

Electronic systems based on solid state devices have changed to be more complicated and miniaturized as the electronic systems developed. If the electronic systems are exposed to HPEM (high power electromagnetics), the systems will be destroyed by the coupling effects of electromagnetic waves. Because the HPEM has fast rise time and high voltage of the pulse, the semiconductors are vulnerable to external stress factor such as the coupled electromagnetic pulse. Therefore, we will discuss about malfunction behavior and DFR (destruction failure rate) of the semiconductor caused by amplitude and repetition rate of the pulse. For this experiment, the pulses were injected into the pins of general purpose IC due to the fact that pulse injection test enables the phenomenon after the HPEM is coupled to power cables. These pulses were produced by pulse generator and their characteristics are 2.1 [ns] of pulse width, 1.1 [ns] of pulse rise time and 30, 60, 120 [Hz] of pulse repetition rate. The injected pulses have changed frequency, period and duty ratio of output generated by Timer IC. Also, as the pulse repetition rate increases the breakdown threshold point of the timer IC was reduced.

In this paper, we investigated the hot carrier reliability of two kinds of device with low threshold voltage (LVT) and regular threshold voltage (RVT) in 65 nm CMOS technology. Contrary to the previous report that devices beyond 0.18 μm CMOS technology is dominated by channel hot carrier(CHC) stress rather than drain avalanche hot carrier(DAHC) stress, both of LVT and RVT devices showed that their degradation is dominated by DAHC stress. It is also shown that in case of LVT devices, contribution of interface trap generation to the device degradation is greater under DAHC stress than CHC stress, while there is little difference for RVT devices.

For feasible study of opto-electrical application regarding to oxide semiconductor, weimplemented the N doped ZnO growth using a atomic layer deposition technique. The p-type ZnOdeposition, necessary for ZnO-based optoelectronics, has considered to be very difficulty due tosufficiently deep acceptor location and self-compensating process on doping. Various sources of N such asN2, NH3, NO, and NO2 and deposition techniques have been used to fabricate p-type ZnO. Hallmeasurement showed that p-type ZnO was prepared in condition with low deposition temperature anddopant concentration. From the evaluation of photoluminescence spectroscopy, we could observe defectformation formed by N dopant. In this paper, we exhibited the electrical and optical properties of N-dopedZnO thin films grown by atomic layer deposition with NH3OH doping source.

CaNb2O6:RE3+ (RE=Sm or Eu) phosphor powders were prepared with different contents of activatorions by using solid-state reaction method. The X-ray diffraction patterns exhibited that the phosphors synthesized with different activator ions showed an orthorhombic system with a main (131) diffraction peak. The maximum size of the grain particles, determined from the measurement of scanning electron microscopy, was observed at 0.05 mol of Eu3+ ions and at 0.01 mol of Sm3+. As for the Eu3+-doped phosphor powders, the excitation spectra were composed of a broad band peaked at 278 nm and several weak bands in the range of 350～500 nm, and the highest red emission spectrum was observed at 0.15 mol of Eu3+ ions. As for the Sm3+-activated phosphor powders, three strong emission bands under excitation at 273 nm were observed at 570, 612, and 659 nm, respectively. The intensities of all the emission bands approached maxima for 0.05mol of Sm3+ ions. The optical properties show that the Eu3+- or Sm3+-doped CaNb2O6 powders are promising red-orange emitting phosphor powders applicable to full-color photonic devices.

We have investigated the effects of spacer layer inserted between blue and red doped emissionlayers on the emission and efficiency characteristics of phosphorescent OLEDs. N,N``-di-carbazolyl-3,5-benzene(mCP) was used as a host layer. Iridium(III)bis[(4,6-di-fluorophenyl)- pyridinato-N,C2``]picolinate (FIrpic) andtris(1-phenyl-isoquinolinato-C2,N)iridium(III) [Ir(piq)3] were used as blue and red dopants, respectively. Theemission layer structure was mCP (1-x) nm/mCP:Ir(piq)3 (5 nm, 10%)/mCP (x nm)/mCP:FIrpic (5 nm, 10%). The thickness of mCP spacer layer was varied from 0 to 15 nm. The emission from Ir(piq)3 and theefficiency of the device were dominated by energy transfer from mCP host and FIrpic molecules, and bydiffusion of mCP host triplet excitons.

This paper dealt with the development of a LED floodlight for naval vessels to replace the conventional floodlight using an incandescent and a halogen lamp. We found a technical solution for current problems of conventional lights and also improved optical characteristics by developing a LED floodlight which has a typical long-lived light source with high efficiency. To satisfy the requirements specified in Korea Standard Vessels (KS V), the optical structure was designed with selected LED package and lens. A LED module was composed of 10 LEDs in series for stable luminous output, and an aluminium heat sink was adopted for effective heat-radiation design. The LED floodlight was fabricated as a module type so that it can easily replace the conventional light source. The power consumption of the prototype floodlight was only a tenth of a conventional one with the same optical performance. Also, a test showed the floodlight satisfied the electrical, optical and environmental requirements of the standards.

In order to develop a LED luminaire for naval-submarines which can replace a conventional one with two-compact fluorescent lamp (CFL) of 18 W, we analyzed the electrical and optical performance of the conventional luminaire. A LED luminaire was fabricated as compact as possible based on the analyzed data. The weight of the prototype LED luminaire is 1.8 kg, reducing up to 58% of the conventional one. The use of LED package for the submarine luminaire could reduce the power consumption from 38 W to 14.5 W with the same optical performance. The reason is that the optical efficacy of the LED luminaire improved by 2.47 times as 61.9 lm/W, compared to 25.1 lm/W for the conventional one.

To study emission properties of white phosphorescent organic light emitting devices (PHOLEDs), we fabricated white PHOLEDs of ITO (150 nm) / NPB(30 nm) / TcTa(10 nm) / mCP(7.5 nm) / light-emitting layer(25 nm) / UGH3(5 nm) / Bphen(50 nm) / LiF(0.5nm) / Al(200 NM) structure. The total thickness of light-emitting layer with co-doping and blue-doping/ co-doping using a host-dopant system was 25 nm and the dopant of blue and red was FIrpic and Bt2Ir(acac) in UGH3 as host. respectively. The OLED characteristics were changed with position and thickness of doping layer and co-doping layer as light-emitting layer and the best performance seemed in structure of blue-doping(5 nm)/co-doping(20 nm) later. The white PHOLEDs showed the maximum current density of 34.5 mA /cm², maximum brightness of 5,731 cd/ m², maximum current efficiency of 34.8 cd/A, maximum power efficiency of 21.6lm/w, maximum quantum effiency of 15.6%, and a Commission International de L`Eclairage (CIE) coordinate of (0.367, 0.436) at 1,000 cd/m².

We studied the emission characteristics of white phosphorescent organic light-emitting diodes (PHOLEDs), which were fabricated using a two-wavelength method. The best blue emitting OLED and red emitting OLED characteristics were obtained at a concentration of 12 vol.% FIrpic and 1 vol.% Bt2Ir(acac) in UGH3, respectively. And the optimum thickness of the total emitting layer was 25 nm. To optimize emission characteristics of white PHOLEDs, white PHOLEDs with red/blue/red, blue/red, red/blue and co-doping emitting layer structures were fabricated using a host-dopant system. In case of white PHOLEDs with co-doping structure, the best efficiency was obtained at a structure UGH3: 12 vol. % FIrpic: 1 vol.% Bt2Ir(acac) (25 nm). The maximum brightness, current efficiency, power efficiency, external quantum efficiency, and CIE (x, y) coordinate were 13,430 cd/㎡, 40.5 cd/A, 25.3 lm/W, 17 % and (0.49, 0.47) at 1,000 cd/㎡, respectively.