The reactive co-sputtering was developed as a new way of preparing high quality CuInGaSe<sub>2</sub>(CIGS) films from two sets of targets; Cu<sub>0.6</sub>Ga <sub>0.4</sub> and Cu<sub>0.4</sub>In<sub>0.6</sub> alloy and Cu and (In<sub>0.7</sub>Ga<sub>0.3</sub>)<sub>2</sub>Se<sub>3</sub> compound targets. During sputtering, Cu, In, Ga metallic elements as well as the compound materials were reacted to form CIGS simultaneously in highly reactive elemental Se atmosphere generated by a thermal cracker. CIGS layer had been grown on Mo/soda-lime glass(SLG) at 500°C. For both sets of targets, we controlled the composition of CIGS thin film by changing the RF power for target components. All the films showed a preferential (112) orientation as observed from X-ray diffraction analysis. The composition ratios of CIGS were easily set to 0.71-0.95, 0.10-0.30 for [Cu]/[III] and [Ga]/[III], respectively. The grain size and the surface roughness of a CIGS film increased as the [Cu]/[III] ratios increased. The solar cells were fabricated using a standard base line process in the device structure of grid/ITO/i-ZnO/CdS/CIGS/Mo/ SLG. The best performance was obtained the performance of V<sub>oc</sub> = 0.45 V, J<sub>sc</sub> =35.6, FF = 0.535, η = 8.6% with a 0.9 μm-CIGS solar cell from alloy targets while V<sub>oc</sub> = 0.54 V, J<sub>sc</sub> =30.8, FF = 0.509, η = 8.5% with a 0.8 μm-CIGS solar cell from Cu and (In<sub>0.7</sub>Ga<sub>0.3</sub>)<sub>2</sub>Se<sub>3</sub>.
Organic light-emitting diode (OLED) has a good candidate for next generation flat panel display (FPD). However, it is very difficult to fabricate high performance OLEDs on plastic substrate because its mechanical and thermal properties are very poor. Before the ITO deposition, we used a new plasma treatment for good contact with ITO and PES. PES substrate is stayed in vacuum above 12 hours to reduce humidity and unknown chemical gas.
We successfully fabricate OLED on PES substrate using PLD-ITO anodes. We can observe more uniform and bright emission image from the OLED and fix the optimum conditions for fabrication process for OLED. Maximum electro luminescence (EL) and current density at a 100 cd/m<sup>2</sup> are 2500 cd/m<sup>2</sup>, 2mA/cm<sup>2</sup>, respectively and external quantum efficiency of OLED is about a 2.0%.
The role of the size of amorphous silicon quantum dots in the Er luminescence at 1.54 µm was investigated. As the dot size was increased, the more Er ions were located near one dot due to its large surface area and more Er ions interacted with other Er ions. This Er-Er interaction caused a weak photoluminescence intensity despite the increase in the effective excitation cross section. The critical dot size, needed to take advantage of the positive effect on Er luminescence, is considered to be about 2.0 nm, below which a small dot is very effective in the efficient luminescence of Er. However, the hydrogenation is considered to suppress this Er-Er interaction.
Proc. SPIE. 5284, Wireless Communications and Networks
KEYWORDS: Internet, Control systems, Telecommunications, Local area networks, Multimedia, Wireless communications, Data communications, Error control coding, Automatic repeat request, Mobile communications
In recent years, multimedia services are developing rapidly in mobile communication systems. The multimedia services consist of many kinds of data which have different characteristics. To enable these services to be provided, because of large amount of data, there needs more effective utilization of radio resources in limited bandwidth. One of the solutions is making an effective DLC (Data Link Control) for QoS (Quality of Service) assurance. In this paper, we propose a structure of radio protocol and the DLC protocol layer which consists of hierarchical component based functional entities and an effective radio link control. The DLC is operated by the state of current traffic volume. For the efficiency of radio resource utilization, different adequate components will be taken by the current traffic state. Especially fraction based data transmission buffer control method with ARQ scheme, which is dynamic parameter change scheme, based on logical channel priority and DLC state for the QoS assurance in Wireless LAN system.
We fabricated the white light-emitting diodes without phosphor materials using phase-separated InGaN active layers. The white luminescence was attributed to the broad distributions of indium composition and size of quantum dot- like In-rich regions in the phase-separated InGaN Ternary alloys.