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Research
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Design of efficient phosphors for display and lighting devices
A luminescence material, also called as a phosphor, is a solid which converts certain types of energy, such as electron beam, energetic photons, and electric fields, into electromagnetic radiation in visible region. Phosphors are widely being used in many kinds of display and lighting devices such as plasma display panels (PDPs), field emission displays (FEDs), inorganic electrolumimescence devices (ELDs), cathode ray tubes (CRTs), liquid crystal dispaly (LCD) backlight units (BLUs), white light emitting diodes (LEDs), and general fluorescence lamps. Performances of the display and lighting devices are strongly depended on luminescence properties of phosphors used in the same, and thus design of efficient phosphors is one of the most important research topics in display materials laboratory. We have experiences to find new high performance phosphors and we are trying to design new efficient phosphors by quantum chemical calculation.
Development of flexible display
Flexible display technologies offer many potential advantages, such as very thin profile, lightweight and robust display systems, the ability to flex, curve, conform, roll, and fold a display for extreme portability, high-throughput manufacturing (roll to roll process), wearable displays integrated in garments and textiles and ultimate engineering design freedoms. Currently technical level of flexible display is only bendable and conformable. In flexible display research, Final goal of developing flexible display is disposable display (fully flexible). To enable a flexible display, a flexible substrate must be used to replace conventional glass substrates, which can be either flexible plastic substrate or fabric type substrate. In future society, A well-designed flexible display should facilitate the access of information Anytime, Anyplace, Anyone by applying to wearable display. Because humans are always enjoy clothing and this comfortable interface of clothing can be tailored to fit the individual's preferences.
Application of phosphors into bio-technology and special purposes
You want to find it when it is really small, before cancer gets too big. Other ways of looking inside the body can work but you need to label the cancer cells so that you can see them. Quantum dots are one way to label cells. They are really small, around five nanometers in size and because they are really tiny they can make it through the body to the cancer. Once the quantum dots reach the cancer a special kind of light is used, that can penetrate deep into the body. The quantum dots glow and you can see them with a special camera besides, bio-labeling, nano-sized luminescent materials are necessary in security field. Micro-sized phosphors can be detected by using some instruments. For high security, highly luminescent quantum dots can be good candidates.
Packaging materials for optoelectronic modules
One of the most critical levels of optoelectronic packaging is that of packaging and interconnecting semiconductor chips such as microprocessor, memory, and optical devices in order to obtain their performances. Especially, parts used in optoelectronic system such as vertical cavity surface emitting laser (VCSEL), polymeric waveguide, and photo detector are very weak to heat during integration process. Moreover, heat generated from the devices may cause serious problems such as junction/metallization failure, electromigration in interconnecting parts, and delaminations. Therefore, research in this topic covers the low-temperature multiple flip chip bonding using In and AuSn solder bumps for integrating of vertical cavity surface emitting laser (VCSEL) and developing of thermal interface material using multiwalled carbon nanotubes (MWCNTs). Our work so far revealed reliability issues in low temperature flip chip bonding using In solder bumps and provided a process guideline for multiple chip integration on a single platform. Also we have formed Sn-MWCNT composite layers by using Sn-decorated MWCNTs for efficient heat dissipation. We are recently focusing on investigation on thermal conducting properties of the Sn-MWCNT composite and systematic prediction of effective thermal conductivity by a simple modeling.
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