• 산업기술연구
• /
• 제29권B호
• /
• pp.187-191
• /
• 2009

Recently, we have used LEDs to illumination because it has a high luminous efficiency and prolong lifespan. However the light power and lifetime is reduced by junction temperature increment of LED. So it is important to measure the junction temperature accurately. In case of using a electrical method measuring junction temperature of LED. Temperature measurement errors are spontaneously generated because of a parasitic capacitances in LED. In this paper, we proposed a method that reducing LED's parasitic capacitance effects for electrical measurement. It was demonstrated by the experimental result that is more correct than established method.

• 한국조명전기설비학회:학술대회논문집
• /
• 한국조명전기설비학회 2004년도 춘계학술대회 논문집
• /
• pp.167-170
• /
• 2004

A high light lantern system using LEDs is composed of power supply, flash controller, and daylight controller and proper case considering work condition. The performance of developed LED lantern is better than that of the existing marine lantern using an incandescent electric lamp and that of foreign products(Vega LED lantern made in New Zealand, Tideland system made in America). The electric consumption of our products is 30% compared with that of existing marine lantern using an incandescent electric lamp, and the luminous Intensity of them is 200% to 400% compared with that of existing marine lantern and foreign LED lantern. In addition, our LED lantern system is easy to repairing something wrong and changing the LED module and other controllers on the sea when they are in accident.

• 한국전기전자재료학회논문지
• /
• 제20권8호
• /
• pp.731-735
• /
• 2007

We developed the 4channel Light Medical Therapy Apparatus for External Injury Cure using a high brightness LED. This equipment was fabricated using a micro-controller and a high brightness LED, and designed to enable us to control light irradiation time, intensity, frequency and so on, Especially, to control the light irradiation frequency, FPGA was used, and to control the change of output value, TLC5941 was used. Control stage is divided into 4 levels by program. Consequently, the current value could be controlled by the change of level in Continue Wave(CW) and the output of a high brightness LED could be controlled stage by stage. Compared with one LED irradiation, several LEDs irradiation could increase optical power.

• 한국진공학회:학술대회논문집
• /
• 한국진공학회 2012년도 제43회 하계 정기 학술대회 초록집
• /
• pp.115-116
• /
• 2012

The demand for flexible electronic systems such as wearable computers, E-paper, and flexible displays has increased due to their advantages of excellent portability, conformal contact with curved surfaces, light weight, and human friendly interfaces over present rigid electronic systems. This seminar introduces three recent progresses that can extend the application of high performance flexible inorganic electronics. The first part of this seminar will introduce a RRAM with a one transistor-one memristor (1T-1M) arrays on flexible substrates. Flexible memory is an essential part of electronics for data processing, storage, and radio frequency (RF) communication and thus a key element to realize such flexible electronic systems. Although several emerging memory technologies, including resistive switching memory, have been proposed, the cell-to-cell interference issue has to be overcome for flexible and high performance nonvolatile memory applications. The cell-to-cell interference between neighbouring memory cells occurs due to leakage current paths through adjacent low resistance state cells and induces not only unnecessary power consumption but also a misreading problem, a fatal obstacle in memory operation. To fabricate a fully functional flexible memory and prevent these unwanted effects, we integrated high performance flexible single crystal silicon transistors with an amorphous titanium oxide (a-TiO2) based memristor to control the logic state of memory. The $8{\times}8$ NOR type 1T-1M RRAM demonstrated the first random access memory operation on flexible substrates by controlling each memory unit cell independently. The second part of the seminar will discuss the flexible GaN LED on LCP substrates for implantable biosensor. Inorganic III-V light emitting diodes (LEDs) have superior characteristics, such as long-term stability, high efficiency, and strong brightness compared to conventional incandescent lamps and OLED. However, due to the brittle property of bulk inorganic semiconductor materials, III-V LED limits its applications in the field of high performance flexible electronics. This seminar introduces the first flexible and implantable GaN LED on plastic substrates that is transferred from bulk GaN on Si substrates. The superb properties of the flexible GaN thin film in terms of its wide band gap and high efficiency enable the dramatic extension of not only consumer electronic applications but also the biosensing scale. The flexible white LEDs are demonstrated for the feasibility of using a white light source for future flexible BLU devices. Finally a water-resist and a biocompatible PTFE-coated flexible LED biosensor can detect PSA at a detection limit of 1 ng/mL. These results show that the nitride-based flexible LED can be used as the future flexible display technology and a type of implantable LED biosensor for a therapy tool. The final part of this seminar will introduce a highly efficient and printable BaTiO3 thin film nanogenerator on plastic substrates. Energy harvesting technologies converting external biomechanical energy sources (such as heart beat, blood flow, muscle stretching and animal movements) into electrical energy is recently a highly demanding issue in the materials science community. Herein, we describe procedure suitable for generating and printing a lead-free microstructured BaTiO3 thin film nanogenerator on plastic substrates to overcome limitations appeared in conventional flexible ferroelectric devices. Flexible BaTiO3 thin film nanogenerator was fabricated and the piezoelectric properties and mechanically stability of ferroelectric devices were characterized. From the results, we demonstrate the highly efficient and stable performance of BaTiO3 thin film nanogenerator.

• Design & Manufacturing
• /
• 제7권1호
• /
• pp.55-59
• /
• 2013

A Light Emitting Diode(LED) is a semiconductor device which converts electricity into light. LEDs are widely used in a field of illumination, LCD(Liquid Crystal Display) backlight, mobile signals because they have several merits, such as low power consumption, long lifetime, high brightness, fast response, environment friendly. In general, LEDs production does die bonding and wire bonding on board, and do silicon and phosphor dispensing to protect LED chip and improve brightness. Then lens molding process is performed using mixed liquid silicon rubber(LSR) by resin and hardener. A mixture of resin and hardener affect the optical characteristics of the LED lens. In this paper, computational design of static mixer was performed for mixing of liquid silicon. To evaluate characteristic of mixing efficiency, finite element model of static mixer was generated, and fluidic analysis was performed according to length of mixing element. Finally, optimal condition of length of mixing element was applied to static mixer from result of fluidic analysis.

• 한국전기전자재료학회논문지
• /
• 제29권4호
• /
• pp.237-240
• /
• 2016

The improvement of irradiation intensity and irradiation uniformity is essential for large area and high power UVA light source application. In this study, large number of chips bonded by micro soldering technique were driven by low current, and current limiting diodes were configured to supply constant current to parallel circuits consisting of large number of series strings. The dimension of light source module circuit board was $350{\times}90mm^2$ and 16,650 numbers of 385 nm flip chip LEDs were used with a configuration of 90 parallel and 185 series strings. The space between LEDs in parallel and series strings were maintained at 1.9 mm and 1.0 mm distance, respectively. The size of the flip chip was $750{\times}750{\mu}m^2$ were used with contact pads of $260{\times}669{\mu}m^2$ size, and SAC (96.5 Sn/3.0 Ag/0.5 Cu) solder was used for flip chip bonding. The fabricated light source module with 7.5 m A supply current showed temperature rise of $66^{\circ}C$, whereas irradiation was measured to be $300mW/cm^2$. Inaddition, 0.23% variation of the constant current in each series string was demonstrated.

• Transactions on Electrical and Electronic Materials
• /
• 제16권3호
• /
• pp.124-129
• /
• 2015

Organic electronics are the domain in which the components and circuits are made of organic materials. This new electronics help to realize electronic and optoelectronic devices on flexible substrates. In recent years, organic materials have replaced conventional semiconductors in many electronic components such as, organic light-emitting diodes (OLEDs), organic field-effect transistors (OFETs) and organic photovoltaic (OPVs). It is well known that organic light emitting diodes (OLEDs) have many advantages in comparison with inorganic light-emitting diodes LEDs. These advantages include the low price of manufacturing, large area of electroluminescent display, uniform emission and lower the requirement for power. The aim of this paper is to model polymer LEDs and OLEDs made with small molecules for studying the electrical and optical characteristics. The purpose of this modeling process is, to obtain information about the running of OLEDs, as well as, the injection and charge transport mechanisms. The first simulation structure used in this paper is a mono layer device; typically consisting of the poly (2-methoxy-5(2'-ethyl) hexoxy-phenylenevinylene) (MEH-PPV) polymer sandwiched between an anode with a high work function, usually an indium tin oxide (ITO) substrate, and a cathode with a relatively low work function, such as Al. Electrons will then be injected from the cathode and recombine with electron holes injected from the anode, emitting light. In the second structure, we replaced MEH-PPV by tris (8-hydroxyquinolinato) aluminum (Alq₃). This simulation uses, the Poole-Frenkel -like mobility model and the Langevin bimolecular recombination model as the transport and recombination mechanism. These models are enabled in ATLAS- SILVACO. To optimize OLED performance, we propose to change some parameters in this device, such as doping concentration, thickness and electrode materials.

• 대한금속재료학회지
• /
• 제46권10호
• /
• pp.683-690
• /
• 2008

In order to develop transparent electrodes for high efficiency GaN-based light emitting diodes (LEDs), the electrical and optical properties of the electron beam evaporated ITO contacts have been investigated as a function of the deposition temperature and flow rate of oxygen during the deposition. As the deposition temperature increases from $140^{\circ}C$ to $220^{\circ}C$, the resistivity of the ITO films decreases slightly from $4.0{\times}10^{-4}{\Omega}cm$ to $3.3{\times}10^{-4}{\Omega}cm$, meanwhile the transmittance of the ITO films significantly increases from 67% to 88% at the wavelength of 470 nm. When the flow rate of oxygen during the deposition increases from 2 sccm to 4 sccm, the resistivity of the ITO films increases from $3.6{\times}10^{-4}{\Omega}cm$ to $7.4{\times}10^{-4}{\Omega}cm$, meanwhile the transmittance of the ITO films increases from 86% to 99% at 470 nm. Blue LEDs fabricated with the electron beam evaporated ITO electrode show that the ITO films deposited at $200^{\circ}C$ and 3 sccm of the oxygen flow rate give a low forward-bias voltage of 3.55 V at injection current of 20 mA with a highest output power.

• 한국재료학회지
• /
• 제19권8호
• /
• pp.443-446
• /
• 2009

This study develops a highly transparent ohmic contact scheme using indium oxide doped ZnO (IZO) as a current spreading layer for p-GaN in order to increase the optical output power of nitride-based lightemitting diodes (LEDs). IZO based contact layers of IZO, Ni/IZO, and NiO/IZO were prepared by e-beam evaporation, followed by a post-deposition annealing. The transmittances of the IZO based contact layers were in excess of 80% throughout the visible region of the spectrum. Specific contact resistances of $3.4\times10^{-4}$, $1.2\times10^{-4}$, $9.2\times0^{-5}$, and $3.6\times10^{-5}{\Omega}{\cdot}cm^2$ for IZO, Ni/Au, Ni/IZO, and NiO/IZO, respectively were obtained. The forward voltage and the optical output power of GaN LED with a NiO/IZO ohmic contact was 0.15 V lower and was increased by 38.9%, respectively, at a forward current of 20 mA compared to that of a standard GaN LED with an Ni/Au ohmic contact due to its high transparency, low contact resistance, and uniform current spreading.

• 한국태양에너지학회 논문집
• /
• 제31권2호
• /
• pp.113-119
• /
• 2011

LED lighting has received much attention in recent years due to its high energy efficiency and environmental friendliness. As the color of light can be obtained by adjusting the light intensity of LEDs, the quality of visual environment can be improved. The aims of this study are to develop a wavelength adjustable LED lighting system and to examine its lighting performances. The LED lighting system and experimental cell for assessment of the lighting performance were constructed. This LED lighting system is able to materialize the various spectral power distribution and color temperature of light through the control of the four dimmers. Up to $432^4$ kinds of light combinations are possible. The range of illuminance on workplane were measured as 7~1,831 ㏓. Improvement of psychological and physical functions for occupants can be expected according to control of lighting performances.