• Electronics and Telecommunications Trends
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• v.34 no.2
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• pp.10-18
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• 2019

Since the introduction of CRT(Cathode Ray Tube) in the 1950s, display technologies have been developed continuously. Flat panel displays such as PDP(Plasma Display Panel) and LCD(Liquid Crystal Display) were commercialized in the late 1990s, and OLED(Organic Light Emitting Diodes) and Micro-LED(Micro-Light Emitting Diodes) are now being developed and are becoming widespread. In the future, we expect to develop ultra-realistic, flexible, embedded sensor displays. Ultra-realistic display can be applied to AR/VR(Augmented Reality/Virtual Reality) devices and spatial light modulators for holography. The sensor-embedded display can be applied to robots; electronic skin; and security devices, including iris recognition sensors, fingerprint recognition sensors, and tactile sensors. AR/VR technology must be developed to meet technical requirements such as viewing angle, resolution, and refresh rate. Holography requires optical modulation technology that can significantly improve resolution, viewing angle, and modulation method to enable wide-view and high-quality hologram stereoscopic images. For electronic skin, stable mass production technology, large-area arrays, and system integration technologies should be developed.

• Transactions on Electrical and Electronic Materials
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• v.10 no.1
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• pp.28-30
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• 2009

We have studied organic layer-thickness dependent electrical and optical properties of bottom- and top-emission devices. Bottom-emission device was made in a structure of ITO(170 nm)/TPD(x nm)/$Alq_3$(y nm)/LiF(0.5 nm)/Al(100 nm), and a top-emission device in a structure of glass/Al(100 nm)/TPD(x nm)/$Alq_3$(y nm)/LiF(0.5 nm)/Al(25 nm). A hole-transport layer of TPD (N,N'-diphenyl-N,N'-di(m-tolyl)-benzidine) was thermally deposited in a range of 35 nm and 65 nm, and an emissive layer of $Alq_3$ (tris-(8-hydroxyquinoline) aluminum) was successively deposited in a range of 50 nm and 100 nm. Thickness ratio between the hole-transport layer and the emissive layer was maintained to be 2:3, and a whole layer thickness was made to be in a range of 85 and 165 nm. From the current density-luminance-voltage characteristics of the bottom-emission devices, a proper thickness of the organic layer (55 nm thick TPD and 85 nm thick $Alq_3$ layer) was able to be determined. From the view-angle dependent emission spectrum of the bottom-emission device, the peak wavelength of the spectrum does not shift as the view angle increases. However, for the top-emission device, there is a blue shift in peak wavelength as the view angle increases when the total layer thickness is thicker than 140 nm. This blue shift is thought to be due to a microcavity effect in organic light-emitting diodes.

• Journal of Mechanical Science and Technology
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• v.20 no.7
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• pp.1089-1097
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• 2006

The market demand of display devices is drastically increasing in the information technology age. The research on OLED (Organic Light Emitting Diodes) display with the luminescence in itself is being more paid attention than LCD (Liquid Crystal display) with the light source from the back. The vapor deposition process is most essential in manufacturing OLED display. The temperature distribution of the linear cell in this process is closely related to securing the uniformity of organic materials on the substrate. This work analyzed the temperature distribution depending on the intervals between the crucible and the heating band as well as on the amount of the heat flux from the heating band. Moreover, the roles of the water jacket and the configuration of the cover within the linear cell were examined through the temperature analysis for six configurations of the linear cell. Under the above temperature analysis, the variations in the intervals and the amount of the heat flux were considered to have an effect on building the uniform temperature distribution within the crucible. It is predicted that the water jacket and the adequate configuration of the cover will prevent the blowout and clogging phenomena, respectively. The results can be used as the fundamental data for designing the optimal linear cell.

• Journal of Information Display
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• v.13 no.4
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• pp.139-143
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• 2012

In this study, optical simulation was used to compare three optical structures that could be applied to the typical organic light-emitting diode to increase the outcoupling efficiency. These were spherical scattering particles (treated as Mie scatterers) embedded in the glass substrate, microlenses formed on the glass substrate, and a diffusing layer (DL) with a Gaussian scattering distribution function inserted between the indium tin oxide (ITO) and the glass substrate. It was found that the application of microlens array and that of scattering particles in the glass substrate exhibited similar enhancements in the outcoupling efficiency when the density and the refractive index of the scattering particles were optimized. The DL located at the interface between the glass and the ITO further enhanced the efficiency because it could further extract the trapped light in the waveguide mode. The appropriate combination of these three structures increased the outcoupling efficiency to about 42%, which is much greater than the typical values of 15-20% when there is no optical structure for light extraction.

• Proceedings of the Optical Society of Korea Conference
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• 2005.07a
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• pp.204-205
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• 2005

Studies on display has been requested some major changes due to the high growth of the handheld terminal market. Therefore, the self emitting OLED(Organic Light Emitting Diode) has been interested as a next generation flat plane display because of its preeminent characteristics such as quick response characteristics, higher performance viewing angle, low power consumption, and panel floating. However, a trend of the display market is moving to three dimensional image processing instead of two dimensional flat display and various researches on display using hologram makes up for the difficulty in three dimensional display using typical flat display. In this study the Lenticular Screen Printing method is presented so that it can be applicable to organic semiconductor display devices and makes possible three dimensional display using flat display for complement the drawback of inorganic semiconductor.

• 한국정보디스플레이학회:학술대회논문집
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• 2008.10a
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• pp.461-464
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• 2008

We have developed low voltage driving red phosphorescent organic light-emitting devices using a new electron transport layer. $Ir(piq)_3$ and CBP were used as a phosphorescent dopant and an emission host, respectively. The device exhibits a luminance of $1000\;cd/m^2$ at a voltage of 2.8 V. This high luminance at low voltage results from a high electron conduction behavior of the new electron transport layer.

• 한국정보디스플레이학회:학술대회논문집
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• 2008.10a
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• pp.416-419
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• 2008

In this study, we report on the characteristics of Aldoped ZnO (AZO) co-sputtered indium tin oxide (ITO) films prepared by dual target direct current (DC) magnetron sputtering at room temperature for organic light emitting diodes (OLEDs). The electrical and optical properties of co-sputtered IAZTO electrode were critically dependent on the DC power of AZO. Furthermore, the characteristics of co-sputtered IAZTO electrode were influenced by rapid thermal annealing temperature.

• 한국정보디스플레이학회:학술대회논문집
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• 2006.08a
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• pp.571-576
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• 2006

We review work performed by our group and collaborators in the area of exciton formation. There are three components: (i) measurement of singlet fractions, (ii) analysis of magnetic resonance measurements, and (iii) models of exciton formation. We find that the fraction of singlet excitons is a controllable quantity, pointing the way to a new generation of all-fluorescent organic light emitting devices.

• 한국정보디스플레이학회:학술대회논문집
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• 2005.07b
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• pp.1133-1137
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• 2005

In this paper, a renovated approach in the fabrication of red organic light-emitting diodes (OLEDs) is described. The hard-to-control doping process required for dopant-based red OLEDs can be avoided due to the novel red fluorophores that are not concentration quenching in solid state. Doping is in general a must for phosphorescence OLEDs because of the triplet-triplet annihilation, a common problem for phosphorophore dopants. However, we have recently found that extraordinary red iridium complex showing relatively short emission lifetime render the non-doped phosphorescence red OLED possible.

• 한국정보디스플레이학회:학술대회논문집
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• 2006.08a
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• pp.1805-1808
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• 2006

In this paper, we describe a versatile use of fullerene(C60) as a charge transporting material for organic light-emitting diodes. The use of fullerene as a buffer layer for an anode, a doping material for hole transport layer, and an electron transport layer was investigated. Fullerene improved the hole injection from an anode to a hole transport layer by lowering the interfacial energy barrier and enhanced the lifetime of the device as a doping material for a hole transport layer. In addition, it was also effective as an electron transporting material to get low driving voltage in the device.