The Experts below are selected from a list of 276 Experts worldwide ranked by ideXlab platform
Kyung Cheol Choi - One of the best experts on this subject based on the ideXlab platform.
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8.1: Improvement of the Discharge Time lag and Luminous Efficiency in an AC ‐ PDP with 200μm Sustain Gap
SID Symposium Digest of Technical Papers, 2004Co-Authors: Bhum Jae Shin, Kyung Cheol ChoiAbstract:The characteristics of 200 μm sustain-gap discharge in an AC PDP with auxiliary electrode and high Xe content were investigated. When the voltage of the pulse applied to auxiliary electrode during sustain period was the range of 20–50 volt, the luminance and Luminous Efficiency of Ne+13% gas mixture discharges in an AC PDP with 200 μm sustain-gap had their maximum value. The Luminous Efficiency was improved by 166% in comparison with that of the conventional structure with Ne+4% Xe gas-mixture. Using the pulse applied to the auxiliary electrode during address period, the discharge time lag of address pulse was improved by 55%.
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Improved luminance and Luminous Efficiency of AC plasma display panel
IEEE Transactions on Consumer Electronics, 2003Co-Authors: Kyung Cheol ChoiAbstract:The effect of applying auxiliary pulses to the address electrode during the sustain period on the discharge characteristics of an AC plasma display panel was investigated. When auxiliary pulses of 100 V and 250 kHz were applied to the address electrode during the sustain period, the maximum sustain voltage was found to decrease by 14%, while the minimum sustain voltage increased by 15% when compared to the case of a grounded address. It was also found that higher frequency auxiliary pulses resulted in a higher luminance in the sustain discharge. Consequently, the application of a pulse of 100 V and 250 kHz to the address electrode during the sustain period improved the Luminous Efficiency by 12%.
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improvement of luminance and Luminous Efficiency using address voltage pulse during sustain period of ac pdp
IEEE Transactions on Electron Devices, 2001Co-Authors: Sanghuan Jang, Kyung Cheol ChoiAbstract:To improve the luminance and Luminous Efficiency of a surface-discharge alternate current plasma display panel (ac PDP), auxiliary voltage pulses were applied to the address electrode during a sustain-period. The luminance and Luminous Efficiency exhibited maximum values at an address voltage of 100 V and pulse width of 1 /spl mu/s. An improved luminance of 21.4% and Luminous Efficiency of 24% were simultaneously obtained based on the proper adjustment of the widths and amplitudes of the address voltage pulse. Accordingly, the proper control of the amplitudes and pulse widths of the auxiliary address voltage during a sustain-period can improve both the luminance and the Luminous Efficiency in a surface-discharge ac PDP.
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Improvement in the Luminous Efficiency using ramped-square sustain waveform in an AC surface-discharge plasma display panel
IEEE Transactions on Electron Devices, 2001Co-Authors: Sang-hun Jang, Kyung Cheol ChoiAbstract:This paper proposes a new sustain waveform to improve the Luminous Efficiency of an AC plasma display panel (AC-PDP). The new sustain waveform is a superimposed waveform, which adds a ramp-waveform to a square-waveform, and has an increasing voltage slope between the rising and falling edge. This waveform can induce a longer-sustained discharge at the rising edge plus a self-erasing discharge at the falling edge, thereby improving the Luminous Efficiency, When compared with the conventional square sustain waveform, the proposed sustain waveform with a 9.3 V//spl mu/s voltage slope achieved a 65% higher Luminous Efficiency in a 4-in AC-PDP test panel even at a low frequency (62 kHz).
Sang Hyuk Im - One of the best experts on this subject based on the ideXlab platform.
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effects of thermal treatment on organic inorganic hybrid perovskite films and Luminous Efficiency of light emitting diodes
Current Applied Physics, 2016Co-Authors: Sang Hyuk ImAbstract:Abstract To improve the electroluminescence Efficiency of organic-inorganic hybrid perovskite (OIP) films, we need to consider several different types of post-treatments after film formation such as thermal annealing and solvent annealing. Here, we only applied thermal treatment on the film excluding all the other treatments. Then, we analyzed the effects of annealing time tann on crystallinity of methylammonium lead bromide (CH3NH3PbBr3) films and on Luminous Efficiency of CH3NH3PbBr3-based perovskite light-emitting diodes (PrLEDs). When thermal annealing of CH3NH3PbBr3 films was conducted at 90 °C, tann ≤ 10 min increased its crystallinity by eliminating residual solvent and completing the conversion of precursor to crystal, but tann > 10 min reduced crystallinity and caused slight sublimation of CH3NH3Br. This was consistent with trend of the Luminous Efficiency of our PrLEDs that showed the optimum performance at tann = 10 min. These results demonstrate that optimizing tann of CH3NH3PbBr3 films is a simple way to improve the Luminous Efficiency of PrLEDs by controlling their crystallinity.
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Effects of thermal treatment on organic-inorganic hybrid perovskite films and Luminous Efficiency of light-emitting diodes
Current Applied Physics, 2016Co-Authors: Young Hoon Kim, Jin Hyuck Heo, Himchan Cho, Sang Hyuk Im, Tae-woo LeeAbstract:© 2016 Elsevier B.V. All rights reserved. To improve the electroluminescence Efficiency of organic-inorganic hybrid perovskite (OIP) films, we need to consider several different types of post-treatments after film formation such as thermal annealing and solvent annealing. Here, we only applied thermal treatment on the film excluding all the other treatments. Then, we analyzed the effects of annealing time t ann on crystallinity of methylammonium lead bromide (CH 3 NH 3 PbBr 3 ) films and on Luminous Efficiency of CH 3 NH 3 PbBr 3 -based perovskite light-emitting diodes (PrLEDs). When thermal annealing of CH 3 NH 3 PbBr 3 films was conducted at 90 °C, t ann ≤ 10 min increased its crystallinity by eliminating residual solvent and completing the conversion of precursor to crystal, but t ann > 10 min reduced crystallinity and caused slight sublimation of CH 3 NH 3 Br. This was consistent with trend of the Luminous Efficiency of our PrLEDs that showed the optimum performance at t ann = 10 min. These results demonstrate that optimizing t ann of CH 3 NH 3 PbBr 3 films is a simple way to improve the Luminous Efficiency of PrLEDs by controlling their crystallinity.
Tae-woo Lee - One of the best experts on this subject based on the ideXlab platform.
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Effects of thermal treatment on organic-inorganic hybrid perovskite films and Luminous Efficiency of light-emitting diodes
Current Applied Physics, 2016Co-Authors: Young Hoon Kim, Jin Hyuck Heo, Himchan Cho, Sang Hyuk Im, Tae-woo LeeAbstract:© 2016 Elsevier B.V. All rights reserved. To improve the electroluminescence Efficiency of organic-inorganic hybrid perovskite (OIP) films, we need to consider several different types of post-treatments after film formation such as thermal annealing and solvent annealing. Here, we only applied thermal treatment on the film excluding all the other treatments. Then, we analyzed the effects of annealing time t ann on crystallinity of methylammonium lead bromide (CH 3 NH 3 PbBr 3 ) films and on Luminous Efficiency of CH 3 NH 3 PbBr 3 -based perovskite light-emitting diodes (PrLEDs). When thermal annealing of CH 3 NH 3 PbBr 3 films was conducted at 90 °C, t ann ≤ 10 min increased its crystallinity by eliminating residual solvent and completing the conversion of precursor to crystal, but t ann > 10 min reduced crystallinity and caused slight sublimation of CH 3 NH 3 Br. This was consistent with trend of the Luminous Efficiency of our PrLEDs that showed the optimum performance at t ann = 10 min. These results demonstrate that optimizing t ann of CH 3 NH 3 PbBr 3 films is a simple way to improve the Luminous Efficiency of PrLEDs by controlling their crystallinity.
Sedat Nizamoglu - One of the best experts on this subject based on the ideXlab platform.
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quantum dot white leds with high Luminous Efficiency
Optica, 2018Co-Authors: Sadra Sadeghi, Baskaran Ganesh Kumar, Rustamzhon Melikov, Mohammad Mohammadi Aria, Houman Bahmani Jalali, Sedat NizamogluAbstract:Colloidal quantum dots (QDs) have attracted significant attention in the last three decades due to high quantum yield (QY) and tunable electronic properties via quantum confinement effect and material composition. However, their utilization for efficient solid-state lighting sources has remained a challenge due to the decrease of QY from the synthesis batch in the liquid state to the host matrix in the solid state, which is also known as the host material effect. Here, we suppress the host material effect by simple liquid-state integration in light-emitting diodes (LEDs) that lead to a Luminous Efficiency of 64 lm/W for red, green, blue (RGB)-based and 105 lm/W for green, blue (GB)-based white light generation. For that, we maximized the QY of red- and green-emitting QDs by optimizing synthesis parameters and integrated efficient QDs with QY up to 84% on blue LED dies in liquid form at appropriate injection amounts for high-Efficiency white lighting. Liquid-state integration showed two-fold and six-fold enhancement of Efficiency in comparison with incorporation of QDs in polydimethylsiloxane film and close-packed formation, respectively. Our theoretical calculations predicted that the Luminous Efficiency of liquid QD-LEDs can reach over 200 lm/W. Therefore, this study paves the way toward ultra-high-Efficiency QD-based lighting.
Eun Ha Choi - One of the best experts on this subject based on the ideXlab platform.
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Improvement of Luminance and Luminous Efficiency Using New Electrode Structures in AC Plasma Display
IEEE Transactions on Plasma Science, 2009Co-Authors: Eun Ha ChoiAbstract:Two new electrode structures, namely, fence electrode (Fen) and combination of coplanar and fence electrodes (CoFen), employing an elevated bus electrode in the conventional surface discharge structure with three electrodes are suggested. In this paper, various comparisons between the conventional and two new structures are made to validate the effectiveness of the proposed structures. The firing and sustain voltages, displacement and discharge currents, cell capacitance, luminance, and Luminous Efficiency for three electrode structures are measured for various pressure ranges used in the conventional plasma displays. Consequently, the experimental results show that the CoFen structure has lower firing and sustain voltages than the conventional and Fen structures for all pressure ranges from 100 to 700 torr. In addition, the Fen structure realizes over 80% brighter and approximately 18% higher Luminous Efficiency than the conventional one.
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Influence of xenon mole fraction on Luminous Efficiency of the plasma display panel
Thin Solid Films, 2005Co-Authors: Eun Ha ChoiAbstract:The Luminous Efficiency of the plasma display panel is investigated in terms of the xenon mole fraction. A theoretical model of the Luminous Efficiency in a mixed gas is developed, based on the energy balance equation. The Luminous Efficiency η is expressed as η=kχexp(−ɛ*/Tb), where χ is the gas mixture ratio, Tb is the electron breakdown temperature and ɛ* is the xenon excitation energy in eV. As an example, the Luminous Efficiency in neon gas mixed with xenon is investigated. It is shown that the Luminous Efficiency η increases monotonically as the xenon mole fraction increases from zero to unity. A preliminary experiment is carried out for neon gas mixed with a small percentage of xenon. The theoretical results agree reasonably well with experimental data. However, the Efficiency enhancement dampens significantly when the xenon mole fraction is considerably large.
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vacuum ultraviolet Luminous Efficiency and plasma ion density in alternating current plasma display panels
Applied Physics Letters, 2002Co-Authors: Eun Ha Choi, Min Wug Moon, Yoon Jung, Myung Chul Choi, Kunihide Tachibana, Ki Woong Whang, M KristiansenAbstract:The correlation between the vacuum ultraviolet (VUV) Luminous Efficiency and the plasma ion density has been investigated in terms of the xenon mole fraction in the neon filling gas for alternating current plasma display panels. The VUV Luminous Efficiency and plasma ion density are found to have strong correlation and to be saturated at xenon mole fractions greater than 7% and gas pressures of 400 Torr.
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influence of sustaining pulse width on electro Luminous Efficiency in ac plasma display panels
Japanese Journal of Applied Physics, 2000Co-Authors: Jaejun Ko, Eun Ha ChoiAbstract:The influence of sustaining pulse-width on electro-Luminous Efficiency has been experimentally investigated for the surface discharge of AC plasma display panels. A square driving voltage pulse with a variable duty ratio and a fixed rise time of 300 ns has been used in this experiment. It is found that the firing voltage decreases as the sustaining pulse-width increases from 2 µs to 8 µs under a given driving frequency, and also decreases as the frequency increases from 10 kHz to 50 kHz. The memory coefficient is found to be significantly increased from 0.16 to 0.71, as the sustaining pulse-width increases from 3 µs to 4 µs, beyond which it maintains a nearly constant value of approximately 0.8 for the driving frequency range from 30 kHz to 50 kHz. The optimal sustaining pulse-width is shown to be in the range of 3 µs and 4 µs for driving frequencies of 30 kHz and 50 kHz, based on the observations of memory coefficient, wall charge, wall voltage and Luminous Efficiency.
