• 한국정보디스플레이학회:학술대회논문집
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• 2009.10a
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• pp.418-420
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• 2009

The Authors have demonstrated high efficiency hybrid white organic light-emitting diodes (HWOLED) for reduced efficiency roll-off and color stability. It was shown that HWOLED fabricated in this study have the maximum luminance of 46 420 cd/$m^2$ at 8 V (turn-on voltage of 2.7 V), external quantum efficiency of 13.18%, power efficiency of 28.75 lm/W at 1 000 cd/$m^2$, and reduced efficiency roll-off of 2.7 times than control white device. The HWOLED also showed the stable color shift with $\Delta$Commission Internationale de I'Eclairage coordinates coordinates of ${\pm}$ (0.00, 0.00) from 100 to 10000 cd/$m^2$.

• 한국정보디스플레이학회:학술대회논문집
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• 2009.10a
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• pp.192-195
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• 2009

We developed highly efficient blue PHOLEDs with reduced roll-off by using a mixed host structure. The balanced charge carrier injection and the distributed recombination zone within emissive layer resulted in a highly stable efficiency roll-off with quantum efficiencies of 20.1 and 18.1 % at a luminance of 1000 and 10000 cd/$m^2$.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.28 no.7C
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• pp.678-687
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• 2003

8SQAM(8-state Superposed Quadrature Amplitude Modulation) being a new modem technique for use in power and bandwidth limited digital communication system generates output signals which have a mか and continuous phase transition and a reduced envelope fluctuation by keeping correlation between amplitudes and phases of two subsequent symbols. Also, 8SQAM signal is free of inter-symbol interference(ISI), and has a compact power spectrum. Accordingly 8SQAM, as compared with a conventional 8PSK, is influenced a little by inter-modulation(IM), inter-symbol interference(ISI) and adjacent channel interference(ACI) in a nonlinearly amplified multi-channel(SCPC-FDMA) environment. In this paper, the performance of 8SQAM system in a nonlinearly amplified multi-channel interference environment is analyzed via computer simulation The simulation result shows that 8SQAM outperforms 8PSK with roll-off value of $\alpha$ = 0.3 by 2.7dB in CNR to maintain BER=1$\times$10$^{-4}$ when input back-off(IBO) of HPA is 1dB and channel space is 41.7% of the data bit rate(i.e., spectral efficiency = 2.40b/s/Hz).