• 한국정보디스플레이학회:학술대회논문집
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• 2008.10a
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• pp.428-430
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• 2008

We demonstrated high power efficiency and long lifetime for organic light-emitting diode (OLED) using a new electron transport material (ETM-1). A power efficiency of the device with ETM-1 was improved compared to a standard device using tris(8-hydroxy-quinolinate)aluminum ($Alq_3$). Moreover, the lifetime was 4 times longer than the standard device.

• 한국정보디스플레이학회:학술대회논문집
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• 2007.08a
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• pp.625-627
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• 2007

We demonstrated high power efficiency and long lifetime in organic light-emitting diode (OLED) using new electron transport materials (ETMs). Electroluminescent device with these ETMs showed lower driving voltage than that with $Alq_3$. The device lifetime with a new ETM was 2 times longer than that with $Alq_3$.

• 한국정보디스플레이학회:학술대회논문집
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• 2005.07b
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• pp.964-967
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• 2005

The search for stable electron transporters and hole injectors has become particularly intense over the last 18 months as OLED manufacturers are poised to start production of OLED panels. We report here a proprietary electron transporter (E246), which reduces the operating voltage, increases the efficiency and the lifetime of OLEDs made of fluorescent or phosphorescent systems when compared with Alq3 as an electron transporter. We also report a novel proprietary hole injector (buffer, E9363) which also reduces the operating voltage, increases the efficiency and doubles the lifetime compared to CuPC. These two materials are now available commercially for display manufacturers.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.28 no.5
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• pp.338-343
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• 2015

Dye sensitized solar cells (DSSCs), which is one of the contending renewable energy sources, have the problem of low efficiency. To improve the efficiency, the fast electron transport and long electron lifetime are required. In this study, one-dimensional sodium hexatitanate, which is expected to have an advantageous structure for electron transports, was synthesized and the feasibility of the material on DSSC was tested. Its physical properties were characterized by the SEM, XRD, and BET method. The dye adsorption and solar cell properties were also characterized. In addition to the expectation of fast electron transport, sodium hexatitanate showed longer electron lifetime: This means sodium hexatitanate can improve the DSSC efficiency. However, it showed low current and voltage because of the low surface area leading to the low amount of dye adsorbed. Therefore, it should be mixed with titanium oxide with high surface area for the optimal performance.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.49 no.3
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• pp.165-168
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• 2000

Improvement on the switching characteristic of IGBT by means of the uniform and local lifetime control is studied numerically using two-dimensional simulator, MEDICI. In the case of uniform lifetime control, the on-state and switching characteristics are simulated as a function of lifetime, and compared with the experimental results reported, which allows a relationship between dose of electron irradiation and controlled lifetime. In the case of local lifetime control, simulations are carried out by varying the position, width, and lifetime of the locally controlled region, and the results are compared with the characteristics for the case of the uniform lifetime control. The turn-off time of the device with an optimized locally controlled region is found to decrease from about $4.5\mus$ to 0.11$mutextrm{s}$ while the forward voltage drop increases from 1.37V to 2.61V in comparison with that for the uniform lifetime control.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.19 no.3
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• pp.216-221
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• 2006

Lifetime control technique by proton implantation has become an useful tool for production of modern power devices. In this work, punch-through type diodes were irradiated with protons for the high speed power diode fabrication. Proton irradiation which was capable of controlling carrier's lifetime locally was carried out at the various energy and dose conditions. Characterization of the device was performed by current-voltage, capacitance-voltage and reverse recovery time measurement. We obtained enhanced reverse recovery time characteristics which was about $45\;\%$ of original device reverse recovery time and about $73\;\%$ of electron irradiated device reverse recovery time. The measurement results showed that proton irradiation technique was able to effectively reduce minority carrier lifetime without degrading the other characteristics.

• Transactions on Electrical and Electronic Materials
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• v.13 no.2
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• pp.60-63
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• 2012

Enhancement of efficiency and luminance of organic light-emitting diodes was investigated by the introduction of a lithium carbonate ($Li_2CO_3$) electron-injection layer. Electron-injection layer is used in organic light-emitting diodes to inject electrons efficiently between a cathode and an organic layer. A device structure of ITO/TPD (40 nm)/$Alq_3$ (60 nm)/$Li_2CO_3$ (x nm)/Al (100 nm) was manufactured by thermal evaporation, where the thickness of $Li_2CO_3$ layer was varied from 0 to 3.3 nm. Current density-luminance-voltage characteristics of the device were measured and analyzed. When the thickness of $Li_2CO_3$ layer is 0.7 nm, the current efficiency and luminance of the device at 8.0 V are improved by a factor of about 18 and 3,000 compared to the ones without the $Li_2CO_3$ layer, respectively. The enhancement of efficiency and luminance of the device with an insertion of $Li_2CO_3$ electron-injection layer is thought to be due to the lowering of an electron barrier height at the interface region between the cathode and the emissive layer. This is judged from an analysis of current density-voltage characteristics with a Fowler-Nordheim tunneling conduction mechanism model. In a study of lifetime of the device that depends on the thickness of $Li_2CO_3$ layer, the optimum thickness of $Li_2CO_3$ layer was obtained to be 1.1 nm. It is thought that an improvement in the lifetime is due to the prevention of moisture and oxygen by $Li_2CO_3$ layer. Thus, from the efficiency and lifetime of the device, we have obtained the optimum thickness of $Li_2CO_3$ layer to be about 1.0 nm.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.41 no.7
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• pp.21-29
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• 2004

Hot carrier degradation characteristics of Nano-scale CMOSFETs with dual gate oxide have been analyzed in depth. It is shown that, PMOSFET lifetime dominate the device lifetime than NMOSFET In Nano-scale CMOSFETs, that is, PMOSFET lifetime under CHC (Channel Hot Carrier) stress is much lower than NMOSFET lifetime under DAHC (Dram Avalanche Hot Carrier) stress. (In case of thin MOSFET, CHC stress showed severe degradation than DAHC for PMOSFET and DAHC than CHC for NMOSFET as well known.) Therefore, the interface trap generation due to enhanced hot hole injection will become a dominant degradation factor in upcoming Nano-scale CMOSFET technology. In case of PMOSFETs, CHC shows enhanced degradation than DAHC regardless of thin and thick PMOSFETs. However, what is important is that hot hole injection rather than hot electron injection play a important role in PMOSFET degradation i.e. threshold voltage increases and saturation drain current decreases due to the hot carrier stresses for both thin and thick PMOSFET. In case of thick MOSFET, the degradation by hot carrier is confirmed using charge pumping current method. Therefore, suppression of PMOSFET hot carrier degradation or hot hole injection is highly necessary to enhance overall device lifetime or circuit lifetime in Nano-scale CMOSFET technology

• Nuclear Engineering and Technology
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• v.51 no.3
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• pp.731-737
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• 2019

In this study, a new measurement method based on voltage transients in CdZnTe detectors response to low energy photon irradiations is applied to measure the electron mobility (${\mu}_e$) and electron mobility-lifetime product $({\mu}{\tau})_e$ in a CdZnTe detector. In the proposed method, the pulse rise times are derived from low energy photon response to 59.5 keV($^{241}Am$), 88 keV($^{109}Cd$) and 122 keV($^{57}Co$) ${\gamma}-rays$ for the irradiation of the cathode surface at each detector for different bias voltages. The electron $({\mu}{\tau})_e$ product was then determined by measuring the variation in the photopeak amplitude as a function of bias voltage at a given photon energy using a pulse-height analyzer. The $({\mu}{\tau})_e$ values were found to be $(9.6{\pm}1.4){\times}10^{-3}cm^2V^{-1}$ for $1000mm^3$, $(8.4{\pm}1.6){\times}10^{-3}cm^2V^{-1}$ for $1687.5mm^3$ and $(7.6{\pm}1.1){\times}10^{-3}cm^2V^{-1}$ for $2250mm^3$ CdZnTe detectors. Those results were then compared with the literature $({\mu}{\tau})_e$ values for CdZnTe detectors. The present results indicate that, the electron mobility ${\mu}_e$ and electron $({\mu}{\tau})_e$ values in CdZnTe detectors can be measured easily by applying voltage transients response to low energy photons, utilizing a fast signal acquisition and data reduction and evaluation.

• Proceedings of the KIEE Conference
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• 1999.07d
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• pp.1947-1949
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• 1999

Carrier lifetime in silicon power devices caused switching delay and excessive power loss at high frequency switching. We studied transient turn-on/turn-off transient characteristics of electron irradiated and proton irradiated silicon pn junction diodes. Both the electron and proton irradiation of power devices have already become a widely used practice to reduce minority carrier lifetime locally[1]. The sample is n+p junction diode, made by ion implantation on a $20\Omega.cm$ p-type wafer. We investigated turn-on/turn-off transient & breakdown voltage characteristics by digital oscilloscope. Our data show that proton irradiated samples show better performance than electron irradiated samples.