• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2006년도 6th International Meeting on Information Display
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• pp.1692-1696
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• 2006

Dopant and host molecules for charge transport layer in OLED have been developed. They enable implementation of the PIN OLED technology in mass production. We review the status of PIN OLED with main focus on top-emission structures and operation stability at elevated temperatures. A green phosphorescent top-emission device with 2.5 V operating voltage and 90 lm/W at 1000 $cd/m^2$ is presented. For a red top-emission device, lifetime exceeding 100,000 h at 500 $cd/m^2$ initial brightness is reported. Operational stability at $80^{\circ}C$ has been investigated. A lifetime of 17,000 h at 500 $cd/m^2$ has been achieved. Finally, we comment on further reduction of the operating voltage in OLED.

• 한국결정성장학회지
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• 제9권4호
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• pp.377-380
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• 1999

Erbium (Er) doped $LiNbO_{3}(Er:LiNbO_{3})$ single crystal fibers were grown free of creacks along the c-axis by micro-pulling down method. The $Er^{3+}$ concentration was distributed homogeneously along the growth axis. The samples for optical characterization were cut from as-grown single crystal fibers and polished. When the 980nm light was incident on the sample, upconversion phenomena were observed at the green range of wavelength 510~570nm. In addition, the intensity of upconversion was remarkably increased by increasing the concentration of $Er_{2}O_{3}$ dopant in as-grown $Er:LiNbO_{3}$ crystals.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제50권9호
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• pp.434-437
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• 2001

ZnSe, ZnSe:Ho/sup 3+/, Mg/sub x/Zn/sub 1-x/Se and Mg/sub x/Zn/sub 1-x/Se:Ho/sup 3+/ crystals were grown by the chemical transport reaction method. The crystal structures and optical energy band gaps of the single crystals were investigated. Their photoluminescence(PL) spectra were measured at 10 [K]. Sharp emission peaks in the blue-green wavelength range and broad emission peaks in the yellow-red wavelength range were observed. The single crystals doped with 1.0 [mol%] of holmium did not show the sharp emission peaks because of defects which were thought to be originated to the holmium dopant.

• 한국산학기술학회논문지
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• 제11권3호
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• pp.827-834
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• 2010

발광층에 도펀트가 도핑된 다층 유기발광다이오드 소자 구조에서의 발광 메카니즘을 검증하기 위해 전기적인 특성요인들을 수치해석 하였다. 본 논문에 적용한 유기발광다이오드 소자는 ITO/NPB/$Alq_3$:C545T(%)/$Alq_3$/LiF/Al으로 이루어져 있으며 도펀트인 C545T의 도핑 농도를 변화시킨 4종류의 소자 구조에 대해 특성 변화를 검토하였다. 그 결과 도펀트의 도핑 농도 변화에 따라서 전압-전류 특성이 변화되어짐을 확인하였고, 이는 참고 문헌에 제시되어 있는 전압-전류밀도 실험 데이터와 매우 잘 일치되었다. 또한 도펀트를 도핑시킨 소자 구조들에서 전압-휘도 특성이 대폭 향상되어 발광효율이 3배정도 향상되었다. 이와 같은 guest-host system이 적용된 유기발광다이오드 소자의 동작 메카니즘을 분석하기 위하여 소자 내부에서의 전계분포, 전하분포, 재결합율 등의 전기적인 항목들에 대한 특성의 변화를 관찰하였다.

• 한국세라믹학회지
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• 제50권1호
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• pp.87-91
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• 2013

The doping effect of Sn on the microstructure evolution and dielectric properties was studied in $CaCu_3Ti_{4-x}Sn_xO_{12}$ polycrystals. Samples were produced by a conventional solid-state reaction method. Sintering was carried out at $1115^{\circ}C$ for 2-16 h in air. The dielectric constant and loss were examined at room temperature over a frequency range between $10^2$ and $10^6$ Hz. The microstructure was found to evolve into three stages. Addition of $SnO_2$ led to an increase in density and advanced formation of abnormal grains. The formation of coarse grains with a reduced thickness of the boundary brought about an enhanced dielectric constant and a lower dielectric loss below ~1 kHz. EDS data showed the Cu-rich phase along the grain boundary, which should contribute to the improved dielectric constant according to the internal barrier layer capacitor model. After all, $SnO_2$ was an effective dopant to elevate the dielectric characteristics of $CaCu_3Ti_{4-x}Sn_xO_{12}$ polycrystals as a promoter for abnormal grain growth.

• 한국세라믹학회지
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• 제47권5호
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• pp.457-460
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• 2010

$SmCoO_3$ system was investigated for their application to themoelectric materials. All specimens showed p-type semiconducting behavior and their electrical conductivity ($\sigma$), Seebeck coefficient (S) and power factor were measured at high temperature. And the effect of dopant ions on their thermoelectrical properties were also investigated. $Fe^{3+}$ ion doped into $Co^{3+}$ site enhanced the Seebeck coefficient and decreased the electrical conductivity simultaneously. The maximum Seebeck coefficient value for 60% doping case reached to 780 ${\mu}V$/K at $240^{\circ}C$. However $Fe^{3+}$ doped system cause an negative effect on power factor value. In case of the pure phase, the maximum Seebeck coefficient value reached to 290 ${\mu}V$/K at $240^{\circ}C$ and the maximum electrical conductivity was obtained 748 1/(ohm$\times$cm) at $960^{\circ}C$. As a result, the maximum power factor was obtained $1.49\times10^{-4}$ W/$mK^2$ at $550^{\circ}C$.

• 한국표면공학회지
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• 제48권5호
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• pp.211-217
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• 2015

To fabricate white LED having a high color rendering index value, red color phosphor mixed with the green color phosphor together in the blue chip, namely the blue chips with RG phosphors packaging is most favorable for high power white LEDs. In our previous papers, we reported on successful syntheses of $Sr_{2-}$ $Si_5N_8:Eu^{2+}$ and $CaAlSiN_3$ phosphors for red phosphor. In this work, for high power green phosphor, greenemitting ternary nitride $Ba_3Si_6O_{12}N_2:Eu^{2+}$ phosphor was synthesized in a high frequency induction furnace under $N_2$ gas atmosphere at temperatures up to $1400^{\circ}C$ using $EuF_3$ as a raw material for $Eu^{2+}$ dopant. The effects of molar ratio of component and experimental conditions on luminescence property of prepared phosphors have been investigated. The structure and luminescence properties of prepared $Ba_3Si_6O_{12}N_2:Eu^{2+}$ phosphors were investigated by XRD and photoluminescence spectroscopy. The excitation spectra of $Ba_3Si_6O_{12}N_2:Eu^{2+}$ phosphors indicated broad excitation wavelength range of 250 - 500 nm, namely from UV to blue region with distinct enhanced emission spectrum peaking at ${\approx}530nm$.

• 대한화학회지
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• 제43권2호
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• pp.206-212
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• 1999

본 연구의 목적은 기존의 $Zn_2SiO_4:Mn$형광체에 새로운 co-dopant를 첨가하여 발광특성을 향상시키는 것이다. co-dopant로서 선정한 Mg와 Cr이온들은 Zn자리를 치환하는 것으로 알려져 있으며 실제로 co-doping 시 각각 발광휘도와 decay time을 개선시키는 효과를 거두었다. $Zn_2SiO_4:Mn$에 Mg와 Cr이온들이 co-doping될 시에는 lattice 및 $Mn^{2+}$의 에너지 준위를 변화시키는 것으로 추정되어 발광휘도 및 decay time의 변화를 일으키는 것으로 해석된다. 특히 이 원소들은 발광과정에 긍정정인 영향을 끼쳐 Mg는 발광휘도를 중가시키고 Cr은 decay time을 감소시키는 결과를 얻었다. $Zn_2SiO_4:Mn,\;Mg$ 형광체의 발광휘도 개선은 DV-X${\alpha}$ embedded cluster 계산방법으로 설명할 수 있었고 반면에 $Zn_2SiO_4:Mn,\;Cr$ 형광체가 decay time을 줄이는 원인은 Mn이온과 Cr이온사이에 energy transfer가 일어나 발생되는 것으로 추정된다.

• 대한전자공학회논문지SD
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• 제38권12호
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• pp.1-7
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• 2001

낮은 동작전압에서 안정하게 동작하고 고효율을 갖는 단층 폴리머 녹색광소자를 갖는 새로운 물질을 합성하였으며 이는 폴리머물질인 PC(B79)에 유기단분자인 전자수송성이 ?어난 NIDI와 정공수송성이 뛰어난 TTA를 분자분산하여 첨가색소인 C6의 도핑농도에 변화를 주어 스핀코팅으로 녹색발광소자를 제작하였다. 소자 구조는 glass/ITO/PC:TTA:NIDI:C6/cathode이고 음극전극으로 일함수가 낮은 Ca과 Mg 그리고 Ca/Al을 진공증착하여 전기적${\cdot}$광학적 특성을 비교조사하였다. C6의 도핑농도가 0.08mole%에서 양자효율이 최대인 0.52%를 얻었고 이것은 도핑하지 않을때보다 약 50배 높았고, 동작개시전압도 2.4V의 낮은 동작 개시전압에서 안정하게 동작하였다. 한편 PL과 EL측정결과 C6의 도핑농도를 변화하여도 발광파장의 최대값은 거의 일정하였다. PL강도의 최대발광파장은 495nm였고 EL강도의 최대발광파장은 520nm이고 FWHM은 약 70nm를 얻었다.

• Journal of Information Display
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• 제3권1호
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• pp.6-10
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• 2002

We have synthesized a new green Ir(III) complex fac-tris-(3-methyl-2-phenyl pyridine)iridium(III) $Ir(mpp)_3$ and fabricated phosphorescent polymer light-emitting device using it as a triplet emissive dopant in PVK. $Ir(mpp)_3$ showed absorption centered at 388 nm corresponding to the $^1MLCT$ transition as .evidenced by its extinction coefficient of the order of $10^3{\cdot}$ From the PL and EL spectra of the $Ir(mpp)_3$ doped PVK film, the emission maximum was observed at 523 nm, due to the radiative decay from the $^3MLCT$ state to the ground state, confirming a complete energy transfer from PVK to $Ir(mpp)_3$. The methyl substitution has probably caused a red shift in the absorption and emission spectrum compared to $Ir(mpp)_3$. The device consisting of a 2 % doped PVK furnished 4.5 % external quantum efficiency at 72 $cd/m^2$ (current density of 0.45 $mA/cm^2$ and drive voltage of 13.9 V) and a peak luminance of 25,000 $cd/m^2$ at 23.4 V (494 $mA/cm^2$). This work demonstrates the impact of the presence of a methyl substituent at the 3-position of the pyridyl ring of 2-phenylpyridine on the photophysical and electroluminescence properties.