• Bulletin of the Korean Chemical Society
• /
• v.34 no.9
• /
• pp.2609-2615
• /
• 2013

A series of fluorene-carbazole copolymers containing the pendant phosphor chromophore $Ir(absn)_2(acac)$ (absn: 2-(1-naphthyl)benzothiazole; acac: acetylacetone) were designed and synthesized via Yamamoto coupling. In the film state, these copolymers exhibited absorption and emission peaks at approximately 389 and 426 nm, respectively, which originated from the fluorene backbone. However, in electroluminescent (EL) devices, a significantly red-shifted emission at approximately 611 nm was observed, which was attributed to the pendant iridium(III) complex. Using these copolymers as a single emission layer, polymer light-emitting devices with ITO/PEDOT:PSS/polymer:DNTPD/TmPyPb/LiF/Al configurations exhibited a saturated red emission at 611 nm. The attached iridium(III) complex had a significant effect on the EL performance. A maximum luminous efficiency of 0.85 cd/A, maximum external quantum efficiency of 0.77, maximum power efficiency of 0.48 lm/W, and maximum luminance of 883 $cd/m^2$ were achieved from a device fabricated with the copolymer containing the iridium(III) complex in a 2% molar ratio.

• Bulletin of the Korean Chemical Society
• /
• v.30 no.9
• /
• pp.1933-1938
• /
• 2009

New $\pi$-conjugated polymer with vinylene linkage, poly((10-hexyl-3,7-phenothiazine)-alt-(4-(4-butyl-phenyl)- 3,5-diphenyl-4H-[1,2,4]triazole)-3,5-vinylene) (PTV-TAZ) was synthesized by the Heck coupling reaction. The photoluminescence (PL) maximum wavelength and the band gap energy of PTV-TAZ film were 555 nm and 2.41 eV, respectively. The HOMO energy level of PTV-TAZ was -4.99 eV, which was slightly lower than that of PTV (-4.89 eV). Electron deficient aromatic 1,2,4-triazole (TAZ) in the polymer backbone does not affect the HOMO energy level significantly. The maximum efficiency and brightness of double layer structured electroluminescent (EL) device (ITO/PEDOT (30 nm)/PTV-TAZ (60 nm)/Al) were 0.247 cd/A and 553 cd/$m^2$, respectively, which were significantly higher than those of the device based PTV (1.65 ${\times}\;10^{-4}$ cd/A and 4.3 cd/$m^2$). This is due to that TAZ unit improves electron transporting ability in the emissive layer. The turn-on voltage (defined as the voltage required to give a luminescence of 1 cd/$m^2$) of brightness of the device based on PTV-TAZ was 12.0 V, which was similar to that the based on PTV (11.5 V). This is due to that the ionization potential of PTV-TAZ is very similar to that of PTV.

• Journal of the Institute of Electronics Engineers of Korea SD
• /
• v.37 no.1
• /
• pp.36-43
• /
• 2000

The sulfur pressure and TRA(rapid thermal annealing) conditions of the fabricated SrS:CuCl TFEL devices were optimized to improve blue color luminance. The thickness of the phosphor layer of SrS:CuCl TFEL devices fabricated by electron beam deposition system was 6000 ~ 8000 ${\AA}$. The fabricated TFEL devices were annealed at 800 $^{\circ}C$ for 3 min. It was shown that the crystallinity of SrS:CuCl phosphor was improved by an increase in RTA temperature and RTA time. Blue color was emitted from the TFEL device with emission peak wavelength of 468 nm and 500 nm. The CIE color coordinates were x = 0.21, y = 0.33. The luminance($L_{40}$) of TFEL device strongly depended on the sulfur pressure of deposition chamber and increased from 262 cd/$m^2$ to 728 cd/m2 as the sulfur pressure increased from $8{\times}10^{-6}$ torr to $2{\times}10^{-5}$ torr.

• Journal of the Institute of Electronics Engineers of Korea SD
• /
• v.37 no.1
• /
• pp.29-35
• /
• 2000

Luminescent characteristics of SrS:Cu,X TFeL devices fabricated by electron-beam deposition system were studied. The SrS powders were used as the host materials and Cu, $CuF_2,\;Cu_2S$ or CuCl powders were added as the luminescent center. The emission spectra of the SrS:Cu,X TFEL devices strongly depended on coactivators. The luminance($L_{40}$) and efficiency(${\eta}_{20}$) of SrS:$Cu_2S$ TFEL device were 1443 cd/$m^2$ and 2.44 lm/w, respectively. Green color was observed from this TFEL device. The luminous efficiency of SrS:$Cu_2S$ TFEL device was higher than that of ZnS:Tb TFEL device, and it also could be good green phosphors for TFEL devices. The luminance($L_{40}$) and efficiency(${\eta}_{20}$) of SrS:CuCl TFEL device were 262 cd/$m^2$ and 0.26 lm/w, respectively. Blue color was emitted from this TFEL device.

• The Journal of the Korea Contents Association
• /
• v.2 no.3
• /
• pp.146-151
• /
• 2002

The $Ca_{1-x}$Sr$_{x}$S:CuCl TFEL devices were fabricated by electron-beam deposition system and luminescent characteristics of the TFEL devices were studied. The SrS and CaS powders were mixed to form $Ca_{1-x}$Sr$_{x}$S host materials and 0.2 at% of CuCl was added as the activator. The luminance(lao) and peak emission wavelength of CaS:CuCl TFEL devices were 9.5 cd/m$^2$ and 492 nm, respectively. The luminance(L$_{30}$) and peak emission wavelength of SrS:CuCl TFEL devices were 633 cd/m$^2$ and 500 nm, respectively. It seems that the addition of CaS into the SrS host material generates blue shift of the EL emission characteristics but reduces the luminance and the luminous efficiency of the $Ca_{1-x}$Sr$_{x}$S:CuCl TFEL devices drastically.

• Journal of the Institute of Electronics Engineers of Korea SD
• /
• v.39 no.8
• /
• pp.17-23
• /
• 2002

The SrS:CuCl TFEL devices were fabricated by electron-beam deposition and the luminescent characteristics of the fabricated SrS:CuCl TFEL devices were studied. The SrS powder was used as the host materials and 0.05 ~ 0.6 at% of CuCl powder was added as the luminescent center. The deposition conditions of substrate temperature, electron beam current, and deposition rate were 500 $^{\circ}C$ , 20 ~ 40 mA, and 5 ~ 10 /sec, respectively The total thickness of the phosphor layer deposited was 6000 . The blue emission at low CuCl concentrations was observed from the luminescent centers of monomer, dimer, trimer, and tetramer, The bright greenish blue emission at high CuCl concentrations was observed from the dimer and trimer luminescent centers. The maxium luminance was observed from the SrS:CuCl TFEL devices doped with 0.2 at% of CuCl concentration and the threshold voltage, luminance(L$_{40}$ ), efficiency(η$_{20}$) and CIE coordinate obtained were 55 V, 728 cd/$m^2$, 0.49 lm/w, and (0.21, 0.33), respectively..

• Korean Journal of Materials Research
• /
• v.33 no.10
• /
• pp.400-405
• /
• 2023

Tb³⁺-doped CaNb₂O₆ (CaNb₂O₆:Tb³⁺) thin films were deposited on quartz substrates at a growth temperature of 300 ℃ using radio-frequency magnetron sputtering. The deposited thin films were annealed at several annealing temperatures for 20 min and characterized for their structural, morphological, and luminescent properties. The experimental results showed that the annealing temperature had a significant effect on the properties of the CaNb₂O₆:Tb³⁺ thin films. The crystalline structure of the as-grown CaNb₂O₆:Tb³⁺ thin films transformed from amorphous to crystalline after annealing at temperatures greater than or equal to 700 ℃. The emission spectra of the thin films under excitation at 251 nm exhibited a dominant emission band at 546 nm arising from the ⁵D₄→⁷F₅ magnetic dipole transition of Tb³⁺ and three weak emission bands at 489, 586, and 620 nm, respectively. The intensity of the ⁵D₄→⁷F₅ (546 nm) magnetic dipole transition was greater than that of the ⁵D₄→⁷F₆ (489 nm) electrical dipole transition, indicating that the Tb³⁺ ions in the host crystal were located at sites with inversion symmetry. The average transmittance at wavelengths of 370~1,100 nm decreased from 86.8 % at 700 ℃ to 80.5 % at an annealing temperature of 1,000 ℃, and a red shift was observed in the bandgap energy with increasing annealing temperature. These results suggest that the annealing temperature plays a crucial role in developing green light-emitting CaNb₂O₆:Tb³⁺ thin films for application in electroluminescent displays.

• Journal of the Korean Vacuum Society
• /
• v.7 no.1
• /
• pp.51-58
• /
• 1998

ZnS and TB-doped ZnS (ZnS:Tb) thin films were grown by traveling wave reactor atomic layer epitaxy (AKE) and characterized using materials and surface analysis techniques. $ZnCl_2$, $H_2$S,and tris(2,26,6-tetramethyl-3,5-heptandionato) terbium ($Tb(TMHD)_3$) were used as the precursors in the growth of ZnS:Tb films. The dependence of Cl content in ZnS films on growth temperature was investigated using Rutherford backscattering spectrometry. The Cl content decreased from approximately 9 at.% to 1 at. % as increasing the growth temperature from 400 to $500^{\circ}C$. The segregation of Cl in near surface region was also observed by depth profiling using Auger electron spectroscopy. Scanning electron microscopic studies showed that the ALE-grown ZnS and ZnS:Tb film during ALE process using $Tb(TMHD)_3$was also investigated. Approximately 1 at.% of O in ZnS:Tb(0.5 at.%) film which showed a good crystallinity of hexagonal 2H structure.