• Current Optics and Photonics
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• v.3 no.2
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• pp.164-171
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• 2019

Photoluminescence (PL) properties of GaN-based light-emitting diodes (LEDs) were analyzed to study the effects of carrier leakage on the luminescence properties at room temperature. The electrical leakage and PL properties were compared for LEDs showing leakages at forward bias and an LED with an intentional leakage path formed by connecting a parallel resistance of various values. The leakages at the forward bias, which could be observed from the current-voltage characteristics, resulted in an increase in the excitation laser power density for the maximum PL efficiency (ratio of PL intensity to excitation power) as well as a reduction in the PL intensity. The effect of carrier leakages on PL properties was similar to the change in PL properties owing to a reduction of the photovoltage by a reverse current since the direction of the carrier movement under photoexcitation is identical to that of the reverse current. Valid relations between PL properties and electrical properties were observed as the PL properties deteriorated with an increase in the carrier leakage. The results imply that the PL properties of LED chips can be an indicator of the electrical properties of LEDs.

• 한국정보디스플레이학회:학술대회논문집
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• 2008.10a
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• pp.788-791
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• 2008

ZnO nanoparticle was successfully prepared by microwave irradiation method in various oxygen/nitrogen ratio atmospheres. The product prepared in a low oxygen ratio atmosphere showed tetra pod shape with high aspect ratio, c/a. PL spectra of the products showed higher UV emission intensity than the others when it was prepared in the atmosphere oxygen/nitrogen=40/60.

• 한국정보디스플레이학회:학술대회논문집
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• 2005.07a
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• pp.717-720
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• 2005

Nanocrystalline $GdBO_3:Eu^{3+}$ was prepared by a hydrothermal method. The as-synthesized powders were spherical shaped agglomerates of nano particles. The luminescent properties were compared with samples synthesized by conventional solid-state reaction method. Both the photoluminescence intensity and chromaticity were improved and a red-shift in the CT band was observed for the hydrothermally synthesized samples.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.07a
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• pp.355-357
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• 2001

ZnO thin films were deposited on (001) sapphire substrate at various ambient gas pressure by pulsed laser deposition(PLD). Oxygen was used as ambient gas, and oxygen gas pressure was varied from 1.0${\times}$10$\^$-6/ Torr to 500 mTorr during the film deposition. As oxygen gas pressure increase in the region below critical pressure photoluminescence(PL) intensity in UV and green region increase. As oxygen gas pressure increase in the region above critical pressure photoluminescence(PL) intensity in UV and green region decrease. Each of critical ambient gas Pressures was 350 mTorr for UV emission and 200 mTorr for green emission.

• 한국정보디스플레이학회:학술대회논문집
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• 2002.08a
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• pp.803-806
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• 2002

Flame spray pyrolysis was applied to improve the photoluminescence characteristics of blue-emitting $Sr_5(PO_4)_3Cl:Eu^{2+}$ phosphor particles with high brightness for the application to LED phosphor. $Sr_5(PO_4)_3Cl:Eu^{2+}$ prepared from conventional spray pyrolysis had poor PL intensity than that of commercial products under long-wavelength ultraviolet(UV). $Sr_5(PO_4)_3Cl:Eu^{2+}$ phosphor particles prepared by flame spray pyrolysis had PL intensity as same as that of commercial products under long-wavelength UV. Hollow morphology and porous structure of the particles prepared by the flame spray pyrolysis disappeared after posttreatment. Even though the $Sr_5(PO_4)_3Cl:Eu^{2+}$ phosphor particles prepared by the flame spray pyrolysis had irregular shape, the particles had dense structure and clear surface property.

• Journal of Information Display
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• v.13 no.3
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• pp.97-100
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• 2012

We have conducted two kinds of the so-called charge-compensated aliovalent element substitutions to control the photoluminescence properties of $NaAlSiO_4:Eu^{2+}$ with a special focus on the enhancement of the excitation intensity at 400 nm. The aliovalent element substitutions include cation-cation and cation-anion co-substitutions according to the general formulas $Na_{1-x}M_xAl_{1+x}Si_{1-x}O_4:Eu^{2+}$ and $Na_{1-x}M_xAlSiO_{4-x}N_x:Eu^{2+}$ (M = $Mg^{2+}$, $Ca^{2+}$, and $Sr^{2+}$), respectively. The increase in the relative excitation intensity at 400 nm has been achieved in both types of the co-substitutions. Thus, the present research has demonstrated the effectiveness of the charge-compensated element substitution.

• Transactions on Electrical and Electronic Materials
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• v.5 no.5
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• pp.194-198
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• 2004

The influences of the deep-level concentration of p-type Si substrates on the optical properties of nano-porous silicon (PS) are investigated by deep level transient spectroscopy (DLTS) and photoluminescence (PL). Utilizing a Si substrate with Fe contaminations significantly enhanced the PL intensity of PS. All the PS samples formed on Fe-contaminated silicon substrates had stronger PL yield than that of reference PS without any intentional Fe contamination but the emission peak is not significantly changed. For the PS 1000 sample with Fe contamination of 1,000 ppb, the maximum PL intensity showed about ten times stronger PL than that of the reference PS sample. From PL and DLTS results, the PL efficiency strongly depends on the Fe-related trap concentration in Si substrates.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.11a
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• pp.195-197
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• 2002

CdTe quantum dots(QDs) were synthesized in aqueous solution by colloidal method. Photoluminescence(PL) spectra of the synthesized CdTe QDs revealed the intensity of PL peaks was stronger as the condensation time was longer. This result was thought because annealing effect by thermal energy transferred during condensation eliminated defects which act as traps and recombination centers in CdTe particle. PL intensity has stron dependence of Te precursor concentration. It confirmed the ratio of Te ion to Cd ion added during synthesis affected the particle size and size distribution of the CdTe QDs. Finally, the synthesized CdTe QDs were identified to be cubic structured CdTe quantum dots by X-ray diffraction(XRD).

• Bulletin of the Korean Chemical Society
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• v.25 no.8
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• pp.1202-1206
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• 2004

Novel naphthyl-containing biphenyl analogues were prepared by Suzki reaction for the chemiluminescent blue fluorophores. UV-Vis absorption, photoluminescence, chemiluminescence and CIE chromaticities were measured. The fluorophores displayed blue photoluminescence in solution with a maximum intensity around 378-415 nm. Sodium salicylate-catalyzed reaction of them with bis(2 carbopentyloxy-3,5,6-trichlorophenyl)-oxalate with hydrogen peroxide provided a strong chemiluminescent red light emission with wavelengths of 398-427 nm; these were similar to the photoluminescent spectra. The chemiluminescent intensity decayed exponentially and the glow of chemiluminescence, which was visible with naked eyes, was maintained for more than 4 h.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.16 no.8
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• pp.663-668
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• 2003

CdTe quantum dots(QDs) were synthesized in aqueous solution by colloidal method. The synthesized CdTe QDs were identified to be cubic-structured ones by x-ray diffraction(XRD). The photoluminescence(PL) was performed for CdTe QDs prepared as a function of Te precursor concentration, condensation time and aging time. The PL intensity is strongly dependent on Te precursor concentration, indicating that the ratio of Te to Cd ions affects the particle size and size distribution of the CdTe QDs. Our PL study reveals that the intensity of PL peaks strengthens as the condensation time elongates, implying that annealing by thermal energy transferred during condensation would eliminate defects which act as killing centers in CdTe particles. Our photocurrent study suggests that the CdTe QDs materials are one of the prospective materials for optoelectronics including photodetectors.