• Current Optics and Photonics
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• 제3권2호
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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.

• 한국재료학회지
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• 제19권7호
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• pp.356-361
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• 2009

The optical characterization of self-assembled InAs/AlAs Quantum Dots(QD) grown by MBE(Molecular Beam Epitaxy) was investigated by using Photoluminescence(PL) spectroscopy. The influence of thin AlAs barrier on QDs were carried out by utilizing a pumping beam that has lower energy than that of the AlAs barrier. This provides the evidence for the tunneling of carriers from the GaAs layer, which results in a strong QD intensity compared to the GaAs at the 16 K PL spectrum. The presence of two QDs signals were found to be associated with the ground-states transitions from QDs with a bimodal size distribution made by the excitation power-dependent PL. From the temperature-dependent PL, the rapid red shift of the peak emission that was related to the QD2 from the increasing temperature was attributed to the coherence between the QDs of bimodal size distribution. A red shift of the PL peak of QDs emission and the reduction of the FWHM(Full Width at Half Maximum) were observed when the annealing temperatures ranged from 500 $^{\circ}C$ to 750 $^{\circ}C$, which indicates that the interdiffusion between the dots and the capping layer was caused by an improvement in the uniformity size of the QDs.

• Macromolecular Research
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• 제10권5호
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• pp.278-281
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• 2002

We investigated the photoluminescence (PL) characteristics of a highly soluble, fullerene-containing copolymer in both solution and film states. In solution state, the copolymer showed different PL characteristics depending on the aromaticity of the solvent. The PL from polystyrene segments of the copolymer was strongly quenched in an aromatic solvent, while the PL from fullerene remained unchanged. However, the films cast from an aromatic and a nonaromatic solvent demonstrated very similar PL characteristics, implying that the chain alignment or orientation and packing in the films occur in a similar way irrespective of the solvent.

• 한국세라믹학회지
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• 제32권5호
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• pp.608-616
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• 1995

Porous silicon (PS) was prepared under different anodization conditions and the photoluminescence (PL) was measrued. In addition PL of the naturally and thermally oxidized PS was measured. It was found that the PL peak was shifted to shorter wavelength as the anodization current density and the extent of the oxidation increased. The absence of correlation between the PL behavior and the surface hydrogen species (Si-H2, Si-H) implies that the mechanism of PL of PS is not likely related to the surface hydrogen species effect but to the quantum confinement effect.

• 한국재료학회지
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• 제32권10호
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• pp.419-424
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• 2022

Halide perovskite solar cells (PSCs) have improved rapidly over the past few years, and research on the optoelectrical properties of halide perovskite thin films has grown as well. Among the characterization techniques, photoluminescence (PL), a method of collecting emitted photons to evaluate the properties of materials, is widely applied to evaluate improvements in the performance of PSCs. However, since only photons emitted from the film in the escape cone are included, the photons collected in PL are a small fraction of the total photons emitted from the film. Unlike PSCs power conversion efficiency, PL measuring methods have not been standardized, and have been evaluated in a variety of ways. Thus, an in-depth study is needed of the methods used to evaluate materials using PL spectra. In this study, we examined the PL spectra of the perovskite light harvesting layer with different measurement protocols and analyzed the features. As the incident angle changed, different spectra were observed, indicating that the PL emission spectrum can depend on the measuring method, not the material. We found the intensity and energy of the PL spectra changes were due to the path of the emitted photons. Also, we found that the PL of halide perovskite thin films generally contains limited information. To solve this problem, the emitted photons should be collected using an integrating sphere. The results of this study suggest that the emission spectrum of halide perovskite films should be carefully interpreted in accordance with PL measuring method, since PL data is mostly affected by the method.

• 한국광학회지
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• 제13권2호
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• pp.128-133
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• 2002

최근 주목을 받고 있는 고분자 발광다이오드의 개발에 있어서, 발광고분자의 Photoluminescence(PL)와 Electroluminescence (EL) 양자효율 측정은 소자의 성능개선 연구 등에 있어서 가장 핵심적인 요소 중 하나로 여겨진다. 이러한 이유에서 본 연구에서는 잘 알려진 발광고분자인 Poly(2-methoxy-5(-(2-ethyl-hexyloxy)- 1,4-phenylenevinylene) (MEH- PPV)를 이용하여 시편을 제작하고, 적분구 측정법을 이용하여 이의 P교라 EL 양자효율을 구하였다. 그 결과 본 연구진이 개발한 MEH-PPV의 PL 양자효율은 8$\pm$2%로 측정되었는데, 이는 세계적으로 알려져 있는 ～9%의 결과에 거의 접근함을 보였다. 한편, 이 물질을 이용하여 고분자 발광다이오드를 제작한 결과, 이의 EL양자효율은 0.02 1m/W로 측정되었다. 본 연구를 통하여 확립된 발광고분자의 양자효율 측정법은 국내의 유기발광소자 연구에 큰 기여를 하리라 기대된다.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2009년도 하계학술대회 논문집
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• pp.328-329
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• 2009

This paper presents the effect of organic Ag complex sintering temperature on the MEH-PPV photoluminescence (PL) properties. MEH-PPV and organic Ag complex was coated on the glass substrate by spin coating method. The coated Ag complex was sintered in an air atmosphere. The sintering temperature was varied from 100 to $200^{\circ}C$ and sintering time was 5 min. The Ag film sintered at temperature higher than $120^{\circ}C$ shows very low sheet resistance less than $0.5\;{\Omega}{/\square}$. The coated MEH-PPV measure photoluminescence (PL) intensity at 580 nm. The PL peak was shifted to the higher wavelength with increasing the sintering temperature.

• 한국진공학회지
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• 제2권3호
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• pp.294-298
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• 1993

CuGaSe2 단결정을 고순도(99.9999%)의 Cu, Se 원소를 화학조성비로 칭량한 후 Se을 3mole% 과잉으로 첨가하여 합성된 ingot를 사용하여 iodine(99.9999%)을 수송매체로 한 화학수송법으로 성장시켰다. 성장된 단결정은 검정색을 띠고 있었으며, 10K에서 optical energy gap이 1.755eV로 주어졌다. Ar-ion laser로 여기시켜 측정한 photoluminescence(PL) 스펙트럼으로부터 1.667eV, 1.085eV, 1.025eV에 위치한 세 개의 PL peak를 얻었다. Thermally stimulated current(TSC) 측정에서 0.660eV, 0.720eV의 deep donor level을 관측하였으며, PL peak intensity의 thermal quenching으로 구한 activation energy는 0.010eV이었다. CuGaSe2 단결정에서 PL mechanism은 edge emission 및 donor-acceptor pair recombination임을 규명했다.

• Journal of Photoscience
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• 제12권3호
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• pp.171-174
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• 2005

The relationship between porous surfaces and photoluminescence (PL) behavior of porous silicon carbide (PSC) in various solvents has been studied. The porous surfaces of p-type silicon carbide can be fabricated by electrochemical anodization from the 6H, 15R, 4H-${\alpha}$-SiC substrates in dark-current mode (DCM) condition. We have been investigated the dependence of the PL spectra of PSC under the medium having the different dielectric constants. It has been found that PL depends sensitively on the environment surrounding the surface. The extent of chemically stability on the surface of PSC due to the various solvents was confirmed by reflectance Fourier transform infrared (FTIR) spectroscopy. Detailed IR experiments on the PSC samples were carried out before and after various solvents immersion. These results will be offered important information on the origin of PL in porous structure.

• 한국진공학회지
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• 제18권5호
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• pp.365-371
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• 2009

크기가 다른 양자점 (chirped 양자점) 구조에 대하여 전기발광 (Electroluminescence, EL) 특성과 광발광 (Photoluminescence, PL) 특성을 측정하고 비교 분석하였다. PL 특성에서는 양자점의 기저준위에 의한 피이크가 우세하게 나타난 반면, EL 특성에서는 여기준위에 의한 특성이 우세하게 나타났다. 이와 같은 특성비교로부터 기저준위도 EL 특성에 영향을 미칠 수 있도록 chirped 양자점 구조를 설계하면 파장대역폭이 더욱 넓은 고휘도 발광소자 개발이 가능할 것임을 제안하였다.