• Journal of the Korean Vacuum Society
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• v.9 no.3
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• pp.216-220
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• 2000

Photoluminescence (PL) results of $Si^+$-implanted $SiO_2$films on crystalline silicon are reported. Visible and infrared PL are observed for all the samples. The PL spectrums have about 7000 $\AA$, 7400 $\AA$ and 8400 $\AA$ peak positions. As amount of $Si^+$ ion dose changed, the PL peak positions and intensity are changed. In particular, the PL spectrum has three peaks and more intensity than the other $Si^+$ ion implantation samples for $1{\times}10^{17}/cm^2$ $Si^+$ ion implantation. Not nanocrystal but defects that $Si^+$ ions treated are contributed to the PL spectrum. For the changes of $Si^+$ ion dose and annealing time, O rich radiative defects, Si rich radiative defects, and nonradiative defects control the PL spectrum. We confirmed that more radiative defects can be created by control of $Si^+$ ion dose.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.24 no.4
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• pp.10-16
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• 2010

In this paper, synthesis here Mn add to Ar injection the state and a vacuum an atomosphere $ZnGa_2O_4$ : Mn, ZnO and $Ga_2O_3$ power of 1 : 1 mole ratio mixture. Manufacture a close examination of oxygen a component variation luminescence a specific character reach an in fluence of $ZnGa_2O_4$ : Mn, luminescence spectrum observation also an explanation of Mn site symmetry and at luminescence spectrum reach an influence from low temperature photoluminescence spectrum.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1998.11a
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• pp.57-60
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• 1998

Poly(3-hexylthiophene)(P3HT) was synthesized by use of FeCl$_3$ as a oxidizing agent at $25^{\circ}C$. The infrared spectrum of our polymer gave good evidence for the conjugation of 3-hexylthiophene monomer unit. P3HT contains the HT(head-to-tail) linkage larger than 64% based on NMR analysis. Electronic absorption and photoluminescence studies show that cast films of P3HT have three exciting state. Absorption spectrum was separated with three maximum peaks by Giese-French method and shifted to the shorter wavelength with increasing temperature. Separated absorption spectrum of P3HT is well adapted to PL peak appeared at longer wavelength. Low temperature PL spectrum is well separated at 669nm, 733nm and 812nm.

• Korean Journal of Materials Research
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• v.32 no.10
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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.

• Bulletin of the Korean Chemical Society
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• v.26 no.11
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• pp.1776-1782
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• 2005

ZnSe/ZnS, UV-blue luminescent core shell quantum dots, were synthesized via a thermal decomposition reaction of organometallic zinc and solvent coordinated Selenium (TOPSe) in a hot solvent mixture. The synthetic conditions of the core (ZnSe) and the shell (ZnS) were independently studied at various reaction temperature conditions. The obtained colloidal nanocrystals at corresponding temperatures were characterized for their optical properties by UV-vis, room temperature solution photoluminescence (PL) spectroscopy, and further obtained powders were characterized by XRD, TEM, and EDXS analyses. The synthetic temperature condition to obtain the best PL emission intensity for the ZnSe core was 300 ${^{\circ}C}$, and for the optimum shell capping, the temperature was 135 ${^{\circ}C}$. At this temperature, solution PL spectrum showed a narrow emission peak at 427 nm with a PL efficiency of 15%. In addition, the measured particle sizes for the ZnSe/ZnS nanocomposite via TEM were in the range of 5 to 12 nm. Furthermore, we have synthesized water-soluble ZnSe/ZnS nanoparticles by capping the ZnSe/ZnS hydrophobic surface with mercaptoacetate (MAA) molecules. For the obtained aqueous colloidal solution, the UV-vis spectrum showed an absorption peak at 250 nm, and the solution PL emission spectrum showed a peak at 425 nm, which is similar to that for hydrophobic quantum dot ZnSe/ZnS. However, the calculated PL efficiency was relatively low (0.1%) due to the luminescence quenching by water and MAA molecules. The capping ligand was also characterized by FT-IR spectroscopy, with the carbonyl stretching peak in the mercaptoacetate molecule appearing at 1575 $cm ^{-1}$. Finally, the particle sizes of the MAA capped ZnSe/ZnS were measured by TEM, showing a range of 12 to 17 nm.

• Electrical & Electronic Materials
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• v.8 no.6
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• pp.752-758
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• 1995

Red emitting CaS:Eu,S electroluminescent(EL) device prepared at 550.deg. C by an electron-beam evaporation technique, demonstrated luminance of 175cd/m$\^$2/ and efficiency of 0.311m/W with 3kHz drive. Luminance was increased with the increase of applied voltage and frequency. From the results of the PL spectrum and the EL spectrum, the CaS:Eu, S device showed emission peak near 640nm resulted from the transition of EU$\^$2+/ 4f$\^$6/5d.rarw.4f$\^$7/. The capacitance of the phosphor layer from the Sawyer-Tower circuit was 10.5nF/cm$\^$2/.

• Proceedings of the Korean Vacuum Society Conference
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• 2015.08a
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• pp.222.1-222.1
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• 2015

Recently, graphene quantum dots (GQDs) have attracted great attention due to various properties including cost-effectiveness of synthesis, low toxicity, and high photostability. Nevertheless, the origins of photoluminescence (PL) from GQDs are unclear because of extrinsic states of the impurities, disorder structures, and oxygen-functional groups. Therefore, to utilize GQDs in various applications, their optical properties generated from the extrinsic states should be understood. In this work, we have focused on the effect of oxygen-functional groups in PL of the GQDs. The GQDs with nanoscale and single layer are synthesized by employing graphite nanoparticles (GNPs) with 4 nm. The series of GQDs with different amount of oxygen-functional groups were prepared by the chain of chemical oxidation and reduction process. The fabrication of a series of graphene oxide QDs (GOQDs) with different amounts of oxygen-contents is first reported by a direct oxidation route of GNPs. In addition, for preparing a series of reduced GOQDs (rGOQDs), we employed the conventional chemical reduction to GOQDs solution and controlled the amount of reduction agents. The GOQDs and rGOQDs showed irreversible PL properties even though both routes have similar amount of oxyen-functional groups. In the case of a series of GOQDs, the PL spectrum was clearly redshifted into blue and green-yellowish color. On the other hand, the PL spectrum of rGOQDs did not change significantly. By various optical measurement such as the PL excitation, UV-vis absorbance, and time-resolved PL, we could verify that their PL mechanisms of GOQDs and rGOQDs are closely associated with different atomic structures formed by chemical oxidation and reduction. Our study provides an important insights for understanding the optical properties of GQDs affected by oxygen-functional groups. [1]

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.351.2-351.2
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• 2016

Graphene quantum dots (GQDs) have attracted much attention because of various advantages such as cost-effectiveness of synthesis, low toxicity, and photostability. The origins of photoluminescence (PL) in GQDs were suggested as the intrinsic states for localized sp2 carbon domains and the extrinsic states formed by oxygen-functional groups.[1,2] Nevertheless, it is still unclear to understand the information of electric band structure in GQD. Here, we observed excitation energy induced S-shaped PL behavior. The PL peak energy position shows an S-shaped shift (redshift-blueshift-redshift) as function of the excitation wavelengths. From various samples, we only observed S-shaped PL shift in the GQDs with both luminescent origins of intrinsic and extrinsic states. Therefore, this S-shaped PL shift is related to different weight of intrinsic and extrinsic states in PL spectrum depending on the excitation wavelengths. This would be the key result to understand the electric band structure of the GQDs and its derivatives.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1997.11a
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• pp.525-528
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• 1997

In this study, Eu(TTA)$_3$(phen) was synthesized and its films were prepared by vapor deposition method. Its films were characterized by UV-Vis absorption spectroscopy, Atomic Force Microscopy(AFM) and Photoluminescence(PL) measurements. Their electroluminescent(EL) characteristics were investigated by PL measurements, where a cell structure of glass substrate/ITO/Eu(TTA)$_3$(phen)/Al was employed. It was found that its films were well prepared without any decomposition and the film thickness could be controlled by adjusting the amount of Eu(TTA)$_3$(phen) in a boat. The EL spectrum of these films was almost the same as that of PL spectrum of these films.

• Journal of the Korean Vacuum Society
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• v.10 no.2
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• pp.247-251
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• 2001

Photoluminescence(PL) were observed from room temperature to 8K on $Si^+$-implanted silicon-oxide films. The PL intensities are increased from room temperature to 50~80K and decreased below 50K. The blue-shift occurs during the increasing of PL intensity. Also, temperature-dependent PL were measured at peak wavelengths. The first peak is the most sensitive to the measuring temperature. The experimental results are explained by quantum size effect of O rich defects or(and) Si rich defects rather than nanocrystal silicon.