• Journal of Sensor Science and Technology
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• v.8 no.1
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• pp.10-15
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• 1999

White emission thin film electroluminescent device was fabricated using ZnS for phosphor layer and BST ferroelectric thin film for insulating layer. For fabrication conditions of BST thin film, stoichiometry of target was $Ba_{0.5}Sr_{0.5}TiO_3$, substrate temperature was $400^{\circ}C$, working pressure was 30 mTorr, and A:$O_2$ ratio was 9:1. At this time, dielectric constant was 209 at 1kHz frequency. For phosphor layer ZnS:Mn, ZnS:Tb, and ZnS:Ag were used. Mixing rates of activators were respectively 0.8, 0.8, and 1 wt%. Total thickness of phosphor tapers was 500 nm, thickness of lower insulating layer was 200 nm, and thickness of upper insulating layer was 400 nm. In this conditions, luminescence threshold voltage of thin film electroluminescent device was $95\;V_{rms}$, maximum brightness was $3,000\;cd/m^2$ at $150\;V_{rms}$. Luminescence spectrum peak was observed at region of blue(450 nm), green(550 nm), and red(600 nm).

• Korean Journal of Crystallography
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• v.8 no.1
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• pp.48-58
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• 1997

[ $CuInTe_2$ ] synthesised in a horizontal electric furnace was found to be polycrystalline. Single crystals of $CuInTe_2$ were grown with the vertical Bridgman technique. The photoconductivity and photoluminescence of the crystals were measured in the temperature range 20 to 293 K. From the photocurrent peaks measured for the samples both perpendicular and parallel to c-axis, the energy band gaps of the samples were found to be 0.948 eV and 0.952 eV at room temperature respectively. The energy difference of the photocurrent and photoluminescence peaks of the samples both perpendicular and parallel to the c-axis measured at room temperature was a phonon energy, and its values were 22.12 meV and 21.4 meV respectively. The splitting of the valence band due to spin-orbit and crystal field interaction was calculated from the photocurrent spectra of the samples, The ${\Delta}cr\;and\;{\Delta}so$ are 0.046,0.014 eV respectively.

• Progress in Medical Physics
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• v.5 no.2
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• pp.13-20
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• 1994

The thermoluminescence(TL) glow curves and the optical absorption of $Al_2O_3$ irradiated with ${\gamma}$-ray, electron, and $Li^{+}$ ion followed by electron irradiation have been investigated to determine the relation of TL peak to its defect type. The TL glow curve of $Al_2O_3$ irradiated with ${\gamma}$-ray shows TL peaks at 380 K, 415 K, and 475 K. The UV photobleached TL glow curve of $Al_2O_3$ irradiated with ${\gamma}$-ray shows that the 380 K and 475 K TL peaks completely disappear while the 415 K TL peak still exists. The electron beam induced TL glow curve of $Al_2O_3$ after $Li^{+}$ ion implantation shows that the TL peak at 440 K is enhanced by a factor of 2 over the TL intensity of unimplanted $Al_2O_3$ while the TL peak at 380 K evidently disappears The implanted $Li^{+}$ ions are assumed to form singly charged interstitial cations and then recombine with electron trapped in F centers to produce F+ centers. The 380 K and 475 K TL peaks are proposed to be associated with F center, while the 415 K and 440 K TL peak are connected with F$^{+}$ center.

• Journal of the Korean Vacuum Society
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• v.7 no.1
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• pp.66-71
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• 1998

Two kinds of $Ga_2S_3:Er$ (type A and type B) single crystals were grown by the chemical transport reaction method using iodine as a transport agent. The single crystals were crystallized into a monoclinic structure. The optical energy band gaps were found to 3.375 eV for the $Ga_2S_3:Er$ (type A) single crystal and 3.365 eV fir the $Ga_2S_3:Er$ (type B) single crystal at 13K. When the $Ga_2S_3:Er$ (type A and type B) single crystals were excited by the 325 nm-line of a Cd-He laser, Photoluminescence spectra of the $Ga_2S_3:Er$ (type A) single crystal exhibited blue emission band peaked at 444 nm and green and red emission bands peaked at 518 nm and 690 nm. Pgitikynubescebce soectra if the $Ga_2S_3:Er$ (typeB) single crystal showed green and red emission bands peaked at 513 nm and 695 nm. Sharp emission peaks in the two kinds if $Ga_2S_3:Er$ single crystal were observed near 525 nm, 553 nm, 664 nm, 812 nm, 986 nm, and 1540 nm and analysed as originating from the electron transitions between the energy levels of $Er^{3+}$ ion.

• Korean Journal of Optics and Photonics
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• v.25 no.2
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• pp.102-107
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• 2014

In this paper the spectra of correlated color temperature (CCT) tunable white light-emitting diode (LED) luminaires, consisting of commercial red, green, blue, and amber LED chips, were optimized to increase color rendering index (CRI), and a special CRI of R9 for deep red color was obtained. To improve the design's accuracy, measured LED spectra were used instead of mathematically modeled ones. Real CCT tunable LED luminaires with CRIs of 87-90 and R9s of 34-93 were fabricated and demonstrated at CCTs of 3000-6000 K.

• Solar Energy
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• v.17 no.2
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• pp.55-66
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• 1997

The structural and optoelectronic properties of polycrystalline CdS films up to several microns in thickness, fabricated by three different methods, are compared to one another for the purpose of preparing CdTe/CdS solar cells. All films were deposited on an indium tin oxide on glass substrate. The three methods are: 1) alternated spraying of cation and anion solution at room temperature; 2) spray pyrolysis with substrate temperature up to $500^{\circ}C$; 3) chemical bath deposition (CBD). Deposited films were thermally treated in various ways. All films showed a well-developed wurtzite structure. Films grown by the alternated-spray method and the chemical bath method consist of randomly-oriented crystallites with dimensions <0.5 microns. Annealing at $400^{\circ}C$ increases the crystallite size slightly. Films which were grown by pyrolysis at substrate temperatures from $400^{\circ}C\;to\;500^{\cir\c}C$ were oriented in the <002> direction. For growth by pyrolysis at $500^{\circ}C$, the surface is rough on a lateral scale of 0.1 to 0.3 microns. The optical band gap and defect states are investigated by optical absorption, photoluminescene, Raman, and photothermal deflection spectroscopies.

• Journal of the Korean Vacuum Society
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• v.15 no.3
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• pp.308-313
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• 2006

We report a photoluminescence (PL) study on the growth process of self-assembled InAs quantum dots (QDs) under the various growth conditions. Distinctive double-peak feature was observed in the PL spectra of the QD samples grown at the relatively high substrate temperature. From the excitation power-dependent PL and the temperature-dependent PL measurements, the double-peak feature is associated with the ground state transitions from InAs QDs with two different size branches. In addition, the variation in the bimodal size distribution of the QD ensembles with different InAs coverage is demonstrated.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.382-382
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• 2011

보다 저렴한 다결정 실리콘 웨이퍼를 사용한 다결정 실리콘 태양전지의 발전효율개선을 위해서는 태양광스펙트럼의 표면 흡수기구를 최적화하고, 전자-정공쌍의 생성극대화 및 재결합 기구 제어를 통한 전하운바자들의 안정적인 분리와 전극으로의 효율적인 수집이 필수적인다. 현재 양질의 다결정 실리콘 웨이퍼에 기반한 다결정 실리콘 태양전지 양산공정에서 16~17% 발전효율이 이루어지고 있으며 18% 이상의 발전효율을 얻기 위해서는 보다 더 우수한 품질의 다결정 실리콘 웨이퍼가 요구된다. 본 연구에서는 15.5~16.5% 대역의 평균 발전효율을 갖는 15.6 cm${\times}$15.6 cm 크기 고효율 다결정 실리콘 태양전지 전면의 전자발광(EL : electroluminescence)데이터로부터 효율기여도가 높은 위치와 상대적으로 기여도가 낮은 위치들을 선정하여 380~1050nm 파장대역의 광선속에 대해 국부적인 외부양자효율(EQE : external quantum efficiency)을 측정하고 투과전자현미경(TEM : tunneling electron microscope) 등을 활용하여 결정방향 등에 기인하는 양자효율 악화기구를 분석하였다. 결론적으로 15%대의 상대적으로 낮은 발전효율을 보이는 태양전지들은 300~600 nm 단파장 영역에서 양자효율이 상대적으로 낮은 저급한 결정성의 웨이퍼에 기인하고 16.5%이상의 높은 발전효율을 갖는 태양전지들은 단파장영역에서 높은 양자효율을 갖는 영역이 수광면적의 80~90%를 차지하는 것으로 밝혀졌다. 이와 더불어 15%대의 발전효율을 갖는 태양전지에서는 600~1100 nm 파장대역에서 상대적으로 악화된 양자효율을 갖는 저급한 결정성 영역이 30~40%를 차지하였으나 16.5%대역의 고효율 태양전지에서는 저급한 결정성 영역이 5~10%를 차지하여 대조를 보였다. 따라서 18%이상의 높은 발전효율을 갖는 다결정 실리콘 태양전지의 양산을 위해서는 양자효율이 우수한 양품의 웨이퍼를 기반으로 표면 texturing을 통해 평균 태양광 흡수율을 90%이상으로 개선하고, 보다 미세한 프론트 전극패턴을 통해 수광면적을 개선하고 선택적인 에미티공정 기술 등을 적용할 필요가 있음을 제안하고자 한다.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.18 no.5
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• pp.217-224
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• 2008

A stoichiometric mixture of evaporating materials for $ZnIn_2Se_4$ single crystal thin films was prepared from horizontal electric furnace. To obtain the single crystal thin films, $ZnIn_2Se_4$ mixed crystal was deposited on thoroughly etched semi-insulating GaAs(100) substrate by the Hot Wall Epitaxy (HWE) system. The source and substrate temperatures were $630^{\circ}C$ and $400^{\circ}C$, respectively. The crystalline structure of the single crystal thin films was investigated by the photoluminescence and double crystal X-ray diffraction (DCXD). The carrier density and mobility of $ZnIn_2Se_4$ single crystal thin films measured from Hall effect by van der Pauw method are $9.41\times10^{16}cm^{-3}$ and $292cm^2/v{\cdot}s$ at 293 K, respectively. The temperature dependence of the energy band gap of the $ZnIn_2Se_4$ obtained from the absorption spectra was well described by the Varshni's relation, $E_g(T)=1.8622eV-(5.23\times10^{-4}eV/K)T^2/(T+775.5K)$. The crystal field and the spin-orbit splitting energies for the valence band of the $ZnIn_2Se_4$ have been estimated to be 182.7 meV and 42.6 meV, respectively, by means of the photocurrent spectra and the Hopfield quasicubic model. These results indicate that the splitting of the ${\Delta}so$ definitely exists in the ${\Gamma}_5$ states of the valence band of the $ZnIn_2Se_4/GaAs$ epilayer. The three photo current peaks observed at 10 K are ascribed to the $A_{1}-$, $B_{1}-exciton$ for n = 1 and $C_{27}-exciton$ peaks for n = 27.

• Journal of Sensor Science and Technology
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• v.11 no.5
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• pp.309-318
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• 2002

A stoichiometric mixture of evaporating materials for $CdIn_2S_4$ single crystal thin films was prepared from horizontal electric furnace. To obtain the single crystal thin films, $CdIn_2S_4$ mixed crystal was deposited on thoroughly etched semi-insulating GaAs(100) substrate by the Hot Wall Epitaxy (HWE) system. The source and substrate temperatures were $630^{\circ}C$ and $420^{\circ}C$, respectively. The crystalline structure of the single crystal thin films was investigated by the photoluminescence and double crystal X-ray diffraction (DCXD). The carrier density and mobility of $CdIn_2S_4$ single crystal thin films measured with Hall effect by van der Pauw method are $9.01{\times}10^{16}\;cm^{-3}$ and $219\;cm^2/V{\cdot}s$ at 293 K, respectively. The temperature dependence of the energy band gap of the $CdIn_2S_4$ obtained from the absorption spectra was well described by the Varshni's relation, $E_g(T)=2.7116\;eV-(7.74{\times}10^{-4}\;eV)T^2/(T+434)$. The crystal field and the spin-orbit splitting energies for the valence band of the $CdIn_2S_4$ have been estimated to be 0.1291 eV and 0.0248 eV, respectively, by means of the photocurrent spectra and the Hopfield quasi cubic model. These results indicate that the splitting of the ${\Delta}so$ definitely exists in the ${\Gamma}5$ states of the valence band of the $AgInS_2$/GaAs epilayer. The three photocurrent peaks observed at 10K areascribed to the $A_1$-, $B_1$-, and C1-exciton peaks for n = 1.