LED용Mg²⁺·Ba²⁺Co-Doped Sr₂SiO₄:Eu 노란색 형광체의 발광특성

최경재,지순덕,김창해,이상혁,김호건,Choi, Kyoung-Jae,Jee, Soon-Duk,Kim, Chang-Hae,Lee, Sang-Hyuk,Kim, Ho-Kun 한국세라믹학회 2007 한국세라믹학회지 Vol.44 No.3

An improvement for the efficiency of the $Sr_{2}SiO_{4}:Eu$ yellow phosphor under the $450{\sim}470\;nm$ excitation range have been achieved by adding the co-doping element ($Mg^{2+}\;and\;Ba^{2+}$) in the host. White LEDs were fabricated through an integration of an blue (InGaN) chip (${\lambda}_{cm}=450\;nm$) and a blend of two phosphors ($Mg^{2+},\;Ba^{2+}\;co-doped\;Sr_{2}SiO_{4}:Eu$ yellow phosphor+CaS:Eu red phosphor) in a single package. The InGaN-based two phosphor blends ($Mg^{2+},\;Ba^{2+}\;co-doped\;Sr_{2}SiO_{4}:Eu$ yellow phosphor+CaS:Eu red phosphor) LEDs showed three bands at 450 nm, 550 nm and 640 nm, respectively. The 450 nm emission band was due to a radiative recombination from an InGaN active layer. This 450 nm emission was used as an optical transition of the $Mg^{2+},\;Ba^{2+}\;co-doped\;Sr_{2}SiO_{4}:Eu$ yellow phosphor+CaS:Eu red phosphor. As a consequence of a preparation of white LEDs using the $Mg^{2+},\;Ba^{2+}\;co-doped\;Sr_{2}SiO_{4}:Eu$ yellow phosphor+CaS:Eu red phosphor yellow phosphor and CaS:Eu red phosphor, the highest luminescence efficiency was obtained at the 0.03 mol $Ba^{2+}$ concentration. At this time, the white LEDs showed the CCT (5300 K), CRI (89.9) and luminous efficacy (17.34 lm/W).

분무열분해 공정에서 붕소 농도에 따른 Gd₂O₃:Eu 형광체의 GdBO₃:Eu 형광체로의 전환

구혜영,정대수,주서희,홍승권,강윤찬,Koo, Hye-Young,Jung, Dae-Soo,Ju, Seo-Hee,Hong, Seung-Kwon,Kang, Yun-Chan 한국재료학회 2006 한국재료학회지 Vol.16 No.3

The transition of europium-doped gadolinium oxide phosphor to gadolinium borate phosphor with the concentration of boron in the spray pyrolysis was investigated. The particles prepared from spray solution below 10 wt% boric acid of prepared phosphor had crystal structure of $Gd_2O_3:Eu$ phosphor, in which the crystallinity of the particles decreased with increasing the boron concentration. A single phase $GdBO_3:Eu$ phosphor particles were prepared from spray solution above 50 wt% boric acid of prepared phosphor. The phosphor particles prepared from spray solution with 20 wt% boric acid of prepared phosphor had no XRD peaks of $Gd_2O_3:Eu$ and $GdBO_3:Eu$ Therefore the phosphor particles prepared from spray solution with 20 wt% boric acid of prepared phosphor had the lowest photoluminescence intensity under ultraviolet and vacuum ultraviolet. $GdBO_3:Eu$ and $Gd_2O_3:Eu$ phosphor particles prepared from spray solutions with proper concentrations of boric acid had good photoluminescence intensity under vacuum ultraviolet. The morphology of the phosphor particles were strongly affected by the concentrations of boric acid added into spray solution.

Flexible micro-scale UV-curable phosphor layers screen-printed on a polymer substrate for planar white light-emitting diodes

Woo Jang, Jin,Kim, Yuri,Hyeon Kwon, Oh,Soo Cho, Yong Elsevier 2018 Materials letters Vol.217 No.-

<P><B>Abstract</B></P> <P>Different types of the remote phosphor have been investigated to enhance the light-emitting performance with less time-dependent degradations of the emission properties. Here, two different remote phosphor approaches are introduced to optimize the effect of red phosphor in the yellow phosphor-driven white light-emitting diodes (LED)s. These approaches combining the printing technology with a UV-curing process are designed for flexible planar white LEDs with a thin layer thickness of a few tens of micrometer-scale. A screen-printing process was utilized to obtain the mixed or stacked phosphor layers based on commercial yellow and red phosphors. The phosphor particles were found to be dispersed uniformly in the cured UV-polymer matrix. The resultant luminescence characteristics depended on the type of remote phosphor and the relative content of red phosphor. The mixing approach was more effective in raising color rendering index (CRI) while minimizing the reduction of luminous efficacy. As a result, a luminous efficacy of ∼101 lm/W and a CRI of ∼83.1 were obtained for the mixed sample with 5 wt% red phosphor, which correspond to a decrease of ∼11.2% and an increase of ∼9.3% compared to the reference sample.</P> <P><B>Highlights</B></P> <P> <UL> <LI> A printing technology of UV-curable phosphor composite layer is introduced. </LI> <LI> Manipulated luminescence characteristics are provided with the phosphor layer. </LI> <LI> Yellow and red phosphors were adjusted for mixing and stacking approaches. </LI> <LI> Only the 20–30 μm-thick phosphor layer was effective in enhancing color quality. </LI> <LI> With the same content of minor red phosphor, the effect of mixed layer was bigger. </LI> </UL> </P>

Blue-white-orange tunable Ba₆Ca₃YAlSi₆O₂₄:Eu²⁺, Mn²⁺ phosphors for NUV-pumped LEDs

Yun, Heejun,Park, Sangmoon Elsevier 2018 Optical materials Vol.86 No.-

<P><B>Abstract</B></P> <P>Near-ultraviolet (NUV)-excitable phosphors composed of Ba<SUB>6-<I>m</I>-<I>n</I> </SUB>Eu<SUB> <I>m</I> </SUB>Mn<SUB> <I>n</I> </SUB>Ca<SUB>3</SUB>YAlSi<SUB>6</SUB>O<SUB>24</SUB> (<I>m</I> = 0.01–0.5, <I>n</I> = 0–0.5) were prepared via a solid-state reaction in a reducing atmosphere. The X-ray diffraction patterns of the single-phase orthosilicate Ba<SUB>6-<I>m</I>-<I>n</I> </SUB>Eu<SUB> <I>m</I> </SUB>Mn<SUB> <I>n</I> </SUB>Ca<SUB>3</SUB>YAlSi<SUB>6</SUB>O<SUB>24</SUB> phosphors were examined to index the peak positions. The photoluminescence (PL) emission spectra of the phosphors were clearly observed under 365-nm excitation. The critical distance and electric multipole interaction were exploited. The dependence of the luminescent intensity of the Mn<SUP>2+</SUP> co-doped host lattice on the Eu<SUP>2+</SUP> content was also investigated. Co-doping Mn<SUP>2+</SUP> and Eu<SUP>2+</SUP> emitters in the Ba<SUB>5.8-<I>n</I> </SUB>Eu<SUB>0.2</SUB>Mn<SUB> <I>n</I> </SUB>Ca<SUB>3</SUB>YAlSi<SUB>6</SUB>O<SUB>24</SUB> phosphors enabled efficient energy transfer from Eu<SUP>2+</SUP> to Mn<SUP>2+</SUP>; the energy-transfer mechanism is also discussed. The Commission Internationale de I'Eclairage (CIE) coordinates near the blue, white, and orange regions of the obtained phosphors were observed. Thermal quenching of Ba<SUB>5.7</SUB>Eu<SUB>0.2</SUB>Mn<SUB>0.1</SUB>Ca<SUB>3</SUB>YAlSi<SUB>6</SUB>O<SUB>24</SUB> phosphor was exploited in the temperature range of 298–448 K and at 193 K. The activation energy for thermal quenching of the phosphors was calculated. The relative quantum efficiency (QE) of Ba<SUB>5.7</SUB>Eu<SUB>0.2</SUB>Mn<SUB>0.1</SUB>Ca<SUB>3</SUB>YAlSi<SUB>6</SUB>O<SUB>24</SUB> phosphor was compared with that of the commercial YAG:Ce and the previously studied Ba<SUB>8.8</SUB>Eu<SUB>0.1</SUB>Mn<SUB>0.1</SUB>Y<SUB>2</SUB>Si<SUB>6</SUB>O<SUB>24</SUB> phosphor. NUV-executable white Ba<SUB>5.7</SUB>Eu<SUB>0.2</SUB>Mn<SUB>0.1</SUB>Ca<SUB>3</SUB>YAlSi<SUB>6</SUB>O<SUB>24</SUB> phosphor with a 365-nm LED chip was fabricated and the internal QE was measured. The color rendering index (CRI, R<SUB>a</SUB>) at correlated color temperature (CCT) with the CIE coordinates was exhibited for the LEDs.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Ba<SUB>6</SUB>Ca<SUB>3</SUB>YAlSi<SUB>6</SUB>O<SUB>24</SUB>: Eu<SUP>2+</SUP>, Mn<SUP>2+</SUP> phosphors were prepared. </LI> <LI> Blue, white and orange regions of the spectra were efficiently achieved. </LI> <LI> Energy-transfer mechanism of the phosphors was characterized. </LI> <LI> White phosphor on a 365 nm NUV-LED chip was fabricated. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

B₂O₃-Bi₂O₃-ZnO계 유리를 이용한 백색 LED용 색변환 렌즈의 광 특성

채유진,이미재,김진호,황종희,임태영,정희석,이영식,김득중,Chae, Yoo-Jin,Lee, Mi-Jai,Kim, Jin-Ho,Hwang, Jong-Hee,Lim, Tae-Young,Jeong, Hee-Suk,Lee, Young-Sik,Kim, Deuk-Jung 한국전기전자재료학회 2013 전기전자재료학회논문지 Vol.26 No.8

Recently, remote phosphor is reported for white LED enhancing of phosphor efficiency compared with conventional phosphor-based W-LED. In this study, Remote phosphor was produced by screen printing coating on glass substrate with phosphor contents rated paste and heat treatment. The paste consists of phosphor, lowest softening glass frit and organic binders. Remote phosphor can be well controlled by varying the phosphor content rated paste. After mounting remote phosphor on top of blue LED chip, CCT, CRI, and luminance efficiency were measured. The measurement results showed that CCT, CRI, and luminance efficiency were 6,645, 68, and 1,16l m/W in phosphor 80 wt.% remote phosphor sintered at $600^{\circ}C$.

Citrate-based sol-gel synthesis of blue- and green-emitting BaLa₂WO₇:Tm³⁺ or Er³⁺ phosphors and their luminescence properties

Hussain, Sk. Khaja,Yu, Jae Su Elsevier 2017 Materials research bulletin Vol.95 No.-

<P><B>Abstract</B></P> <P>BaLa<SUB>2</SUB>WO<SUB>7</SUB>:Tm<SUP>3+</SUP> or Er<SUP>3+</SUP> (BLWO:Tm<SUP>3+</SUP> or Er<SUP>3+</SUP>) single doped phosphors were prepared by a citrate-based sol-gel method. The crystalline properties of the prepared blue- and green-emitting phosphor materials were analyzed by X-ray diffraction (XRD) after annealing at 1350°C. The XRD patterns of the both phosphors revealed monoclinic structure with a space group of P21/b. The morphological properties and elemental mappings of the BLWO:0.02Tm<SUP>3+</SUP> and BLWO:0.01Er<SUP>3+</SUP> phosphors were measured by field-emission scanning electron microscope images and energy dispersive X-ray spectrum, respectively. The photoluminescence (PL) spectra of BLWO:Tm<SUP>3+</SUP> phosphors showed characteristic emission peaks of Tm<SUP>3+</SUP> ions from the visible blue to near-infrared regions with the dominant emission at 799nm (<SUP>3</SUP>H<SUB>4</SUB> → <SUP>3</SUP>H<SUB>6</SUB>) under ultraviolet (UV) and near-UV excitation wavelengths. Similarly, Er<SUP>3+</SUP> ions activated BLWO phosphors exhibited intense green emissions at 548nm (<SUP>4</SUP>S<SUB>3/2</SUB> → <SUP>4</SUP>I<SUB>15/2</SUB>) under the characteristic excitation wavelength of 381nm. Furthermore, the temperature-dependent PL emission spectra and the luminescence decay curves were measured for the optimized BLWO:0.02Tm<SUP>3+</SUP> and BLWO:0.01Er<SUP>3+</SUP> phosphors. The chromaticity coordinates for the optimized blue- and green-emitting phosphors were calculated.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The BLWO:Tm<SUP>3+</SUP> or Er<SUP>3+</SUP> phosphors were prepared by a citrate-based sol-gel method. </LI> <LI> The BLWO:Tm<SUP>3+</SUP> or Er<SUP>3+</SUP> phosphors exhibited blue and green emissions under UV or NUV excitations. </LI> <LI> The blue- and green-emitting BLWO:Tm<SUP>3+</SUP> or Er<SUP>3+</SUP> phosphors exhibited good thermal properties. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Sol-gel synthesis of Eu³⁺/Bi³⁺ ions co-doped BaLa₂WO₇ phosphors for red-LEDs under NUV excitation and FEDs applications

Hussain, Sk. Khaja,Yu, Jae Su Elsevier 2017 Journal of luminescence Vol.183 No.-

<P><B>Abstract</B></P> <P>Eu<SUP>3+</SUP> ions single-doped and Eu<SUP>3+</SUP>/Bi<SUP>3+</SUP> ions co-doped BaLa<SUB>2</SUB>WO<SUB>7</SUB> (BLWO) phosphors were synthesized by a citrate sol-gel method. The X-ray diffraction patterns confirmed their monoclinic phase with a space group P21/b after annealing at 1350°C. The morphological properties of the prepared BLWO: 0.09mol Eu<SUP>3+</SUP> (i.e., BLWO:0.09Eu<SUP>3+</SUP>) and BLWO:0.09Eu<SUP>3+</SUP>/0.01Bi<SUP>3+</SUP> phosphors were observed by field-emission scanning electron microscope and transmission electron microscope images. Under near-ultraviolet (NUV) excitations, the photoluminescence (PL) properties were investigated for the BLWO:Eu<SUP>3+</SUP> and BLWO:Eu<SUP>3+</SUP>/Bi<SUP>3+</SUP> phosphors. The PL results suggest that the both phosphors showed an intense characteristic red emission at 616nm due to the <SUP>5</SUP>D<SUB>0</SUB> → <SUP>7</SUP>F<SUB>2</SUB> electronic transition. The existence of energy transfer mechanism in between Bi<SUP>3+</SUP> and Eu<SUP>3+</SUP> ions was explained by their decay curves. Additionally, temperature-dependent PL emission spectra and quantum yield were studied for the optimized phosphor. By combing a 399nm NUV chip with the BLWO:0.09Eu<SUP>3+</SUP>/0.01Bi<SUP>3+</SUP> phosphor, a red light-emitting diode was implemented. Furthermore, the cathodoluminescence (CL) properties were analyzed for the BLWO:0.09Eu<SUP>3+</SUP> and BLWO:0.09Eu<SUP>3+</SUP>/0.01Bi<SUP>3+</SUP> phosphors as a function of accelerating voltage and filament current. To estimate the CL potentiality, the BLWO:0.09Eu<SUP>3+</SUP>/0.01Bi<SUP>3+</SUP> phosphor was compared with a commercial Y<SUB>2</SUB>O<SUB>3</SUB>:Eu<SUP>3+</SUP> red phosphor. The Commission International de I-Eclairage chromaticity coordinates were calculated for the optimized phosphor samples.</P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Thermal Behavior of Remote Phosphor in Light-Emitting Diode Packages

Kim, J. H.,Shin, M. W. IEEE 2015 IEEE electron device letters Vol.36 No.8

<P>This letter reports on the detailed thermal behavior of remote type light-emitting diode (LED) packages with different positions of a phosphor layer from the substrate. The temperatures of phosphor layers were directly measured using microthermocouples. It was confirmed by both measurement and simulation, for the investigated LED package structure, the phosphor temperatures are always higher than the junction temperature. Both temperatures are found to change as a function of the phosphor-substrate distance. It is demonstrated that the distance determines the effect of back-scattered photons and the thermal resistance between the phosphor layer and the substrate. From both the experiment and simulation results, it is proposed that there exists an optimal distance of phosphor layer in the remote-type LED package, which is about 320 μm for the package structure utilized in this study. The package with the optimal position exhibits an optical output which is 6% higher than that from a package where the phosphor layer directly covers LED chip. It is shown that the heating load at the phosphor layer changes with the position of the phosphor layer and must be implemented for the precise thermal analysis of whole LED package.</P>

Luminescence Properties of Ba₃Si<SUB>6</SUB>O<SUB>12</SUB> N₂:Eu<SUP>2+</SUP> Green Phosphor

Van Duong Luong,Dinh Phuong Doan,Hong-Ro Lee 한국표면공학회 2015 한국표면공학회지 Vol.48 No.5

To fabricate white LED having a high color rendering index value, red color phosphor mixed with the green color phosphor together in the blue chip, namely the blue chips with RG phosphors packaging is most favorable for high power white LEDs. In our previous papers, we reported on successful syntheses of Sr₂-Si5N8:Eu<SUP>2+</SUP> and CaAlSiN₃ phosphors for red phosphor. In this work, for high power green phosphor, greenemitting ternary nitride Ba₃Si6O12N₂:Eu<SUP>2+</SUP> phosphor was synthesized in a high frequency induction furnace under N₂ gas atmosphere at temperatures up to 1400℃ using EuF₃ as a raw material for Eu<SUP>2+</SUP>dopant. The effects of molar ratio of component and experimental conditions on luminescence property of prepared phosphors have been investigated. The structure and luminescence properties of prepared Ba₃Si6O12N₂:Eu<SUP>2+</SUP> phosphors were investigated by XRD and photoluminescence spectroscopy. The excitation spectra of Ba₃Si6O12N₂:Eu<SUP>2+</SUP> phosphors indicated broad excitation wavelength range of 250 - 500 nm, namely from UV to blue region with distinct enhanced emission spectrum peaking at ≈ 530 nm.

코팅형 백색 LED와 이격 형광체형 백색 LED의 분광특성의 전류의존성 연구

최민혁,이헌재,고재현 한국물리학회 2014 새물리 Vol.64 No.12

The conventional white LED (light-emitting diode) is composed of blue LED chips over which a phosphor coating has been formed. Because of the short distance between the LED chips and phosphor particles, the emission efficiency of the phosphors is usually decreased. In order to overcome this problem, the remote-phosphor structure, in which the distance between the chips and the phosphor particles was increased, was adopted in the LED design. The spectral and the color characteristics of conventional and remote-phosphor white LEDs were investigated and were compared as a function of the driving current. The remote-phosphor white LED was found to have advantages over the conventional white LED from the viewpoints of efficiency and color uniformity. This was attributed to the higher phosphor efficiency at high currents, as well as to the reduced absorption by the LED chips of the light emitted from the phosphors. 기존에 가장 많이 사용되는 백색 LED (Light Emitting Diodes, LED)의 경우 청색 LED칩 위에 형광체가 도포되는 방식으로 구성되어 있어 구동 전류나 온도와 같은 조건 변화에 따른 발광효율 및 색도변화가 심해지는 문제점이 있다. 이를 보완하기 위한 방안으로 청색 LED 칩과 형광체 사이에 일정한 거리를 두는 이격 형광체 (Remote Phosphor) 구조의 백색 LED를 제작하여, 전류에 따른 분광 특성을 연구하였다. 구동 전류에 따른 휘도 및 색좌표의 변화를 비교한 결과 이격 형광체형 백색 LED가 기존의 백색 LED보다 발광효율 및 색도 균일성 측면에서 더 우수하다는 것을 알 수 있었다. 이는 구동전류의 증가에 따라 온도가 올라가는 청색 칩과 형광체 사이에 설정된 간격으로 인해 고전류에서 형광체의 효율 저하가 줄어들 뿐 아니라 형광체가 방출하는 황색 빛이 LED 칩에 의해 재흡수되는 비중을 줄이기 때문인 것으로 생각된다.