Electroluminescence properties of an ionic small molecule for solid state lighting

( Shanraj ),최영선 한국공업화학회 2015 한국공업화학회 연구논문 초록집 Vol.2015 No.1

Light-emitting electrochemical cells are the future generation of flatpanel displays and solid state lighting sources. Compared to conventional solid state lighting device such as organic light-emitting diode (OLED), light-emitting electrochemical cell (LECs) possess simple device architecture and air stable electrodes makes LECs more impressive. Mainly LECs are two types, p-LECS and Ir-ITMCs. Polymer lightemitting electrochemical cells are tri-component blend containing emitting polymer, an ion-conducting polymer and an inorganic salt. Currently much research have been focused on cationic iridium complexes due to the phosphorescent, color tuning and an ionic nature of Ir-ITMCs. However, the source and expensive nature of iridium demands new emitters in LECs. Recently non-ionic small molecule light-emitting electrochemical cell containg the device structure as same as the p-LEC were reported by Tang et al. The molecule which is an ionic apart from Ir-ITMCs have great attentions. We designed and synthesized an ionic fluorene derivative in multi-step synthetic procedure having strong luminescence and good charge transporting capabilities. A complete structural, photophysical, electrochemical and electroluminescent properties were investigated. Deep blue light- emissions were achieved by applying the target compound in a LEC device configuration at around 7.5 V.

Study of a QCW Light-emitting-diode (LED)-pumped Solid-state Laser

이강인,배상윤,곽진석,권진혁,이종훈 한국물리학회 2011 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.59 No.51

Lasing of solid-state lasers pumped by light emitting diode (LED) was studied to replace quasi continuous wave (QCW) laser diode in solid-state laser pumping. The investigated solid-state gain media include Nd doped materials (Nd:YAG, Nd:glass, Nd/Cr:YAG), Ti:sapphire, and solid dye. The gain medium was surrounded by arrays of LEDs very closely. The absorbed LED distribution in gain medium was calculated by non-sequential ray tracing software. The calculated data transferred to cavity analysis software and lasing characteristics were simulated. The calculated result of absorbed LED distribution and absorption efficiency in the Nd:YAG rod was compared to experimentally measured fluorescence profile and absorption efficiency and the result calculation is accurate with error of 11%. Among the investigated gain media, Nd/Cr:YAG showed the lowest lasing threshold. It is also found that the use of reflector in the pumping chamber can lower the lasing threshold of Nd:YAG to half of the lasing threshold without the reflector.

Phase formation and luminescence properties of ternary solid-solution among tetragonal systems

Unithrattil, Sanjith,Kim, Ha Jun,Im, Won Bin ELSEVIER SCIENCE 2019 JOURNAL OF ALLOYS AND COMPOUNDS Vol.798 No.-

<P><B>Abstract</B></P> <P>A new strategy for developing solid-solution compounds from three constituent compounds was analyzed. Using this strategy, a series of yellow-light-emitting phosphors derived from ternary solid-solution host compositions were prepared using solid-state synthesis. Three vertex members, Sr<SUB>3</SUB>SiO<SUB>5</SUB> (space group <I>P</I>4/<I>ncc</I>), Sr<SUB>3</SUB>AlO<SUB>4</SUB>F (space group <I>I</I>4/<I>mcm</I>), and LaSr<SUB>2</SUB>AlO<SUB>5</SUB> (space group <I>I</I>4/<I>mcm</I>), were selected from similar crystal structures with slightly different symmetries. The crystallization space group of the composition was found to be dependent on the end members, and from the vertex of the ternary plot to the centroid, the composition assumed the space group that was more tolerant toward substitutions. All the compositions, except those lying at the periphery of the ternary plot, formed a single phase and emitted yellow light when activated with Ce<SUP>3+</SUP> ions. The luminescence properties of the 28 selected compositions on the ternary plot were analyzed. The compound that was formed from a 1:2:1 ratio of end members assumed a <I>I</I>4/<I>mcm</I> structure and showed the highest-intensity emission. Phosphor derived from the developed host lattice was analyzed for application in solid-state lighting devices by preparing a white-light emitting device.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Phase formation in ternary solid-solutions of tetragonal systems. </LI> <LI> Tetragonal structure Sr<SUB>3</SUB>SiO<SUB>5</SUB>, LaSr<SUB>2</SUB>AlO<SUB>3</SUB> and Sr<SUB>3</SUB>AlO<SUB>4</SUB>F are investigated in the preparation of ternary solid solution. </LI> <LI> Structural analysis of all the selected compositions was carried out using the Le Bail method. </LI> <LI> The detailed structural analysis of selected compositions was performed via Rietveld refinement. </LI> <LI> Ternary solid solution present great color tunability in wLED fabrication. </LI> </UL> </P>

Eu³⁺-activated potential red-emitting phosphor for solid-state lighting

Haque, Md.M.,Kudrat-E-Zahan, Md.,Jahan, N.A.,Lee, H.I. Wissenschaftliche Verlagsgesellschaft m. b. H 2017 OPTIK -STUTTGART- Vol.133 No.-

<P>The intense red-emitting NaCaY0.2Eu0.8(MoO4)(3) phosphor was prepared by using a sol-gel method for the first time. Thermogravimetric-diferential thermal analysis, X-ray diffraction, field-emission scanning electron microscopy, FT-IR and luminescent measurements were used to characterize the NaCaY0.2Eu0.8(MoO4)(3) particles. The resulting products obtained by using the sol-gel method have a narrower size distribution and a more regular particle shape than those obtained by using the solid- state reaction. The spectra analysis indicated that the obtained phosphor could be excited by UV light of 395 nm and visible light of 466 nm, also emits intense red light with a maximum at about 614 nm. The luminescent intensity of sol-gel derived is comparable with the solid state product and it is about 84% of solid-state product under 395 nm light excitation. Comparative study with YAG:Ce and CaS:Eu2+ phosphors, suggested that our synthesized phosphor can be used as an efficient red-emitting phosphor to compensate the red deficiency of YAG:Ce phosphor and also can serve as an alternative phosphor to replace sulfide based phosphors in the solid-state lighting applications. (C) 2016 Elsevier GmbH. All rights reserved.</P>

Application of thermally coupled energy levels in Er³⁺ doped CdMoO₄ phosphors: Enhanced solid-state lighting and non-contact thermometry

Ran, Weiguang,Noh, Hyeon Mi,Park, Sung Heum,Lee, Bo Ram,Kim, Jung Hwan,Jeong, Jung Hyun,Shi, Jinsheng Elsevier 2019 Materials research bulletin Vol.117 No.-

<P><B>Abstract</B></P> <P>Er<SUP>3+</SUP>-activated CdMoO<SUB>4</SUB> phosphors were prepared by a traditional high-temperature solid-state method. The crystal structure, photoluminescence (PL) characteristics and performance in non-contact thermometry of as-prepared phosphors were studied in detail. Benefiting from the 3D network structure of CdMoO<SUB>4</SUB> host, the desirable green emission of Er<SUP>3+</SUP>-based phosphors were observed. Especially, based on the thermally coupled energy levels, the obtained phosphors show enhanced emission intensity in high temperatures. When applied to the temperature sensor based on the fluorescence intensity ratio (FIR), the prepared CdMoO<SUB>4</SUB>:0.02Er<SUP>3+</SUP> phosphor show an excellent sensitivity (0.875% K<SUP>−1</SUP>) at 483 K. Therefore, it is demonstrated that the as-prepared Er<SUP>3+</SUP>-activated CdMoO<SUB>4</SUB> phosphors have a promising potential application in both solid-state lighting and non-contact thermometry.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Enhanced emission intensity in high temperatures has been achieved. </LI> <LI> Er<SUP>3+</SUP> doped CdMoO<SUB>4</SUB> phosphor has a potential application in solid-state lighting. </LI> <LI> High sensitivity indicates that CdMoO<SUB>4</SUB>: 0.02Er<SUP>3+</SUP> phosphor can be used in non-contact thermometer. </LI> <LI> Excellent water stability of Er<SUP>3+</SUP> doped CdMoO<SUB>4</SUB> can be used in a complex condition. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

A blue-emitting phosphor of Ba2MgP4O13 : Eu2+ for white light UV light-emitting diodes

서효진,Nuan Xie,Yanlin Huang 한양대학교 세라믹연구소 2010 Journal of Ceramic Processing Research Vol.11 No.3

A novel blue-emitting phosphor of Eu2+-doped Ba2MgP4O13 phosphate was prepared by a high-temperature solid-state reaction method. The phosphor was investigated by X-ray powder diffraction (XRD) measurements and confirmed to be the pure crystalline phase of Ba2MgP4O13. The emission and excitation spectra of the phosphor were studied. The phosphor could be excited by UV light from 220 nm to 400 nm and emitted a blue luminescence peaked at 410 nm, which corresponds to the 4f 65d1→4f 7 transition of Eu2+ ions. The dependence of luminescence intensities of Eu2+-doped Ba2MgP4O13 on the heating temperature and doping concentrations were investigated. The phosphor had an excellent thermal stability to temperature quenching effects. The luminescence decay (lifetimes) of the phosphor is also discussed in order to further investigate its potential applications for white light-emitting diode phosphors pumped by a near-UV chip.

발광 다이오드 (LED) 펌핑 Nd:KGW 레이저 발진 특성

정치현,이종훈,이범준,이상후,임정섭,정우열,김국현 한국물리학회 2018 새물리 Vol.68 No.4

Solid-state lasers were pumped with LEDs (light-emitting diodes) to replace solid-state lasers that are pumped with quasi–continuous-wave (QCW) laser diodes (LD). The LED has a low cost, is easy to operate in the pulse mode, has a wide emission linewidth. Nd:KGW crystals are suitable for pumping by LEDs because the width of the absorption line is very broad. For the structure pumped by an LED on four sides of the Nd:KGW crystal, the distribution of the absorbed pump light was calculated by using ZEMAX. The pump light from the LED is sent directly to the crystal or through the light guide prism to the crystal. The laser output energy versus pump energy was investigated using the calculated results for the distribution of the absorbed pump light. The Nd:KGW crystal has a lower induced-emission cross-section and a shorter fluorescence lifetime than the Nd:YAG crystal, so the lasing threshold is high. However, we found that the energy conversion efficiency of the Nd:KGW laser could be made to be higher than that of the Nd:YAG laser by increasing the overlap with the absorption spectrum when pumping with a LED having a wide emission spectrum. 준연속 (quasi-continuous wave) 레이저 다이오드(laser diode)로 펌핑하는 고체레이저를 대신하기 위하여 발광 다이오드(light-emitting diode, LED)로 펌핑하는 고체레이저를 연구하였다. LED는 저가이고 펄스 동작이 용이하며, 발광 스펙트럼의 선폭이 넓은 특성이 있다. Nd:KGW 결정은 흡수 스펙트럼의 선폭이 매우 넓어서 LED로 펌핑하기에 적절하다. Nd:KGW 결정의 옆면 4곳에서 LED로 펌핑하는 구조에서, 펌핑광의 흡수 분포를 ZEMAX로 계산하였다. LED를 결정 바로 곁에 두어 펌핑광이 직접 결정에 흡수되게 하거나, 도광프리즘을 통하여 펌핑광이 결정에 전달된 후에 흡수되게 하였다. 펌핑광의 흡수 분포를 계산한 결과를 이용하여 레이저의 발진 특성을 조사하였다. Nd:KGW 결정은 Nd:YAG 결정에 비하여 유도방출 단면적이 작고 형광수명이 짧아서 발진 문턱은 높다. 하지만 발광 스펙트럼이 넓은 LED로 펌핑하면 흡수 스펙트럼과 겹치는 부분이 증가하여 Nd:KGW의 에너지 전환 효율이 Nd:YAG 보다 더 높음을 밝혔다.

Fundamentals and applications of light-emitting diodes (LEDs) in in vitro plant growth and morphogenesis

S. Dutta Gupta,B. Jatothu 한국식물생명공학회 2013 Plant biotechnology reports Vol.7 No.3

Advances in plant tissue culture methods withregard to lighting requirements are currently focused on theimproved features of light-emitting diodes (LEDs). Overthe years, the steady development of LED technology, withthe emergence of new types of semi-conductor materials,has made it possible to apply it in an increasing number ofnew areas. As an alternative to conventional lighting systems,LED has been demonstrated to be an artificial flexiblelighting source for plant tissue culture. Numerousstudies have been conducted in order to investigate theeffects of LED on plants, which have led to many satisfactoryresults. Various morphological, anatomical, andphysiological attributes, such as shoot elongation, axillaryshoot formation, somatic embryo induction, rhizogenesis,leaf anatomy, and photosynthetic abilities of plants grownin vitro have found to be regulated by spectral properties ofLEDs. The present review gives an overview of the fundamentalsof LEDs and describes their effects on in vitroplant growth and morphogenesis and their future potentials

Fundamentals and applications of light-emitting diodes (LEDs) in in vitro plant growth and morphogenesis

Gupta, S. Dutta,Jatothu, B. 한국식물생명공학회 2013 Plant biotechnology reports Vol.7 No.3

Advances in plant tissue culture methods with regard to lighting requirements are currently focused on the improved features of light-emitting diodes (LEDs). Over the years, the steady development of LED technology, with the emergence of new types of semi-conductor materials, has made it possible to apply it in an increasing number of new areas. As an alternative to conventional lighting systems, LED has been demonstrated to be an artificial flexible lighting source for plant tissue culture. Numerous studies have been conducted in order to investigate the effects of LED on plants, which have led to many satisfactory results. Various morphological, anatomical, and physiological attributes, such as shoot elongation, axillary shoot formation, somatic embryo induction, rhizogenesis, leaf anatomy, and photosynthetic abilities of plants grown in vitro have found to be regulated by spectral properties of LEDs. The present review gives an overview of the fundamentals of LEDs and describes their effects on in vitro plant growth and morphogenesis and their future potentials.

Solid state solvation effect of a donor-acceptor type fluorescent molecule and its application to white organic light-emitting diodes

Ahn, S.,Kim, J.N.,Kim, Y.C. Elsevier 2015 CURRENT APPLIED PHYSICS Vol.15 No.suppl1

We investigated the solid state solvation effect (SSSE) of a donor-acceptor (D-A) type green fluorescent emitter, 3,7-bis(benzimidazol-2-yl)-10-methylphenothiazine (BBMP), and fabricated white organic light-emitting diodes (OLEDs) by utilizing SSSE. After having confirmed that BBMP showed a large solvatochromic photoluminescence spectral shift not only in liquid solutions but also in solid solutions, we induced a sky-blue electroluminescence (EL) by doping the green-emitting BBMP in non-polar host materials. The emission spectrum of BBMP blue-shifted as the polarity of host material decreased, and white OLEDs were obtained by integrating an additional orange light-emitting material, Rubrene, into this sky-blue-emitting OLED structure. When 9, 10-di(naphtha-2-yl)anthracene(ADN) was employed as a non-polar host of BBMP, the device exhibited a sky-blue (λ<SUB>peak,EL</SUB> = 475 nm) emission by SSSE with evidently improved EL properties: the luminous efficiency, the external quantum efficiency, and the maximum luminance were 10.4 cd/A, 3.5%, and 46,600 cd/m<SUP>2</SUP>, respectively. Finally, the white OLED with an optimized structure of [ITO/NPB (20 nm)/ADN:Rubrene (20 nm)/NPB (2 nm)/ADN:BBMP (20 nm)/TPBi (20 nm)/Alq3 (10 nm)/LiF (1 nm)/Al (100 nm)] demonstrated a luminous efficiency of 5.3 cd/A, an external quantum efficiency of 1.3%, and a maximum luminance of 15,200 cd/m<SUP>2</SUP> with CIE coordinates of (0.32, 0.42) at 100 mA/cm<SUP>2</SUP>.