Effect of Fine Tuning of a tris - Orthometalated Ir(Ⅲ) Complex on Electrophosphorescent Devices

Rupasree Ragini Das,Chang-Lyoul Lee,Yong Young Noh,Jang-Joo Kim 한국진공학회 2002 한국진공학회 학술발표회초록집 Vol.- No.-

Polymer based blue electrophosphorescent light emitting devices

이창렬,Rupasree Ragini Das,김장주 한국물리학회 2005 Current Applied Physics Vol.5 No.4

A series of bis-orthometalated monocyano Ir(III) complexes, [Ir(ppy)2PX3CN], (X¼ Oph, Ph and n-bu) were synthesized and theinuence of the steric and electronic eects of the phosphine ligand on the photophysical and electrochemical properties of com-plexes were studied. These cyano phosphine complexes emit light from an admixture of triplet metal-to-ligand charge-transfer(3MLCT) and ligand centered (LC) states in the region of 455498 nm with a vibronic progression. The trends of the photophysicaland electrochemical properties of metal complexes in the series were well understood by the electronic parameter of the phosphineligands. Polymer light emitting devices were fabricated by doping Ir(ppy)2P(n-bu)3CN in the PVK host and the device performanceswere investigated. The maximum external quantum eciencyðgexÞwas 1.45% for a 10wt% Ir(ppy)2P(n-bu)3CN doped PVK device.A power eciency of 0.99 lm/W at 230 cd/m2 and 6 mA/cm2 was obtained. The corresponding chloro complexes of the generalformula [Ir(ppy)2PX3Cl] were also synthesized and the optical and device properties were compared with the cyano complexes..

Highly stable functionalized cuprous oxide nanoparticles for photocatalytic degradation of methylene blue

Kumar, Mohit,Das, Rupasree Ragini,Samal, Monica,Yun, Kyusik Elsevier 2018 Materials chemistry and physics Vol.218 No.-

<P><B>Abstract</B></P> <P>We report the synthesis and characterization of Cu<SUB>2</SUB>O nanoparticles (NPs) in the presence of the coordinating ligands like <SMALL>L</SMALL>-glutamic acid (Glu-Cu<SUB>2</SUB>O) and <SMALL>D</SMALL>-glucosamine (GlcN-Cu<SUB>2</SUB>O). Even if –NH<SUB>2</SUB> group is common to both the ligands, <SMALL>L</SMALL>-glutamic acid is a straight chain compound containing additional two –COOH groups, whereas, glucosamine is a cyclic compound with additional four –OH groups and an ether (-O-) linkage. Thus the coordinating ligands are different in the nature of the functional groups as well as their molecular skeletons leading to cubic morphology (∼350 nm of average edge length) for <SMALL>L</SMALL>-glutamic acid coordinated Cu<SUB>2</SUB>O and spherical morphology (∼250 nm of average diameter) for glucosamine one as observed by Field Effective Scanning Electron Microscopy (FE-SEM) and Transmission Electron Microscopy (TEM) images. The observed band gap of Cu<SUB>2</SUB>O of 1.89 eV is decreased to 1.84 ev for both the ligated structures. Both the ligated cuprous oxide (Cu<SUB>2</SUB>O) nanoparticles (NPs) were used for the photocatalytic degradation of methylene Blue (MB). The spherical GlcN-Cu<SUB>2</SUB>O showed 98% degradation of MB in 105 min and after 3 cycles of operation, the photocatalytic activity was enough for the 93% degradation of the dye, whereas, the cubic Gu-Cu<SUB>2</SUB>O could degrade MB up to 97% in 135 min and after three cycles, only 86% of the dye was degraded. This indicates, the molecular skeleton and functional groups on the ligand control the shape and size of the Cu<SUB>2</SUB>O nanoparticles as well as the photocatalytic efficiency and stability. It is presumed, the cyclic glucosamine ligand can protect the Cu<SUB>2</SUB>O nanoparticles from erosion during the degradation process.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Different structure of functionalized Cu<SUB>2</SUB>O was synthesized. </LI> <LI> NH<SUB>2</SUB> group is common to both the ligands. </LI> <LI> Photocatalytic dye degradation was done. </LI> <LI> Synthesized nanomaterials were highly stable up to third cycle. </LI> </UL> </P>

Polymer Phosphorescence Device using a New Green Emitting Ir(III) Complex

Lee, Chang-Lyoul,Das, Rupasree Ragini,Noh, Yong-Young,Kim, Jang-Joo The Korean Infomation Display Society 2002 Journal of information display Vol.3 No.1

We have synthesized a new green Ir(III) complex fac-tris-(3-methyl-2-phenyl pyridine)iridium(III) $Ir(mpp)_3$ and fabricated phosphorescent polymer light-emitting device using it as a triplet emissive dopant in PVK. $Ir(mpp)_3$ showed absorption centered at 388 nm corresponding to the $^1MLCT$ transition as .evidenced by its extinction coefficient of the order of $10^3{\cdot}$ From the PL and EL spectra of the $Ir(mpp)_3$ doped PVK film, the emission maximum was observed at 523 nm, due to the radiative decay from the $^3MLCT$ state to the ground state, confirming a complete energy transfer from PVK to $Ir(mpp)_3$. The methyl substitution has probably caused a red shift in the absorption and emission spectrum compared to $Ir(mpp)_3$. The device consisting of a 2 % doped PVK furnished 4.5 % external quantum efficiency at 72 $cd/m^2$ (current density of 0.45 $mA/cm^2$ and drive voltage of 13.9 V) and a peak luminance of 25,000 $cd/m^2$ at 23.4 V (494 $mA/cm^2$). This work demonstrates the impact of the presence of a methyl substituent at the 3-position of the pyridyl ring of 2-phenylpyridine on the photophysical and electroluminescence properties.

Synthesis and Characterization of Bis-Orthometalated Ir(III) Complex Consisting of Non-Carbon-Coordinating Ligand

Lee†, Chang-Lyoul,Das†, Rupasree Ragini,Kim, Jang-Joo Informa UK (TaylorFrancis) 2010 MOLECULAR CRYSTALS AND LIQUID CRYSTALS - Vol.531 No.1

Polymer based blue electrophosphorescent light emitting devices

Lee, Chang-Lyoul,Ragini Das, Rupasree,Kim, Jang-Joo Elsevier 2005 CURRENT APPLIED PHYSICS Vol.5 No.4

<P><B>Abstract</B></P><P>A series of bis-orthometalated monocyano Ir(III) complexes, [Ir(ppy)<SUB>2</SUB>PX<SUB>3</SUB>CN], (X=Oph, Ph and <I>n</I>-bu) were synthesized and the influence of the steric and electronic effects of the phosphine ligand on the photophysical and electrochemical properties of complexes were studied. These cyano phosphine complexes emit light from an admixture of triplet metal-to-ligand charge-transfer (<SUP>3</SUP>MLCT) and ligand centered (LC) states in the region of 455–498 nm with a vibronic progression. The trends of the photophysical and electrochemical properties of metal complexes in the series were well understood by the electronic parameter of the phosphine ligands. Polymer light emitting devices were fabricated by doping Ir(ppy)<SUB>2</SUB>P(<I>n</I>-bu)<SUB>3</SUB>CN in the PVK host and the device performances were investigated. The maximum external quantum efficiency (<I>η</I><SUB>ex</SUB>) was 1.45% for a 10 wt% Ir(ppy)<SUB>2</SUB>P(<I>n</I>-bu)<SUB>3</SUB>CN doped PVK device. A power efficiency of 0.99 lm/W at 230 cd/m<SUP>2</SUP> and 6 mA/cm<SUP>2</SUP> was obtained. The corresponding chloro complexes of the general formula [Ir(ppy)<SUB>2</SUB>PX<SUB>3</SUB>Cl] were also synthesized and the optical and device properties were compared with the cyano complexes.</P>

Effects of Symmetry of Ir (III) Complex on the Photophysical Properties and Device Performances

Lee†, Chang-Lyoul,Das†, Rupasree Ragini,Kim, Jang-JOO Informa UK (TaylorFrancis) 2011 MOLECULAR CRYSTALS AND LIQUID CRYSTALS - Vol.550 No.1

Development of an Image Enhancement Method and a GUI

Rima Deb,Dipali Sengupta,Rupasree Das,Subhankar Mahajan,Sanjoy Mitra 보안공학연구지원센터 2015 International Journal of Signal Processing, Image Vol.8 No.6

This article introduces a new adaptive local image enhancement method and a graphical user. The algorithm for image enhancement will correct contrast for some certain areas of an image which is based on edges contained in the image and some statistical properties; variance of the whole image and mean value of an image block. A contrast correction gain is chosen for each image tile based on statistical properties. The algorithm improves the visual quality of an image and also restricts noise amplification. The algorithm is tested with grayscale images and results are compared with histogram equalization and adaptive histogram equalization techniques by image quality metrics parameters.

Synthesis and properties of a solution-processable truxene derivative for OLED devices.

Choi, Kyu Min,Kim, Kye-Young,Kim, Tae-Dong,Das, Rupasree Ragini,Choi, Byoung Ki,Park, Jong Jin,Kim, Jong-Min,Lee, Kwang-Sup American Scientific Publishers 2010 Journal of nanoscience and nanotechnology Vol.10 No.10

<P>A soluble truxene derivative (TR1) attached with triphenylamine at the peripheral position was designed and synthesized. The structure and purity of TR1 were carefully characterized by 1H NMR, UV/vis and photoluminescent spectroscopy, mass spectroscopy, and thermal analyses. It exhibited good solubility in common organic solvents and good film forming properties. The maximum absorption and emission peaks in THF solution were shown at 358 nm and 415 nm, respectively. Bright blue emission was observed in both solution and solid states under UV excitation. The fluorescent quantum efficiency was 0.46. The best luminous efficiency was found to be 3.65 cd/A with CIE coordinates of (0.163, 0.260) in electroluminescence devices.</P>

Study on a set of bis-cyclometalated Ir(<small>III</small>) complexes with a common ancillary ligand

Byun, Younghun,Jeon, Woo Sung,Lee, Tae-Woo,Lyu, Yi-Yeol,Chang, Seok,Kwon, Ohyun,Han, Eunsil,Kim, Heekyung,Kim, Myeongsuk,Lee, Ha-Jin,Das, Rupasree Ragini Royal Society of Chemistry 2008 Dalton Transactions Vol.2008 No.35

<P>Bis-cyclometalated iridium(<SMALL>III</SMALL>) complexes [Ir(F<SUB>2</SUB>ppy)<SUB>2</SUB>ZN] (FZN), [Ir(F<SUB>2</SUB>CNppy)<SUB>2</SUB>ZN] (FCZN), [Ir(DMAF<SUB>2</SUB>ppy)<SUB>2</SUB>ZN] (FDZN) and [Ir(MeOF<SUB>2</SUB>ppy)<SUB>2</SUB>ZN] (MeOFZN) (F<SUB>2</SUB>ppy = 4′,6′-difluoro-2-phenylpyridinate, F<SUB>2</SUB>CNppy = 5′-cyano-4′,6′-difluoro-2-phenylpyridinate, DMAF<SUB>2</SUB>ppy = 4′,6′-difluoro-4-dimethylamino-2-phenylpyridinate, MeOF<SUB>2</SUB>ppy = 4′,6′-difluoro-4-methyl-2-phenylpyridinate and ZN = 3,5-dimethylpyrazole-<I>N</I>-carboxamide) emitting in the sky blue region were synthesized. We studied the effect of the ancillary ligand ZN and the substituents on the cyclometalating ligands on the crystal structures, photophysical and electrochemical properties and the frontier orbitals. Density functional theory (DFT) calculation results indicate that in FCZN and FDZN the cyclometalating ligands show negligible participation in the HOMO, the ancillary ligand ZN being the main participant along with the Ir(<SMALL>III</SMALL>) d-orbitals. MeOFZN exhibits the maximum photoluminescence quantum efficiency and radiative emission rates along with the dominant low frequency metal–ligand vibrations and maximum reorganization energy in the excited state. All the substituted complexes show more polar characteristics than FZN, FCZN possessing the highest dipole moment among the complexes. The performances of the solution-synthesised organic light emitting devices (OLEDs) of FZN, FCZN and FDZN doped in a blend of mCP (<I>m</I>-bis(<I>N</I>-carbazolylbenzene)) and polystyrene are studied.</P> <P>Graphic Abstract</P><P>The frontier orbitals and photophysical, electrochemical, and electroluminescence properties are influenced by the cyclometalating and ancillary ligands. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=b719205c'> </P>